I’ve written before about Matt Ridley’s recent article and posed some thoughts. Although I have a number of issues with what he suggests, my main one relates to how much warming he thinks we can expect by 2100. Matt Ridley selects a particular set of results that tend to produce lower estimates than other methods, selects a single value from these analyses, and then argues that we won’t see much warming by 2100. Even though this is possible, his own preferred method does not rule out that warming could be substantially higher than he suggests.
Now, most of what he relies on is work by Nic Lewis, an independent climate scientists. Nic Lewis commented here and responded to one of my comments on Mark Lynas’s blog. In neither case did he seem willing to acknowledge that his own work suggests that warming could be substantially more – by 2100 – than Matt Ridley suggests. Instead he decided to nitpick a few minor issues, rather than addressing the broader point. Why would that be? What am I missing? If you look at Table 5 in Lewis & Curry (2014), the 5 – 95% range for TCR is 0.9 – 2.5K. If you consider the basic equation for TCR, then you can write the temperature change as
So, a 5 – 95% range of 0.9 – 25K and an RCP6.0 emission pathway ( by 2100) gives a change in temperature of between 1.5 and 4K (approximately) [Edit : As Troy points out in the comments, this is wrong. By 2100 the RCP6.0 pathway produces a change in forcing of around 5W/m^2 and so the change in temperature would be more like 1.2 – 3.3K, relative to the mid-1800s.]. Matt Ridley suggested it would probably be around 2K. So, Nic Lewis’s own work seems to suggest that we can’t rule out that it could be as high as 4K [Well, probably above 3K, but not likely as high as 4K], but neither Matt Ridley nor Nic Lewis seem willing to acknowledge this. As I said, am I missing something here?
Now, Nic Lewis gets – and should get – a lot of credit for doing research and publishing papers. It’s what a real skeptic should do. However, he is an ex-financier with links to the Global Warming Policy Foundation. His work also tends to produce results that suggest that climate change may not be as much of an issue as we otherwise might think, and which is often used to make this argument. Consequently, it’s not surprising that some might think that what motivates Nic Lewis is his ideological objection to the policy implications associated with mainstream climate science, rather than an intrinsic interest in climate science itself. Now, this may be an entirely unfair interpretation of Nic Lewis’s motives but, if so, maybe he could put a bit of effort into ensuring that it isn’t the obvious one.