NASA Finds 2021 Arctic Summer Sea Ice 12th Lowest on Record

Sea ice in the Arctic appears to have hit its annual minimum extent on Sept. 16, after waning in the 2021 Northern Hemisphere spring and summer. The summertime extent is the 12th lowest in the satellite record, according to scientists at the NASA-supported National Snow and Ice Data Center and NASA.

This year, the minimum extent of Arctic sea ice dropped to 4.72 million square kilometers (1.82 million square miles). Sea ice extent is defined as the total area in which ice concentration is at least 15%.

The average September minimum extent record shows significant declines since satellites began measuring consistently in 1978. The last 15 years (2007 to 2021) are the lowest 15 minimum extents in the 43-year satellite record.

On Sept. 16, 2021, Arctic sea ice reached its minimum summertime extent. Credit: NASA's Goddard Space Flight Center/Scientific Visualization Studio

This visualization above, created at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, shows data provided by the Japan Aerospace Exploration Agency (JAXA), acquired by the Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument aboard JAXA’s Global Change Observation Mission 1st-Water “SHIZUKU” (GCOM-W1) satellite.

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Drought Makes its Home on the Range

In Brief:

Climate change is making droughts more frequent, severe, and pervasive. NASA satellites provide data about water availability to the U.S. Drought Monitor, which helps farmers prepare for drought, determining where and what to feed their livestock.


Cattle grazing on April 16, 2021 on a grassland that has turned brown.
Cattle grazing on April 16, 2021. This year, the annual grasslands in Schohr’s part of California turned brown a month earlier than usual, shortening the grazing season. Credit: Courtesy of Tracy Schohr

As Tracy Schohr goes about her day, water is always on her mind. She’s thinking of it as she rides an all-terrain vehicle around the pasture, looks up hay prices and weather forecasts, and collects data on grazing and invasive weeds for a scientific study.

Schohr is a rancher and farmer in Gridley, California, where her family has raised beef cattle and grown rice for six generations. She also aids in scientific research to study drought and other agricultural issues with the University of California Cooperative Extension.

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Drought—a year with a below-average water supply—is a natural part of the climate cycle, but as Earth’s atmosphere continues to warm due to climate change, droughts are becoming more frequent, severe, and pervasive. The past 20 years have been some of the driest conditions in the American west on record. Right now, the western United States—including the part of California home to Schohr’s ranch—is experiencing extreme or exceptional drought that will likely have long-term impacts on the land and the people who depend on it.

This year not enough precipitation, also known as a meteorological drought, threatened to kill the grass on Schohr’s ranch. Keeping vegetation alive is one of the main parts of her job. “We’re cattle producers, but we’re really grass farmers,” she remarked in June. “If you mismanage your grass then your cattle won’t survive.”

Signs of Drought from Space

“NASA is well-positioned to assess droughts because we have Earth-observing satellites that provide frequent observations,” said John Bolten, associate program manager of water resources for the NASA Applied Sciences Program. We’re not just interested in our backyard; we’re interested in what’s happening regionally and globally.”

Drought is a complicated problem that requires innovative research and lots of data. From the vantage point of space, Earth-observing satellites from NASA and its partners collect data on various signs of drought, such as lack of precipitation (GPM) and snowpack (Landsat, Terra and Aqua), low water levels in reservoirs and streams (Jason-3) or dry soils (SMAP) and depleted groundwater (GRACE-FO). Then scientists at NASA and other institutions use this data to see historical trends, understand the current state of drought, and make projections for the future.


An infographic showing how Jason-3, GPM, SMAP, and GRACE-FO monitor various indications of drought.
Global Precipitation Management (GPM), a joint satellite mission between NASA and the Japanese Aerospace Exploration Agency (JAXA), provides global precipitation data every three hours. Used in conjunction with other weather data and forecasting efforts, GPM data helps quantify when, where, and how much it rains or snows around the world.

