EO (Earth Observation) Topics on Climate Change
Since the start of the space age, Earth observation is providing its share of evidence for a better perception and understanding of our Earth System and its response to natural or human-induced changes.
Earth is a complex, dynamic system we do not yet fully understand. The Earth system comprises diverse components that interact in complex ways. We need to understand the Earth's atmosphere, lithosphere, hydrosphere, cryosphere, and biosphere as a single connected system. Our planet is changing on all spatial and temporal scales.
Over the years, the entire Earth Observation community, the space agencies as well as other governmental bodies, and many international organizations (UN, etc.) are cooperating on a global scale to come to grips with the modeling of the Earth system, including a continuous process of re-assessment and improvement of these models. The goal is to provide scientific evidence to help guide society onto a sustainable pathway during rapid global change.
In the second decade of the 21st century, there is alarming evidence that important tipping points, leading to irreversible changes in major ecosystems and the planetary climate system, may already have been reached or passed. Ecosystems as diverse as the Amazon rainforest and the Arctic tundra, may be approaching thresholds of dramatic change through warming and drying. Mountain glaciers are in alarming retreat and the downstream effects of reduced water supply in the driest months will have repercussions that transcend generations. 1)
Table 1: Overview of some major international bodies involved in global-change research programs 2)
The UN Framework Convention on Climate Change (UNFCCC) is an intergovernmental treaty developed to address the problem of climate change. The Convention, which sets out an agreed framework for dealing with the issue, was negotiated from February 1991 to May 1992 and opened for signature at the June 1992 UN Conference on Environment and Development (UNCED) — also known as the Rio Earth Summit. The UNFCCC entered into force on 21 March 1994, ninety days after the 50th country’s ratification had been received. By December 2007, the convention had been ratified by 192 countries. 3)
In the meantime, there were many UN conferences on Climate Change, starting with the UN climate conference in Kyoto, Japan, in December 1997. The Kyoto Protocol set standards for certain industrialized countries. Those targets expired in 2012.
Meanwhile, greenhouse gas emissions from both developed and developing countries have been increasing rapidly. Even today, those nations with the highest percentage of environment pollution, are not willing to enforce stricter environmental standards in their countries in order to protect their global business interests. It's a vicious cycle between these national interests and the deteriorating environment, resulting in more frequent and violent catastrophes on a global scale. All people on Earth are effected, even those who abide by their strict environmental rules.
The short descriptions in the following chapters are presented in reverse order on some topics of climate change to give the reader community an overview of research results in this wide field of global climate and environmental change.
Note: As of May 2019, the previously single large EO-Topics file has been split into four files, to make the file handling manageable for all parties concerned, in particular for the user community.
• This article covers the period 2020-2019
EO-Topics4 (Time frame: 2020-2019)
New 3D View of Methane Tracks Sources and Movement around the Globe
• March 23, 2020: NASA’s new 3-dimensional portrait of methane concentrations shows the world’s second largest contributor to greenhouse warming, the diversity of sources on the ground, and the behavior of the gas as it moves through the atmosphere. Combining multiple data sets from emissions inventories, including fossil fuel, agricultural, biomass burning and biofuels, and simulations of wetland sources into a high-resolution computer model, researchers now have an additional tool for understanding this complex gas and its role in Earth’s carbon cycle, atmospheric composition, and climate system. 4)
Since the Industrial Revolution, methane concentrations in the atmosphere have more than doubled. After carbon dioxide, methane is the second most influential greenhouse gas, responsible for 20 to 30% of Earth’s rising temperatures to date.
“There’s an urgency in understanding where the sources are coming from so that we can be better prepared to mitigate methane emissions where there are opportunities to do so,” said research scientist Ben Poulter at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Figure 1: NASA’s new 3-dimensional portrait of methane shows the world’s second largest contributor to greenhouse warming as it travels through the atmosphere. Combining multiple data sets from emissions inventories and simulations of wetlands into a high-resolution computer model, researchers now have an additional tool for understanding this complex gas and its role in Earth’s carbon cycle, atmospheric composition, and climate system. The new data visualization builds a fuller picture of the diversity of methane sources on the ground as well as the behavior of the gas as it moves through the atmosphere (video credit: NASA/Scientific Visualization Studio)
A single molecule of methane is more efficient at trapping heat than a molecule of carbon dioxide, but because the lifetime of methane in the atmosphere is shorter and carbon dioxide concentrations are much higher, carbon dioxide still remains the main contributor to climate change. Methane also has many more sources than carbon dioxide, these include the energy and agricultural sectors, as well as natural sources from various types of wetlands and water bodies.
“Methane is a gas that’s produced under anaerobic conditions, so that means when there’s no oxygen available, you’ll likely find methane being produced,” said Poulter. In addition to fossil fuel activities, primarily from the coal, oil and gas sectors, sources of methane also include the ocean, flooded soils in vegetated wetlands along rivers and lakes, agriculture, such as rice cultivation, and the stomachs of ruminant livestock, including cattle.
“It is estimated that up to 60% of the current methane flux from land to the atmosphere is the result of human activities,” said Abhishek Chatterjee, a carbon cycle scientist with Universities Space Research Association based at Goddard. “Similar to carbon dioxide, human activity over long time periods is increasing atmospheric methane concentrations faster than the removal from natural ‘sinks’ can offset it. As human populations continue to grow, changes in energy use, agriculture and rice cultivation, livestock raising will influence methane emissions. However, it’s difficult to predict future trends due to both lack of measurements and incomplete understanding of the carbon-climate feedbacks.”
Researchers are using computer models to try to build a more complete picture of methane, said research meteorologist Lesley Ott with the Global Modeling and Assimilation Office at Goddard. “We have pieces that tell us about the emissions, we have pieces that tell us something about the atmospheric concentrations, and the models are basically the missing piece tying all that together and helping us understand where the methane is coming from and where it’s going.”
To create a global picture of methane, Ott, Chatterjee, Poulter and their colleagues used methane data from emissions inventories reported by countries, NASA field campaigns, like the Arctic Boreal Vulnerability Experiment (ABoVE) and observations from the Japanese Space Agency’s Greenhouse Gases Observing Satellite (GOSAT Ibuki) and the Tropospheric Monitoring Instrument aboard the European Space Agency’s Sentinel-5P satellite. They combined the data sets with a computer model that estimates methane emissions based on known processes for certain land-cover types, such as wetlands. The model also simulates the atmospheric chemistry that breaks down methane and removes it from the air. Then they used a weather model to see how methane traveled and behaved over time while in the atmosphere.
The data visualization of their results shows methane’s ethereal movements and illuminates its complexities both in space over various landscapes and with the seasons. Once methane emissions are lofted up into the atmosphere, high-altitude winds can transport it far beyond their sources.
The Arctic and high-latitude regions are responsible for about 20% of global methane emissions. “What happens in the Arctic, doesn’t always stay in the Arctic,” Ott said. “There’s a massive amount of carbon that’s stored in the northern high latitudes. One of the things scientists are really concerned about is whether or not, as the soils warm, more of that carbon could be released to the atmosphere. Right now, what you’re seeing in this visualization is not very strong pulses of methane, but we’re watching that very closely because we know that’s a place that is changing rapidly and that could change dramatically over time.”
“One of the challenges with understanding the global methane budget has been to reconcile the atmospheric perspective on where we think methane is being produced versus the bottom-up perspective, or how we use country-level reporting or land surface models to estimate methane emissions,” said Poulter. “The visualization that we have here can help us understand this top-down and bottom-up discrepancy and help us also reduce the uncertainties in our understanding of the global methane budget by giving us visual cues and a qualitative understanding of how methane moves around the atmosphere and where it’s produced.”
The model data of methane sources and transport will also help in the planning of both future field and satellite missions. Currently, NASA has a planned satellite called GeoCarb that will launch around 2023 to provide geostationary space-based observations of methane in the atmosphere over much of the western hemisphere.
Greenland, Antarctica Melting Six Times Faster Than in the 1990s
•March 16, 2020: Observations from 11 satellite missions monitoring the Greenland and Antarctic ice sheets have revealed that the regions are losing ice six times faster than they were in the 1990s. If the current melting trend continues, the regions will be on track to match the "worst-case" scenario of the Intergovernmental Panel on Climate Change (IPCC) of an extra 17 cm of sea level rise by 2100. 5) 6)
The two regions have lost 6.4 trillion (6.4 x 1012) tons of ice in three decades; unabated, this rate of melting could cause flooding that affects hundreds of millions of people by 2100.
The findings, published online March 12 in the journal Nature from an international team of 89 polar scientists from 50 organizations, are the most comprehensive assessment to date of the changing ice sheets. The Ice Sheet Mass Balance Intercomparison Exercise team combined 26 surveys to calculate changes in the mass of the Greenland and Antarctic ice sheets between 1992 and 2018. 7)
The assessment was supported by NASA and ESA (European Space Agency). The surveys used measurements from satellites including NASA's ICESat (Ice, Cloud, and land Elevation Satellite) missions and the joint NASA-German Aerospace Center GRACE (Gravity Recovery and Climate Experiment) mission. Andrew Shepherd at the University of Leeds in England and Erik Ivins at NASA's Jet Propulsion Laboratory in Southern California led the study.
