"No theory is carved in stone. Science is merciless when it comes to testing all theories over and over, at any time, in any place. Unlike religion or politics, science is ultimately decided by experiments, done repeatedly in every form. There are no sacred cows. In science, 100 authorities count for nothing. Experiment counts for everything." Michio Kaku, a professor of theoretical physics at City College of New York, writing in the Wall Street Journal about the slim but real possibility that a recent experiment at CERN has caught neutrinos moving faster than Einstein's famous theory of relativity says they are able to.
What about the theory of anthropogenic (human-caused) global warning? What would happen to Dr. Kaku's career if he were writing about the possibility of that being upset despite the current "consensus" of experts? Bill Clinton recently said "If you're an American, the best thing you can do is to make it politically unacceptable for people to engage in denial [of anthropogenic global warming]." Context makes it clear that Clinton considers skepticism to be denial; it's not! Well, as Kaku said, there's a difference between politics and science.
See below for an account of another experiment at CERN which may be more threatening to the theory of anthropogenic warming than the neutrino experiment is to Einstein's speed limit.
Before Einstein postulated the theory of relativity, scientists believed that mass and time were constants and in the Newtonian physics which predicted that, if you continuously apply a force to an object, it will accelerate without limit. Einstein said that, as the object approached what he said was the constant and inviolable speed of light in a vacuum, time would slow down from the object's point of view and the mass of the object would increase from the point of view of an observer who is stationary with respect to the object's initial position.
Physicists did not rush to embrace this strange view of the world, especially given Einstein's poor academic credentials. However, Einstein used his theory both to explain observed anomalies in the orbit of Mercury, which were not explicable with Newtonian physics, and to make some detailed predictions about light bending in the presence of a gravitational force. This prediction was confirmed during a solar eclipse in 1919.
Although these observations disproved Newtonian physics, they didn't "prove" Einstein's theory of general relativity. An accumulation of experiments and observations indicated that general relativity is a more useful way to explain how the universe acts in extreme conditions than Newtonian physics. Kaku says Einstein "quipped that you don't need 100 famous intellectuals to disprove his theory. All you need is one simple fact." Perhaps the CERN experiment has uncovered that fact, probably not but perhaps. And scientists are reacting as they should: poring over the data, looking for experimental error, devising more experiments to confirm or invalidate the CERN experiment, and remaining skeptical but open to possibilities.
It is probably true that human activity – specifically the release of large amounts of carbon dioxide – has some effect on climate. Although there are many theories, we don't know how significant that effect is. It's unscientific to deny the POSSIBILTY that the effect is significant; but it's equally unscientific to deny the POSSIBILITY that we are not affecting the climate significantly. Even the extent of warming – independent of cause – is debatable and ought to debated.
So does global warming exist at all? Depends on your timescale. Twelve thousand years ago there was a mile of ice covering the spot in Vermont where I'm writing. It's gotten warmer since then. On the other hand, the planet spent most of its history being hotter than it is now. It's cooled off periodically during glacial ages like the one which we live in. There is evidence that it's warmed some, not a lot, since the beginning of the industrial age. But even that evidence is – and should be – subject to question since our ways of measuring the temperature of the earth have changed a lot recently and don't go back very far. For example, arctic ice is at a "record" low; but the record keeping has changed completely since we've had satellites to measure the extent of the ice. In 1906 a wooden ship transited the Northwest Passage; we know the ice cap retreated then, too; but we have no direct comparison.
There have been lots of temperature oscillations and there is an apparent correlation between them and the amount of CO2 in the atmosphere. Now is the only time we as a species could have had any influence; the increase in CO2 could be an effect of the warming rather than the cause; there could be a positive feedback loop between the two. Obviously there are other factors besides human activity which affect climate. It is critical that we understand the interplay between these factors and their relative significance so we can gauge how much of an effect our emissions are having. That investigation must be pursued with an open mind – which means a skeptical mind.
Theories are strengthened (not proved) when they both explain past events and accurately predict future events. The theory of anthropogenic global warming has so far not been impressive in either respect. It is one possible explanation for a recent warming trend; but it gives no guidance as far as the temperature changes and oscillations which clearly occurred before we burned any fossil fuels. In the last decade, even proponents of anthropogenic global warming concede that, although the concentration of CO2 in the atmosphere has continued to increase, the observed rate of warming has slowed by 50%. This observation invalidates some of the most extreme models of global warming although it doesn't refute the thesis that, over longer periods of time, increases in greenhouse gasses will lead to higher temperatures. Global warming was supposed to lead to droughts; recently more of the world seems to be suffering from flooding than droughts. Does that prove that all theories of global warming are wrong? No, but it shows that the climate is more complex than the models which predicted the droughts… or that those models are simply wrong. No matter how many scientists say that they are "convinced" that anthropogenic global warming is a fact, it is still a theory which, for credibility, needs to make accurate predictions. On the other hand, there is no proof that we are not forcing the climate warmer.
Coincidentally, the results of another experiment at CERN called CLOUD may be more threatening to the theory of anthropogenic global warming than the neutrinos are to the general theory of relativity. It was recently demonstrated that the same particles which are present in cosmic rays lead to cloud formation in lab conditions. The experiment was actually designed to disprove a suspected link between cosmic rays and clouds (good way to design an experiment), but, instead demonstrated that the link is quite credible (but didn't prove it exists). The cloudier the earth is, the cooler it gets since clouds reflect sunlight back into space. Everything being equal, which it certainly isn't, the more cosmic rays that reach our atmosphere, the cloudier and cooler it'll be. It's also known from observation that the solar wind (a stream of particles from the sun) pushes cosmic rays away. The amount of solar wind varies with storms on the sun's surface (sunspots). There seems to be a correlation between sunspot activity and average temperatures; but, until now, there hasn't been a demonstration of a mechanism to explain that correlation. It could be that the temperature of the earth is much more significantly affected by sunspot activity than by human activity. Coincidence or not, the recent deceleration of warming has coincided with a decrease in sunspot activity. Note that this experiment is not nearly sufficient by itself to establish the relative contribution of sunspot activity to climate – or even whether it is significant.
At least in short term, it's much more important for us to understand the mechanisms behind climate change (acknowledging that climate is something that does change) than it is for us to know whether the speed of light is always a constraint. If CO2 emissions are causing rapid climate change, then we need to start a crash program of building nuclear power plants, fracking for relatively low carbon natural gas, and investing billions in clean technologies for abundant coal and CO2 sequestration. Knowing the emergent demand for cheap energy of the developing world, we can't just tinker around the edge of supply with expensive alternative sources – even though we want to keep doing research into making them more effective. If manmade warming is not significant but the climate is warming and likely to continue to warm for other reasons, then we can continue to use our abundant supplies of coal and should do more to reclaim gas and oil. In that case the money which would have gone into developing and deploying low-carbon energy sources will be needed to protect or relocate low-lying populations and deal with climate-induced catastrophes. If the climate is just oscillating (for the moment), then we can use low cost energy to improve standards of living around the world – including creating jobs here at home.
These are huge decisions and we need science to be at its skeptical best in helping us make them. We likely will have to act on incomplete information since theories are much easier to disprove than prove. But we don't have to act on politically-tainted information. Funding for CLOUD was hard to come by –and long delayed. Apparently for reasons of political correctness, CERN was even more circumspect in announcing the results of CLOUD than it was announcing the speeding neutrinos. Press coverage of CLOUD dwindled after a day or two. There haven't been a rush of announcements from labs seeking to duplicate or disprove the CLOUD work – or even to extend it. If you think global warming is a threat, you ought to be adamant that we increase research into its cause – no matter where that research may lead.