The NASA Soil Moisture Active Passive (SMAP) global observatory measures the amount of liquid water in the top 5 cm of the soil using a microwave-based radar. The effects of low soil moisture on vegetation is apparent in satellite imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra and Aqua satellites, and from the joint NASA and United States Geological Survey (USGS) Landsat satellites. When used together these observations give a comprehensive view of water availability and water use, as well as actual soil moisture conditions in the soil – where farmers grow food.

The Jason-3 satellite – a four-agency international partnership of the National Oceanic and Atmospheric Administration (NOAA), NASA, the French Space Agency CNES (Centre National d'Etudes Spatiales), and EUMETSAT (the European Organization for the Exploitation of Meteorological Satellites) – provides information about the height of rivers and reservoirs, allowing scientists to estimate how much water they contain.

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, a partnership between NASA and the German Research Centre for Geosciences (GFZ), estimates groundwater using a pair of satellites. The satellites fly in tandem about 137 miles apart and use microwaves to measure the distance between them. When one satellite passes over an area with stronger gravity – such as a spot with lots of groundwater and thus more mass – the satellite in the lead is pulled further ahead. By analyzing the distance between the satellites, scientists can track where water is on our planet. Credit: NASA / Jesse Kirsch

NASA’s upcoming Earth System Observatory, together with other planned NASA missions that are part of NASA’s “program of record” will continue many these observations in the future to provide key information that will guide decision-makers confronting challenges posed by climate change, such as drought.

Much of this data is incorporated into drought maps and global groundwater maps produced and distributed by the National Drought Mitigation Center at the University of Nebraska-Lincoln.

“What we’re able to do is bring in all of this data and use the best attributes of those tools,” said Brian Fuchs, a climatologist at the National Drought Mitigation Center. Frequent satellite observations allow Fuchs and his colleagues to track rapidly changing drought conditions. The satellites’ view from space also provides routine, country-wide and world-wide snapshots of drought that can be accessed by local water managers.


A map of drought conditions in the U.S. as of August 17, 2021. Much of the west is in exceptional or extreme drought, shown in red and dark red respectively.
A map of drought conditions in the U.S. as of August 17, 2021. Much of the west is in exceptional or extreme drought, shown in red and dark red respectively. Credit: U.S. Drought Monitor, provided by the National Drought Mitigation Center at the University of Nebraska-Lincoln / USDA / NOAA

“We’re not experts in every part of the country, but we have people on the ground who know their backyards better than we do,” said Fuchs.

Schohr is one of those people. She uses the U.S. Drought Monitor maps, which provide a weekly assessment of drought conditions, to check the state of drought around the country and look at trends to help her make better decisions for the future. She is also one of the many ranchers across the country who sends updates and photos to the scientists at Drought Monitor to help refine their maps.

“That boots on the ground validation really helps us get a good local perspective on what the challenges are,” said Fuchs.

A Snapshot of Drought on the Ranch

Every year in early November, Schohr and her family load their cows into cattle trailers and drive them to annual grasslands about 35 miles away. While there, the herd rotates through several pastures, searching for grass and water. This protects the land from overgrazing, ensuring that the cows have enough to eat and that healthy grasses will regrow in time for the next. “We have to have grass to grow grass,” Schohr explains. “And what’s best for the land is also what’s best for our cattle operation.”


A cow and her calf eat out of a protein supplement tub on California annual grasslands.
During a drought, nutritional supplements and access to reliable water are essential. Here a cow and her calf eat out of a protein supplement tub on California annual grasslands. Credit: Courtesy of Tracy Schohr

With little rain last fall, the Schohrs opted to keep the cattle at their home ranch where the family could easily check on them. Schohr brought hay out to the pasture and checked the water levels in the naturally occurring streams and ponds every few days. She also gave the cows tubs of nutritional supplements, which she says is like a combination multivitamin and protein shake that’s sweetened with molasses.

The Schohrs eventually moved their herd to the annual grasslands in mid-December. The cattle grazed in several pastures last winter, including a purple needle grass restoration site that is part of a research project to restore native species. The cows munch on invasive and non-native grasses, weeding out the competition for the native California purple needle grass that will grow in the spring.

