Monday, August 8, 2011

Tropics will prove climate change first

Environmental Research Web: Where are the best places to look for clear evidence of anthropogenic global warming? Although melting glaciers and ice sheets in the Arctic and Antarctic might seem like the obvious location, it is in fact the low latitudes where man-made climate change signals will appear first, new research shows.

Irina Mahlstein, from the Swiss Federal Institute of Technology, in Zurich, and her colleagues used 23 atmosphere–ocean general circulation models to assess which locations will show evidence of anthropogenic global warming earliest. For each grid cell the team calculated the average climate variability going back to 1900. They then looked at forward projections for climate up to the year 2100 and identified the locations where climate change would exceed normal climate variability first. They found that the earliest emergence of warming will occur in the summer season in low-latitude countries – between 25°N and 25°S. Their findings are published in Environmental Research Letters.

So why do low-latitude countries act as the canary in the coal mine? To detect global warming the local climate change needs to be at least two standard deviations from the mean base-period temperatures. "Regions with low variability have a rather narrow distribution and a smaller amount of warming is needed, which then also implies a smaller global warming," Mahlstein told environmentalresearchweb. "Regions with a high variability have wider distributions and therefore a larger warming is needed, and also a greater global warming."

The data shows that countries with the lowest inter-annual variability are situated in the region between 25° north and south. In particular low-latitude summers tend to be less variable than winters, making summer the most likely time for climate-change signals to emerge....

Generic shot of tropics by Nicolas M. Perrault, Wikimedia Commons, under the Creative Commons CC0 1.0 Universal Public Domain Dedication

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