NASA sent the Atmospheric Infrared Sounder (AIRS) aboard its Aqua satellite into space back in 2002. It has been gathering measurements of global temperatures, greenhouse gases, and clouds. AIRS has been collecting data for over 12 years now.
This data is helping researchers better understand the role cloud cover and water vapor play in global warming.
“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, on the NASA website.
As a potent greenhouse gas, water vapor plays a key role in the global climate. As temperatures rise, water vapor increases, and because water vapor is itself a greenhouse gas, this produces even more warming. This vicious cycle is known as a feedback. By looking at the AIRS water vapor data during both the cold and warm cycles of the ENSO (which constitutes both El Niño and La Niña cycles), NASA can see how water vapor levels are responding to temperature changes and calculate the strength of the water vapor feedback.
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“If the globe warmed seven-tenths of a degree during the last El Niño, I can see in the AIRS data how water vapor changed in response to that. This tells me a lot about how water vapor is going to interact with climate change,” Andrew Dessler, a professor of atmospheric sciences at Texas A&M University, said in a statement.
According to NASA’s satellite data, over the past 12 years, water vapor actually doubled carbon dioxide’s influence on raising global temperatures, an effect researchers described as significant. “It’s kind of an ‘inconvenient truth’—the models that are realistic all happen to be the ones that are predicting a very strong warming in the future,” Hui Su, a research scientist at NASA’s Jet Propulsion Laboratory, said in a statement, according to IBT Pulse.
We now know that water vapor has a powerful effect on the climate system. It is not well understood what role clouds play in affecting climate change. “Models all predict that the water vapor effect doubles the amount of warming, but we’re still pretty uncertain about how clouds amplify warming,” said Hui Su.
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.
“More moisture in the atmosphere means more cloud cover,” said Su. “Based on the AIRS data, we know what the current humidity should be, and that should predict the amount of clouds. So, we’re really using current observations to infer the realism of model predictions.”
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In a recent study, Su and her research team used AIRS observations of humidity to analyze the performance of 15 leading global climate models. What they found was surprising: Only five of the models reproduced humidity levels that matched the current range observed by AIRS and other instruments. Even more startling, those models that did accurately forecast current humidity were the ones that predicted a much warmer future climate—about .7°C (1.3°F) higher than the average warming predicted by all 15 models combined, NASA wrote on their website.
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According to Fetzer, Su’s findings beg two important questions: “First, why are we looking at models that don’t accurately produce what we’re experiencing today? And second, if the models that are accurately forecasting humidity say that future warming is going to be closer to 4 degrees C than 1.5 degrees C, shouldn’t we be concerned?”
The climate change debate continues to have strong responses from both deniers and believers. Ninety-eight percent of scientists worldwide agree that climate change is real, and that it is happening because of humans. Whether you believe it or not, there is something is going on.