I've been carrying on somewhat reluctantly an extended argument for some time with a non-scientist friend of mine, who happens to be a skeptic regarding anthropogenic (i.e., human-caused) global warming (AGW). He's a very smart person and is quite passionate in his belief that AGW is some sort of scandalous conspiracy perpetrated by, among others, the majority of global climate change scientists. He's constantly bombarding me with the little nuggets he searches out on the Web that seem to support his position and challenging me to enter into this argument. For the most part, I prefer not to get sucked into such arguments, largely because I see them as a waste of time (see my discussion of civility in discourse). But like a stone in your shoe, sometimes you just have to respond. I've touched on the AGW topic in other blogs and essays, of course.
The latest thing to stir him up has been the rather intemperate remarks by Dr. James Hansen (head of NASA's Goddard Institute for Space Science), who was paraphrased by the Washington Times:
According to Mr. Hansen, compared to China, we are "the barbarians" with a "fossil-money- 'democracy' that now rules the roost," making it impossible to legislate effectively on climate change. Unlike us, the Chinese are enlightened, unfettered by pesky elections.
Democracies are infamous for being a poor and inefficient form of government. However, democracy is widely accepted by many of us (including me) as being better than any other known form of government. I'm certainly no fan of the current Chinese government - it's an oligarchical Communist autocracy coupled to corporate greed. However, pure majority rule is something the so-called founding fathers of the US feared, because the majority can be convinced easily to trample on the rights of minorities, which is the main reason for the Bill of Rights. The public apparently can be led down paths that might not be very good for their societies, and what is right and best for a society may not be popular enough at a given time to carry the day. I'm sure if the German public had been allowed to vote in 1914 when they were on the brink of WWI, they would have voted heavily in favor of the coming war. WWI turned out to be disastrous for them, of course.
Who knows what's best for a society? That can be a tough question. Opinions will vary but, to my knowledge, no one can be certain. When it comes to scientific issues, though, it seems logical to me to trust the scientists who study those topics. Science, like anything else done by humans, is not perfect. Individual scientists can stray from scientific ethics in disturbing ways (see here and here for examples). And consensus science is not inevitably correct (more on that later). Nevertheless (not unlike democracy), science is the best we have, in this case to answer questions regarding the natural world and how it affects society. We choose to disregard what science has to offer at our peril.
Hence, I think I understand Dr. Hansen's remarks as being a reflection of his passion about trying to do something substantial about AGW in the face of all the vocal and influential opposition marshaled by those who have something to lose if something is done to mitigate AGW. No doubt Dr. Hansen's comments will be spun by right-wing media "pundits" (who speak for and also influence the position of many political conservatives) as Dr. Hansen advocating Communism, of course. It wouldn't surprise me if his remarks will become the catalyst for a witch hunt aimed at removing him from his Federal position!
What bothers me most about all of this is the continuing powerful influence of people who are not global change scientists in the public discourse about AGW. The scientific debate on AGW is effectively over, at least for the moment - the vast majority of climate change scientists have accepted the consensus position represented by the IPCC Reports. I'm not going to discuss the particulars of that debate in this blog, but if science is to be the basis for making public policy decisions in certain situations, the scientific part of the AGW argument is no longer in much doubt.
What puzzles me is how AGW skeptics who are non-participants in global climate science have so much to say and have so much influence on the AGW public policy debate. From the point of view of a democracy, they're simply exercising their right to take a position favoring their own interests. They're equal to anyone in regard to the functioning of a democracy. No responsible scientist truly wants to take that right away, but when the continuing debate hampers efforts to mitigate a serious danger to our society's well-being, it's understandable how some scientists could become frustrated enough to make intemperate remarks. On the scientific side, the playing ground is far from level; it's highly tilted one way by the preponderance of evidence and our current understanding of how the atmosphere works. Those skeptics who aren't global climate change scientists are not equal partners in the scientific debate, regardless of their equality in a political debate!
The skeptics generally have chosen not to present their views in scientific journals or at scientific conferences where their peers can judge the validity of their evidence - that is, the appropriate venues for a scientific debate. Rather, some of them loudly proclaim themselves in the media to be the victims of a vast conspiracy to silence their point of view and routinely impugn the motives of the vast majority of climate change scientists. They represent the IPCC reports as political propaganda for a left-wing conspiracy to destroy capitalism (or whatever). In fact, their tactics are precisely those of a politician trying to stir up public support by using propaganda on behalf of the self-interests of the skeptics. I know of no global change scientists who are enriching themselves by doing their science (although I don't know them all), but I certainly can see the hand of powerful corporate interests behind the brouhaha associated with AGW skeptics. Some of them may be getting support from corporations who have a pecuniary interest in the outcome of the debate over public policy. Remember the scientists who proclaimed in the media that no one had 'proven' a connection between smoking and health?
