Comments on: What is That Threshold?

By: Phil Hays

Phil Hays — Fri, 04 Dec 2009 18:29:49 +0000

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.

By: Mike

Mike — Wed, 02 Dec 2009 18:41:12 +0000

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%.

By: Mark

Mark — Tue, 01 Dec 2009 01:57:08 +0000

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.