global warming

Antarctica’s Effect on Sea Level Rise in Coming Centuries

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Esprit Smith

Jet Propulsion Laboratory, Pasadena, Calif.

  

 

Thwaites Glacier. animation shows projections of ice sheet retreat in Antarctica Thwaites Glacier. Credit: NASA/James Yungel

 

 

There are two primary causes of global mean sea level rise – added water from melting ice sheets and glaciers, and the expansion of sea water as it warms. The melting of Antarctica’s ice sheet is currently responsible for 20-25 percent of global sea level rise.

 

But how much of a role will it play hundreds of years in the future?


 

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2018 Fourth Warmest Year in Continued Warming Trend, According to NASA, NOAA

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In 2018, the temperature was 1.5 degrees Fahrenheit warmer than the average from 1951 to 1980. (Animated GIF) Credit: NASA Goddard Space Flight Center

 

Ahead of tomorrow’s press teleconference on climate change and global warming, NASA just released its 2018 statistics on temperature readings worldwide.

 

Earth’s global surface temperatures were the fourth warmest since 1880, according to independent analyses by NASA and the National Oceanic and Atmospheric Administration (NOAA).

 

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NASA, NOAA to Announce 2018 Global Temperatures, Climate Conditions

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Media Advisory: M19-003
NASA, NOAA to Announce 2018 Global Temperatures, Climate Conditions

 

2017_Worldwide_Temperature_Map.jpg
NASA and NOAA are two keepers of the world’s temperature data and independently produce a record of Earth’s surface temperatures and changes. Shown here are 2017 global temperature data: higher than normal temperatures are shown in red, lower than normal temperatures are shown in blue. Credits: NASA’s Scientific Visualization Studio

 

Climate experts from NASA and the National Oceanic and Atmospheric Administration (NOAA) will provide the annual release of global temperatures data and discuss the most important climate trends of 2018 during a media teleconference at 11:30 a.m. EST Wednesday, Feb. 6.

 

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NASA Finds New Way to Track Ocean Currents from Space

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NASA’s GRACE satellites (artist’s concept) measured Atlantic Ocean bottom pressure as an indicator of deep ocean current speed. In 2009, this pattern of above-average (blue) and below-average (red) seafloor pressure revealed a temporary slowing of the deep currents. Image credit: NASA/JPL-Caltech

A team of NASA and university scientists has developed a new way to use satellite measurements to track changes in Atlantic Ocean currents, which are a driving force in global climate. The finding opens a path to better monitoring and understanding of how ocean circulation is changing and what the changes may mean for future climate.

In the Atlantic, currents at the ocean surface, such as the Gulf Stream, carry sun-warmed water from the tropics northeastward. As the water moves through colder regions, it sheds its heat. By the time it gets to Greenland, it’s so cold and dense that it sinks a couple of miles down into the ocean depths. There it turns and flows back south. This open loop of shallow and deep currents is known to oceanographers as the Atlantic Meridional Overturning Circulation (AMOC) — part of the “conveyor belt” of ocean currents circulating water, heat and nutrients around the globe and affecting climate.

Because the AMOC moves so much heat, any change in it is likely to be an important indicator of how our planet is responding to warming caused by increasing greenhouse gases. In the last decade, a few isolated measurements have suggested that the AMOC is slowing down and moving less water. Many researchers are expecting the current to weaken as a consequence of global warming, but natural variations may also be involved. To better understand what is going on, scientists would like to have consistent observations over time that cover the entire Atlantic

“This [new] satellite approach allows us to improve projections of future changes and — quite literally — get to the bottom of what drives ocean current changes,” said Felix Landerer of NASA’s Jet Propulsion Laboratory, Pasadena, California, who led the research team.

Landerer and his colleagues used data from the twin satellites of NASA’s Gravity Recovery and Climate Experiment (GRACE) mission. Launched in 2002, GRACE provides a monthly record of tiny changes in Earth’s gravitational field, caused by changes in the amount of mass below the satellites. The mass of Earth’s land surfaces doesn’t change much over the course of a month; but the mass of water on or near Earth’s surface does, for example, as ice sheets melt and water is pumped from underground aquifers. GRACE has proven invaluable in tracking these changes.

