Winter Cold & Climate Change
Whenever we have a period of colder-than-average weather, like we’ve been having in the Northeast since before Thanksgiving and through the first half of December (see the Northeast Regional Climate Center for details), some people will start claiming it proves that global warming and climate change aren’t really happening.
Climate scientists, in turn, must explain each time that climate change, which is real and steadily changing our relationship to the world, does not mean that we don’t still have weather. We do, and the concept of weather can encompass regional hot and cold spells lasting weeks or months as well as day to day variation.
Simultaneous regional weather patterns in different parts of the globe often deviate from local norms (climate) in contrasting ways, because they are being driven by patterns in the jet streams and other global atmospheric phenomena. These atmospheric systems can sometimes have opposite effects in different regions so that the full global average has a different relationship to its historic norms than what is experienced in any particular zone.
November and December’s weather patterns this year are a good example. According to the National Climatic Data Center, while much of North America has been experiencing below average temperatures, southern Russia and many parts of Asia have been setting new all-time high temperature records.
Despite the local chill in the Northeast, with one of the best early ski seasons in recent years, when averaged over the whole globe, it was actually the warmest November on record and a front runner in the observed trend of rising global temperatures.
This is what we expect in a warming world: there will still be cold spells as well as heat waves, but the cold spells will rarely be extraordinary compared with long term historical averages, while the heat waves break world records again and again and again.
While late fall temperatures have been chilly in the Northeast, other parts of the world have been having warmer-than-average or even record warm temperatures, as shown in the map below from NOAA’s National Climatic Data Center. (See this and other maps from the Center: http://www.ncdc.noaa.gov/temp-and-precip/global-maps.php)
Update [2013-01-22]: December NOAA map tells a similar story.
Category: What's With the Weather