As the cows mow down grass, Schohr is also checking that they have access to enough water. Cows need to drink between eight and 15 gallons of water per day. The annual grasslands don’t have much natural drinking water—especially this year, as reservoirs are depleted and streamflow is abnormally low, conditions signifying a hydrological drought, which California is currently experiencing. In winter, Schohr relies on solar-powered wells to keep her cattle hydrated. In the spring, she moves the cows to a pasture with seasonal ponds that are home to many California plant species and provide the cows with natural drinking water.

Later in the season, the cows move to a field filled with oak trees. The trees provide shade to keep the cattle cool as spring turns to summer, and the cattle mow down the grass so there’s less kindling in the form of dry grass come fire season.

The herd will usually stay on these annual grasslands until mid-June, but this year Schohr brought the cattle home in mid-May. California was not only dealing with low reservoirs and streams, but also low soil moisture, called agricultural drought, that causes plants—including that all important grass—to die. As green vegetation started to turn into swaths of brown, Schohr irrigated the pasture on her home ranch on April 1 to keep the grass alive so that the cows would have food to eat when they returned.

However, the natural food supply will only last so long. The current outlook suggests California will be in a severe drought at least through the fall, so Schohr is selling calves and stocking her barn with hay, corn and soybean stock in preparation.

Generations of Change


Tracy’s partner, Ryan Imbach (left), takes their son Colton (right) to the corral to check on the herd. The grass in the pasture where the Schohrs keep their cows during the winter was drying up.
Tracy’s partner, Ryan Imbach (left), takes their son Colton (right) to the corral to check on the herd. The grass in the pasture where the Schohrs keep their cows during the winter was drying up, prompting the Schohr family to decide which cows to sell and which to move back to their home ranch. Credit: Courtesy of Tracy Schohr

The challenges of drought that Schohr faces today are the same ones her grandfather dealt with. However, she says it’s easier to make better decisions and prepare for the future with the scientific data that’s available from sources like the U.S. Drought Monitor.

“We know the world we’re working in, whereas before—for my grandpa—he just knew the community he worked in,” Schohr said.

The Schohr family had to make a lot of tough decisions during the 1980s farm crisis, when farmers’ debt soared due to an economic recession, and the intense California drought in the 1990s. At one point, the family sold all the cows to instead focus on growing rice. After that, Schohr recalls her grandfather was always the first one there when a new calf was born or a cow was sick.

Her grandfather has since passed away, but Schohr remembers the lessons he taught her. She recalls riding on an ATV with him to check the water level in the troughs during a drought, listening to him talk about water management and seeing the sense of peace that came over him from watching the cattle grazing. “He loved the cows just like I do,” she said. “He believed that if he took care of the land, it would take care of him too.”

Humans’ Fingerprint on the Future of Drought

Climate science tells us that the world will be warmer and droughts are likely to be more frequent in the future. In addition, climate science models provide a better sense of what the future may hold, helping farmers, ranchers and water managers to make better decisions in preparation. However, it’s impossible to pinpoint exactly when and where droughts will occur in the future or predict how severe their impacts will be. But we do know that in certain regions, the fingerprint of human influence on drought is already visible.

For the first time, scientists at NASA GISS have linked human activities with patterns of drought around the world. Getting clues from tree ring atlases, historical rain and temperature measurements, and modern satellite-based soil moisture measurements, the researchers found the data "fingerprint" showing that greenhouse gases were influencing drought risk as far back as the early 1900's. Credit: NASA Goddard / LK Ward
This video is free to download at NASA's Scientific Visualization Studio.

Human activities emit carbon dioxide and other greenhouse gases that warm the planet. A warmer planet is a thirstier planet, because warmer air drives more evaporation of water vapor from the surface,” explains Kate Marvel, a research scientist at NASA GISS. As the climate changes on Earth, some places will become drier – and thus more prone to drought – while others become wetter and thus more susceptible to flooding.

