A long list of National Academy of Science members, including several Nobel Prize winners, have published a letter in Science supporting the idea that humans have caused/will cause serious global warming. The letter is striking in several ways — how preachy it is, how it overstates its case, how it fails to provide evidence, and how it ignores the main arguments of skeptics (at least, intelligent skeptics).
All citizens should understand some basic scientific facts. There is always some uncertainty associated with scientific conclusions; science never absolutely proves anything. When someone says that society should wait until scientists are absolutely certain before taking any action, it is the same as saying society should never take action.
“Citizens”, huh? This might interest third-graders; if they think that the brighter skeptics or most readers of Science don’t know these “basic scientific facts” they are mistaken.
The letter goes on to claim that the idea that humans are seriously warming the planet is as well established — at least, in the same category of firmly-established theories — as the conclusion that “today’s organisms evolved from ones living in the past”. That is an overstatement.
And the letter ends with hand-waving. In place of evidence that supports what they claim, they simply repeat the claims in detail (e.g., “Natural causes always play a role in changing Earth’s climate, but are now being overwhelmed by human-induced changes”).
The letter is unintentionally revealing. Here’s what I would consider reasonable evidence for serious human-generated global warming:
- Temperature higher now than in the past.
- Temperature increasing at a higher rate now than in the past.
- Good (= verified) model shows serious human-generated warming.
No. 1 isn’t clearly true; the Medieval Warm Period appears to be as warm as now. (Mann et al. understood this point; they tried to diminish the Medieval Warm Period.) No. 2 isn’t clearly true. For example, the 1930s may have been as warm as recent decades. No. 3 isn’t true. Models such as Hansen’s haven’t been shown to predict correctly. There’s no reason to take them seriously.
So No. 3 is off the table (current models are untrustworthy). That leaves Nos. 1 and 2, the failure of which to be clearly true points in the direction of no serious human-generated warming. If a theory makes two predictions, both of which appear wrong, it would be wise to start doubting the theory rather than lecture the rest of us on “basic scientific facts”.
This line of reasoning (ask whether the humans-have-caused-serious-warming idea makes correct predictions) isn’t complicated or obscure but does require you think for yourself rather than accept what you’re told. Apparently no one in this long list of distinguished scientists has done so.
If a letter from 100 United States Senators was full of spelling and grammar errors, would you trust it? Well, no . . . and you might wonder about a world with such a poorly-educated ruling class.