Figure 2: An aerial view of the icebergs near Kulusuk Island, off the southeastern coastline of Greenland, a region that is exhibiting an accelerated rate of ice loss (image credit: NASA Goddard Space Flight Center)
The team calculated that the two ice sheets together lost 81 billion tons per year in the 1990s, compared with 475 billion tons of ice per year in the 2010s - a sixfold increase. All total, Greenland and Antarctica have lost 6.4 trillion tons of ice since the 1990s.
The resulting meltwater boosted global sea levels by 17.8 mm. Together, the melting polar ice sheets are responsible for a third of all sea level rise. Of this total sea level rise, 60% resulted from Greenland's ice loss and 40% resulted from Antarctica's.
"Satellite observations of polar ice are essential for monitoring and predicting how climate change could affect ice losses and sea level rise," said Ivins. "While computer simulations allow us to make projections from climate change scenarios, the satellite measurements provide prima facie, rather irrefutable, evidence."
The IPCC in its Fifth Assessment Report issued in 2014 predicted global sea levels would rise 71 cm by 2100. The Ice Sheet Mass Balance Intercomparison Exercise team's studies show that ice loss from Antarctica and Greenland tracks with the IPCC's worst-case scenario.
Combined losses from both ice sheets peaked at 552 billion tons per year in 2010 and averaged 475 billion tons per year for the remainder of the decade. The peak loss coincided with several years of intense surface melting in Greenland, and last summer's Arctic heat wave means that 2019 will likely set a new record for polar ice sheet loss, but further analysis is needed. IPCC projections indicate the resulting sea level rise could put 400 million people at risk of annual coastal flooding by the end of the century.
The IMBIE (Icesheet Mass Balance Inter-comparison Exercise) led by Andrew Shepherd from the University of Leeds and Erik Ivins at NASA’s Jet Propulsion Laboratory, compared and combined data from 11 satellites – including ESA’s ERS-1, ERS-2, Envisat and CryoSat missions, as well as the EU’s Copernicus Sentinel-1 and Sentinel-2 missions – to monitor changes in the ice sheet’s volume, flow and gravity.
Using observation data spanning three decades, the team has produced a single estimate of Greenland and Antarctica’s net gain or loss of ice – known as mass balance. "Every centimeter of sea level rise leads to coastal flooding and coastal erosion, disrupting people's lives around the planet," said Shepherd.
As to what is leading to the ice loss, Antarctica's outlet glaciers are being melted by the ocean, which causes them to speed up. Whereas this accounts for the majority of Antarctica's ice loss, it accounts for half of Greenland's ice loss; the rest is caused by rising air temperatures melting the surface of its ice sheet.
The Intergovernmental Panel on Climate Change (IPCC)’s latest report predicted that global sea levels will rise by 60 centimeters by 2100, and it is estimated that this would put 360 million people at risk of annual coastal flooding. However, the IMBIE teams studies shows that ice losses from Antarctica and Greenland are rising faster than expected, tracking the IPCC’s worst-case climate warming scenario. 8)
Figure 3: Antarctica and Greenland’s contribution to sea level change. Of the total sea level rise, around 60% (10.6 mm) was due to Greenland ice losses and 40% was due to Antarctica (7.2 mm), [video credit: CPOM (Center for Polar Observation and Modelling), University of Leeds]
Antarctic ice walls protect the climate
• February 26, 2020: The ocean can store much more heat than the atmosphere. The deep sea around Antarctica stores thermal energy that is the equivalent of heating the air above the continent by 400 degrees. Now, a Swedish-led international research group has explored the physics behind the ocean currents close to the floating glaciers that surround the Antarctic coast. 9)
“Current measurements indicate an increase in melting, particularly near the coast in some parts of Antarctica and Greenland. These increases can likely be linked to the warm, salty ocean currents that circulate on the continental shelf, melting the ice from below,” says Anna Wåhlin, lead author of the study and professor of oceanography at the University of Gothenburg.
”What we found here is a crucial feedback process: the ice shelves are their own best protection against warm water intrusions. If the ice thins, more oceanic heat comes in and melts the ice shelf, which becomes even thinner etc. It is worrying, as the ice shelves are already thinning because of global air and ocean warming”, says Céline Heuzé, climate researcher at the Department of Earth Sciences of Gothenburg University.
Figure 4: The Getz ice shelf. Inland Antarctic ice contains volumes of water that can raise global sea levels by several meters. A new study published in the journal Nature shows that glacier ice walls are vital for the climate, as they prevent rising ocean temperatures and melting glacier ice (image credit: Anna Wåhlin, University of Gothenburg) 10)
The stability of ice is a mystery
Inland Antarctic ice gradually moves towards the ocean. Despite the ice being so important, its stability remains a mystery – as does the answer to what could make it melt faster. Since the glaciers are difficult to access, researchers have been unable to find out much information about the active processes.
More knowledge has now been obtained from studying the measurement data collected from instruments that Anna Wåhlin and her researcher colleagues placed in the ocean around the Getz glacier in West Antarctica.
The ice’s edge blocks warm seawater
Getz has a floating section that is approximately 300 to 800 meters thick, beneath which there is seawater that connects to the ocean beyond. The glacier culminates in a vertical edge, a wall of ice that continues 300–400 meters down into the ocean. Warm seawater flows beneath this edge, towards the continent and the deeper ice further south", says Anna Wåhlin.
“Studying the measurement data from the instruments, we found that the ocean currents are blocked by the ice edge. This limits the extent to which the warm water can reach the continent. We have long been stumped in our attempts to establish a clear link between the transport of warm water up on the continental shelf and melting glaciers", says Anna Wåhlin.
Now, we understand that only a small amount of the current can make its way beneath the glacier. This means that around two-thirds of the thermal energy that travels up towards the continental shelf from the deep sea never reaches the ice.”
Can lead to better prognoses
The results of the studies have provided researchers with a greater understanding of how these glacier areas work.
“From the Getz glacier, we are receiving measurements of heat transport in the ocean that correspond with the melting ice being measured by satellites. This also means that the floating glaciers – the ice fronts in particular – are key areas that should be closely monitored. If the ice walls were to disappear, much greater levels of thermal energy would be released towards the ice on land."
"Consequently, we no longer expect to see a direct link between increasing westerly winds and growing levels of melting ice. Instead, the increased water levels can be caused by the processes that pump up warmer, heavier water to the continental shelf, for example as low-pressure systems move closer to the continent.”
Researchers believe that the studies have provided them with significantly better tools to be able to predict future water levels and create more accurate climate prognoses.
Picturing permafrost in the Arctic
• February 25, 2020: According to the latest Intergovernmental Panel on Climate Change Special Report, permafrost temperatures have increased to record high levels from the 1980s to present. As a consequence, concern is growing that significant amounts of greenhouse gases could be mobilized over the coming decades as it thaws, and potentially amplify climate change. 11)
According to the latest Intergovernmental Panel on Climate Change Special Report, permafrost temperatures have increased to record high levels from the 1980s to present. As a consequence, concern is growing that significant amounts of greenhouse gases could be mobilized over the coming decades as it thaws, and potentially amplify climate change.
Permafrost is any ground that remains completely frozen for at least two consecutive years – these permanently frozen grounds are most common in high latitude regions such as Alaska and Siberia, or at high altitudes like the Andes and Himalayas.
Near the surface, Arctic permafrost soils contain large quantities of organic carbon and materials leftover from dead plants that cannot decompose or rot, whereas permafrost layers deeper down contain soils made of minerals. When permafrost thaws, it releases methane and carbon dioxide – adding these greenhouse gases to the atmosphere.
Figure 5: Permafrost extent for the northern hemisphere in the period 2003 to 2017 (image credit: Permafrost CCI, Obu et al, 2019 via the CEDA archive)
Since permafrost is a subsurface phenomenon, understanding it is challenging without relying strictly on in situ measurements. Satellite sensors cannot measure permafrost directly, but a dedicated project as part of ESA’s Climate Change Initiative (CCI), has used complementary satellite measurements of landscape features such as land-surface temperature and land cover to estimate permafrost extent.
Figure 6: This animation shows the permafrost extent in the northern hemisphere from 2003 to 2017. The maps, produced by ESA’s Climate Change Initiative, are providing new insights into thawing permafrost in the Arctic. Continuous permafrost is defined as a continuous area with frozen material beneath the land surface, except for large bodies of water. None-continuous permafrost is broken up into separate areas and can either be discontinuous, isolated or sporadic. It is considered isolated if less than 10% of the surface has permafrost below, while sporadic means 10%-50% of the surface has permafrost below, while discontinuous is considered 50%-90% (video credit: Permafrost CCI, Obu et al,. 2019 via the CEDA archive)
These data combined with in situ observations allow the permafrost team to get a panoptic view – improving the understanding of permafrost dynamics and the ability to model its future climate impact.
Annett Bartsch, science lead of the Permafrost CCI project, comments, “The maps show there is a clear variability in the extent of permafrost. This can be seen in North America as well as Northern Eurasia.”
