This is a guest post by Climate Nexus.
Judith Curry’s latest op-ed in the Wall Street Journal touts her new study co-authored with Nic Lewis. The takeaway of the piece – that the need for emissions reductions is “less urgent” than policymakers assume – is not even supported by her own study, much less the scientific mainstream.
Curry provides a highly biased and skewed overview of climate sensitivity studies, which makes sense for publication in the Wall Street Journal. In reality, the IPCC sensitivity estimate remains the most reliable and comprehensive expression of the state of knowledge on the topic, and scientists agree that this sensitivity range implies an urgent need for climate action.
- Curry’s study doesn’t reveal new information that would affect IPCC estimates.
- She examines only a small group of studies that agree with her conclusion, while the IPCC took many additional methods and factors into account.
- Even low climate sensitivities still carry an urgent need to reduce greenhouse gas pollution.
- Curry has growing ties to denier groups and her consulting business serves fossil fuel companies.
Curry’s study doesn’t reveal new information that would affect IPCC estimates. Her methodology is very similar to many previous studies, including Otto et al from 2013. The range of values her study finds for transient climate response (a measure of short-term climatic response to carbon dioxide) is nearly identical to the IPCC range, although her median value is half a degree lower than the IPCC’s. This is hardly the bombshell some would have you believe.
In her opinion piece, she references only a small set of climate studies. There are a few different ways of calculating climate sensitivity, including paleoclimate, model-based, and instrumental studies. Scientists have long known that instrumental studies tend to return the lowest values for the climate’s sensitivity to carbon dioxide. Not surprisingly, that’s the type of study the Curry and Lewis have done, and the only type Curry even acknowledges- leaving her WSJ audience in the dark about the variety of other methods. However, there is little basis for excluding the other study types.
Paleoclimate and model-based studies add value by taking hundreds of thousands of years worth of data about the climate’s distant past into account, which instrumental studies cannot do. Instrumental studies are much less complex, and some outside analysis suggests they are strongly influenced by relatively small choices in the time period from which to draw data. They assume that climate forcings will remain constant over time, which other research has found might not actually be the case.
The IPCC deals with this by taking a comprehensive look at all three methods, along with other concerns about uncertainties in measurements, assumptions, and projections. For example, one study has found that the record of average global temperature itself may be biased low due to undersampling of the Arctic. Curry takes none of this into account, yet she claims that her interpretation should take precedence over the IPCC’s.
Even low climate sensitivities still imply a need to strongly reduce greenhouse gas pollution. The author of the aforementioned Otto et al., another study that found a low transient climate response, said that his study does “not at all” support relaxing the push to cut emissions. He continued, “even with 30 per cent lower values of TCR … we would still look at significantly higher temperatures than the two degree target at the end of the century.”
Curry claims that only the highest emissions pathway would be dangerous, but by arguing to delay climate action, she works to ensure that that’s exactly the pathway we’ll end up on. Reducing the output of greenhouse gas pollution is the only way to meet this target and ensure a safe climate future. Furthermore, experts have consistently found that taking action now is cheaper and safer than waiting.
Curry has growing ties to denier groups and her consulting business serves fossil fuel companies. She recently participated in a forum held by the discredited, fossil-fuel funded George Marshall Institute, which advocates outright climate denial and has denied the link between tobacco and cancer in the past. Her consulting company has received funding from the fossil fuel industry since 2007, at her own admission. Finally, her work has been repeatedly criticized by reputable scientists including those at RealClimate and the Union of Concerned Scientists.