Bret Stephens, the newly appointed Op-Ed writer for the New York Times, has released his first column to much criticism. It’s a rather strawman-laden column in which he essentially argues that it’s okay to doubt climate science, and/or climate policy, because some people are too certain.
Rather than commenting on what Stephens’ article says, I thought I would – instead – point out what I think the key issue is. The figure on the right shows some recent estimates for equilibrium climate sensitivity (ECS). The ECS is essentially an indicator of how sensitive our climate is to external perturbations, which is often quantified in terms of the resulting change in global average surface temperature.
So, what does this figure tell us? Well, it tells us that there is a range for climate sensitivity from possibly quite low (< 2K) to what most would agree is very high (> 6K). What will largely determine how much we warm is how much we emit (mostly CO2). So, even if we manage to limit our total emissions, we could still warm substantially if climate sensitivity turns out to be high. Similarly, we have the potential to emit enough to produce substantial warming even if climate sensitivity is low.
There’s another factor that is often not discussed; the sensitivity of the carbon cycle itself. At the moment, the oceans and biosphere have taken up just over 50% of our emissions. We don’t expect this to continue and would expect a smaller fraction to be taken up by the natural sinks if we continue to increase our emissions. There is, however, some uncertainty and we could end with a larger increase in atmospheric CO2, for a given emission pathway, than expected. Therefore, we could still see a substantial amount of warming even if we manage to limit our emissions and climate sensitivity is low.
Of course, it could all work the other way; we could be lucky and climate sensitivity could turn out to be low and the natural sinks could continue to take up a significant fraction of our emissions. However, none of this changes that we could see substantial warming and, consequently, substantial changes to our climate. These changes will include surface warming, changes to precipitation, and changes to extreme weather events. This is on top of other factors like sea level rise, and ocean acidification. There is another factor that is also important to recognise; these changes are probably irreversible on human timescales.
What I’m trying to get at is that even if we aren’t certain as to exactly what will happen, we are certain that there is a possibility (and not a negligible one) that we could see substantial, and probably irreversible, changes to our climate if we simply continue to pump CO2 into the atmosphere. We are also not certain of the impact of these changes, but there is a clear possibility of them being severe and negative. Being dismissive of this possibility is what most people regard as now largely unacceptable, especially coming from someone who has been hired by a newspaper claiming that Truth: It’s more important now than ever.
None of the above, however, tells us what we should do, or how we should do it. There are valid debates to be had about the various policy options and also about the various technological solutions (some of which include continuing to use fossil fuels). However, such discussions are difficult if they involve people who think there isn’t really anything to discuss, because everything could be fine. The possibility of everything being fine doesn’t somehow negate the possibility of it being severe and negative, especially as the outcome will depend on what we chose to do. The irony (as I may have mentioned before) is the more that we dismiss the possibility of it being dangerous, the more we are likely to emit, and the greater the probability of it ending up being dangerous.
Ken Caldeira: Climate of Risk and Uncertainty.
Greg Laden:Out of the gate, Bret Stephens punches the hippies, says dumb things.
Sou: Bret Stephens lowers the bar for intellectual honesty and more @NYTimes.
Tamino: Cancelling the New York Times, because truth is now more important than ever.
Roger Jones: Trolling. It’s more important now than ever.