However, she is careful to point out, “Although the maps provide useful insight with regard to interannual variability over a 14-year period, drawing conclusions regarding climate trends is not possible.”
Dr Bartsch advises researchers, “To wait and use permafrost maps covering the full 30 year time-series, which are expected to be ready for release by the project around the mid-2020.”
The use of Earth observation data can provide spatially consistent permafrost data coverage, even in the most remote and inaccessible areas such as the Arctic. The maps are provided by the Permafrost CCI team and cover the period 2003-17 at a spatial resolution of 1 km. The Permafrost CCI data are available online.
ESA Director of Earth Observation Programs, Josef Aschbacher, adds, "The role of permafrost is believed to be underestimated in the climate change context. Therefore ESA and NASA have launched a joint initiative to call on the scientists in Europe and the US to study the impact of permafrost and other Arctic regions on global methane emissions. The initiative was jointly launched in December 2019 and a first science workshop is planned for June this year."
Figure 7: This animation shows the mean ground temperature of the northern hemisphere in 2017. The animation shows ground temperature at 2 m depth – the commonly used depth used to indicate presence of permafrost (video credit: Permafrost CCI, Obu et al, 2019 via the CEDA archive) 12)
Arctic Ice Melt Is Changing Ocean Currents
• February 6, 2020: A major ocean current in the Arctic is faster and more turbulent as a result of rapid sea ice melt, a new study from NASA shows. The current is part of a delicate Arctic environment that is now flooded with fresh water, an effect of human-caused climate change. 13) 14)
Using 12 years of satellite data, scientists have measured how this circular current, called the Beaufort Gyre, has precariously balanced an influx of unprecedented amounts of cold, fresh water — a change that could alter the currents in the Atlantic Ocean and cool the climate of Western Europe.
The Beaufort Gyre keeps the polar environment in equilibrium by storing fresh water near the surface of the ocean. Wind blows the gyre in a clockwise direction around the western Arctic Ocean, north of Canada and Alaska, where it naturally collects fresh water from glacial melt, river runoff and precipitation. This fresh water is important in the Arctic in part because it floats above the warmer, salty water and helps to protect the sea ice from melting, which in turn helps regulate Earth's climate. The gyre then slowly releases this fresh water into the Atlantic Ocean over a period of decades, allowing the Atlantic Ocean currents to carry it away in small amounts
Figure 8: Arctic sea ice was photographed in 2011 during NASA's ICESCAPE (Impacts of Climate on Ecosystems and Chemistry of the Arctic Pacific Environment) mission, a shipborne investigation to study how changing conditions in the Arctic affect the ocean's chemistry and ecosystems. The bulk of the research took place in the Beaufort and Chukchi seas in the summers of 2010 and 2011 (image credit: NASA/Kathryn Hansen)
But the since the 1990s, the gyre has accumulated a large amount of fresh water — 1,920 cubic miles (8,000 km3) — or almost twice the volume of Lake Michigan. The new study, published in Nature Communications, found that the cause of this gain in freshwater concentration is the loss of sea ice in summer and autumn. This decades-long decline of the Arctic's summertime sea ice cover has left the Beaufort Gyre more exposed to the wind, which spins the gyre faster and traps the fresh water in its current.
Persistent westerly winds have also dragged the current in one direction for over 20 years, increasing the speed and size of the clockwise current and preventing the fresh water from leaving the Arctic Ocean. This decades-long western wind is unusual for the region, where previously, the winds changed direction every five to seven years.
Scientists have been keeping an eye on the Beaufort Gyre in case the wind changes direction again. If the direction were to change, the wind would reverse the current, pulling it counterclockwise and releasing the water it has accumulated all at once.
"If the Beaufort Gyre were to release the excess fresh water into the Atlantic Ocean, it could potentially slow down its circulation. And that would have hemisphere-wide implications for the climate, especially in Western Europe," said Tom Armitage, lead author of the study and polar scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
Fresh water released from the Arctic Ocean to the North Atlantic can change the density of surface waters. Normally, water from the Arctic loses heat and moisture to the atmosphere and sinks to the bottom of the ocean, where it drives water from the north Atlantic Ocean down to the tropics like a conveyor belt.
This important current is called the Atlantic Meridional Overturning Circulation and helps regulate the planet's climate by carrying heat from the tropically-warmed water to northern latitudes like Europe and North America. If slowed enough, it could negatively impact marine life and the communities that depend it.
"We don't expect a shutting down of the Gulf Stream, but we do expect impacts. That's why we're monitoring the Beaufort Gyre so closely," said Alek Petty, a co-author on the paper and polar scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The study also found that, although the Beaufort Gyre is out of balance because of the added energy from the wind, the current expels that excess energy by forming small, circular eddies of water. While the increased turbulence has helped keep the system balanced, it has the potential to lead to further ice melt because it mixes layers of cold, fresh water with relatively warm, salt water below. The melting ice could, in turn, lead to changes in how nutrients and organic material in the ocean are mixed, significantly affecting the food chain and wildlife in the Arctic. The results reveal a delicate balance between wind and ocean as the sea ice pack recedes under climate change.
"What this study is showing is that the loss of sea ice has really important impacts on our climate system that we're only just discovering," said Petty.
NASA, NOAA Analyses Reveal 2019 Second Warmest Year on Record
• January 15, 2020: According to independent analyses by NASA and the National Oceanic and Atmospheric Administration (NOAA), Earth's average global surface temperature in 2019 was the second warmest since modern record-keeping began in 1880. Globally, 2019's average temperature was second only to that of 2016 and continued the planet's long-term warming trend: the past five years have been the warmest of the last 140 years. 15)
This past year was 1.8 degrees Fahrenheit (0.98 degrees Celsius) warmer than the 1951 to 1980 mean, according to scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.
“The decade that just ended is clearly the warmest decade on record,” said GISS Director Gavin Schmidt. “Every decade since the 1960s clearly has been warmer than the one before.”
Figure 9: The past five years have been the warmest of the past 140 years (image credit: NASA, GISS)
The average global surface temperature has risen since the 1880s and is now more than 2º Fahrenheit (a bit more than 1º Celsius) above that of the late 19th century. For reference, the last Ice Age was about 10º Fahrenheit colder than pre-industrial temperatures.
Figure 10: Earth’s long-term warming trend can be seen in this visualization of NASA’s global temperature record, which shows how the planet’s temperatures are changing over time, compared to a baseline average from 1951 to 1980. The record is shown as a running five-year average (video credit: NASA’s Scientific Visualization Studio/Kathryn Mersmann)
Using climate models and statistical analysis of global temperature data, scientists have concluded that this increase has been driven mostly by increased emissions into the atmosphere of carbon dioxide and other greenhouse gases produced by human activities.
Figure 11: This plot shows yearly temperature anomalies from 1880 to 2019, with respect to the 1951-1980 mean, as recorded by NASA, NOAA, the Berkeley Earth research group, the Met Office Hadley Centre (UK), and the Cowtan and Way analysis. Though there are minor variations from year to year, all five temperature records show peaks and valleys in sync with each other. All show rapid warming in the past few decades, and all show the past decade has been the warmest (image credit: NASA GISS/Gavin Schmidt)
“We crossed over into more than 2 degrees Fahrenheit warming territory in 2015 and we are unlikely to go back. This shows that what’s happening is persistent, not a fluke due to some weather phenomenon: we know that the long-term trends are being driven by the increasing levels of greenhouse gases in the atmosphere,” Schmidt said.
Because weather station locations and measurement practices change over time, the interpretation of specific year-to-year global mean temperature differences has some uncertainties. Taking this into account, NASA estimates that 2019’s global mean change is accurate to within 0.1 degrees Fahrenheit, with a 95 percent certainty level.
Weather dynamics often affect regional temperatures, so not every region on Earth experienced similar amounts of warming. NOAA found the 2019 annual mean temperature for the contiguous 48 United States was the 34th warmest on record, giving it a “warmer than average” classification. The Arctic region has warmed slightly more than three times faster than the rest of the world since 1970.
Rising temperatures in the atmosphere and ocean are contributing to the continued mass loss from Greenland and Antarctica and to increases in some extreme events, such as heat waves, wildfires and intense precipitation.
NASA’s temperature analyses incorporate surface temperature measurements from more than 20,000 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations.
These in-situ measurements are analyzed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heat island effects that could skew the conclusions. These calculations produce the global average temperature deviations from the baseline period of 1951 to 1980.
NOAA scientists used much of the same raw temperature data, but with a different interpolation into the Earth’s poles and other data-poor regions. NOAA’s analysis found 2019's average global temperature was 1.7 degrees Fahrenheit (0.95 degrees Celsius) above the 20th century average.
NASA’s full 2019 surface temperature dataset and the complete methodology used for the temperature calculation and its uncertainties are available at: https://data.giss.nasa.gov/gistemp
GISS is a laboratory within the Earth Sciences Division of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The laboratory is affiliated with Columbia University’s Earth Institute and School of Engineering and Applied Science in New York.
