Yesterday I was running shopping errands in 95-degree heat, which according to my rules of weather (that are followed nowhere but in Camelot) should not happen in September. I do not like hot weather. I prefer moderation in many things, weather being but one, and my numerous friends in Dallas have had my sympathies this summer as they have endured absurdly long stretches of 100-degree (and even 110-degree) days.
In the midst of winter, when there is a southward movement of an arctic air mass, there are inevitable jokes about global warming. I didn't hear any of those this summer. But I am always bemused when people confuse weather (a short-term phenomenon) with climate (a long-term phenomenon). If you'll allow a medical analogy, it's similar to the folks who come to the emergency department panic-stricken over high blood pressure readings, apparently unaware that high blood pressure has its harmful effects over years or decades, not days or weeks.
Having been educated as a scientist, I am fascinated by all sciences, not only the life sciences and human medicine. And so the studies in climate science published in recent decades have drawn my attention, even though my background in that area is rather thin. But the most striking thing about climate science is how politically charged it has been. I love to blame things on Al Gore, because I thought it was rude of him to heave deep sighs and roll his eyes while George W. Bush was answering questions in debate, and so I will do it now. In his 1992 book Earth in the Balance Gore advocated the death of the internal combustion engine. Nineteen years later I find myself inclined to agree with him, as you will soon see, but in 1992 this was a much less popular view, and Gore was labeled by those who disagreed as a left-wing, loony, tree-hugging environmental whacko. An unfair characterization, perhaps, but he does not help himself when he intones, in his preachy manner, that "the planet has a fever."
So what do we know? Based on what I've read, I think we know there is a warming trend in global climate. We have some idea how this warming trend compares with others in the planet's history, and here is the first place where I find significant disagreement, between those who say the current warming trend is faster and of greater magnitude than seen in any prior era and those who say we lack robust data to substantiate that thesis.
Once we accept the evidence that there is a warming trend, and allow the possibility (albeit uncertain) that it may be more pronounced than any previous such trends, the next question is what is causing it. Here, I think, is where we venture into opinion that often seems far more political than scientific. Our planet's history includes many previous warming and cooling trends, and we have some rough ideas about what causes them. And there is some reason to believe that human activity, especially since the industrial revolution, may be contributing to warming. It is the magnitude of our contribution that is quite controversial. Debates over this are intense, vociferous, and political. At times they are imbued with religious fervor from all sides. Interestingly, both sides invoke the notion of hubristic arrogance. From the minimizers comes the idea that it is supremely and presumptuously human-centric to think that we could be doing anything that would have a large effect on the planet and its natural trends. From the other side we hear that it is supremely and presumptuously human-centric to think we can do whatever we want without dire consequences.
(This echoes the debate over disappearance of species, in which one side blames the human race and the other side says speciation is a dynamic process in which species appear and disappear all the time, so don't sweat it. I'm pretty sure those who blame humans have a point here.)
Scientists have constructed sophisticated computer models that take the evidence we have and use it to predict future climatic events based on established trends and using various assumptions of human activity. Some of these models tell us we are burning fossil fuels and generating greenhouse gases, thereby contributing very substantially to the global warming trend. They tell us further that if we don't alter this behavior very dramatically and very soon, the warming trend will accelerate and become self-propagating and doom all life on the planet (except cockroaches, which it always seems will survive any doomsday scenario ever created).
I realize computer models for climate are very different from those for predicting the weather, but the accuracy of weather forecasts doesn't give me much confidence. For example, predictions of the effects of Hurricane Irene on New England last weekend were wildly inaccurate.
However, as an avid student of the history of science, I am more interested (as regular readers already know) in how convinced we are of things that later turn out to be completely wrong. I have written about this in medicine, and astronomy provides some even more striking examples. One of the most famous - and one of my favorites - is the mathematical model developed by Ptolemy, who lived nearly two thousand years ago, that supported the view of an earth-centric universe.
When one constructs a theory, it should do two things. First, it should be consistent with all available observations (empiric data). Second, it should predict all future observations. Ptolemy's remarkably complex theory was consistent with all contemporary astronomical observations, and it placed Earth at the center of the universe. As that was what people wanted to believe, his theory was readily embraced. But over a period of several centuries, as astronomical observations accumulated - and became increasingly precise, thanks to ever-improving telescopes - the weight of evidence eventually proved Ptolemy wrong.
A mere few decades ago, scientists (they weren't called climate scientists yet) were convinced of the coming - within a century - of another ice age. An intense cooling trend was anticipated, and there was much discussion of ways of modifying it, including spreading some sort of dark material (such as volcanic ash) over the north polar ice cap to absorb more of the sun's energy and thereby counter the cooling.
Sophisticated computer models didn't exist in the 70s, and we have a good deal more historic climate data now than we did then. But what we "know" now is nevertheless diametrically opposed to what we "knew" 35 years ago. And so I find myself wondering what we will "know" 35 years from now.
Yet I agree with Al Gore about the internal combustion engine. I believe we should stop burning fossil fuels for energy, regardless of what we believe about global warming or its causes. The simple fact is that we are going to run out of fossil fuels. The best data I've seen tell me we are on the downslope of global production of oil (past the peak, that is), at a time when global consumption is still on the rise, and that upslope is getting steeper. Yes, we have coal and natural gas, and we will surely find ways to extract more oil from the earth than we have in proven reserves. But we need petroleum for other things (think plastics and other polymers), and future generations will take a very dim view of our behavior if we burn up most of it for energy instead of finding renewable resources and saving the petroleum for them.
No comments:
Post a Comment