I'm a professor at U Michigan and lead a course on climate change problem solving. These articles often come from and contribute to the course.
By: RickyRood, 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.
Updated: 9:04 PM GMT on February 23, 2009
By: RickyRood, 3:48 AM GMT on February 16, 2009
Learning about Ice:
First, thanks to Jeff for covering for me. I’ve been overwhelmed with some of those official duties provided by the U of Michigan. This included a trip to Florida to talk about climate change to alumni. Of course the question of the cold winter in the U.S. came up. It’s already old news that even with the cold in the East of the U.S., the warmth in the West was enough to make the January 2009 just about average. Plus the fires in Australia brought attention to the record heat in Australia.
Part of my job in the last month has led to me learning a lot more about ice sheets. Some may recall that when the 2007 Fourth Assessment Report was issued by the IPCC, that there was some controversy about whether or not the melting of the polar ice sheets had been underestimated.
It is my opinion that the melting of the ice sheets was underestimated in the IPCC report. This is based on two reasons. The first reason is that the dynamics of ice sheets and the melting of ice sheets have only been crudely estimated in climate models. Only in the past few years have we been making serious progress on this problem. As we incorporate the melting of ice to form water and the flow of water through the ice sheets we discover processes that speed up melting. The second reason is – that in a situation of such uncertainty arguments of extreme melting are not well posed. These both lead to what, in my opinion, is an underestimate of ice sheet melting, and likely therefore, sea level rise.
Remember, ice sheet melting is compensated for by increased ice being deposited at high elevations in both Greenland and Antarctic. (I usually ask, why is this the case?) Sea level rise is related to whether or not there is net loss to ice sheets.
What I have learned in the last week is that we have made some progress in understanding the physics of ice sheet melting. Our old ways of thinking about ice melting because the air was warm, perhaps like the ice cubes that I drop on the floor, leads to it being centuries before the ice sheets melt. More recently we have seen the pictures of lakes forming on the ice sheets and disappearing, flowing into the ice sheets. This leads to a lubrication of the base of the ice sheet and increases the flow. This process definitely leads to fast melting, but the thermodynamics of this process suggest that it is not likely to lead to ice sheet collapse.
Some may recall early on in my blog a collection of blogs on melting ice. (Warm Snow, Fast Ice, The End of Ice?). In these blogs the importance of ice shelves and, perhaps, sea ice in buttressing the ice sheets flowing into the sea was discussed. Both the buttressing and insulating effects of ice shelves and sea ice is emerging as important. This allows the glaciers flowing from the ice sheets to “feel” the sea water. The heat associated with the sea water leads to accelerated melting. There is a lot of heat in the sea. This interaction between the sea and the ice is emerging as the most important melt mechanism.
What does this mean? A couple of things come to mind. One is the possibility of episodic mass loss. As the glacier retreats from the sea, it losses contact with the sea, the warmth. Therefore it gets some time to recover, until the leading edge gets to the sea again. This, I assert, still leads to accelerated mass loss. (Assertion based on years of studying irreversible transport in the atmosphere.) The second thing that comes to mind is that we have a physical reason to expect cyclical behavior in ice melt associated with atmospheric-oceanic cycles, i.e. the North Atlantic Oscillation.
The basic conclusions that the surface global temperature will rise, sea level will rise and the weather will change are robust. Also in the news this week is that the presidents of the Maldives and Kiribati are aggressively planning the evacuation of their nations.
Updated: 3:50 AM GMT on February 16, 2009
By: RickyRood, 6:35 PM GMT on February 13, 2009
The antarctic ozone hole is a loss of stratospheric ozone in springtime over Antarctica that peaks in September each year. The hole first opened up in 1979, and has been proven to be the result of human emissions of large quantities of chlorofluorocarbons (CFCs) and other ozone-depleting substances into the atmosphere. The 2008 hole was the fifth largest on record, according to NASA. On September 12, 2008, the hole reached it maximum size of 27 million square kilometers, which was 12% larger than the 24 million square kilometers of the 2007 hole. The 2008 hole was larger than North America, which is 25 million square kilometers. Record ozone holes were recorded in both 2000 and 2006, when the size of the hole reached 29 million square kilometers. The 2008 hole was bigger than the 2007 hole due to the fact that the jet stream was quite stable over Antarctica this September, which allowed very cold air in the so-called "polar vortex" over Antarctica to remain isolated from the warmer regions farther to the north. As a result, when sunlight began shining on the Polar Stratospheric Clouds (PSCs) in the Antarctic during their spring (September), the resultant chemical reactions were able to destroy more ozone than in 2007.
Figure 1. Antarctic ozone hole size over the past few years. Image credit:NOAA's Climate Prediction Center.
Thanks for an international agreement called the Montreal Protocol in 1987, emissions of ozone-depleting gases have been sharply curtailed. NASA estimates that levels of ozone-depleting substances in the stratosphere peaked in 2000, and had fallen by 3.8% by 2008. The ozone hole is expected to disappear by 2050. The wunderground Ozone Hole page has more information.
--Jeff Masters, filling in for Ricky Rood this week.