NASA uses the unique vantage point of space to better understand Earth as an interconnected system. The agency also uses airborne and ground-based measurements, and develops new ways to observe and study Earth with long-term data records and computer analysis tools to better see how our planet is changing. NASA shares this knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.
Seasonal forecasts challenged by Pacific Ocean warming
• December 17, 2019: CSIRO [Commonwealth Science and Industrial Research Organization (Canberra, Australia)] research has found global warming will make it more difficult to predict multi-year global climate variations, a consequence of changes to long-term climate variability patterns in the Pacific Ocean. 16)
The results, published today in Nature Climate Change, shed light on how the Pacific Decadal Oscillation (PDO) was responding to a changing climate, with implications for assessing multi-year risks to marine ecosystems, fisheries and agriculture. 17)
The PDO is a decadal-spanning pattern of Pacific climate variability, operating in the Pacific Ocean, and exerting a substantial influence on global climate and marine conditions from the US and Japan to Australia and New Zealand. - The PDO has two phases, cold and warm.
During a PDO cold phase, the tropical Pacific Ocean temperatures are lower, and Australia's decadal rainfall tends to be above average.
Under warm phases, the opposite occurs, with below average rainfall.
The PDO also modulates climate variations such as El Niño, which causes warm and dry conditions north west and east of Australia and is associated with heightened risk of bushfire and drought.
"When we're in a Pacific Decadal Oscillation cold phase, El Niño is more likely to affect Australian rainfall and surface temperatures," researcher Dr Wenju Cai from CSIRO's Centre for Southern Hemisphere Oceans Research (CSHOR) said.
"With a less predictable PDO, it may be more difficult to predict the likely impact of El Niño."
The research found that the PDO would become less predictable as the planet warms, because warming conditions result in a significantly shortened PDO lifespan.
An oceanic feature called upper ocean stratification causes upper ocean layers to warm faster than deeper ones. - Stratification intensifies under warming.
Rossby waves, an underwater wave feature, move faster in more stratified waters, which shortens the PDO lifespan further and reduces the time it has to gain strength and intensity.
Using various greenhouse gas emissions scenarios, researchers found that the predictability of the PDO sharply declined depending on the intensity of warming.
Although PDO cold phases are associated with colder tropical Pacific temperatures, cold phases manifest as warmer sea surface temperatures in the Tasman Sea and off southeast Australia.
Elevated sea surface temperatures can stimulate high production in fisheries, but may negatively affect other ecosystems through marine heatwaves and coral bleaching.
The results pose a challenge for predicting regional climates on multi-year timescales, as well as year-on-year climate variability.
"In our current climate, we can potentially predict the PDO approximately eight years ahead. That lead time will likely be reduced to three years by the end of the 21st century," Dr Cai said.
This knowledge can be used by fisheries and aquaculture sectors to manage production risks associated with these conditions, and likewise can support strategic and investment scale decisions by these sectors, as well as insurers, especially in assessing multi-year risks.
Long-term forecasts can also assist in planning conservation actions and harvesting levels that build the resilience of marine ecosystems to biological changes associated with environmental conditions.
"Because the Pacific Decadal Oscillation can span for some time — from a season, six months, or up to a decade or even more — the ability to predict changes to marine ecosystems on these timescales can help plan responses to shifts in fish distribution or abundance," Dr Cai said.
CSIRO is currently developing skilled forecasting models to help guide decision makers manage risk under a warming climate.
”The findings will help us to mitigate the negative impact of greenhouse warming on the PDO. The next step will be to improve model systems to fully realize the potential predictability of the PDO," Dr Cai said.
"Many people are familiar with the role that the El Niño-Southern Oscillation plays in climate but might be surprised that there are bigger forces at play like the PDO, which influences our marine environment, as well as climate extremes."
The Centre for Southern Hemisphere Oceans Research is a $20 million five-year collaboration between CSIRO, Qingdao National Laboratory for Marine Science and Technology with the University of Tasmania and University of New South Wales.
Greenland ice loss much faster than expected
• December 10, 2019: The Greenland ice sheet is losing mass seven times faster than in the 1990s, according to new research. 18)
A paper published today in Nature details how an international team of 89 polar scientists, working in collaboration with ESA and NASA, has produced the most complete picture of Greenland ice loss to date. 19)
They estimate that Greenland lost 3.8 trillion (3.8 x 1012) tons of ice between 1992 and 2018 – enough to push global sea level up by 10.6 mm. Over the study period, the rate of ice loss was found to have increased seven-fold from 33 billion (33 x 109) tons per year in the 1990s to 254 billion tons/year in the last decade.
Figure 12: Between 1992 and 2017, Greenland lost 3.8 trillion tons of ice. This corresponds to a 10.6 mm contribution to global sea-level rise – about seven times faster than expected. The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) compared and combined data from 11 satellites – including ESA’s ERS-1, ERS-2, Envisat and CryoSat missions, as well as the EU’s Copernicus Sentinel-1 and Sentinel-2 missions – with regional climate models to provide an up-to-date assessment of changes across the Greenland ice sheet (image credit: Pixabay)
The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), led by Andrew Shepherd from the University of Leeds and Erik Ivins at NASA’s Jet Propulsion Laboratory, compared and combined data from 11 satellites – including ESA’s ERS-1, ERS-2, Envisat and CryoSat missions, as well as the EU’s Copernicus Sentinel-1 and Sentinel-2 missions – to monitor changes in the ice sheet’s volume, flow and gravity.
Figure 13: The video shows the cumulative change in ice sheet thickness from 1993 to 2019. It also presents the global sea-level contribution from Greenland ice sheet mass change according to the IMBIE study and the IPCC AR5 projections between 1992 and 2100 (video credit: ESA/NASA/IMBIE/Planetary Visions)
Using observation data spanning three decades, the team has produced a single estimate of Greenland’s net gain or loss of ice, known as mass balance.
Marcus Engdahl from ESA, one of the co-authors of the paper comments, “Satellite observations show that the Greenland ice sheet has reacted rapidly to environmental change by losing mass. This is especially worrying as the global mean sea-level rise caused by the melting ice sheet is irreversible in human or societal time scales.”
This study condenses the available data and provides a consensus regarding Greenland’s ice loss, enabling more accurate projections of future sea-level rise to be made.
And, with coastal areas being some of the most densely populated areas on the planet, the findings will not only help communities to prepare, but also illustrate the urgent need for greenhouse-gas emissions to be curtailed worldwide.
In its last major assessment, the Intergovernmental Panel on Climate Change’s (IPCC) central climate warming scenario predicted a 60 cm rise in global sea level by 2100, putting 360 million people at risk of coastal flooding every year. The faster-than-expected rate reported by the IMBIE team shows that ice loss is following the IPCC’s worst-case climate warming scenario, which predicts that sea level will rise by an additional seven cm.
Prof. Shepherd explains, “As a rule of thumb, for every centimeter rise in global sea level, another six million people are exposed to coastal flooding around the planet. With this current trend, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century – so 400 million in total due to sea-level rise. These are not unlikely events or small impacts; they are happening and will be devastating for coastal communities.”
Using satellite observations in combination with regional climate models, the team shows that just over half of the ice loss was because of increased surface meltwater runoff, driven by warming air. The remaining losses were the result of increased glacier flow triggered by rising ocean temperatures.
Ice losses reached a peak of 335 billion tons per year in 2011, a trend that since dropped to an average of 238 billion tons per year through to 2018 – but, nevertheless, remained seven times higher than observed during the 1990s.
Prof. Shepherd comments, “The variable nature of the ice losses from Greenland over the three decades is a consequence of the wide range of physical processes affecting different sectors of the ice sheet and reflects the value of monitoring year-to-year fluctuations when attempting to close the global sea-level budget.”
ESA’s Director of Earth Observation Programs, Josef Aschbacher, adds, “The findings reported by IMBIE illustrate the fundamental importance of satellites in monitoring the evolution of ice sheets, and for evaluating and refining the models used to predict the effects of climate change. Greenhouse-gas emissions are still going up, not down. We are leaving future generations to be confronted with increasingly severe impacts of climate change, such as rising sea levels. By taking the pulse of our planet, ESA is measuring change and highlighting the need to increase efforts to meet the internationally agreed goal to limit global warming to 1.5°C over pre-industrial levels.”
IMBIE is supported by ESA's EO Science for Society program and ESA's Climate Change Initiative, which generates accurate and long-term satellite-derived datasets for 21 Essential Climate Variables, to characterize the evolution of the Earth system.
Satellites key to '10 Insights in Climate Science' report
• December 6, 2019: A new easy-to-read guide, ‘10 New Insights in Climate Science’ has been presented to the United Nations Framework Convention on Climate Change’s Executive Secretary, Patricia Espinosa, at the COP25 climate conference. The report provides an assessment of the key advances that have been made over the last 12 months in understanding the drivers, effects and impacts of climate change, as well as societal responses. 20)
The report was compiled by Future Earth and The Earth League – two major international organizations representing networks of global sustainability scientists. It summarizes new findings on 10 specific aspects of climate change, such as the record high in greenhouse gas concentrations, sea-level rise, forests under threat and extreme weather being the ‘new norm’.