If we continue emitting greenhouse gases, this trend is likely to continue. NASA’s climate models and others show that – under high emission scenarios – droughts could become much worse across the U.S. and globally. Drought-prone areas could enter persistent megadroughts, precipitation patterns and snowmelt could change drastically, the risk of dry soils could increase in many areas and some places could see more frequent and severe wildfires.

“The worst-case scenarios don’t have to come true. It’s not a prediction,” Marvel said. To prevent those worst-case scenarios from happening, greenhouse gas emissions will need to be reduced, she said. “That’s the main determinant of drought risk in the future.”


A banner image showing cows, cow print, drought maps, and satellite images of a reservoir during drought.
The signs of drought are visible from space, from satellite images of depleted reservoirs to drought maps using soil moisture and other satellite data. These indicators are important for ranchers trying to care for their cattle and the land. Credit: NASA/Jesse Kirsch/Drought Map from the U.S. Drought Monitor/Image courtesy of Tracy Schohr

NASA at Your Table: Climate Change and Its Environmental Impacts on Crop Growth

In Brief:

Climate change is impacting agriculture in a number of ways. Researchers use satellite data and computer modeling to monitor and mitigate these impacts.

The Earth is heating up. The effects of human-caused global climate change are becoming more and more apparent as we see more record-breaking heat waves, intense droughts, shifts in rainfall patterns and a rise in average temperatures. And these environmental changes touch every part of crop production.


Alt: Panel of six satellite images of crops fields from around the world that show the different field layouts.
Around the world, agricultural practices have developed as a function of topography, soil type, crop type, annual rainfall, and tradition. This montage of six images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor on NASA’s Terra satellite shows differences in field geometry and size in different parts of the world. Credit: NASA's Earth Observatory

NASA, along with partner agencies and organizations, monitors all of these environmental changes happening today. In addition, NASA uses advanced computer models that pull in satellite data and then simulate how Earth’s climate will respond to continued greenhouse gas emissions in the future. Researchers do this for a range of future scenarios – and then they use the resulting climate projections to see how climate change will affect global agriculture.

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“When we look at future climate change, it's not the same as the current hot years that we experience,” said Alex Ruane, co-Director of the Climate Impacts Group at NASA’s Goddard Institute for Space Studies (GISS) in New York City. He coordinates and leads the climate team for the Agricultural Model Intercomparison and Improvement Project (AgMIP), an international project connecting climate science, crop modeling and economic modeling to look at the potential future of crop yields and food security.

“If we were to find a location and look at a hot year that was recently experienced, it would likely have been a heat wave that would have raised the overall temperature,” Ruane said. “Climate change is different. Climate change is every day, a little bit more and more. When those heat waves come [in the future], they're just a little bit more intense or extreme, and that has a different physiological impact [on plants].”

Those physiological changes on plants can be complex and are tied to crop type and the climate effects seen at the regional and local level.

Carbon Dioxide as a Fertilizer

Carbon dioxide is the primary greenhouse gas responsible for the increase in Earth’s global temperature. Emitted from the burning of fossil fuels, it can stay in the atmosphere for hundreds of years, which means that every year we are adding carbon dioxide to the amount that has accumulated since the start of the Industrial Revolution over 200 years ago.


Image of a small garden plot surrounded by plexiglass walls like a greenhouse.
The U.S. Department of Agriculture conducts experiments on the rate of crop growth in controlled environment chambers, including with glasshouses and field plots in which they control the temperature, humidity and atmospheric carbon dioxide. Credit: USDA

Carbon dioxide is removed from the atmosphere by plants during photosynthesis, (though not in quantities sufficient enough to remove everything humans emit.) In fact, greenhouse and field experiments have shown that higher levels of carbon dioxide in the atmosphere can act as a fertilizer and increase plant growth. The amount of benefit a crop receives depends on its type. Wheat, barley and rice for example benefit more from higher carbon dioxide concentrations than corn. More carbon dioxide in the air makes the plant more efficient at absorbing the gas, and consequently it loses less water during the process, which is better for the plant’s growth. With sufficient water and other nutrients, crop yields can increase significantly.

