In their study A Less Cloudy Future: The Role of Subtropical Subsidence in Climate Sensitivity published in the most recent issue of Science, John Fasullo and Kevin Trenberth warn that sophisticated climate models that accurately capture the complicated process associated with relative humidity and weather patterns reveal that global temperatures could rise by as much as 7 degrees F by the end of the 21st century.
Different data, different results
There are roughly two dozen climate projection models around the planet that each use a different data set to predict how increased carbon dioxide and other greenhouse gases will change the planet’s weather patterns.
These models predictably have different results that have made it difficult to know exactly how much temperatures are expected to rise.
But Fasullo and Trenberth, who work for the National Center for Atmospheric Research (NCAR), wrote that projections showing a greater rise in global temperature are probably more accurate.
“There is a striking relationship between how well climate models simulate relative humidity in key areas and how much warming they show in response to increasing carbon dioxide,” Fasullo says. “Given how fundamental these processes are to clouds and the overall global climate, our findings indicate that warming is likely to be on the high side of current projections.”
Equilibrium Climate Sensitivity (ECS)
“The most common benchmark for comparing model projections is equilibrium climate sensitivity (ECS), or the amount of warming that eventually occurs in a model when carbon dioxide is doubled over preindustrial values. At current rates of global emission, that doubling will occur well before 2100,” according to the University Corporation for Atmospheric Research.
For the last three decades, ECS values from various models have ranged from 3 degrees F and 8 degrees F, which has made accurate predictions impossible. Most scientists have urged governments to cut emissions in order to avoid temperatures rising above 2 degrees, beyond which the planet is expected to be largely uninhabitable.
Relying on observations from two NASA satellite instruments — the Atmospheric Infrared Sounder (AIRS) and Clouds and Earth’s Radiant Energy System (CERES) – and used a NASA data analysis, the Modern-Era Retrospective Analysis for Research and Applications (MERRA), Fasullo and Trenberth found that models that incorporate relative humidity into their projections are more reliable than those that don’t.
7 Degrees Hotter
“Estimates based on observations show that the relative humidity in the dry zones averages between about 15 and 25 percent, whereas many of the models depicted humidities of 30 percent or higher for the same period, according to UCAR.
“The models that better capture the actual dryness were among those with the highest ECS, projecting a global temperature rise for doubled carbon dioxide of more than 7 degrees F.”
A rise of 7 degrees F will have a catastrophic effect on life. Extreme weather events will become more fierce, dry countries such as most of those in the Middle East and North Africa will bake, and sea levels will swallow swaths of land.
Take this to COP 18 in Qatar to make this year’s UN Climate Change Conference less than a farce than those past.
Image of flooding in off-limits area, Shutterstock