NASA Outlines Recent Breakthroughs in Greenhouse Gas Research

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

News release: 2009-196 Dec. 15, 2009

NASA Outlines Recent Breakthroughs in Greenhouse Gas Research

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2009-196&cid=kintera_release_2009-196

PASADENA, Calif. -- Researchers studying carbon dioxide, a leading greenhouse gas and a key
driver of global climate change, now have a new tool at their disposal: daily global measurements of
carbon dioxide in a key part of our atmosphere. The data are courtesy of the Atmospheric Infrared
Sounder (AIRS) instrument on NASA's Aqua spacecraft.

Moustafa Chahine, the instrument's science team leader at NASA's Jet Propulsion Laboratory,
Pasadena, Calif., unveiled the new product at a briefing on recent breakthroughs in greenhouse gas,
weather and climate research from AIRS at this week's American Geophysical Union meeting in San
Francisco. The new data have been extensively validated against both aircraft and ground-based
observations. They give users daily and monthly measurements of the concentration and distribution
of carbon dioxide in the mid-troposphere--the region of the atmosphere located between 5 and 12
kilometers, or 3 to 7 miles, above Earth's surface, and track its global transport. Users can also access
historical AIRS carbon dioxide data spanning the mission's entire seven-plus years in orbit. The
product represents the first-ever release of global daily carbon dioxide data that are based solely on
observations.

"AIRS provides the highest accuracy and yield of any global carbon dioxide data set available to the
research community, now and for the immediate future," said Chahine. "It will help researchers
understand how this elusive, long-lived greenhouse gas is distributed and transported, and can be
used to develop better models to identify 'sinks,' regions of the Earth system that store carbon
dioxide. It's important to study carbon dioxide in all levels of the troposphere."

Chahine said previous AIRS research data have led to some key findings about mid-tropospheric
carbon dioxide. For example, the data have shown that, contrary to prior assumptions, carbon dioxide
is not well mixed in the troposphere, but is rather "lumpy." Until now, models of carbon dioxide
transport have assumed its distribution was uniform.

Carbon dioxide is transported in the mid-troposphere from its sources to its eventual sinks.
More carbon dioxide is emitted in the heavily populated northern hemisphere than in its less
populated southern counterpart. As a result, the southern hemisphere is a net recipient, or sink, for
carbon dioxide from the north. AIRS data have previously shown the complexity of the southern
hemisphere's carbon dioxide cycle, revealing a never-before-seen belt of carbon dioxide that circles
the globe and is not reflected in transport models.

In another major finding, scientists using AIRS data have removed most of the uncertainty about the
role of water vapor in atmospheric models. The data are the strongest observational evidence to date
for how water vapor responds to a warming climate.

"AIRS temperature and water vapor observations have corroborated climate model predictions that
the warming of our climate produced as carbon dioxide levels rise will be greatly exacerbated -- in
fact, more than doubled -- by water vapor," said Andrew Dessler, a climate scientist at Texas A&M
University, College Station, Texas.

Dessler explained that most of the warming caused by carbon dioxide does not come directly from
carbon dioxide, but from effects known as feedbacks. Water vapor is a particularly important
feedback. As the climate warms, the atmosphere becomes more humid. Since water is a greenhouse
gas, it serves as a powerful positive feedback to the climate system, amplifying the initial warming.
AIRS measurements of water vapor reveal that water greatly amplifies warming caused by increased
levels of carbon dioxide. Comparisons of AIRS data with models and re-analyses are in excellent
agreement.

"The implication of these studies is that, should greenhouse gas emissions continue on their current
course of increase, we are virtually certain to see Earth's climate warm by several degrees Celsius in
the next century, unless some strong negative feedback mechanism emerges elsewhere in Earth's
climate system," Dessler said.

Originally designed to observe atmospheric temperature and water vapor, AIRS data are already
responsible for the greatest improvement to five- to six-day weather forecasts than any other single
instrument, said Chahine. JPL scientists have shown a major consequence of global warming will be
an increase in the frequency and strength of severe storms. Earlier this year, a team of NASA
researchers showed how AIRS can significantly improve tropical cyclone forecasting. The researchers
studied deadly Typhoon Nargis in Burma in May 2008. They found the uncertainty in the cyclone's
landfall position could have been reduced by a factor of six had more sophisticated AIRS
temperature data been used in the forecasts.

AIRS observes and records the global daily distribution of temperature, water vapor, clouds and
several atmospheric gases including ozone, methane and carbon monoxide. With the addition of the
mid-tropospheric carbon dioxide data set this week, a seven-year digital record is now complete for
use by the scientific community and the public.

For more on AIRS, see http://airs.jpl.nasa.gov/ .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

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