New study: Pace of climate zone shifts quickens as climate warms

NOAA April 22, 2013

As our planet is warming, not only have Earth's climate zones begun to shift – they will actually continue to shift at an accelerating pace, according to a new study led by a scientist at the NOAA Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado. This acceleration of change means that the species inhabiting each zone have less time to adapt to the climatic changes.   

"The warmer climate gets, the faster the climate zones are shifting. This could make it harder for plants and animals to adjust," said lead author Irina Mahlstein, a CIRES scientist who is located at the NOAA Earth System Research Laboratory in Boulder, Colo. A paper by Mahlstein and collaborators at NOAA and the Massachusetts Institute of Technology is now online in the journal Nature Climate Change   

 The study is the first to look at the accelerating pace of the shifting of climate zones. For this study, the scientists used a climate zone classification system known as the Koppen-Geiger classification, which defines areas of the Earth by annual and seasonal cycles of temperature and precipitation, as well as temperature and precipitation thresholds of plant species. This system identifies more than 30 different climate zones. 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 to look at the shifts between Koppen-Geiger climate zones over a two-century period, 1900 to 2098. The team found that for the initial two degrees Celsius 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 two degrees of warming, and an additional 10 percent of the land area shifts to a new climate zone.   

Certain regions of the globe, such as North America, Europe and others at the middle and high latitudes of the globe, will undergo more changes than other regions, such as the tropics, the scientists found. In the tropics, mountainous regions will experience bigger changes than their surrounding low-altitude areas.   

In the coming century, the findings suggest that frost climates — the coldest climate zone of the planet — are largely decreasing. Generally, dry regions in different areas of the globe are increasing, and a large fraction of land area is changing from cool summers to hot summers.     

The scientists also investigated whether temperature or precipitation made the 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 coauthored the study.  

NOAA's mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. 

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