Figure 14: The report highlights the most recent advances over the last 12 months in the scientific understanding of the drivers, effects, and impacts of climate change, as well as societal responses. It is the third annual publication by Future Earth and The Earth League, two major international organizations representing networks of global sustainability scientists. It summarizes recent Earth-system science, policy, public health, and economic research (video credit: Future Earth/The Earth League)
Climate change is faster and stronger than expected
The pace at which greenhouse-gas concentrations are increasing is unprecedented in climate history. Carbon dioxide reached 407 ppm in 2018 with methane also at a record high. A global temperature rise of 1.5°C above pre-industrial levels could be reached in 2030, rather than 2040 as projected by the Intergovernmental Panel on Climate Change.
To predict the future impact on the climate, it is necessary to monitor and identify the natural and human-made sources of these gases. Satellites give us this information.
ESA's Climate Change Initiative greenhouse-gas project, for example, has used data from ESA’s Envisat satellite and JAXA’s GOSAT satellite to map the global distribution of near-surface carbon dioxide and methane, and how they changed from year to year between 2003 and 2017. The smallest changes in concentration can be detected, to within one part per million of carbon dioxide, enabling scientists to improve the models that predict future global warming.
Figure 15: Committed emissions from fossil fuel infrastructure compared to pathways to 1.5ºC (IPCC SR1.5 P1) and 2ºC (RCP2.6). The committed emissions exclude some of the current CO2 sources, such as land-use change and the calcination process in cement manufacturing. Therefore, the 1.5ºC and 2ºC scenarios start at higher levels [image credit: Based on Tong et al, Nature, 2019 and Grubler et al, Nature Energy, 2018 (extracted from 10 New Insights in Climate Science report)] 21)
Looking forward, the Copernicus Anthropogenic Carbon Dioxide Monitoring satellite – one of six new high-priority missions ESA is developing for the European Commission’s Copernicus environmental monitoring program – will measure and monitor atmospheric carbon dioxide resulting from human activity.
These measurements will reduce uncertainties in estimates of emissions of carbon dioxide from the combustion of fossil fuel at national and regional scales. This will provide a unique and independent source of information to assess the effectiveness of policy measures on decarbonisation.
Rising seas and melting ice
Sea-level rise is now three times higher than the average for the 20th century. Critically, the rate of rise is much faster than the historical average. Without fast and ambitious emission reductions, models predict it could rise a further 60–110 cm by 2100, increasing the risks to 1.9 billion people living in low-lying coastal regions.
One major cause for the current rising sea level is loss of ice through melting of glaciers and the Greenland and Antarctic ice sheets over recent decades.
ESA’s Climate Change Initiative has been central in charting and understanding the changes occurring across vast and often inaccessible areas of the planet.
For example, satellite observations have been used to identify widespread and increasing surface melting, ice flow and glacier discharge from the West Antarctic ice sheets. Recent research revealed that ice loss from Antarctica has increased global sea levels by 7.6 mm since 1992, with two-fifths of this rise (3.0 mm) coming in the last five years alone.
Worldwide, glaciers have also lost mass. A study involving members of the ESA Climate Change Initiative glaciers team, combined glaciological field observations with information from various satellite missions to estimate changes in glacier ice-mass balance for 19 different regions around the world.
They found that glaciers lost 9625 gigatons of ice between 1961 and 2016, raising global sea level by 27mm. Using these multidecadal satellite datasets in combination helps to address complex scientific questions and, in turn, give communities time to prepare and adapt to the anticipated consequences.
Sophie Hebden, Future Earth liaison seconded to ESA’s Climate Office and co-author of the report, said, “The Climate Office is ESA’s focal point for climate. The partnership between ESA and Future Earth works to strengthen the collaboration between experts in the physical Earth system and those studying the impacts of the climate crisis on society. This report summarizes key climate insights from the past 12 month and identifies any steps we can take to mitigate against the worst climate impacts.”
Figure 16: A paper published in Nature describes how an international team led by the University of Zurich in Switzerland used classical glaciological field observations combined with a wealth of information from various satellite missions to painstakingly calculate how much ice has been lost from and gained by 19 different glacierized regions around the world. They reveal that 9625 gigatons of ice was lost from 1961 to 2016, raising sea level by 27 mm.
New biomass map to take stock of the world’s carbon
• December 6, 2019: The first of a series of global maps aimed at quantifying change in carbon stored as biomass across the world’s forests and shrublands has been released today by ESA’s Climate Change Initiative at COP25 – the United Nation Climate Change Conference currently taking place in Madrid. 22)
As plants grow, they remove carbon dioxide from the atmosphere and store it as biomass. This is then released back to the atmosphere through processes such as deforestation, disturbance or wildfires. Assessing these dynamic changes is key to understanding the cycling of carbon and also for informing global climate models that help predict future change.
Tracking biomass change is also becoming increasingly important as decision-makers work towards the Global Stocktake – an aspect of the global Paris climate deal -- that will periodically check international progress towards meeting emissions reduction commitments to limit global warming.
Figure 17: Biomass: quantifying carbon. Satellite data was used to create a map of above-ground Biomass for 2017-18. The new map uses optical, lidar and radar data acquired in 2017 and 2018 from multiple Earth observation satellites, and is the first to integrate multiple acquisitions from the Copernicus Sentinel-1 mission and Japan’s ALOS mission (image credit: Biomass_cci project funded under ESA's Climate Change Initiative)
Introducing data from these satellite’s sensors improves the accuracy of forest biomass detection across different biomes, and is a significant advance on the previous 2010 map generated by the GlobBiomass project.
Richard Lucas, who manages the research project team that developed the map, comments, “Much of the carbon in forests is stored in the rainforests of the wet tropics but the new map shows that biomass is widely distributed across other biomes, particularly the dry tropics, subtropics and boreal zones.”
“All of these biomes are experiencing unprecedented changes associated with human activities, which are being exacerbated by climate change. Knowing how much carbon these forests hold and how this has changed – and is changing – is a major step towards ensuring their long-term future and addressing climate change.”
The next step for the research team is to develop a map covering the 2018-19 period and to quantify changes between years.
Richard explains, “A key strength of the maps derived from satellite observations is that they provide a globally consistent approach. Repeated and consistent measurements from space helps to track change in biomass distribution and density over time, and in turn informs policies that promote carbon emission reduction and forest conservation initiatives such as the United Nations Reducing Emissions from Deforestation and Degradation program.”
Reflecting on the importance in understanding the dynamics of the world’s forest carbon store, ESA plans to launch a new Earth Explorer Biomass mission in 2022. The mission will carry the first P-band synthetic aperture radar, whose data will enable even more accurate maps of tropical, temperate and boreal forest biomass and will witness at least eight growth cycles in the world’s forests during its operational lifetime.
35-year data record charts sea temperature change
• December 5, 2019: Four trillion satellite measurements, taken over four decades from 1981 to 2018, have been merged to create a continuous global record that will help to understand the science behind Earth’s climate. 23)
A paper published recently in Nature Scientific Data describes how this new dataset of global sea-surface temperature is one of the longest satellite climate data records available. The dataset will play a key role in evaluating global models used to predict how our oceans will influence future climate change. 24)
With the demand for action on climate change louder than ever before, scientific evidence such as this underpins policy on combatting climate change – as being highlighted at the current UN COP25 Climate Change Conference in Madrid, Spain.
Monitoring the skin, or surface, temperature of the world’s oceans is important for climate science, with the United Framework Convention on Climate Change considering it as an Essential Climate Variable.
Exchanges of heat and water vapor between the ocean and the atmosphere influence the generation and intensity of tropical hurricanes and can also modify regional weather patterns, causing serious drought and flood events by diverting storms – a key signature of the El Niño and Indian Ocean dipole climate phenomena.
By raising the humidity and warming the overlying atmosphere, sea-surface temperatures exert a major influence on global climate, driving the wind and ocean circulation systems that distribute heat energy from the equator to the poles. Circulation systems for instance account for northern Europe’s generally mild conditions compared to other locations at the same latitude.
Figure 18: Global sea-surface temperature through the course of a typical year. The satellite record spans 37 years (image credit: ESA Climate Change Initiative)
Historic sampling along shipping routes or from ocean-going buoys show a rise in sea-surface temperature during the 20th century, larger than 0.06°C per decade. But over recent decades, satellites have provided scientists with a detailed global perspective.
Using data from satellite radiometers, which act as ‘thermometers’, researchers working as part of ESA’s Climate Change Initiative have generated a long-time series that captures the changes in the surface temperature across the planet’s oceans spanning nearly four decades.
Data from 14 satellite sensors – 11 AVHRR (Advanced Very High Resolution Radiometers) and three ATSR (Along-Track Scanning Radiometers) – have been recalibrated, reprocessed and merged to create a consistent record by the research team.
In addition to the global coverage and multidecadal length, the data record’s consistency across multiple satellites, its long-term stability and its rigorous quantification of uncertainties all make it extremely valuable as a tool for climate scientists.
Chris Merchant from the University of Reading, UK, who leads the research project, said, “When looking to detect climate signals, scientists need assurance that the observation data are the most accurate possible.
