14 DAY TRIAL // After an extensive, 10-year-old review of data from NASA and other sources, a researchers was able to determine that clouds play an important role in global warming, in the sense that they amplify temperature rise generated by the release of carbon dioxide into the planet's atmosphere.
The finding brings a new angle to the discussion about climate change and pollution, and provides climate modelers with a new factor to consider in their calculations.
So, to recap, we have warming produced by the release of greenhouse gases, especially carbon dioxide, and then additional warming on top of that, caused by the way clouds influence heat in the atmosphere.
This type of effect is called “positive feedback,” researchers say in the December 10 issue of the top journal Science. Texas A&M University scientist Andrew Dessler conducted the investigation.
One of the most difficult problems in long-term climate prediction has until now been the uncertainty associated with the effects and type of feedback that clouds have on global temperatures.
Increased greenhouse gas emissions and an overall warmer climate were known to elicit feedback from clouds, but experts did not determine whether it was positive and negative until now.
This particular study is very important to the field because it's one of the few to include, and base its conclusions on, real-world observations of global clouds at both low and high altitudes.
A reassuring conclusion in the research was that, despite not knowing whether cloud feedback was positive or negative, existing climate models demonstrated their worth. The predictions they made have more than reasonable accuracy, Dessler says.
“We've used observations to show that clouds amplify the warming we get from carbon dioxide. No one has really rigorously quantified this feedback, and that's basically what I've done,” he adds.
“The cloud feedback is indeed positive. It does amplify the warming we get from greenhouse gases. The results suggest that our understanding and the models' simulation is actually quite good,” he says.
“This really emphasizes the need for continuity in our long term satellite observing systems. Breaks in the continuity of the observations would continue to add uncertainty,” adds Michael Bosilovich.
The expert is the overseer of the NASA Modern Era Retrospective-analysis for Research and Application (MERRA) project. He is based at the Goddard Space Flight Center’s Global Modeling and Assimilation Office (GMAO), in Greenbelt, Maryland.
“It also shows that long re-analyses of satellite data can make critical contributions to climate studies. Those two things, a long satellite data record and the reanalysis, came together in this study,” he says.
Datasets from the NASA Clouds and the Earth's Radiant Energy System (CERES) satellite and the European Center for Medium-Range Weather Forecasting were also included in the research.
“If you ask the question, how could mainstream science be wrong about climate change? There would have to be something in the climate system that would cancel the warming,” Dessler explains.
“One of the main places that could be would be clouds. Based on this work, I don't really see any evidence that that would happen,” he concludes.