What is That Threshold?
And climate advocates wonder why the public is confused about global warming. Thus writes David Biello in SciAm:
Despite decades of effort, scientists do not know precisely what temperatures or greenhouse gas concentrations in the atmosphere constitute a danger.
Biello goes on to survey leading climate scientists on various threshold levels, who bascially throw up their hands, (except, of course, James Hansen). Among others quoted, Columbia University’s Wallace Broecker continues to talk about the inevitably of some frightening numbers:
We’re at 387 now and we’re going up at two ppm per year. That means 450 is only 30 years away. We’d be lucky if we could stop at 550.
The reason scientists don’t know “precisely what temperatures or greenhouse gas concentrations in the atmosphere constitute a dange” is that there is no precise level that constitutes a danger.
Try substituting some words in that sentence:
Despite decades of effort, physicians and medical scientists do not know precisely what blood pressure constitutes a danger.
Despite decades of effort, environmental scientists do not know precisely what air pollution concentration constitutes a danger.
I could go on, but I think the shallowness of the original comment is indicated.
Or what if rewrote the numbers using percentages of atmospheric volume (not including water vapor) instead of parts per million. Then it would read:
We’re at 0.000387% now and we’re going up at 0.000002% per year. That means 0.00045% is only 30 years away. We’d be lucky if we could stop at 0.00055%.
Ah yes, 0.0000000001% sure sounds tiny, but if I counted zeros correctly, that is a lethal dose of tetanus toxin. 1 nanogram per kilogram.
Of course, the effect of tetanus toxin is well known as we can poison mice. It is hard to see how we do the equivalent experiment on our climate. Or why we would want to. Or why we are.