“The observations are highly stable throughout the record, with the uncertainty in the global trend estimated to be no more than 0.03°C per decade. This means that a measurement taken in 1981 can be confidently compared with data from the end of the record 37 years later.”
A final defining quality of the dataset stands in how it is calibrated. Instead of using in situ data, from sensor-laden buoys that drift across the world’s oceans, this dataset is referenced against the series of along-track scanning radiometers satellite sensors. According to Prof. Merchant, “This makes the dataset highly independent from time series derived from ships and buoys. When we see similar climate signals in data collected from space and on Earth, we can be very sure they truly reflect what happened in nature.”
The climate data record is freely available from ESA’s Climate Change Initiative’s open data portal at different processing levels, allowing users to investigate specific phenomena in detail or to take a global, long-term view.
ESA’s Director of Earth Observation Programs, Josef Aschbacher, added, “Thousands of representatives from governments, international organizations, UN agencies and NGOs are currently taking part in COP25 to calve out the next steps on combatting climate change – an issue we take extremely seriously at ESA. The satellite data we and other space agencies provide are fundamental in understanding how our world is changing so that vital polices such as these can be adopted.”
The UN COP25 Climate Change Conference is currently taking place in Madrid, Spain. It focuses on encouraging governments to increase their commitments to combatting climate change. ESA is present highlighting the vital importance of observing our changing world from space and showing how data from satellites ‘take the pulse of our planet.’
ESA at COP25 (Conference of the Parties 25)
• December 3, 2019: The European parliament declared a climate emergency ahead of the latest UN COP25 Climate Change Conference taking place over the next two weeks in Madrid, Spain. The 12-day (2-13 December) summit will focus on encouraging governments to increase their commitments to combatting climate change. ESA is present highlighting the vital importance of observing our changing world from space and showing how data from satellites play a critical role in underpinning climate policy. 25)
With more evidence of the impacts of climate change, including extreme weather events and the highest emissions of greenhouse gases, this year’s COP25 is referred to as the ‘Time for Action’ COP owing to the need for all countries to expand their commitments to limit global warming.
With more than 20,000 participants from governments, intergovernmental organizations, UN agencies and NGOs participating, COP25 will be one of the most important events leading to the defining year 2020 – when many nations will submit new climate action plans.
COP25 will address a vast array of topics including impact on Antarctica and the Arctic, oceans and seas, biodiversity, ecosystems and forests and renewable energies. For many of these topics, data from Earth observation is essential.
Europe is a world leader in observing Earth from space. ESA’s Earth Explorer research missions along with the Copernicus Sentinel missions, developed with the European Commission, provide a wealth of information and will pave new ways in understanding specific aspects of our climate.
Figure 19: COP25 Madrid –
Opening Ceremony. This year’s COP25 is referred to as the 'Time
for Action' COP owing to the need for all countries to expand their
commitments to limit global warming. The 12-day summit will focus on
encouraging governments to increase their commitments to combat climate
change – where ESA will be present highlighting the vital
importance of Earth observation data (image credit: COP25)
These observations provide us with a global coverage, revisiting the same region every few days and proving a good understanding of the health and behavior of our planet – and how it is affected by climate change.
Together, their data are used to ‘take the pulse of our planet,’ and provide key information on which mitigating strategies and policies can be based. Earth observation has not only revolutionized the way we perceive our planet, but it has also changed the way we comprehend our profound impact on the environment.
Satellites provide unprecedented information on the retreat of glaciers, sea level rise, the increase of greenhouse gases in the atmosphere and deforestation worldwide. ESA will address some of these issues at COP25 at its ESA exhibit and dedicated side events.
At last week’s ESA’s Council at Ministerial Level, Space19+, Member States whole-heartedly endorsed ESA’s activities and invested significantly in Earth Observation Programs.
The increased budget will allow for the development, for example, of six new high-priority Copernicus missions, one of which that will track global carbon dioxide emissions.
Josef Aschbacher, director of ESA’s Earth observation programs. “This is the highest subscription that our Earth Observation Program has ever seen. It is a clear signal that our Member States have serious concerns about the environment and climate change and that space has a major role in understanding and addressing the challenges that humanity faces.
“We really hope that COP25 conference succeeds in gaining further commitments to tackling the climate crisis. We are ready to deliver the hard facts required to tackle the challenge.”
Figure 20: Climate change is high on the global agenda. To tackle climate change, a global perspective is needed and this can be provided by satellites. Their data is key if we want to prepare ourselves for the consequences of climate change. While the European Space Agency's Earth Explorers gather data to understand how our planet works and understand the impact that climate change and human activity are having on the planet, the European Union’s Copernicus Sentinels provide systematic data for environmental services that help adapt to and mitigate change. The video offers an overview of how European satellites keep watch over our world. It includes interviews with Josef Aschbacher, ESA's Director of Earth Observation Programs, and Michael Rast, ESA's Earth Observation Senior Advisor (video credit: ESA)
NASA's Sea Level Change Portal
• November 12, 2019: Planet Earth is losing the battle of the bulge. Rotation makes it slightly fatter in the middle and flatter at the poles; though still quite round, it is not a perfect sphere. 26)
This flattening is called “oblateness,” and measuring its changes is a key part of tracking ice loss from polar regions. A recent paper combines measurements of gravity by different methods to more accurately capture how this oblateness changes with time, and improve calculations of ice loss. 27)
This new method reveals more ice loss and larger increases in ocean water than previously estimated: an increase of 0.08 mm/year for sea level rise, along with an additional 15.4 Gt (gigatons) of ice loss each year for the Antarctic Ice Sheet and 3.5 Gt for the Greenland Ice Sheet.
“The ice sheets are losing more mass, and the ocean is gaining more, than we previously thought,” said Bryant D. Loomis of Goddard Space Flight Center in Greenbelt, Maryland, the paper’s lead author.
One way scientists measure the loss of melting ice and the resulting shifting of mass, from ice sheets to the ocean, is by NASA’s GRACE satellites (Gravity Recovery and Climate Experiment) — both the now-ended original mission and its sequel, GRACE-FO (Follow-On).
For both missions, a pair of satellites was designed to keep sharp track of each other’s movements as they pass over Earth’s surface. Large masses on or near the surface below — mountains, glaciers or hidden expanses of subsurface groundwater — give a gravitational tug on the first of the passing spacecraft. That causes a slight increase in speed; the microwave link with the second satellite is stretched a bit, changing again as the second satellite passes over. The size of these changes in distance between the satellites reveals the mass of the objects below.
When it comes to measuring changes in the oblateness, however, GRACE and GRACE-FO are not as accurate as another method.
“That’s the only part of the gravity field GRACE doesn’t observe well,” Loomis said.
Fortunately, changes in the oblateness are well-observed by the other method, called SLR (Satellite Laser Ranging). This technology, which dates back to the 1960s, involves shooting a laser beam at a satellite from a ground station and measuring how quickly it bounces back from a specially designed mirror on the satellite.
Combined Measurements Improve Accuracy
Measurements of the effect of surface gravity on satellites in orbit can be used to calculate the mass of objects on Earth. While not as accurate as GRACE at smaller spatial scales, it does an excellent job of measuring oblateness.
“Since early in the GRACE mission, scientists have been replacing the GRACE values of oblateness (called ‘J2’) with the more accurate SLR solution,” Loomis said.
Correctly accounting for this slight polar flattening can make a big difference in estimating the loss of ice mass in polar regions as planet Earth warms.
But Loomis and his team discovered important differences between previous estimates of oblateness and their own values. He and his co-authors decided to include the valuable GRACE gravity information at the smaller spatial scales when processing the SLR measurements and found that it improved the results.
They showed that the new approach led to more accurate estimation of ice loss that was in better agreement with other types of measurements. One of these is known as the “sea level budget,” or the sum of all known contributions to changes in sea level. These are the thermal expansion of the ocean (measured by drifting floats called Argo), plus the change in ocean mass, measured by GRACE and GRACE-FO with a little help from SLR. The two measurements must add up to the total sea level change measured by satellite radar altimeters, like the one aboard the current Jason-3 satellite.
The improvement in measurements of loss of ice mass brought the sea level budget closer to being “closed” — that is, accounting for all contributions in a way that matches up with known rates of sea level rise.
Their new solution is now becoming more widely adopted in the scientific community, Loomis said — and all because of more precise “weighing” of a slightly rotund planet Earth.
“Even though it’s a relatively small change, it nudges it in the right direction to improve the sea level budget closure,” Loomis said.
2019 Ozone Hole is the Smallest on Record Since Its Discovery
• October 21, 2019: Abnormal weather patterns in the upper atmosphere over Antarctica dramatically limited ozone depletion in September and October, resulting in the smallest ozone hole observed since 1982, NASA and NOAA scientists reported today. 28)
Figure 21: Scientists from NASA and NOAA work together to track the ozone layer throughout the year and determine when the hole reaches its annual maximum extent. This year, unusually strong weather patterns caused warm temperatures in the upper atmosphere above the South Pole region of Antarctic, which resulted in a small ozone hole (video credit: NASA Goddard/ Katy Mersmann)
The annual ozone hole reached its peak extent of 6.3 million square miles (16. 4 million km2) on Sept. 8, and then shrank to less than 3.9 million square miles (10 million km2) for the remainder of September and October, according to NASA and NOAA satellite measurements. During years with normal weather conditions, the ozone hole typically grows to a maximum area of about 8 million square miles in late September or early October.