Science is not inherently democratic. Scientific issues are not decided by majority vote, but on the basis of evidence. The consensus (i.e., the majority) interpretation of that evidence can be wrong, of course. In fact, it has been wrong about some things in the past, is wrong about some things now, and will be wrong about some things again in the future. But this is the way science works! Don't be asking for definitive "scientific proof"! Science never provides absolute "proof" of anything. New ideas replace the old ones in science all the time by a well-established process that is described loosely by the 'scientific method' phrase.
The current situation regarding the AGW debate isn't a scientific argument at all - that's been settled, for the time being, as already noted - rather, it's been transformed into a political conflict. It's about winning the hearts and minds of the American public. If science is supposed to be the basis for deciding public policy issues that involve science, then this endless back and forth is simply using up precious time, delaying meaningful responses to what has been established by science to be a problem. I can see how Dr. Hansen might wish to command American society to start moving toward mitigation of AGW, but I don't agree with allowing scientists become our society's oligarchical dictatorship. I don't seek that power and don't believe any scientist should. However frustrating it might be, grasping for the power to move society in directions we want it to go is not about science - it's ultimately only about power. That's what many of the skeptics are seeking, it seems to me, since they're not engaged in the scientific process.
Wednesday, January 19, 2011
Sunday, January 16, 2011
Scientific "proof"?
I've had many occasions to take issue with the notion of scientific "proof" and how that notion is understood by non-scientists. In particular, non-scientists have trouble accepting that scientific proof is, in fact, impossible!
Perhaps if one thinks back to one's happy days learning geometry in high school, the notion of mathematical "proof" will be recalled with fond memories! Or perhaps not. In any case, in mathematics, "proof" of a theorem is accomplished when one follows the laws of mathematical logic, beginning with some premise, say X, and then asserting that Y follows from X. If that theorem can be shown to be derivable from the axioms of the mathematical system in question (e.g., Euclidean geometric axioms) according to the laws of mathematical logic, proof is obtained. Once established, a proof cannot be contravened. No one disputes the Pythagorean Theorem of Euclidean geometry, for instance. Once proven, it remains proven for all time. There might be a different proof that's more "elegant" in some way, but the theorem has been established beyond doubt in any case. You can dispute the premises associated with a theorem (theorems typically involve an "if X, then Y" statement, so X might be disputed, but if you grant X, then a proof of the theorem makes Y inevitable), or you might see that in a different axiom system, that proof isn't valid, but within the constraints of the exercise, there can be no further dispute regarding that theorem. A proof in mathematics is forever, and has no qualifications whatsoever, other than the aforementioned possibilities: dispute the premise or consider a different set of axioms.
What about science? Many people believe that such a thing as "scientific proof" exists. For instance, one might argue that the Law of Gravity has been proven beyond any question. A large number of experiments (and common experience) suggests that it might be very difficult to come up with an example where the Law of Gravity has been shown to be invalid. However, "absolute proof" is tricky. No number of experiments can ever establish absolute proof, although they certainly can make a compelling case for those scientific hypotheses that survive a large number of rigorous experimental tests. Nevertheless, from a purely logical standpoint, it might be the case that we simply haven't done the right experiments to test the hypothesis in question adequately. In fact, it's impossible to "prove" that no experiment exists that would be capable of invalidating any scientific hypothesis. So we are entitled in certain cases to behave as if absolute proof has been obtained, since the hypotheses in question have survived some tough tests, but we must submit to the logical possibility that a counter-example might someday be found, even though we have yet to find any.
Scientific hypotheses are always provisional and can never be subjected to absolute proof! Einstein has, in fact, created a new version of the Law of Gravity that differs in very interesting and subtle ways from that first formulated by Isaac Newton. Thus, in this sense, Newton's Law of Gravity has been "disproven" and replaced by Einstein's Law of Gravity, even though for centuries no one ever dreamed of looking at the circumstances associated with what Einstein figured out regarding gravity. So far, Einstein's version has survived every test, as did Newton's version for centuries. There can be no logical guarantees for Einstein's version, however. Our understanding of gravity is limited and our hypotheses about it are always subject to re-examination, new tests, and possible revision. The putative Law of Gravity has nothing like the rock-solid standing of the Pythagorean Theorem, and never will.
