Responding to "Green Politics," Part Three
- Wednesday, June 27, 2007
Next, we will begin to dissect the global warming debate, look at what is really happening relative to climate, and evaluate its alleged causes.
The conflict between those who view humanity as an enemy of nature and those who view man as nature's steward culminates in the dispute over global warming. At odds in this debate is not the question of whether or not we are experiencing a period of warmer temperatures, we are. Rather, it is the competing theories relative to the causes of the present temperature increase and the implications thereof.
Humans have only been trying to measure the temperature on a consistent basis since about 1850, during which time we think the world may have warmed by about 0.6 degrees centigrade, within a margin or error of 0.2 degrees plus or minus. Most of the climate community has agreed since 1988 that global mean temperatures have increased about one degree Fahrenheit, or roughly one half degree centigrade, over the past century. The majority of this increase occurred from 1919 to 1940, then decreased between 1940 and the early '70s, increased again until the '90s, and has remained essentially flat since 1998.
The fact is, these temperature fluctuations are nothing new. Scientists have long understood that the earth's climate naturally experiences cyclical changes--even sometimes dramatic changes. In addition, when you stop to consider the massive variables involved in trying to pinpoint the earth's mean temperature; it is very difficult to achieve a precise measurement even when exact measurements are available. The land heats and cools differently than the oceans or the atmosphere, temperatures are taken on a very disparate basis in proportion to land and water volume, location, seasonal fluctuations, and so on and so forth. Simply consider your local forecast. Temperatures vary between cities that are only a few miles apart. The bottom line: determining an accurate mean global temperature is a very complex and difficult challenge.
So, how did these long-recognized natural changes in climate and temperature suddenly transform into apocalyptic conditions that threaten to "send our entire planet into a tail-spin of epic destruction," according to Al Gore?
Michael Mann is a well-known climatologist whom you may not have heard of but you are probably familiar with his famous conclusion: that the present temperature increase is "likely to have been the largest of any century during the past 1,000 years" and that the "1990s was the warmest decade and 1998 the warmest year" of the millennium.
How could Mann make such claims when we have only consistently collected temperature readings since the latter 19th century? In the absence of direct temperature measurements, i.e. thermometer readings, Mann reconstructed temperatures in the Northern Hemisphere over the last 1000 years using what are known as "proxy" methods. Essentially, scientists compare proxy data such as recent isotope data from snow and tree rings to local temperatures. This real time comparison then serves as a sort-of scale from which scientists can examine similar proxy sources to infer temperatures in the distant past. These proxy reconstructions are indirect inferences of temperature and obviously have less accuracy than data collected by direct methods such as the thermometer. Remember, the global warming debate centers around temperature variables of less than 1 degree centigrade within a margin of error of 0.2 degrees plus or minus even using the most sophisticated measuring devices.
Mann published his findings in 1998, producing the infamous "hockey stick" graph illustrating cooler temperatures throughout the last 1000 years until the last decade of the 20th century, at which point temperatures seemed to rise "dramatically." If you watched Al Gore's An Inconvenient Truth this graphic featured prominently. In simple visual terms, it was very compelling.
Mann's findings were arguably the single most influential study in swaying the public debate, and in 2001 they became the official view of the International Panel for Climate Change (IPCC), the UN body that is organizing the worldwide effort to combat global warming.
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