Wednesday, November 24, 2010

Wild Weather and Warming Climate

Climate is what you expect, weather is what you get.  Lately there has been some more "extreme: weather in North America, extreme because it is not what we expect based on long-term averages. There is a strong differential in temperatures in the continental US, with record warmth in the southeast and cold and snow in the central west and Pacific NW.
From the Weather Channel, Tuesday Nov. 2
Along with advancing cold air there were severe thunderstorms and rare November tornadoes in Illinois. The wild weather year continues.

That's the weather, but what to expect? The world continues to warm. NASA scientists using satellite data for 104 large inland lakes found that on average they have warmed two-and-a-half times the increase in atmospheric temps in the same time period. This past summer's Arctic sea ice melt was not as much as in 2007, but it was still well below the baseline. Amazingly, it is lagging in reforming and the ice extent is below 2007 for this time of the year:
Arctic sea ice extent as 11/21, from the National Snow and Ice Data Center,(click for larger image).
Not surprisingly, a record level of greenhouse gases was reached in 2009, and the threat of methane release from bogs and permafrost made the mainstream news with a report this week of methane bubbling up from Siberian lakes.

We label the weather patterns this year as "extreme" or "wild" or simply unusual because they are outside the expected climactic norms (this does not require them to be record breaking BTW). Of course if these weather patterns continue, they would soon constitute new norms and a new climate. This is what we could expect with continued global warming, extreme years punctuated with "normal" years (see this older post).

But what about the possibility of abrupt climate change? The next IPCC report could be dramatically worse, and reports of methane release are indeed alarming because methane is a very potent greenhouse gas and would accelerate warming. We just had a very snowy and/or cold winter in 2010, which could be due to warming in the arctic as sea ice loss in the arctic would shift atmospheric circulation.

Unfortunately, we can not answer the question with confidence and probably will not know it until we are several years or more into an abrupt shift. If it is the case, I expect to see denialism ramp up, not be defeated because denial is not just economic driven propaganda, but a human reaction to threatening news.

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