At the bottom of the atmosphere — on Earth’s surface — changes in air pressure (a measure of the mass of the air) tell us about flowing air, or wind. At the bottom of the ocean, changes in pressure tell us about flowing water, or currents. Landerer and his team developed a way to isolate in the GRACE gravity data the signal of tiny pressure differences at the ocean bottom that are caused by changes in the deep ocean currents.

“We’ve wanted to observe this phenomenon with GRACE since we launched 13 years ago, but it took us this long to figure out how to squeeze the information out of the data stream,” said Michael Watkins, director of the Center for Space Research at the University of Texas at Austin, former GRACE project scientist and a co-author of the study.

The squeezing process required some very advanced data processing, but not as many data points as one might think. “In principle, you’d think you’d have to measure every 10 yards or so across the ocean to know the whole flow,” Landerer explained. “But in fact, if you can measure the farthest eastern and western points very accurately, that’s all you need to know how much water is flowing north and south in the entire Atlantic at that section. That theory has long been known and is exploited in buoy networks, but this is the first time we’ve been able to do it successfully from space.”

The new measurements agreed well with estimates from a network of ocean buoys that span the Atlantic Ocean near 26 degrees north latitude, operated by the Rapid Climate Change (RAPID) group at the U.K.’s National Oceanography Centre, Southampton. The agreement gives the researchers confidence that the technique can be expanded to provide estimates throughout the Atlantic. In fact, the GRACE measurements showed that a significant weakening in the overturning circulation, which the buoys recorded in the winter of 2009-10, extended several thousand miles north and south of the buoys’ latitude.

Gerard McCarthy, a research scientist in the RAPID group who was not involved with the study, said, “The results highlight synergies between [direct measurements] like [those from] RAPID and remote sensing — all the more important given the rapid and surprising changes occurring in the North Atlantic at the present time.” Eric Lindstrom, NASA’s Physical Oceanography Program manager at the agency’s headquarters in Washington, pointed out, “It’s awesome that GRACE can see variations of deep water transport, [but] this signal might never have been detected or verified without the RAPID array. We will continue to need both in situ and space-based systems to monitor the subtle but significant variations of the ocean circulation.”

A paper in the journal Geophysical Research Letters describing the new technique and first results is available online in prepublication form: http://onlinelibrary.wiley.com/doi/10.1002/2015GL065730/abstract?campaign=wolacceptedarticle

Excitement Grows as NASA Carbon Sleuth Begins Year Two

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Global average carbon dioxide concentrations as seen by NASA's Orbiting Carbon Observatory-2 mission, June 1-15, 2015. OCO-2 measures carbon dioxide from the top of Earth's atmosphere to its surface. Higher carbon dioxide concentrations are in red, with lower concentrations in yellows and greens. Credit: NASA/JPL-Caltech
Global average carbon dioxide concentrations as seen by NASA’s Orbiting Carbon Observatory-2 mission, June 1-15, 2015. OCO-2 measures carbon dioxide from the top of Earth’s atmosphere to its surface. Higher carbon dioxide concentrations are in red, with lower concentrations in yellows and greens. Credit: NASA/JPL-Caltech

Scientists busy poring over more than a year of data from NASA’s Orbiting Carbon Observatory-2 (OCO-2) mission are seeing patterns emerge as they seek answers to the science questions that drive the mission.

Launched in July 2014, OCO-2, an experimental carbon-dioxide measurement mission, is designed to give the international science community a new view of the global carbon cycle in unprecedented detail. During its two-year primary mission, the satellite observatory is tracking the large-scale movement of carbon between Earth’s atmosphere, its plants and soil, and the ocean, from season to season and from year to year. OCO-2 began routine science operations in September 2014.

“We can already clearly see patterns of seasonal change and variations in carbon dioxide around the globe,” said Annmarie Eldering, OCO-2 deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “Far more subtle features are expected to emerge over time.”

