Data from NASA’s Terra satellite shows that, when the climate warms, the atmosphere’s more efficient at releasing energy to space than believed.
As a result, says Dr Roy Spencer of the Earth System Science Center at the University of Alabama in Huntsville, climate forecasts don’t reflect the true picture.
The finding’s likely to fuel the debate about how much human activity is affecting the climate. For the last couple of decades, differences between model-based forecasts of rapid global warming and actual meteorological data have remained unexplained, and have caused quite some controversy.
The UA team compared what a half dozen climate IPCC models say the atmosphere should do with actual satellite data for the 18 months before and after warming events between 2000 and 2011.
“The satellite observations suggest there is much more energy lost to space during and after warming than the climate models show,” says Spencer. “There is a huge discrepancy between the data and the forecasts that is especially big over the oceans.”
Not only does the atmosphere release more energy than previously thought, it starts releasing it earlier in a warming cycle. The models forecast that the climate should continue to absorb solar energy until a warming event peaks.
Instead, the satellite data shows the climate system starting to shed energy more than three months earlier on average.
Applied to long-term climate change, the findings might indicate that the climate is less sensitive to warming by increased carbon dioxide than climate modelers have theorized.
“The main finding from this research is that there is no solution to the problem of measuring atmospheric feedback, due mostly to our inability to distinguish between radiative forcing and radiative feedback in our observations,” says Spencer.