Most commentators on climate change issues recognise the uncertainty attached to specific climatic forecasts. A few denialists even question the AGW hypothesis itself. Fewer scientists have commented on the irreversibility issues associated with AGW. In today's press there are reports on this latter issue - this one interestingly from FOX. Even if the smokesacks stop emitting GGEs the damages in terms of enhanced warming will persist for 1,000 years. The complete report by NOAA scientist Susan Soloman is here.
Economists have done much work analysing policy problems where there is high uncertainty as well as irreversibility. They can be modelled as optimal stopping problems.
Here one could calculate expected damages from climate change and the expected economic costs of dealing with these problems via mitigation and adaptation measures. Then, unless you are an extreme denialist, you would time an intervention to deal decisively with the problem and allocate a certain amount of resources to address the problem based on these expected value calculations.
With irreversibility calculating expected values is inappropriate. Not taking action or taking inadequate action to address the costs of climate change has more serious consequences than taking action inappropriately (too early or with an excessive use of resources) because the costs of climate change persist for very long periods due to irreversibility*. The respective benefits from taking action promptly and intensively are greater than the benefits from holding back on the response somewhat and underinvesting in the response. This asymmetrical loss of benefits provides a case for a prompter and more determined response than would be suggested by using expected values.
In short acting decisively (promptly and with significant public and private investments) to deal with climate change - and beyond levels suggested by replacing random variables by their means - makes sense if uncertainty is coupled with irreversibility. The argument is particularly strong because it does not rely on decision-maker risk aversion. With risk-aversion the argument is, of course, stronger still.
This argument is related to the economic case for managing natural resource assets such as wilderness 'conservatively'. This was originally put forward by Ken Arrow, Anthony Fisher and, in a separate argument, by Claude Henry - I discussed it 20 years ago here.
* There are 'sunk cost' irreversibilities associated with wasted-excessively early investment but these are less long-lived and less significant irreversibilities.