Is global warming real and caused by human manipulation of the environment or a manufactured crisis? The politically correct position is that it is real and we are at fault. Anyone who questions that assumption is lumped in with Neanderthals and other liberal discredited miscreants like George Bush, Hitler, and the Devil. To suggest there is actual science discrediting any aspect of the global warming hypothesis is tantamount to committing career suicide, especially in the university environment. Despite that heavily weighted milieu, evidence is coming out that the basic assumption on which the human-driven global warming argument is based is flawed, if not dishonest.
Appearing in of all places, MIT’s Technology Review, Richard Muller examines the furor over the mathematical model used by University of Massachusetts geoscientist Michael Mann and his colleagues to arrive at the “hockey stick” increase in temperature that apparently began just over a 100 years ago when man began to extensively utilize hydrocarbon fuels. This cornerstone analysis of human-driven global warming was called into serious question by Stephen McIntyre and Ross McKitrick, two Canadian scientists who have discovered a fundamental mathematical flaw in the computer model that Mann used to produce the hockey stick temperature rise.
The esoteric statistical math aside, what you end up with is
The net result: the principal component will have a hockey stick shape even if most of the data do not.
In essence, the Canadians used a classic test called Monte Carlo analysis to show that Mann’s hockey stick was an artifact of analysis and not really present in the data. The way they normalized their data set tended to emphasize any data that has the hockey stick shape, and to suppress all data that does not; a fatal flaw.
When McIntryre and McKitrick submitted their work to Nature it was rejected (surprise, surprise). If this had been ten years ago, it probably would have ended there, but we now live in the Internet age, so they put together a website for anyone who wanted to see the facts, which included the entire record of their submission as well as the refereed reports of their work. They did an end run around the naysayers.
It should be noted that demonstrating the errors in Mann’s analysis doesn’t end the debate over global warming. It only means that what most scientists thought they knew was proven is now no longer valid, that is that man’s consumption of hydrocarbans is the primary cause of whatever warming trend that can be discerned.
In closing, Richard Mueller makes an important observation that should guide all of our thinking in this matter as we go forward.
It is our responsibility as scientists to look at the data in an unbiased way, and draw whatever conclusions follow. When we discover a mistake, we admit it, learn from it, and perhaps discover once again the value of caution.
Why is this important? The important issue at the moment is not whether or not global warming is occuring, but if we, as human consumers of hydrocarbons, are causing it. If we are not, as this new analysis seems to say, and any warming is a fundamental and long term climate process, then sacrificing our economies and our cultures in a vain attempt to alter its course is not only suicidal, but stupid. We must keep an open mind and not be drawn into the politicization of this potentially serious situation.
Just a few more thoughts from the rim…
Hat tip to Jeremy Pierce.
Update (10-20-2004): It appears the analysis was flawed, due to the failure of using radians instead of degrees in their calculations. Yet, the last paragraph still rings true, keeping an open mind is still paramount.