A few months ago a friend of mine engaged me in a discussion about the controversy surrounding global warming. If you are surprised to hear that there is still controversy, read on; I was equally surprised.
The controversy is not so much whether the atmosphere is heating up, but rather the cause and projected magnitude. As anyone familiar with modeling complex systems understands, the time horizon for accurate predictions is inherently short due to chaotic and otherwise complex feedback dynamics. So it shouldn’t really be a surprise to learn that climate predictions even with the most detailed and best crafted models have a hard time with accuracy in predicting more than a year out. As a consequence, it should also not be a surprise to learn that the role CO2 plays in changing global temperature — and the extent to which it does — is highly uncertain. There are good reasons why we should seek to reduce carbon emissions, but whether global warming is one of them is unclear. What struck home for me was learning that the uncertainty for a 50 year projection was plus or minus 55 degrees centigrade. This does not necessarily mean that it is possible for the atmosphere heat up or cool down by that much, but rather the models used in making temperature predictions are useless for long-range projections. And it matters not whether all the different models converge to the same prediction if the uncertainty factor (as measured by propagated error) is large for all of them. For a good overview of these arguments and the data, see Patrick Frank’s article.
Just because the prediction game is difficult and uncertain doesn’t mean we shouldn’t take action to protect against disaster scenarios. Even if we feel 99% certain that a catastrophe will not occur, we should be looking really hard at how to prevent or mitigate it in the 1%. The more dire the consequences, the harder we should try. The data is clear that global warming has been happening, nobody really refutes that anymore. Logic dictates that without further evidence to the contrary, we should assume that the atmosphere will continue to warm, at least for some period of time. The aggregate effects of global warming are also hard to predict, but at the very least we can be pretty sure that many people will die, through famine, lack of clean drinking water, disease, drowning, and a number of other factors. There are several schools of thought on how to react to this sobering situation. One is to try to reverse global warming and stabilize the temperature. Another is to mitigate the toll on life and suffering (both human and non-human). A third approach is to attempt both in some combination. Ultimately the debate over global warming is over which of these routes we should take. And the route that you advocate should depend on your belief in the certainty of the various predictions.
If you believe with high certainty that CO2 is the main culprit (this is called the “anthropogenic global warming” hypothesis or AGW for short) then it makes a lot of sense to put all your eggs into basket number one, assuming that you can have an impact in time. If you are highly certain that CO2 is not to blame, you might prefer to take the second approach, using the massive resources that would otherwise have been spent curbing emissions to instead address the more direct causes of death and suffering that will be greatly exacerbated by global warming. But given Frank’s arguments (and that of many other highly respected climatologists), it would be foolish to feel certain enough of either claim to put all your eggs into one basket. The only rational approach is to do both in some combination.
But how do we know how to spend our limited resources appropriately, especially when new data unfolds constantly which should feed into our approach and spending decisions? My skeptical friend wrote me the following email the other day, which put a smile on my face:
You know where I stand on the science here, but there are obviously strong feelings on both sides and I’m not more than 90% confident we won’t experience a catastrophic AGW outcome.
Ross McKitrick has come up with an absolutely brilliant scheme that allows each side to put its money where its mouth is. It turns out that the climate models predict a very specific AGW heat signature–with warming occurring first and foremost in the tropical troposphere. So he proposes to tie a carbon tax to temperature rises there. If AGW is true, then this tax will steadily increase. If it’s false, it will remain near zero (ignoring subsidies under global cooling) regardless of warming from other sources. Then we can all just shut up and let nature and the economy take their courses.
This is a plan I would strongly back. Hooray for clever people!
Presumably, tax revenues from this scheme could be put directly towards mitigating death and suffering, and voila, we have a self-tuning adaptive solution. The astute reader will realize though that in the event that carbon emissions are not a significant factor in global warming (but warming persists nonetheless) there is no way to pay for tragedy prevention/relief. While this is true under McKitrick’s model, there’s nothing that says we can’t as a society decide to throw carbon emissions under the gas guzzling bus (so to speak) and let the tax float with global average temperature.
Your thoughts welcome.