Addendum: two days after this post, Randi clarified:
"I do not deny that [Anthropogenic Global Warming is a] possibility. In fact, I accept it as quite probable."
Though this subject is not one that directly concerns the JREF, I'm very frequently asked if I'll turn my skeptical eye to it. As a year-end fling, I'll give it a try. To wit:
An unfortunate fact is that scientists are just as human as the rest of us, in that they are strongly influenced by the need to be accepted, to kowtow to peer opinion, and to "belong" in the scientific community. Why do I find this "unfortunate"? Because the media and the hoi polloi increasingly depend upon and accept ideas or principles that are proclaimed loudly enough by academics who are often more driven by "politically correct" survival principles than by those given them by Galileo, Newton, Einstein, and Bohr. (Granted, it's reassuring that they're listening to academics at all -- but how to tell the competent from the incompetent?) Religious and other emotional convictions drive scientists, despite what they may think their motivations are.
The Intergovernmental Panel on Climate Change (IPCC) -- a group of thousands of scientists in 194 countries around the world, and recipient of the 2007 Nobel Peace Prize -- has issued several comprehensive reports in which they indicate that they have become convinced that "global warming" is and will be seriously destructive to life as we know it, and that Man is the chief cause of it. They say that there is a consensus of scientists who believe we are headed for disaster if we do not stop burning fossil fuels, but a growing number of prominent scientists disagree. Meanwhile, some 32,000 scientists, 9,000 of them PhDs, have signed The Petition Project statement proclaiming that Man is not necessarily the chief cause of warming, that the phenomenon may not exist at all, and that, in any case, warming would not be disastrous.
Happily, science does not depend on consensus. Conclusions are either reached or not, but only after an analysis of evidence as found in nature. It's often been said that once a conclusion is reached, proper scientists set about trying to prove themselves wrong. Failing in that, they arrive at a statement that appears -- based on all available data -- to describe a limited aspect about how the world appears to work. And not all scientists are willing to follow this path. My most excellent friend Martin Gardner once asked a parapsychologist just what sort of evidence would convince him he had erred in coming to a certain conclusion. The parascientist replied that he could not imagine any such situation, thus -- in my opinion -- removing him from the ranks of the scientific discipline rather decidedly.
History supplies us with many examples where scientists were just plain wrong about certain matters, but ultimately discovered the truth through continued research. Science recovers from such situations quite well, though sometimes with minor wounds.
I strongly suspect that The Petition Project may be valid. I base this on my admittedly rudimentary knowledge of the facts about planet Earth. This ball of hot rock and salt water spins on its axis and rotates about the Sun with the expected regularity, though we're aware that lunar tides, solar wind, galactic space dust and geomagnetic storms have cooled the planet by about one centigrade degree in the past 150 years. The myriad of influences that act upon Earth are so many and so variable -- though not capricious -- that I believe we simply cannot formulate an equation into which we enter variables and come up with an answer. A living planet will continually belch, vibrate, fracture, and crumble a bit, and thus defeat an accurate equation. Please note that this my amateur opinion, based on probably insufficient data.
It appears that the Earth is warming, and has continued to warm since the last Ice Age, which ended some 10,000 to 20,000 years ago. But that has not been an even warming. Years of warming followed by years of cooling have left us just a bit warmer than before. This conclusion has been arrived at from data collected at some 1,200+ weather stations in the USA, though bear in mind that there are very few weather stations over the vast oceans that cover 70% of our planet, or on the continents Africa, South America, and especially Antarctica.
We can now record temperatures with much better than the former fraction-of-a-degree accuracy we had just a decade ago, but that temperature change appears to be just about half a degree Centigrade.
Our Earth's atmosphere is approximately 80% nitrogen, 20% oxygen. Just .04% is carbon dioxide -- a "trace" amount. But from that tiny percentage is built all the plants we have on Earth. CO2 is a natural molecule absolutely required for plant life to survive, and in the process of growing, those plants give off oxygen. We -- and all animal life -- consume that oxygen and give off CO2. (No, this is not an example of Intelligent Design.) If that balance is sufficiently disturbed, species either adapt or perish. And the world turns...
Incidentally, we have a convenient phenomenon that contributes to our survival. Doubling the amount of CO2 in our atmosphere will not double the temperature rise, small though it is. The basic principle of what's known as the "greenhouse effect" is quite simple: in a glass-enclosed environment, sunlight enters through the glass and strikes a surface, where it is transformed into longer infrared rays which do not easily reflect back through the glass; they're trapped. and raise the temperature. However, the greenhouse effect as applied to our planet is more complicated. The infrared rays that are reflected back from the Earth are trapped by the greenhouse gases, water vapor and CO2 -- a process that warms those gases and heats the Earth. This effect makes Earth habitable, preventing extremes of temperature. The limit of the influence of CO2 is dictated, not by the amount of greenhouse gases in the atmosphere, but by the amount of solar radiation reflected back from the Earth. Once all the infrared rays have been "captured" by the greenhouse gases there is no additional increase in carbon dioxide.
Yes, we produce CO2, by burning "fossil fuels" and by simply breathing. And every fossil fuel produces CO2. Some products produce more than others, varying with their chemical composition. Methane gas produces less CO2, wood produces more. But almost paradoxically, when wood burns it produces CO2, and when a tree dies and rots it produces yet more CO2. Oceans are huge storage tanks for CO2, but as they warm up, they hold less of the dissolved gas. They release it into the atmosphere, then more of it is absorbed back into the oceans. And as far as humans are concerned, ten times more people die each year from the effects of cold than die from the heat. This a hugely complex set of variables we are trying to reduce to an equation...
It's easy enough to believe that drought, floods, hurricanes, and earthquakes are signs of a coming catastrophe from global warming, but these are normal variations of any climate that we -- and other forms of life -- have survived. Earth has undergone many serious changes in climate, from the Ice Ages to periods of heavily increased plant growth from their high levels of CO2, yet the biosphere has survived. We're adaptable, stubborn, and persistent -- and we have what other life forms don't have: we can manipulate our environment. Show me an Inuit who can survive in his habitat without warm clothing... Humans will continue to infest Earth because we're smart.
In my amateur opinion, more attention to disease control, better hygienic conditions for food production and clean water supplies, as well as controlling the filth that we breathe from fossil fuel use, are problems that should distract us from fretting about baking in Global Warming. From Sir Arthur Conan Doyle's 1891 A Scandal in Bohemia, I quote:
Watson: "This is indeed a mystery," I remarked. "What do you imagine that it means?"
Holmes: I have no data yet. It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts...