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Twelve years of satellite data help decode climate change

This animation portrays the flow of atmospheric water vapor around the world. Water vapor is the most abundant greenhouse gas, but importantly, it acts as a feedback to the climate.
NASA/Goddard Space Flight Center Scientific Visualization Studio.

Imagine trying to figure out your car’s fuel economy by driving only 20 miles. Sure, the number might look pretty good, but it wouldn’t be a very accurate picture of how your vehicle burns fuel over the long term.

Predicting how the climate will change is a bit more complicated than calculating miles per gallon, but scientists who estimate Earth’s future temperatures face a similar challenge—having enough data to see the big picture.

The big goal is to gauge how the atmosphere responds to changes, and to fully understand the long-term trends, you’d better understand the short-term trends really well.- Eric Fetzer, project scientist

“The big goal is to gauge how the atmosphere responds to changes, and to fully understand the long-term trends, you’d better understand the short-term trends really well,” said Eric Fetzer, a project scientist at NASA’s Jet Propulsion Laboratory.

In 2002, NASA launched the Atmospheric Infrared Sounder (AIRS) aboard its Aqua satellite, designed to make precise measurements of global temperatures, greenhouse gases and clouds. Now that the instrument has amassed 12 years of data, researchers are using its cutting-edge observations to better understand how climate feedbacks will impact warming rates.

Water vapor: The hot and cold cycles of El Niño

When it comes to global climate, one of the strongest triggers of short-term variability is the El Niño Southern Oscillation (ENSO). Normally, most of the Earth’s warm water is concentrated in a deep pool in the western Pacific. But every three to five years, El Niño makes its appearance, bringing warm water to the surface and making the tropical Pacific Ocean warmer than average. (Conversely, during La Niña, sea-surface temperatures become colder than normal.)

For climate researcher Andrew Dessler, El Niño isn’t just a weather phenomenon to be studied—it’s a rough analogue to the Earth’s long-term warming and cooling cycles. “If I want to understand how water vapor responds to climate change, I need to look at a time when the Earth is cold and a time when the Earth is warm,” said Dessler, a professor of atmospheric sciences at Texas A&M University.