It's the very nature of the scientific enterprise that we test our ideas against evidence. This is the fundamental basis of the so-called "scientific method." There is no simple formulaic way to describe the "scientific method," however. Hypothesis testing is dependent on the nature of the evidence available to use to test our ideas, and is a source for considerable creativity in science. It is by no means a simple algorithm to be applied to all scientific ideas. In some sciences (including meteorology, geology, and astronomy), it's impossible to run controlled experiments to test our ideas. Hence, such sciences depend on how to use and interpret whatever observational evidence is available, rather than running tightly controlled experiments (as in a laboratory). This doesn't diminish the scientific standing of those disciplines, however. They just have to be more creative in how to test their ideas and more cautious in their interpretations of the results of their tests.
To the extent that we can conduct experiments that can give our ideas a rigorous test, we can have some faith in accepting our current understanding as "not yet invalidated" hypotheses. But no scientific experiments can provide the sort of logical inevitability that mathematical logic offers. "Scientific proof" is not a valid understanding of how science actually works!
Hence, whenever you hear someone talk of "scientific proof," you can be assured that this person has an incorrect understanding of science!
Perhaps if one thinks back to one's happy days learning geometry in high school, the notion of mathematical "proof" will be recalled with fond memories! Or perhaps not. In any case, in mathematics, "proof" of a theorem is accomplished when one follows the laws of mathematical logic, beginning with some premise, say X, and then asserting that Y follows from X. If that theorem can be shown to be derivable from the axioms of the mathematical system in question (e.g., Euclidean geometric axioms) according to the laws of mathematical logic, proof is obtained. Once established, a proof cannot be contravened. No one disputes the Pythagorean Theorem of Euclidean geometry, for instance. Once proven, it remains proven for all time. There might be a different proof that's more "elegant" in some way, but the theorem has been established beyond doubt in any case. You can dispute the premises associated with a theorem (theorems typically involve an "if X, then Y" statement, so X might be disputed, but if you grant X, then a proof of the theorem makes Y inevitable), or you might see that in a different axiom system, that proof isn't valid, but within the constraints of the exercise, there can be no further dispute regarding that theorem. A proof in mathematics is forever, and has no qualifications whatsoever, other than the aforementioned possibilities: dispute the premise or consider a different set of axioms.
What about science? Many people believe that such a thing as "scientific proof" exists. For instance, one might argue that the Law of Gravity has been proven beyond any question. A large number of experiments (and common experience) suggests that it might be very difficult to come up with an example where the Law of Gravity has been shown to be invalid. However, "absolute proof" is tricky. No number of experiments can ever establish absolute proof, although they certainly can make a compelling case for those scientific hypotheses that survive a large number of rigorous experimental tests. Nevertheless, from a purely logical standpoint, it might be the case that we simply haven't done the right experiments to test the hypothesis in question adequately. In fact, it's impossible to "prove" that no experiment exists that would be capable of invalidating any scientific hypothesis. So we are entitled in certain cases to behave as if absolute proof has been obtained, since the hypotheses in question have survived some tough tests, but we must submit to the logical possibility that a counter-example might someday be found, even though we have yet to find any.
Scientific hypotheses are always provisional and can never be subjected to absolute proof! Einstein has, in fact, created a new version of the Law of Gravity that differs in very interesting and subtle ways from that first formulated by Isaac Newton. Thus, in this sense, Newton's Law of Gravity has been "disproven" and replaced by Einstein's Law of Gravity, even though for centuries no one ever dreamed of looking at the circumstances associated with what Einstein figured out regarding gravity. So far, Einstein's version has survived every test, as did Newton's version for centuries. There can be no logical guarantees for Einstein's version, however. Our understanding of gravity is limited and our hypotheses about it are always subject to re-examination, new tests, and possible revision. The putative Law of Gravity has nothing like the rock-solid standing of the Pythagorean Theorem, and never will.
It's the very nature of the scientific enterprise that we test our ideas against evidence. This is the fundamental basis of the so-called "scientific method." There is no simple formulaic way to describe the "scientific method," however. Hypothesis testing is dependent on the nature of the evidence available to use to test our ideas, and is a source for considerable creativity in science. It is by no means a simple algorithm to be applied to all scientific ideas. In some sciences (including meteorology, geology, and astronomy), it's impossible to run controlled experiments to test our ideas. Hence, such sciences depend on how to use and interpret whatever observational evidence is available, rather than running tightly controlled experiments (as in a laboratory). This doesn't diminish the scientific standing of those disciplines, however. They just have to be more creative in how to test their ideas and more cautious in their interpretations of the results of their tests.
To the extent that we can conduct experiments that can give our ideas a rigorous test, we can have some faith in accepting our current understanding as "not yet invalidated" hypotheses. But no scientific experiments can provide the sort of logical inevitability that mathematical logic offers. "Scientific proof" is not a valid understanding of how science actually works!
Hence, whenever you hear someone talk of "scientific proof," you can be assured that this person has an incorrect understanding of science!
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