The Fifth Intergovernmental Panel on Climate Change report states that it is 95 percent certain that humans are the main cause of global warming.
The 95 percent confidence level reported in the IPCC document is surprising, because it is extraordinarily high. Climate scientists asked about the confidence level say that they are about as certain that global warming is a man-made condition as they are that smoking cigarettes causes cancer, and more sure about the human cause of global warming than they are that vitamins are good for you or that dioxin is dangerous. In fact, the climate scientists say that one of the few things that they consider to be more certain than human-caused climate change is the existence of gravity. One scientist is quoted as saying that climate change “is not as sure as if you drop a stone it will hit the Earth,” and adds that “It’s not certain, but it’s close.”
There remains, however, a huge discrepancy between the scientific view of global warming and skepticism on the part of significant portions of the American public about the concept. A recent poll showed that less than half of Americans believe that climate change is real and caused by humans — and that number seems to be declining, even as scientific certainty apparently is increasing.
Why is this so? Some people suspect that there are just a lot of scientifically illiterate Americans out there. I think that may be part of the answer, but there may be other motivating factors. I think some Americans, at least, have grown increasingly suspicious of academics generally and believe that science has become increasingly politicized. Still others argue that weather systems are extraordinarily complex, that the Earth’s climate has changed countless times over the course of planetary history, and that it takes enormous hubris for scientists to believe they can determine what influences the Earth’s climate.
It will be interesting to see whether the latest IPCC report moves public opinion one way or the other. One thing is clear: if politicians want to take expensive or disruptive action on the ground that climate change is an impending disaster, they had better figure out how to first convince the American people that the problem truly exists.