A new animation depicting the first full year of OCO-2 science operations is available at:

Armed with a full annual cycle of data, OCO-2 scientists are now beginning to study the net sources of carbon dioxide as well as their “sinks” — places in the Earth system that store carbon, such as the ocean and plants on land. This information will help scientists better understand the natural processes currently absorbing more than half the carbon dioxide emitted into the atmosphere by human activities. This is a key to understanding how Earth’s climate may change in the future as greenhouse gas concentrations increase.

The first year of data from the mission reveals a portrait of a dynamic, living planet. Between mid-May and mid-July 2015, OCO-2 saw a dramatic reduction in the abundance of atmospheric carbon dioxide across the northern hemisphere, as plants on land sprang to life and began rapidly absorbing carbon dioxide from the air to form new leaves, stems and roots.

During this intense, two-month period, known as the “spring drawdown,” OCO-2 measurements show the concentration of atmospheric carbon dioxide over much of the northern hemisphere decreased by two to three percent. That’s 8 to 12 parts per million out of the global average background concentration of 400 parts per million.

“That’s a big but expected change,” said Eldering.

“This is the first time we’ve ever had the opportunity to observe the spring drawdown across the entire northern hemisphere with this kind of spatial resolution, seeing changes from week to week.”

Also as expected, OCO-2 data show increased concentrations of carbon dioxide associated with human activities. Higher carbon dioxide levels of several parts per million are seen in regions where fossil fuels are being consumed by large power plants or megacities. Enhanced levels are also seen in the Amazon, Central Africa and Indonesia, where forests are being cleared and burned to create fields for agricultural use.

Researchers Abhishek Chatterjee of the Global Modeling and Assimilation Office at NASA’s Goddard Space Flight Center, Greenbelt, Maryland; and Michelle Gierach and Dave Schimel of JPL are investigating a strong correlation observed between atmospheric carbon dioxide over the Pacific Ocean and the current El Nino.

Fluctuations in carbon dioxide appear to be strongly linked with warmer sea surface temperatures. OCO-2’s unprecedented density of measurements is giving researchers a unique data set to understand and separate the roles that sea surface temperatures, winds, regional emissions and other variables may be playing in the carbon dioxide concentrations.

“We believe 2016 will see breakthrough OCO-2 research results, as scientists work to unravel the mysteries of finding carbon dioxide sources and natural sinks,” said Eldering.

Through most of OCO-2’s first year in space, the mission team was busy calibrating its science instrument, learning how to process its massive amount of data, and delivering data products to NASA’s Goddard Earth Sciences Data and Information Services Center (GES-DISC) in Greenbelt, Maryland, for distribution to the world’s science community.

Scientists are comparing OCO-2 data to ground-based measurements to validate the satellite data and tie it to internationally accepted standards for accuracy and precision.

Routine delivery of OCO-2 data — calibrated spectra of reflected sunlight that reveal the fingerprints of carbon dioxide — began in late 2014, while estimates of carbon dioxide derived from cloud-free OCO-2 observations have been delivered since March 2015. Recently, the OCO-2 team reprocessed the OCO-2 data set to incorporate improvements in instrument calibration and correct other known issues with the original data release.

Every day, OCO-2 orbits Earth 14.5 times and collects and returns about a million measurements. After eliminating data contaminated by clouds, aerosols and steep terrain, between 10 to 13 percent of the measurements are of sufficient quality to derive accurate estimates of the average carbon dioxide concentration between Earth’s surface and space. That’s at least 100 times more carbon dioxide measurements than from all other sources of precise carbon dioxide data combined.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information on OCO-2, visit: http://www.nasa.gov/oco-2

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth

NASA Study Finds Indian, Pacific Oceans Temporarily Hide Global Warming

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An Argo float, foreground. The new study included direct measurements of ocean temperatures from the global array of 3,500 Argo floats and other ocean sensors. Image credit: Argo program. (Image Credit: Germany/Ifremer)

A new NASA study of ocean temperature measurements shows that in recent years, extra heat from greenhouse gases has been trapped in the waters of the Pacific and Indian oceans. Researchers say this shifting pattern of ocean heat accounts for the slowdown in the global surface temperature trend observed during the past decade.

Researchers Veronica Nieves, Josh Willis and Bill Patzert of NASA’s Jet Propulsion Laboratory, Pasadena, California, found a specific layer of the Indian and Pacific oceans between 300 and 1,000 feet (100 and 300 meters) below the surface has been accumulating more heat than previously recognized. They also found the movement of warm water has affected surface temperatures. The results were published Thursday in the journal Science.

During the 20th century, as greenhouse gas concentrations increased and trapped more heat energy on Earth, global surface temperatures also increased. However, in the 21st century, this pattern seemed to change temporarily.

“Greenhouse gases continued to trap extra heat, but for about 10 years starting in the early 2000s, global average surface temperature stopped climbing and even cooled a bit,” said Willis.


In the study, researchers analyzed direct ocean temperature measurements, including observations from a global network of about 3,500 ocean temperature probes known as the Argo array. These measurements show temperatures below the surface have been increasing.

Maps of temperature trends at four layers in the global ocean show the patterns of heat below the surface, 2003-2012. The warmest water appears at depths of about 330-660 feet (100-200 meters, third panel from the top) in the western Pacific and Indian oceans, left of center. Image credit: NASA Earth Observatory

The Pacific Ocean is the primary source of the subsurface warm water found in the study, though some of that water now has been pushed to the Indian Ocean. Since 2003, unusually strong trade winds and other climatic features have been piling up warm water in the upper 1,000 feet of the western Pacific, pinning it against Asia and Australia.

“The western Pacific got so warm that some of the warm water is leaking into the Indian Ocean through the Indonesian archipelago,” said Nieves, the lead author of the study.

The movement of the warm Pacific water westward pulled heat away from the surface waters of the central and eastern Pacific, which resulted in unusually cool surface temperatures during the last decade. Because the air temperature over the ocean is closely related to the ocean temperature, this provides a plausible explanation for the global cooling trend in surface temperature.

Cooler surface temperatures also are related to a long-lived climatic pattern called the Pacific Decadal Oscillation, which moves in a 20- to 30-year cycle. It has been in a cool phase during the entire time surface temperatures showed cooling, bringing cooler-than-normal water to the eastern Pacific and warmer water to the western side. There currently are signs the pattern may be changing to the opposite phase, with observations showing warmer-than-usual water in the eastern Pacific.

“Given the fact the Pacific Decadal Oscillation seems to be shifting to a warm phase, ocean heating in the Pacific will definitely drive a major surge in global surface warming,” Nieves said.

Previous attempts to explain the global surface temperature cooling trend have relied more heavily on climate model results or a combination of modeling and observations, which may be better at simulating long-term impacts over many decades and centuries. This study relied on observations, which are better for showing shorter-term changes over 10 to 20 years. In shorter time spans, natural variations such as the recent slowdown in global surface temperature trends can have larger regional impacts on climate than human-caused warming.

Pauses of a decade or more in Earth’s average surface temperature warming have happened before in modern times, with one occurring between the mid-1940s and late 1970s.

“In the long term, there is robust evidence of unabated global warming,” Nieves said.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information about NASA’s Earth science activities, visit: http://www.nasa.gov/earth

NASA Finds Good News on Forests and Carbon Dioxide

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A new NASA study suggests that tropical forests, like this one in Malaysia, absorb more atmospheric carbon dioxide than is absorbed by forests in Alaska, Canada and Siberia. (Image credit: Wikimedia Commons)
A new NASA study suggests that tropical forests, like this one in Malaysia, absorb more atmospheric carbon dioxide than is absorbed by forests in Alaska, Canada and Siberia. (Image credit: Wikimedia Commons)

PRESS RELEASE (NASA/JPL) – A new NASA-led study shows that tropical forests may be absorbing far more carbon dioxide than many scientists thought, in response to rising atmospheric levels of the greenhouse gas. The study estimates that tropical forests absorb 1.4 billion metric tons of carbon dioxide out of a total global absorption of 2.5 billion — more than is absorbed by forests in Canada, Siberia and other northern regions, called boreal forests.

