tropics moving poleward faster than predicted
Sure, global warming will expand the tropical belt around our planet. Yet we’re now learning that this growth is much faster than predicted.
Sunday’s release of new NOAA findings in Nature Geoscience is sounding warning bells throughout the climate modeling community. Why? When the models are tweaked to account for this newly observed growth rate, we’re likely to see even more dire predictions for climate change (via celsias).
Since 1979, tropical boundaries have moved poleward by 2 degrees of latitude or 172 miles, adding 8.5 million sq miles to this climatic region …which is more than the models anticipated for the entire 21st century.
For one thing, the jet streams (and their associated storm tracks) are shifting farther poleward, which means that more of the planet will see drier weather than previously predicted…not to mention the even drier outlook for the tropics regions.
Equally alarming, the expansion of the tropical belt could feed global warming by increasing the rate at which water vapor (a greenhouse gas) is pumped naturally into the upper atmosphere.
Here’s the study’s conclusion:
“Widening of the tropics may also lead to changes in the distribution of climatically important trace gases in the stratosphere. The Brewer–Dobson circulation moves air upwards from the troposphere into the stratosphere in the tropics. If the area over which this upwelling occurs increases, transport of water vapour into the stratosphere might be enhanced. This could lead to an enhanced greenhouse effect, including tropospheric warming and stratospheric cooling, and reduced ozone.
More far-reaching changes in the climate system include the oceans and biosphere. Because atmospheric winds and air-sea exchanges drive the ocean currents, changes in the Hadley circulation may induce changes in the ocean circulation.
These may have important feedbacks on tropospheric climate, marine ecosystems (including fisheries) and biogeochemical cycles, which have been hypothesized to lead to irreversible climate change.”
So, where are these newly tropical climes? Says the report:
“Of particular concern are the semi-arid regions poleward of the subtropical dry belts, including the Mediterranean, the southwestern United States and northern Mexico, southern Australia, southern Africa, and parts of South America. “
Guess we need to reexamine the notion that weather more like the tropics is a good thang…
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