In WSJ, Ridley presents medley of long-debunked climate claims

In the Wall Street Journal, Matt Ridley has made yet another attempt to convince the public that global warming won’t be that bad. The facts just don’t align with Ridley’s portrayal.

[Updated September 14 8:40 p.m.]

The following is a guest post by Climate Nexus. (Text of post in PDF format here.)

In WSJ, Ridley Presents Medley of Long-Debunked Climate Claims

In the Wall Street Journal, Matt Ridley has made yet another attempt to convince the public that global warming won’t be that bad. This time he claims the Intergovernmental Panel on Climate Change, in its forthcoming Fifth Assessment Report (AR5), is going to reduce its estimate of future warming. He also claims the warming we will experience is likely to be beneficial. He ties this to the IPCC’s estimate of climate sensitivity — the amount the world will warm with each doubling of CO₂ concentration in the atmosphere (see an FAQ on climate sensitivity here). The facts just don’t align with Ridley’s portrayal. In reality:

• Sensitivity is very likely to be higher than Ridley’s suggestion (based on only two studies, one from 1937) of 1.6º C.
• Even a low sensitivity would mean bad news for our climate on our current, business-as-usual emissions track.
• The benefits of CO₂ that Ridley cites are wildly overstated.

Ridley’s quoted estimate is only one of a great many estimates of climate sensitivity that prompted the IPCC Fourth Assessment Report (AR4) in 2007 to give us a range of likely values from 2-4.5º C. New research indicates that the IPCC may indeed reduce the lower bound of this range to 1.5º C — but that would mean that a value of 1.5º C is possible, not that it is likely. In fact the other end of the range, at 4.5º C, remains just as likely, and would produce disastrous consequences.

If by some extreme twist of good fortune the climate sensitivity ends up at only 1.5º C, we’re not out of the woods. 1.5º C is the amount of warming projected with a doubling of CO₂, but under current emissions trends, CO₂ levels are on track to go well beyond doubling. In fact, under the IPCC’s unmitigated emissions scenario, CO₂ levels will reach almost 1000ppm by the end of the century, more than tripling the pre-industrial level. This would send us into the 4º C warmer world of which the World Bank paints a bleak picture in a comprehensive report.

Now, exact timing of this catastrophe might vary. Ridley mentions transient climate sensitivity, or TCS, which is the amount of warming that happens immediately with each doubling of CO₂ (as opposed to eventually at equilibrium). If TCS is 1º C as in Ridley’s best-case scenario, then 1000ppm won’t immediately put us quite at 4º C. But we will be committed to that warming and more. Arguing about whether this catastrophic outcome will arrive a bit sooner or a bit later completely misses the point when we are already experiencing severe and costly impacts of climate change.

Ridley’s claims about the benefits of CO₂ are unconnected to reality. Rising nighttime temperatures hurt crop yields, and do not improve them as Ridley states. The CO₂ fertilization effect — or “greening” — that Ridley mentions, will be countered by other side effects and is unlikely to help crop yields either.

Few have suggested that below 2º C of warming the effects will be beneficial; the goal of setting that target is to avoid the most dangerous impacts of climate change, and it’s too high.

Finally, despite Ridley’s passing mention of a “warming pause,” unconnected with any other part of his argument: warming hasn’t stopped.