Do “90% of the scientists” believe in anthropogenic global warming? “Climate change” is a meaningless term; the climate is always changing. “Global warming” is also meaningless in a policy sense, as warming due to natural changes can’t be reversed by political policy. I have seen plenty of claims of “consensus” on AGW, but I’ve never seen anyone claim that agreement on AGW totals to 90% of all scientists, or even all climate scientists.
The better evaluation is whether the modeling for the claims of AGW bear out in terms of data. On that score, the answer is an emphatic no, as one former AGW theorist discovered. Bruce McQuain wrote about David Evans last weekend and his conversion to AGW skepticism:
This is the core idea of every official climate model: For each bit of warming due to carbon dioxide, they claim it ends up causing three bits of warming due to the extra moist air. The climate models amplify the carbon dioxide warming by a factor of three — so two-thirds of their projected warming is due to extra moist air (and other factors); only one-third is due to extra carbon dioxide.
That’s the core of the issue. All the disagreements and misunderstandings spring from this. The alarmist case is based on this guess about moisture in the atmosphere, and there is simply no evidence for the amplification that is at the core of their alarmism.
What did they find when they tried to prove this theory?
Weather balloons had been measuring the atmosphere since the 1960s, many thousands of them every year. The climate models all predict that as the planet warms, a hot spot of moist air will develop over the tropics about 10 kilometres up, as the layer of moist air expands upwards into the cool dry air above. During the warming of the late 1970s, ’80s and ’90s, the weather balloons found no hot spot. None at all. Not even a small one. This evidence proves that the climate models are fundamentally flawed, that they greatly overestimate the temperature increases due to carbon dioxide.
This evidence first became clear around the mid-1990s.