The relationship between climate change and cloud cover has long been a hotly debated, and largely unresolved, topic of discussion among scientists. While clouds rich in ice crystals slow global warming by reflecting heat and radiation back into space, recent studies have shown that most climate models have overestimated the amount of ice in the clouds, suggesting they play a smaller role than previously believed in curbing the harmful effects of climate change.
Now, a new paper published in the journal Nature has further cleared the air surrounding the role of clouds in regulation Earth’s climate. The study shows that the inexorable rise in the planet’s temperature is leading to a change in the distribution of clouds all over the Earth.
“What this paper brings to the table is the first credible demonstration that the cloud changes we expect from climate models and theory are currently happening,” lead author Joel Norris, a climate researcher at Scripps Institution of Oceanography, said in a statement.
The study, which is based on data gathered by weather satellites between 1983 and 2009, found that not only are the mid-latitude storm tracks moving poleward, leaving the populated regions in subtropical latitudes — located between 23.5 and 40 degrees in both hemispheres — drier than they were before, the height of the highest cloud tops has also increased.
These changes have the potential to further exacerbate global warming. Since the solar radiation intensity is much higher in the subtropics, the movement of low-lying clouds away from this region means less radiation would be reflected back into space. On the other hand, the increase in height of cloud tops creates a thick blanket around the planet, reducing reflection and increasing absorption of solar radiation.
“Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes,” the researchers wrote in the study. “The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling.”
Earlier this year, a monitoring station in Tasmania recorded a major milestone — the concentration of atmospheric carbon dioxide, one of the most potent greenhouse gases, had crossed the symbolic “red line” of 400 parts per million. Similar readings by several other monitoring stations around the world have, in recent years, triggered fears that atmospheric carbon dioxide levels may now never dip below 400 ppm — the highest level in 650,000 years.