However, those higher yields often come with drawbacks for nutrition. “Crops grow faster and bigger under higher CO2,” said Jonas Jägermeyr, the coordinator for the Global Gridded Crop Model Intercomparison project under AgMIP at GISS. “But the protein and micronutrient content is proportionally lower.”

Quantity versus quality is one complication when looking at climate effects on crops. Another is that while higher carbon dioxide levels bring some benefits, they also bring the heat.

Turning up the Heat

Increases in regional temperatures due to climate change, especially in the tropics, can lead to heat stress for all types of crops. Many crops start feeling stressed at temperatures above about 90 to 95 degrees Fahrenheit (32 to 35 degrees Celsius), said Jägermeyr, although this will vary by crop type and depend on water availability. Heat stress’s most visible sign is wilting from water loss, and can lead to permanent damage to the plant.


Flat global map showing the increase in global temperatures since the 1951-1980 average temperature.
This color-coded map displays a progression of changing global surface temperature anomalies. Normal temperatures are the average over the 30-year baseline period 1951-1980. Higher than normal temperatures are shown in red and lower than normal temperatures are shown in blue. The final frame represents the 5-year global temperature anomalies from 2016-2020. Scale in degrees Celsius. Credit: NASA's Scientific Visualization Studio

Different regions will experience different heat intensities in the future climate, especially during extreme events like heat waves. “The pattern of where crops are grown decides the pattern of impacts,” Jägermeyr said. “The more you grow in the tropics, the harder you will be hit. Because it's already pretty warm, an additional amount of warming will be more severe than at high latitudes.”

A 2019 model study simulated future global wheat production with projected global temperatures 1.5 degrees Celsius and 2.0 degrees Celsius above pre-industrial temperatures. Taking into account carbon dioxide’s fertilization effect, the results showed that grain yields for winter or spring-planted wheat rose by about 5% in more temperate regions such as the United States and Europe, and declined by about 2 to 3% in warmer regions such as Central America and parts of Africa. Additionally, in hot regions including India, which produces 14% of global wheat, they more frequently saw years with low wheat yields.

Temperature also affects the life cycle of crops. A small increase in every-day temperatures during the growing season accelerates the plant’s lifecycle, said Ruane. “So what ends up happening is the plant matures more rapidly and at the end of the season when it puts the grain down, it just has not spent as much time building up leaves, collecting sunlight and making that energy that you need for the grain.” The result is fewer grains and smaller crop yields.

Show Me the Water

The last major piece of the puzzle is water. Climate change is affecting rain and snowfall patterns and giving rise to more extremes in droughts and rainfall.

“Some areas will see additional rainfall and therefore benefits,” said Jägermeyr. “Some regions will receive too much additional rainfall and then see adverse effects from excess rain. And a ton of regions will actually see drought.” For example, monsoons may bring more rain to Southeast Asia, and droughts may become more intense in the Western United States, Australia, Africa and Central America.

The amount of water available for irrigation is already seeing climate change impacts. Mountain snow packs are shrinking in the Himalayas and California’s Sierra Nevada, which are primary sources of both drinking and irrigation water.

Groundwater levels are also sensitive to changes in climate like persistent drought and excessive rain. A 2018 study showed that where groundwater is used for agriculture, groundwater levels are generally decreasing both from the water having been extracted and its sensitivity to change. Additionally, plants access water in the soil, which in hotter regions and a hotter future is more prone to evaporation, leaving less for plants to use.

Access to water has a direct effect on crop health, and satellite observations are one of the key inputs to tools that NASA researchers and partners are building to help manage our warmer future.

Adaptation

“We care about climate change not because of degrees Celsius or parts per million CO2, but because those in turn affect all sectors and our lives,” said Ruane, referring to not only the large-scale agricultural sector and economy, but also the everyday changes that will happen as communities respond to climate change.

In addition to looking at the direct consequences of environmental factors of climate change on crops, research teams within AgMIP are also looking at the potential for adaptations, management practices and economic incentives that will help mitigate the worst outcomes.