“This is good news, because uptake in boreal forests is already slowing, while tropical forests may continue to take up carbon for many years,” said David Schimel of NASA’s Jet Propulsion Laboratory, Pasadena, California. Schimel is lead author of a paper on the new research, appearing online today in the Proceedings of National Academy of Sciences.

Forests and other land vegetation currently remove up to 30 percent of human carbon dioxide emissions from the atmosphere during photosynthesis. If the rate of absorption were to slow down, the rate of global warming would speed up in return.

The new study is the first to devise a way to make apples-to-apples comparisons of carbon dioxide estimates from many sources at different scales: computer models of ecosystem processes, atmospheric models run backward in time to deduce the sources of today’s concentrations (called inverse models), satellite images, data from experimental forest plots and more. The researchers reconciled all types of analyses and assessed the accuracy of the results based on how well they reproduced independent, ground-based measurements. They obtained their new estimate of the tropical carbon absorption from the models they determined to be the most trusted and verified.

“Until our analysis, no one had successfully completed a global reconciliation of information about carbon dioxide effects from the atmospheric, forestry and modeling communities,” said co-author Joshua Fisher of JPL. “It is incredible that all these different types of independent data sources start to converge on an answer.”

The question of which type of forest is the bigger carbon absorber “is not just an accounting curiosity,” said co-author Britton Stephens of the National Center for Atmospheric Research, Boulder, Colorado. “It has big implications for our understanding of whether global terrestrial ecosystems might continue to offset our carbon dioxide emissions or might begin to exacerbate climate change.”

As human-caused emissions add more carbon dioxide to the atmosphere, forests worldwide are using it to grow faster, reducing the amount that stays airborne. This effect is called carbon fertilization. “All else being equal, the effect is stronger at higher temperatures, meaning it will be higher in the tropics than in the boreal forests,” Schimel said.

But climate change also decreases water availability in some regions and makes Earth warmer, leading to more frequent and larger wildfires. In the tropics, humans compound the problem by burning wood during deforestation. Fires don’t just stop carbon absorption by killing trees, they also spew huge amounts of carbon into the atmosphere as the wood burns.

For about 25 years, most computer climate models have been showing that mid-latitude forests in the Northern Hemisphere absorb more carbon than tropical forests. That result was initially based on the then-current understanding of global air flows and limited data suggesting that deforestation was causing tropical forests to release more carbon dioxide than they were absorbing.

In the mid-2000s, Stephens used measurements of carbon dioxide made from aircraft to show that many climate models were not correctly representing flows of carbon above ground level. Models that matched the aircraft measurements better showed more carbon absorption in the tropical forests. However, there were still not enough global data sets to validate the idea of a large tropical-forest absorption. Schimel said that their new study took advantage of a great deal of work other scientists have done since Stephens’ paper to pull together national and regional data of various kinds into robust, global data sets.

Schimel noted that their paper reconciles results at every scale from the pores of a single leaf, where photosynthesis takes place, to the whole Earth, as air moves carbon dioxide around the globe. “What we’ve had up till this paper was a theory of carbon dioxide fertilization based on phenomena at the microscopic scale and observations at the global scale that appeared to contradict those phenomena. Here, at least, is a hypothesis that provides a consistent explanation that includes both how we know photosynthesis works and what’s happening at the planetary scale.”

NASA monitors Earth’s vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique 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.

For more information about NASA’s Earth science activities in the last year, visit:

http://www.nasa.gov/earthrightnow

Media Contact

Alan Buis
Jet Propulsion Laboratory, Pasadena, California
818-354-0474
Alan.Buis@jpl.nasa.gov

Written by Carol Rasmussen
NASA Earth Science News Team

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