No, I do not intend to present some other “sweeping” Climategate-like “proofs” that all those climate scientists warning since the 1960’s that human activities influence the global climate have been wrong. Quite the contrary, to date, science tells us clearly that the Earth is warming and that we are those responsible. Moreover, it tells us that it is likely to keep warming unless we do something about it, and if we do not, the consequences may be very unpleasant. So, the title question is entirely hypothetical. Nevertheless, I still find it very interesting because climate science may be wrong.
At least since Karl Popper we know that science does not provide “last answers” or “final proofs” in the literal sense of these terms. Every scientific theory, no matter how widely acknowledged and uncontroversial, may someday be unable to explain a new observation. The theory is then falsified. It can potentially be “immunized” or reformulated so as to accommodate the new observation in some way. But, and this is important to stress, every scientific theory can be falsified (indeed, this is the indispensable condition a theory has to fulfil to be called scientific – it has to be falsifiable). Not only the theory behind anthropogenic climate change, but also quantum mechanics, evolutionary biology, the Big Bang theory or any other theoretical model that deserves the name “science”.
What would be a possible falsification of the “climate change theory”? The obvious case would be if the Earth’s atmosphere would cease warming over a longer period of time (say, 50 years; shorter periods like the slowed warming of the 2000’s and 2010’s are mostly explainable by some countering phenomena, e.g., Sun activity, heat uptake by the deep oceans, the ENSO variation, anthropogenic and natural aerosols etc.) despite continued greenhouse gas emissions. Or if we would stop emitting greenhouse gases, but the Earth would continue warming over a really long period (due to climate system inertia, warming for some decades after an emissions stop is guaranteed). So, what then?
The answer to the question “What if we are wrong about global warming?” is partly dependent on what is the reality then. If the world is to continue warming no matter what we do, the answer should be different from that given in the case of the current warming being just “natural variability” of the climate (though the term “natural” is somewhat problematic here due to the unprecedented pace of the warming until now). In the former case, we would have wasted resources in mitigation efforts, cutting down fossil fuel use more quickly than public health-related reasons alone would justify. On the other hand, resources invested in adaptation would not be wasted at all. In the latter case, the degree of waste would be higher, since no particularly large investments in adaptation would be justified. Given our state of knowledge and the climate denialists’ arguments, however, the latter case could be assumed, somewhat arbitrary though, to be more probable. So, if we are wrong about global warming, we are wasting large amounts of resources, although by far not as much as we should if global warming is anthropogenic. Conversely, it would also mean, in the “natural variability” case at least, that many human lives and livelihoods would be saved compared to the “climate change is real” scenario. This is certainly a point “in favour” of being wrong after all.
This was, however, only one side of the coin. What is its other side? I would argue that the psychological effects of being wrong in this case could be dire. First of all, the credibility of science as such would be undermined deeply. In the end, scientists have been telling us for some 30-40 years that there is anthropogenic climate change, and since the beginning of the 90’s virtually everyone knows that. Most people trust the science in this regard. But if those scientists have been wrong – why should others be right? Especially if they say something we do not like to hear. Widespread science denialism and dismissal would be a typical human reaction in such a case. Which leads us to another problem. As shown impressively in the book Merchants of Doubt by Naomi Oreskes and Erik Conway, there is a huge lobby behind climate change denialists. Those people, who were also engaged in campaigns against pesticide restrictions, the science of second-hand smoking and others, are not concerned with science. They do not care about who is right and who is wrong. What they care about are economic interests. And those people, centred around a few US-American conservative think tanks, would gain a lot if we were wrong about global warming. I do not want to insinuate that all denialists or, as they mostly call themselves, sceptics are “bad”. I firmly believe that many of them just listen to the wrong people and let mislead themselves about climate science. But there are “bad” people among those denying the reality of anthropogenic global warming, and climate science’s “failure” would be their great success. And that would be a defeat to almost anybody else.