“It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland. “But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”
Ozone is a highly reactive molecule comprised of three oxygen atoms that occurs naturally in small amounts. Roughly seven to 25 miles above Earth’s surface, in a layer of the atmosphere called the stratosphere, the ozone layer is a sunscreen, shielding the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and also damage plants.
The Antarctic ozone hole forms during the Southern Hemisphere’s late winter as the returning Sun’s rays start ozone-depleting reactions. These reactions involve chemically active forms of chlorine and bromine derived from man-made compounds. The chemistry that leads to their formation involves chemical reactions that occur on the surfaces of cloud particles that form in cold stratospheric layers, leading ultimately to runaway reactions that destroy ozone molecules. In warmer temperatures fewer polar stratospheric clouds form and they don’t persist as long, limiting the ozone-depletion process.
NASA and NOAA monitor the ozone hole via complementary instrumental methods.
Satellites, including NASA’s Aura satellite, the NASA-NOAA Suomi National Polar-orbiting Partnership satellite and NOAA’s Joint Polar Satellite System NOAA-20 satellite, measure ozone from space. The Aura satellite’s Microwave Limb Sounder also estimates levels of ozone-destroying chlorine in the stratosphere.
At the South Pole, NOAA staff launch weather balloons carrying ozone-measuring “sondes” which directly sample ozone levels vertically through the atmosphere. Most years, at least some levels of the stratosphere, the region of the upper atmosphere where the largest amounts of ozone are normally found, are found to be completely devoid of ozone.
“This year, ozonesonde measurements at the South Pole did not show any portions of the atmosphere where ozone was completely depleted,” said atmospheric scientist Bryan Johnson at NOAA’s Earth System Research Laboratory in Boulder, Colorado.
Uncommon but not unprecedented
This is the third time in the last 40 years that weather systems have caused warm temperatures that limit ozone depletion, said Susan Strahan, an atmospheric scientist with Universities Space Research Association, who works at NASA Goddard. Similar weather patterns in the Antarctic stratosphere in September 1988 and 2002 also produced atypically small ozone holes, she said.
“It’s a rare event that we’re still trying to understand,” said Strahan. “If the warming hadn’t happened, we’d likely be looking at a much more typical ozone hole.”
There is no identified connection between the occurrence of these unique patterns and changes in climate.
The weather systems that disrupted the 2019 ozone hole are typically modest in September, but this year they were unusually strong, dramatically warming the Antarctic’s stratosphere during the pivotal time for ozone destruction. At an altitude of about 12 miles (20 km), temperatures during September were 29º F (16ºC) warmer than average, the warmest in the 40-year historical record for September by a wide margin. In addition, these weather systems also weakened the Antarctic polar vortex, knocking it off its normal center over the South Pole and reducing the strong September jet stream around Antarctica from a mean speed of 161 miles per hour to a speed of 67 miles per hour. This slowing vortex rotation allowed air to sink in the lower stratosphere where ozone depletion occurs, where it had two impacts.
First, the sinking warmed the Antarctic lower stratosphere, minimizing the formation and persistence of the polar stratospheric clouds that are a main ingredient in the ozone-destroying process. Second, the strong weather systems brought ozone-rich air from higher latitudes elsewhere in the Southern Hemisphere to the area above the Antarctic ozone hole. These two effects led to much higher than normal ozone levels over Antarctica compared to ozone hole conditions usually present since the mid 1980s.
As of October 16, the ozone hole above Antarctica remained small but stable and is expected to gradually dissipate in the coming weeks.
Figure 22: This time-lapse photo from Sept. 9, 2019, shows the flight path of an ozonesonde as it rises into the atmosphere over the South Pole from the Amundsen-Scott South Pole Station. Scientists release these balloon-borne sensors to measure the thickness of the protective ozone layer high up in the atmosphere (image credit: Robert Schwarz/University of Minnesota)
Antarctic ozone slowly decreased in the 1970s, with large seasonal ozone deficits appearing in the early 1980s. Researchers at the British Antarctic Survey discovered the ozone hole in 1985, and NASA’s satellite estimates of total column ozone from the TOMS (Total Ozone Mapping Spectrometer) confirmed the 1985 event, revealing the ozone hole’s continental scale.
Thirty-two years ago (16 September 1987), the international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer. This agreement regulated the consumption and production of ozone-depleting compounds. Atmospheric levels of man-made ozone depleting substances increased up to the year 2000. Since then, they have slowly declined but remain high enough to produce significant ozone loss. The ozone hole over Antarctica is expected to gradually become less severe as chlorofluorocarbons— banned chlorine-containing synthetic compounds that were once frequently used as coolants—continue to decline. Scientists expect the Antarctic ozone to recover back to the 1980 level around 2070.
Can oceans turn the tide on the climate crisis?
• October 8, 2019: As we pump more greenhouse gases into the atmosphere, the world is warming at an alarming rate, with devastating consequences. While our vast oceans are helping to take the heat out of climate change, new research shows that they are absorbing a lot more atmospheric carbon dioxide than previously thought – but these positives may be outweighed by the downsides. 29)
Covering over 70% of Earth’s surface, oceans play an extremely important role in our climate and in our lives.
The recent IPCC Special Report on the Ocean and Cryosphere highlights how we all depend on oceans and ice, and how they are intrinsic to the health of our planet – but stresses the many ways in which they are being altered by climate change.
It states, for example, that through the 21st century, the global ocean is projected to transition to unprecedented conditions where seawater temperatures rise as they remove more heat from the air and undergo further acidification as they take in more atmospheric carbon dioxide.
Over the last 50 years, oceans have absorbed over 90% of the extra heat in the atmosphere caused by greenhouse gases from human activity, but oceans also help cool the planet by absorbing carbon dioxide. - However, exactly how much atmospheric carbon dioxide oceans are absorbing has been a matter of some debate – until now.
Figure 23: Sea roughness key to carbon flux. Oceans help cool the plant by absorbing atmospheric carbon dioxide. Estimating the size of the oceanic carbon sink depends on calculating upward and downward flows of carbon dioxide at the sea surface and, in turn, this flow is governed largely by turbulence – the relative movement and mixing of air and water at the sea surface. According to new research, three Gigatons of carbon a year are being drawn down into the ocean, which is about a third of the emissions caused by human activity (image credit: Pixaby/dimitrisvetsikas196, CC BY-SA 3.0 IGO)
Estimating the size of the oceanic carbon sink depends on calculating upward and downward flows of carbon dioxide at the sea surface and, in turn, this flow is governed largely by turbulence – the relative movement and mixing of air and water at the sea surface.
It was previously estimated that around a quarter of the carbon dioxide we release into the atmosphere ends up in the ocean.
To gain a more accurate figure on this downward flow, researchers used new knowledge of the transfer processes at the sea surface along with data from the Surface Ocean Carbon Dioxide Atlas, which is an ongoing large international collaborative effort to collect and compile measurements of carbon dioxide in the upper ocean.
Measurements from satellites were also critical to their results, which have been published in Global Biogeochemical Cycles.
Lead author of the study David Woolf from Heriot-Watt University in Scotland, UK, said, “Our research shows that three Gigatons of carbon a year are being drawn down into the ocean, which is about a third of the emissions caused by human activity.
“Importantly, we now know this with unprecedented accuracy – to within 0.6 Gigatons of carbon per year – and conclude that the earlier figure of around a quarter underestimated the role of the ocean in its ability to sequester carbon.
“We were able to do this research also thanks to satellites developed by ESA, such as SMOS, the MetOp series and Copernicus Sentinel-3 that give us measurements of salinity, surface wind speeds and sea-surface temperature.”
Figure 24: Carbon dioxide flow between atmosphere and ocean. Carbon dioxide continually flows into (blue) and out (red) of the ocean. The oceans store carbon for thousands of years, so most of the carbon dioxide coming out of the ocean within the equatorial pacific was previously in the atmosphere before the time of the industrial revolution (image credit: University of Exeter College of Life and Environmental Sciences)
In terms of helping to counteract climate change, this new discovery may sound like a good thing, but warming ocean waters are leading to issues such as sea-level rise through thermal expansion and continental ice melt and the more carbon dioxide that dissolves into the oceans, the more it leads to ocean acidification – a serious environmental problem that makes it difficult for some marine life to survive.
Jamie Shutler, from the University of Exeter said, “These results give us a much better idea of ocean carbon uptake, but this increased rate of uptake implies more rapid ocean acidification, which is already having a detrimental effect on ocean health.
“We need to maintain the best measurements from space, and from in situ, to support modelling predictions, so that important climate-policy decisions can be made to preserve the health of our oceans and planet.”