There are three types of adaptation strategies, said Ruane: things decided upon every year, such as when to plant and a field’s crop rotation; longer term investments, such as a new tractor, improved irrigation systems or new irrigation infrastructure in currently rain-fed areas; and transformative actions, such as breeding new crop varieties or responding to large-scale shifts in a population’s diet.

“We can test different options in the virtual fields [of the model],” Ruane said. “We can also ask questions about how do the prices [calculated in] our economic models shift if people adopt the type of diet that we have here in the U.S. versus the Mediterranean diet or east Asian diet.” For example, what happens when a population eats more or less meat, or shifts from eating more wheat-based foods to eating more rice-based foods, or vice versa? The models can also explore other secondary effects of these big changes, especially unanticipated ones.

Ruane adds, “If we really want to know what's going to happen to farmers or consumers, we have to bring in the economics of the situation.” As climate change impacts food systems in the future, the effects will ripple out through the economy and into households, shaped by how people respond.

NASA Drought Research Shows Value of Both Climate Mitigation and Adaptation

In Brief:

New NASA research is showing how drought in the western U.S. is expected to change in the future, providing stakeholders with crucial information for decision making.

Seasonal summer rains have done little to offset drought conditions gripping the western United States, with California and Nevada seeing record July heat and moderate-to-exceptional drought according to the National Oceanic and Atmospheric Administration (NOAA). Now, new NASA research is showing how drought in the region is expected to change in the future, providing stakeholders with crucial information for decision making.

The study, published in the peer-reviewed journal, Earth’s Future, was led by scientists at NASA’s Goddard Institute for Space Studies (GISS) and funded by NOAA’s Climate Program Office and NASA’s Modeling, Analysis and Prediction (MAP) Program. It found that the western United States is headed for prolonged drought conditions whether greenhouse gas emissions continue to climb or are aggressively reined in.


Figure showing that predicted levels of soil dryness increase with increasingly high greenhouse gas emissions scenario.
While the risk of intense single-year droughts increases as greenhouse gas emissions increase in the model results, the risk of multi-year droughts is high regardless of the emissions scenario, the study found. Credit: NOAA Climate Program Office / Anna Eshelman

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However, the study also showed that the severity of acute, extreme drought events and the overall severity of prolonged drought conditions can be reduced with emissions-curbing efforts compared to a high-emissions future. This is important information for decision-makers considering two tools they can use to reduce climate impacts: Adaptation and mitigation.

Adaptation is a term used by the scientific community and policymakers to describe policies that address impacts that will occur or are already occurring. For example, adaptation to rising sea levels might include relocating low-lying infrastructure. By contrast, mitigation – efforts to reduce the amount of greenhouse gases in the atmosphere – can limit the severity of future impacts or even prevent them from happening by limiting how much the climate changes. Switching to cleaner energy sources and reducing greenhouse warming-driven ice melt are examples of mitigation to sea level rise.

Rather than representing competing options, adaptation and mitigation can both be used to address climate impacts. This new research shows how the two can complement each other when it comes to drought.

“Mitigation has clear benefits for reducing the frequency and severity of single-year droughts,” said lead author Ben Cook, a research scientist at GISS and an adjunct associate research scientist at Columbia University. “We may have more of these 20-year drought periods, but if we can avoid the really sharp, short-term, extreme spikes, then that may be something that’s easier to adapt to.”

Turning to the Past to Understand the Future

Both acute single-year and prolonged multi-year droughts occur naturally due to variations in ocean currents, precipitation and other factors. But climate change is turning up the heat in addition to these natural variations, causing even more water to evaporate from plants and soil, resulting in increased dryness even in the absence of major precipitation deficits.


Figure showing that, while risk of single-year droughts increases with increasing greenhouse gas emissions scenario severity, the risk of multi-year droughts is high regardless of future emissions scenario.
As greenhouse gas emissions increase and Earth's temperature rises, the southwestern United States is forecasted to become drier, with the risk of future soil moisture deficits increasing as emissions increase. Credits: NOAA Climate Program Office / Hunter Allen and Anna Eshelman

To understand the southwest’s vulnerability and tendency towards drought and the factors that contribute to it, the team selected the severe single-year drought of 2002 and the extended drought of 2000 to 2020 as examples of acute and prolonged droughts respectively. They then looked at how common these acute and prolonged droughts were, not only during the period of instrumental records, but also using reconstructed drought conditions stretching back more than a thousand years and state-of-the-art supercomputer simulations of the future.

