IN THE not-too-distant past, the tobacco industry funded scientists who raised the shadow of a doubt that the shadows on people’s lungs were cancers caused by smoking. There were other causes, they said. And many people who wanted to believe them did, kept smoking, and died. Today those who don’t want to believe that climate change is caused by human activities keep saying there’s no consensus among scientists. Well, that’s just not true. It’s been proven again and again that a great majority of scientists have concluded there is a causal connection between human activity and global warming. Now the journal Environmental Research Letters has published a careful new study of thousands of peer-reviewed papers showing that when scientists take a position on the issue, a full 97 percent blame human causes. This is important because press reports that cite doubters representing “the other side of the question,” without saying how minuscule the proportion, have convinced the public there’s an even split. There are many issues on which scientists really do disagree, like the specific link, or lack of it, between global warming and killer tornadoes. But about the general cause of the warming itself, there’s barely any dissent at all.