While reading a recent post on RealClimate, something that I noticed several years ago was reinforced: climate scientists are more careful at math than their detractors are. Even in a simple blog post, Ray Pierrehumbert is careful to avoid double-counting emissions. This is a nice contrast to the ‘skeptics’ who typically double-count the cost of avoiding emissions, while often not counting the costs caused by emissions. I’m thinking in particular of the skeptics who admit that humans can impact climate, but deny the severity of the issue, claiming that we should do nothing or delay action; the pure denialists are an issue for another day.
A good example of double-counting is Bjørn Lomborg’s Cool It. Lomborg’s book seemed to be based on counting the costs of addressing human-caused climate change multiple times, while creating low estimates for the costs of not addressing the problem. Pierrehumbert’s post, on the other hand, is simply about trying to accurately estimate the climate impact of exploiting oil sands, a more basic and important question. This is comparing a set of scientific numbers to a set of speculative numbers, but in either case it is important to try for accurate numbers. When basing an argument on something that can be quantified, it is important that you quantify it properly. Otherwise you weaken your argument.
If you are using numbers to support your position, be sure to take the time to use the correct numbers and calculations. Of course, for the issue of anthropogenic climate change it isn’t just a matter of finding the right numbers: the ethical and moral aspects of our damage to the earth are also important. But when done properly, the accurate numbers and correct ethical treatment will always agree. The fact that the numbers all support the current best scientific understanding of the issue provides a little extra evidence (beyond logical consistency) for those of us who see the ethical problem with causing unnecessary damage to the planet.