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Last Year and This Year - and the Next Big Story?

By: Dr. Ricky Rood, 8:47 PM GMT on February 23, 2009

Last Year and This Year:

I continue to get asked questions and to field comments about the cold winter in the northeast of the U.S. As many of you know, this has fueled a lot of discussion about whether or not the basic tenets of global warming are real. I have argued in previous blogs that the northeastern part of the U.S. is not representative of the temperatures of the globe as a whole, and, yes, it still gets cold in the Arctic and Antarctic in the winter. The Sun goes down for a long time. (Cold in a Warm World and Opinions and Anecdotal Evidence). Globally, January 2009 turned out to be the seventh warmest on record. (see Jeff Master’s blog)

As I was poking around I decided to look at the average temperatures from January 2008. The temperatures from January 2008 and 2009 are shown in the figures below.

Figure 1: Temperature anomalies for the U.S. in January 2008 and January 2009. These are differences from a thirty year mean calculated from the observations between 1971 and 2000.

What is remarkable about these pictures is the placement of the warmer than average and colder than average regions in the two years. In 2009 the Northeast was cold; in 2008 it was warm. In 2009 the US West was warm; in 2008 it was cold. This could be viewed as the warmer and cooler regions of a wave in temperature being at different locations in the two years. Interestingly, I don’t remember a lot of rhetoric that "global warming is spurious" coming out in 2008, from say, Seattle. (Perhaps someone can find something?)

As a curiosity, I note the differences in some of the smaller features, say, Florida, Alabama and Georgia, and Missouri and Oklahoma. I point out that Alaska is, mostly, cold in both years.

Wunderground.com readers tend to be more weather savvy than average and appreciate that the weather at middle latitudes is closely associated with waves of different wave lengths. There are very long waves whose positions are largely determined by the placement of mountain ranges and the temperature contrast between the continents and the oceans. On top of these waves the smaller weather disturbances move; they vary with time periods of a few days. The long waves effectively guide the weather disturbances.

The long waves that are strongly influenced by the mountain range location and the ocean and land temperature contrast, generally, are more persistent in time than the weather disturbances. Sometimes these long waves become stuck and persist for many days, perhaps a few weeks. In the case of a persistent long wave pattern, a particular region can have persistent weather, a period of storminess or drought or heat or cold. When we say El Nino and La Nina influence weather patterns, we are saying that the changes in the geographical structure of the ocean temperature are influencing the long waves in the atmosphere and guiding weather systems to particular locations.

This waviness is part of the natural variability, and the difference between January 2008 and January 2009 shows typical observed variability. With regard to climate change, one has to pose the question of whether or not the long waves that are sensitive to sea and land temperatures will be forced into more persistent patterns. If yes, this would lead to more extended periods of drought, storminess, hot, and cold. This does not mean that cold winter temperatures are eliminated; it still gets cold in the Arctic and the Antarctic when the Sun goes down. And if Arctic cold is pushed from Canada to south and east it will make the eastern half of the U.S. cold for a while - perhaps very cold. One way to look for dynamic variability is to look for compensating warm and cold regions.

The Next Big Climate Story? I have stated before, not in the spirit of fun, we do have one proven way to reduce carbon dioxide emissions. That is, economic collapse. I expect that the current economic turn down will have measurable impact on carbon dioxide emissions. Minimally, the rate of increase will be reduced. It is a large down turn, and there could, ultimately, be an observed decrease in carbon dioxide emissions. If this is true, then I expect that there will be much to fuel the arguments that global warming is a problem that is there to be dismissed. Keep an eye open for this one.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.