The team reconstructed soil moisture from the years 800 to 1900 using tree ring data from the region. The thickness of tree rings varies due to the wetness or dryness of each year, providing scientists with a reliable way of estimating how much rain fell in a given year. For years after 1900, they used directly measured soil moisture values. To look at a range of possible futures, the team used data from the latest version of the Coupled Model Intercomparison Project, or CMIP6. CMIP6 is an ensemble of climate model simulations that provide climate change projections depending on a range of possible greenhouse gas emission scenarios, allowing scientists and policymakers to directly compare the impacts of different emissions policies. And under different emissions scenarios, drought behaves differently.

The southwestern United States has been prone to drought for millennia. But warming temperatures dry the soil further, and the region’s natural aridity becomes the backdrop for a higher risk of severe and prolonged droughts if greenhouse gas emissions continue to climb, said Kate Marvel, a research scientist at GISS and Columbia University.

“The paleoclimate record shows that this region is prone to drought,” she said. “There have been really, really severe droughts in the past: For instance, we know there were megadroughts in the 13th century. But against the backdrop of natural climate variability — the things the climate would do even without human influence — we are confident increases in greenhouse gases make the temperature rise, and we’re fairly confident that increases drought risk in this region.”


Figure showing the risk of intense single-year droughts embedded in multi-year droughts, which increases with increasingly severe greenhouse gas emissions scenarios.
In addition to single- and multi-year droughts alone, there's also a risk of intense single-year droughts occurring within longer periods of drought. This risk increases as greenhouse gas emissions increase, according to the study. Credit: NOAA Climate Program Office / Anna Eshelman

A Future Not Yet Set in Stone

Understanding that some amount of increased drought can be expected under high and low emission scenarios alike has implications for adaptation strategies like rationing water usage and changing agricultural practices. At the same time, the study’s finding that greenhouse emissions reductions still matter for extreme drought underscores the value of mitigation.

“The ongoing southwestern drought highlights the profound effects dry conditions have on people and the economy,” said Ko Barrett, senior advisor for climate in NOAA’s Office of Research and vice-chair of the Intergovernmental Panel on Climate Change’s Sixth Assessment Report. “The study clearly highlights the impact that greenhouse gas mitigation could have on the occurrence and severity of Southwestern drought. It is not too late to act and blunt impacts like severe Southwestern drought periods and short-term drought events.”

Marvel agreed. “There’s going to be a new normal regardless,” she said. “There’s going to have to be some adaptation to a drier regional climate. But the degree of that adaptation – how often these droughts happen, what happens to the drought risk – that’s basically under our control.”

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NASA Finds 2021 Arctic Summer Sea Ice 12th Lowest on Record

Sea ice in the Arctic appears to have hit its annual minimum extent on Sept. 16, after waning in the 2021 Northern Hemisphere spring and summer. The summertime extent is the 12th lowest in the satellite record, according to scientists at the NASA-supported National Snow and Ice Data Center and NASA.

This year, the minimum extent of Arctic sea ice dropped to 4.72 million square kilometers (1.82 million square miles). Sea ice extent is defined as the total area in which ice concentration is at least 15%.

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The average September minimum extent record shows significant declines since satellites began measuring consistently in 1978. The last 15 years (2007 to 2021) are the lowest 15 minimum extents in the 43-year satellite record.

On Sept. 16, 2021, Arctic sea ice reached its minimum summertime extent. Credit: NASA's Goddard Space Flight Center/Scientific Visualization Studio

This visualization above, created at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, shows data provided by the Japan Aerospace Exploration Agency (JAXA), acquired by the Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument aboard JAXA’s Global Change Observation Mission 1st-Water “SHIZUKU” (GCOM-W1) satellite.

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