Furthermore, the reality of climate change is one of the main drivers of the sustainability movement, also leading “ordinary” people to the gradual acquisition of what may be called sustainable lifestyles. While climate change is actually only one among many reasons speaking in favour of sustainable behaviour, even not necessarily the most important one, it has certainly been the most convincing so far. Our being wrong about global warming could lead many people to the conclusion that not only global warming, but also sustainability is a “hoax”. In the long run, that could become disastrous.
If we are wrong about global warming, humanity is likely to gain (or, actually, not to lose). No climate change would mean no additional deaths from drought-induced starvation, massive floods, extreme weather events and so on. On the other hand, this would also mean that we have wasted some resources. But, as I suggested above, cutting down on fossil fuels has a lot of co-benefits, so it would not be such a big loss as, say, cutting down a rainforest in the belief that this could “save the world”. What concerns me, however, is the potential loss of credibility science and the sustainability movement would experience, and the gain in influence of the vested interests behind all the Fred Singers, Lord Moncktons, Richard Lindzens and Fred Seitzs of this world. On the balance, all the lives not-lost in the case of our being wrong would likely overweight these downsides. But, unfortunately, there is no rational reason to believe that we are wrong.
The Sceptical Economist 
The degradation of science could be avoided by simply dropping the issue without notice as with overpopulation. Rendezvous with Rama has some funny lines about that.
I guess I do not quite understand what you mean by “dropping the issue” here.
No one knows exactly how much Earth’s climate will warm due to carbon emissions, but a new study this week suggests scientists’ best predictions about global warming might be incorrect. The study, which appears in Nature Geoscience, found that climate models explain only about half of the heating that occurred during a well-documented period of rapid global warming in Earth’s ancient past. The study, which was published online today, contains an analysis of published records from a period of rapid climatic warming about 55 million years ago known as the Palaeocene-Eocene thermal maximum, or PETM.
Could you specify which publication you mean? I only found the letter by McAnena et al., which seems to deal with a different issue than what you are writing about.
These minute particles can be part of volcanic eruptions and be produced by industrial processes. Their effect on climate is complex and suspected of causing both warming and cooling. Their most spectacular effect was on the Ozone layer which protects the Earth from the sun’s worst radiation. Now professor Qing-Bin Lu, former Newcastle university student has done a comprehensive analysis of the effect of aerosols on climate.
Lu’s study has been debunked here. Aerosols are indeed important, but not in the way Lu is claiming they are.
ok. even if global warming doesn’t exist, which i think it does, why not cut down on toxic emissions? what is so bad about getting rid of polution and be more consciencious about how we effect the earth’s ecosystem? I think we all need to think about that because if now there isn’t really global warming it could happen in the future and either way you look at it what we are doing now to our planet is wrong.
Because CO2 isn’t toxic. The only reason to cut down on it is to limit climate change.
CO2 isn’t, but mining and burning fossil fuels leads to other emissions, too (mercury, sulfur…). This stuff IS toxic, and if cutting down CO2 emissions comes with the additional benefit of cutting down those emissions, there are obvious positive welfare effects. In fact, there is research in climate and energy economics showing that this is a reason why emissions trading/carbon tax needs to be complemented by technology-oriented policies (such as feed-in tariffs). See e.g. here.
I think (intuitively, and in ignorance of the evidence) that anthropogenic climate change is just a monsters under the bed story, like the heterosexual AIDS epidemic, or the Y2K computer disaster. In ten years, if global warming catastrophes don’t materialize, the whole thing is going to pass from popular consciousness. There is just no way to suppress carbon dioxide emissions without decreasing standards of living here and everywhere else, which is politically insupportable, so if we really are fomenting a worldwide climate disaster by polluting the air the disaster will be inevitable. So I don’t worry about it. Either the problem is imaginary (my true belief), or it is unsolvable.
@Ian: I am not sure what you mean by “heterosexual AIDS epidemic”, so I won’t comment on that. With regard to anthropogenic climate change’s being real – we have enough evidence. Of course, our understanding of the complex system “climate” is limited in many respects, but this only means that we cannot predict exactly what will be the pace, regional consequences etc. of global warming. We know, however, that it is real. Having said that, I am afraid that you may be right regarding our ability and willingness to actually solve the problem.