Wednesday, October 6, 2010

SUMMER 2010 - Hottest Ever??

(Posted by : Melissa Breyer, Oct 3, 2010,
Link :

Summer 2010? Man, it was a hot one. Unparalleled heat waves in eastern Europe, drought and fires in Moscow, forests aflame in the western U.S. and failing power grids in the East. And just last week, with one foot firmly planted in Autumn, triple digits were defiantly tipping the mercury in California. I’d love to know exactly how many west coast Facebookers mentioned the temperature in their status updates last week.

But was this summer really any hotter than others? I’ve long suspected that we have a strange relationship with how we perceive and remember weather. In the thick of it, it always feels like this is the coldest, wettest, snowiest, driest, hottest, etc season ever. But it seems to me that that is more a function of it just being the weather we are living through, it’s the present; the memory of weather can be so subjective.

So from a global perspective, exactly how hot was this summer? Aside from our personal perspective, what do the statistics look like on paper? And when everyone starts grumbling about the heat and global warming–is there any merit to it? These are the questions that scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York City, led by GISS’s director, James Hansen, addressed as they analyzed summer temperatures for the recent update on the GISS website that tackles these types of issues.

According to the GISS analysis, June through August of 2010 was the fourth-warmest summer, globally, in GISS’s 131-year-temperature record. Last summer (2009) was the second warmest on record. The slightly cooler 2010 summer temperatures were primarily the result of a moderate La Niña (cooler than normal temperatures in the equatorial Pacific Ocean) replacing a moderate El Niño (warmer than normal temperatures in the equatorial Pacific Ocean). But then I wonder, how does that jive with the cold winter we had?

As part of their analysis, Hansen and colleagues created a set of graphs that help explain why perceptions of global temperatures vary, and are often wrong, from season to season and year to year. So for example, my Brooklyn heat wave had New Yorkers uttering “global warming!” as we lumbered through each furnace-blast of a day; while the winter’s unusually frigid temperatures had climate change naysayers smugly tossing out comments of “global warming? ha!”

By looking at data from a more global perspective makes clear that extrapolating global trends based on the experience of one or two regions can be misleading.

“Unfortunately, it is common for the public to take the most recent local seasonal temperature anomaly as indicative of long-term climate trends,” Hansen notes. “[We hope] these global temperature anomaly maps may help people understand that the temperature anomaly in one place in one season has limited relevance to global trends.”

So even if last winter’s chilly temperatures in much of the United States caused many of us to ponder why temperatures seemed to be plummeting if we’re really in the midst of global warming, a more global view (as seen in the graphs) shows that global warming trends had hardly abated. In fact, believe it or not: despite the cool temperatures in the United States, last winter was the second-warmest on record!

Meanwhile, the global seasonal temperatures for the spring of 2010 (March, April, and May) were the warmest on GISS’s record. Does that mean that 2010 is gearing up to be the warmest on record? Since the warmest year on GISS’s record (2005) experienced especially high temperatures during the last four calendar months of the year, the jury is still out on 2010. Stay tuned…if last week’s sizzling start to fall in California was any indication, we may have a “winner.”

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