Climate change appears to have altered cloud coverage around the planet, causing a shift of mid-latitude storm tracks towards the North and South poles and compounding the effects of global warming.
Researchers at the Scripps Institution of Oceanography at the University of California San Diego analyzed satellite imaging during a 27-year period between 1983 and 2009 and discovered large-scale changes including poleward retreat of mid-latitude storm clouds, expansion of subtropical dry zones and increasing height of cloud tops into the atmosphere.
The findings are consistent with previous climate change simulations which predicted that as the planet warms and subtropic dry zones expand, cloud coverage would be pushed further north and south.
The study’s authors were able to conclude that the abrupt changes in cloud patterns are not a product of natural variabilities in weather patterns but instead a result of “external forcing” of the climate system by today’s phenomenon known as global warming. The research team compared cloud patterns over the past three decades with historical simulations dating to pre-industrial periods and found that no other 27-year period over the past 15,000 years exhibited a shift of this nature and magnitude.
“The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling,” say the study’s authors. “These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.”
The primary and immediate consequence of these changes in cloud patterns is a further speeding up of the global warming process, say the scientists, whose new work appears in the journal Nature.
“The expansion of subtropical dry zones results in less reflection of solar radiation back to space,” say the authors. “And as cloud tops rise, their greenhouse effect becomes stronger. Both of these cloud changes have a warming effect on climate.”
The results add further insight into how weather patterns will continue to change during the 21st century, affecting countries and populations around the globe differently.
“This study is a big deal, both generally for climate change science, and also for understanding recent trends in regional hydroclimate,” says Jonathan Overpeck, co-director of the Institute of the Environment at the University of Arizona in Tucson. “The research highlights that there are winners and losers with global warming, and that the US Southwest is one of the losers when it comes to water generating storms moving north.”
Current projections stress the variability in global warming’s impact on different regions and populations around the globe, with the general scientific consensus being that climate change will widen the North-South gap and create further economic strife in much of Africa, Asia, South America and the Middle East. A 2015 study on the global economic effects of climate change states that while some of the more northerly countries like Russia, Mongolia and Canada will likely see upcoming benefits, up to three-quarters of the world’s nations will be more worse off than they are today.
Experts predict that Canada is heading into a period of greater weather variability, with both drought and extreme precipitation forecasted to become the norm.