Climate zones will shift faster as climate warms, new study finds

As the planet warms, Earth’s climate zones are shifting at an accelerating pace, says a new study led by a scientist at the Cooperative Institute for Research in Environmental Sciences, a joint venture between the University of Colorado Boulder and the National Oceanic and Atmospheric Administration.

The acceleration of change means that the species inhabiting each zone have less time to adapt to the climatic changes, said lead author Irina Mahlstein, a CIRES scientist who works at NOAA’s Earth System Research Laboratory in Boulder, Colo. “The warmer the climate gets, the faster the climate zones are shifting.  This could make it harder for plants and animals to adjust.”

The study is the first to look at the accelerating pace of the shifting of climate zones, which are areas of the Earth defined by annual and seasonal cycles of temperature and precipitation, as well as temperature and precipitation thresholds of plant species. Over 30 different climate zones are found on Earth; examples include the equatorial monsoonal zone, the polar tundra zone and cold arid desert zone.

“A shift in the climate zone is probably a better measure of ‘reality’ for living systems, more so than changing temperature by a degree or precipitation by a centimeter,” said Mahlstein.

The scientists used climate model simulations and a well-known ecosystem classification scheme to look at the shifts between climate zones over a two-century period, 1900 to 2098. The team found that for an initial 3.6 degrees Fahrenheit of warming, about 5 percent of Earth’s land area shifts to a new climate zone.

The models show that the pace of change quickens for the next 3.6 F of warming as an additional 10 percent of the land area shifts to a new climate zone.  The paper was published online in the journal Nature Climate Change on April 21.

Certain regions of the globe, such as northern middle and high latitudes, will undergo more changes than other regions, such as the tropics, the scientists found. In the tropics, mountainous regions will experience bigger changes than low-altitude areas.

In the coming century, the findings suggest that frost climates -- the coldest climate zone of the planet -- will largely decrease.  In general, dry regions in different areas of the globe will increase, and a large fraction of land area will change from cool summers to hot summers, according to the study.

The scientists also investigated whether temperature or precipitation had a greater impact on how much of the land area changed zones. “We found that temperature is the main factor, at least through the end of this century,” said Mahlstein.

John Daniel at the NOAA Earth System Research Laboratory and Susan Solomon at the Massachusetts Institute of Technology co-authored the study.

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