ESA’s Craig Donlon, added, “These new results are important to understand how the ocean is regulating climate and we are thrilled to see that the ocean flux research project through ESA’s Science for Society program is pioneering the application of unique Earth observation datasets to gain critical insight into the delicate Earth system balance.”
UN Climate Action Summit 2019
• September 23, 2019: In the face of worsening climate crisis, the UN Summit delivers new pathways and practical actions to shift global response into higher gear. Leaders from government, business, and civil society today announced potentially far-reaching steps to confront climate change at the United Nations Secretary-General’s Climate Action Summit in New York. 30)
Table 2: Opening Press Release 31)
Table 3: Closing Press Release. 32)
Harnessing artificial intelligence for climate science
• September 18, 2019: Over 700 Earth observation satellites are orbiting our planet, transmitting hundreds of terabytes of data to downlink stations every day. Processing and extracting useful information is a huge data challenge, with volumes rising quasi-exponentially. 33)
And, it’s not just a problem of the data deluge: our climate system, and environmental processes more widely, work in complex and non-linear ways. Artificial intelligence and, in particular, machine learning is helping to meet these challenges, as the need for accurate knowledge about global climate change becomes more urgent.
ESA’s Climate Change Initiative provides the systematic information needed by the UN Framework Convention on Climate Change. By funding teams of scientists to create world-class accurate, long-term, datasets that characterize Earth’s changing climate system, the initiative is providing a whole-globe view.
Derived from satellites, these datasets cover 21 ‘essential climate variables’, from greenhouse gas concentrations to sea levels and the changing state of our polar ice sheets. Spanning four decades, these empirical records underpin the global climate models that help predict future change.
Figure 25: Neural networks help map ocean color. Neural networks are used to take account of cloud cover by the ESA Climate Change Initiative Ocean Color project when generating global monthly composite maps of chlorophyll concentrations. This map shows concentrations for August 2018 (image credit: CCI/Ocean Color project)
A book from 1984 – ”Künstliche Intelligenz,” by E. D. Schmitter – bears testimony to Carsten Brockmann’s long interest in artificial intelligence. Today he is applying this knowledge at an ever-increasing pace to his other interest, climate change.
“What was theoretical back then is now becoming best practice,” says Dr Brockmann who believes artificial intelligence has the power to address pressing challenges facing climate researchers.
Artificial intelligence algorithms – computer systems that learn and act in response to their environment – can improve detection rates in Earth observation. For example, it is common to use the ‘random forests’ algorithm, which uses a training dataset to learn to detect different land-cover types or areas burnt by wildfires. In machine learning, computer algorithms are trained, in the statistical sense, to split, sort and transform data to improve dataset classification, prediction, or pattern discovery.
Dr Brockmann says, “Connections between different variables in a dataset are caused by the underlying physics or chemistry, but if you tried to invert the mathematics, often too much is unknown, and so unsolvable. - For humans it’s often hard to find connections or make predictions from these complex and nonlinear climate data.”
Artificial intelligence helps by building up connections automatically. Exposing the data to artificial intelligence methods enables the algorithms to ‘play’ with data and find statistical connections. These ‘convolutional neural network’ algorithms have the potential to resolve climate science problems that vary in space and time.
For example, in Climate Change Initiative scientists in the Aerosol project need to determine changes in reflected sunlight owing to the presence of dust, smoke and pollution in the atmosphere, called aerosol optical depth.
Thomas Popp, who is science leader for the project, thinks there could be further benefits by using artificial intelligence to retrieve additional aerosol parameters, such as their composition or absorption from several sensors at once. “I want to combine several different satellite instruments and do one retrieval. This would mean gathering aerosol measurements across visible, thermal and the ultraviolet spectral range, from sensors with different viewing angles.”
He says solving this as a big data problem could make these data automatically fit together and be consistent.
“Explainable artificial intelligence is another evolving area that could help unveil the physics or chemistry behind the data”, says Dr Brockmann, who is in the Climate Change Initiative’s Ocean Color science team.
“In artificial intelligence, computer algorithms learn to deal with an input dataset to generate an output, but we don’t understand the hidden layers and connections in neural networks: the so-called black box.
“We can’t see what’s inside this black box, and even if we could, it wouldn’t tell us anything. In explainable artificial intelligence, techniques are being developed to shine a light into this black box to understand the physical connections.”
Dr Brockmann and Popp joined leading climate and artificial intelligence experts to explore how to fully exploit Earth observation data during ESA’s φ-week, which was held last week. Things have come a long way since Dr Brockmann bought his little book and he commented, “It was a very exciting week!”
Using a Data Cube to access changes in the Earth System
• September 16, 2019: Researchers all over the world have a wealth of satellite data at their fingertips to understand global change, but turning a multitude of different data into actual information can pose a challenge. Using examples of Arctic greening and drought, scientists at ESA’s φ-week showed how the Earth System Data Lab is making this task much easier. 34)
ESA’s Earth System Data Lab is a new virtual lab to access a wide array of Earth observations across space, time and variables. It consists of two elements: the data cube and an interface to execute different analyses on the data cube.
Last year, ESA put out a call – an Early Adopters Call – for young researchers to explore information from data streams produced by several international scientific teams to help shape the future of the Earth System Data Lab.
Some of these young researchers using the Earth System Data Lab were at ESA’s φ-week presenting their findings on, for example, Arctic greening and drought.
In parts of the Arctic tundra, temperatures are increasing rapidly as a result of climate change. This has resulted in complex changes in plant communities, with satellite data showing that some parts of the Arctic are ‘greening’ whilst other areas are said to be ‘browning’. Understanding changes at high latitudes is crucial as they could be used to predict changes in other places that haven’t yet warmed as much.
Figure 26: Changing Arctic productivity. In parts of the Arctic tundra, temperatures are increasing rapidly as a result of climate change. This has resulted in complex changes in plant communities, with satellite data showing that some parts of the Arctic are ‘greening’ whilst other areas are said to be ‘browning’. Using the Earth System Data Lab, scientists are looking at components such as rock or soil types to understand changes in plant productivity in the Arctic, beyond just temperature. The image shows changes in mean maximum gross primary productivity across five years between 2001–2005 and 2011–2015 at high latitudes (>60°N). Notable changes in gross primary productivity are evident including large increases in northern Canada, and decreases in parts of Alaska and Siberia, highlighting the heterogeneous pattern of productivity change over time (image credit: ESA, derived from FLUXCOM land–atmosphere energy fluxes, hosted on the Earth System Data Lab)
Oliver Baines, from the University of Nottingham in the UK, said, “The work I presented examines whether the inclusion of geodiversity components, such as rock or soil types, can improve our understanding of changes in plant productivity in the Arctic, beyond considering just temperature. Using the Earth System Data Lab, we have been able to examine these relationships to identify the role of abiotic nature at a much larger scale than before.”
By providing a set of pre-processed datasets all in one place, the virtual lab has made it easier to access, manipulate and analyze different variables including climate, gross primary productivity related to photosynthesis, aerosols and sea-surface temperatures.
Mr Baines continues, “The hope is that by including a wider variety of abiotic nature, our understanding of changes in the Arctic can be improved and, subsequently, that any future predictions of Arctic environmental change can be refined.”
The data cube can reveal where big anomalies occur. In the light of the last two summers when Europe was hit by unprecedented heatwaves, and this year’s devastating fires in the Amazon, the relevance of the work being carried out through the virtual lab becomes clear.
Figure 27: Earth System Data Lab. Thanks to satellites a wealth of information is at our fingertips to understand the different components of our planet and how these components interact to form the Earth system as a whole. However, despite unprecedented progress in analyzing and understanding the stream of data we have available, it still remains a challenge to analyze multiple types of data together in order to better understand processes occurring in the different components of the Earth system as well as the interaction between such processes. ESA’s Earth System Data Lab is addressing this challenge by developing a new Virtual Lab that allows simultaneous access to a wide array of Earth observation, modelling and reanalysis datasets that covers space, time and bio-physical variables. — And, ESA would like young researchers to help. The Early Adopters Call invites young researchers to explore information from data streams produced by several international scientific team and help shape the future of the Earth System Data Lab [video credit: Planetary Visions (credit: ESA/Earth System Data Lab/Planetary Visions)]
Miguel Mahecha, from the Max Planck Institute for Biogeochemistry in Germany, said, “Only if we succeed in putting these impacts into a global perspective, will we be able to objectively judge their impacts. And, even more importantly, understand and anticipate their impacts under future climate conditions.”
However, while the question of weather extremes is an issue, long-term change and climate change are a global concern.
“Large parts of South America, for example, have become less productive and drier over the past decade. But there is a need to understand if this is a real change or just decadal variability. And, the Earth System Data Lab is helping us with this research,” continued Mr Mahecha.
Another Early Adopter, Karina Winkler from the Karlsruhe Institute of Technology, Germany, is working on using reconstructed land-use data and multiple satellite-derived variables from the Earth System Data Lab. The objective of the project is to model biomass distribution by using deep learning – which shows the potential of reconstructing changes of above-ground biomass over time and at a global scale.
ESA’s φ-week gave researchers the unique opportunity to share and discuss their research and reflect on the value of this new data cube they have to hand.