I got into an argument a month ago with someone at work about global warming (now being called "global climate change"; I've heard some say this is an attempt to defuse the severity of the problem, while I've heard others say that it's more accurate since there are radical changes happening to all aspects of the world's climate). This person, whose opinion I usually respect, argued that there was a lot of evidence for global warming and a lot against it, so therefore he doubted it.
I, on the other hand, have talked to a bunch of different people about this — including a marine biologist on one of the mailing lists I'm on — who clearly believe a) something is happening to the planet's climate, b) it is the result of human interaction, and c) there could be serious repercussions if nothing is done.
The problem with global warming is that it consists of small fluctuations in temperature over a long period of time, a slow trend in small increments. These small changes can be wiped out in an given year by natural variances in weather. If a given year is warm in the winter, people start saying "Aha! Proof of global warming!" only to have climate scientists say, "Uh, actually, it's an El Nina winter, so it's going to be warmer than normal." Likewise, the next winter could be warmer than usual, allowing skeptics to say, "See, it's all a sham."
Global warming is debated because of what it means to the economy of the world. If global warming is caused by human activity — particularly the generation of greenhouse gases — then the only way to stop this process is to reduce the creation of greenhouse gases. This requires industrial nations to change the amount of pollution they put into the air, a process that costs money, thus making a company less profitable. It's not surprising, then, that most of the skeptical studies have come from scientists employed by various industry and business groups.
For a good look at the debate, see these Wikipedia entries:
This leads me to Dr. Jeff Master's Wunderblog (http://www.wunderground.com/blog/JeffMasters/show.html). This is an interesting blog put out by a meteorologist.
The most recent blog entry talks about 2006 and how it was the warmest on record. He points out that you can't draw too many conclusions from a single year's weather. Global warming is seen through trends, not through individual years. This winter is affected by an El Nino event, so it was likely to generate temperatures above average. Jeff Masters even says, "And I agree that one warm month of winter in one country in its warmest year in 112 years of record keeping is not evidence of global warming, particularly when there is a moderate El Nino episode going on." Further, he goes on to say, "Taking a look at average U.S. December temperatures for all years in the historical record (Figure 2), we see that these temperatures do show quite a bit of noise, and there is no evidence of dramatic warming in the past 30 years."
It's when he investigates the December data a bit deeper that you realize he's concerned about global warming. He compares temperatures from other warm Decembers with December, 2006. December, 1957 is now the second warmest on record. While it was warm in the U.S., it was offset by a cold winter in Alaska, Siberia, and northern Canada. What's really different about December, 2006 is that this offset didn't appear to occur. According to Masters, "In the past, an exceptionally warm winter month in the U.S., like December 1957, was offset by much cooler weather elsewhere, such as we see in Alaska, Greenland, and northern Siberia. However, December 2006 had no such offsetting cool temperatures — it was more than 1° C above average over almost all the land areas of the Northern Hemisphere north of 40° north latitude. Colorado, whose three blizzards were cited as evidence that winter was severe elsewhere, still recorded temperatures about 1° C above normal in December 2006."
He points out that since 1979 the Arctic ice coverage in the summer has decreased quite significantly. This was reported last year with regard to the decline of the polar bear population. It has important implications for the albedo of the planet.
Albedo is the term used to describe the reflectivity of a surface (i.e. how easily a surface can reflect light). Most adults realize that dark colours absorb heat and light colours reflect heat. Anyone who's grabbed a black steering while in the middle of the summer understands this.
Ice increases the albedo of a planet. White ice reflects a lot of sunlight back into space. By corollary, if there is less ice, more of the dark Arctic ocean is exposed. The ocean absorbs heat while ice reflects it. If there is less ice, more heat is absorbed by the Arctic ocean. This increases water temperatures, which hampers the production of ice, and continues a trend toward more heat being abosrbed.
It's this kind of process that worries scientists. Opponents to global warming like to point out how the Earth's temperature hasn't changed that much over the years; about a 1° F rise world-wide over the past century. That doesn't seem like much, not at all something to worry about. Except that it's an average world-wide temperature change. Some places saw virtually no change, while the change is greater in places like the Arctic and the Antarctic. These areas are important because of ice production. That small a temperature increase is enough to shorten the days where ice covers the arctic, and decrease the ice coverage. This gets us into a dynamic situation where a decrease in ice coverage results in more energy absorbed from the sun, and thus global climate change due to more than just greenhouse gases alone.
It should also be pointed out that the world is only 5° F warmer today than at the end of the last ice age, so clearly small temperature changes have a large impact on the global climate.
According to Masters, we may see a total absence of Arctic ice in the summer months by 2040.
The slow pace of climate change gives us the illusion that there's plenty of time to determine if there's a problem, and figure out what to do about it. Unfortunately, the slow pace of climate change suggests that a fix will be slow to take as well. Scientists' big worry is that if we leave it long enough a fix could take decades to work.
I probably won't be around to see the worst of climate change. Logan, though, will be. It's his generation who are going to have to live with what we do, or don't do, in the next few years.
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