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  • Writer's pictureMarco Annunziata

Unsettling Climate Thoughts - Part I

This started as a book review, but turned into a three-part blog on climate change: What we know and don’t know, why action falls so much short of the apocalyptic rhetoric, and why we need a more honest debate on the uncertainty, risks, costs and benefits.

If you confess to your friends that you are reading Steven Koonin’s “Unsettled,” they will warn you Koonin is an untrustworthy hack with a hidden agenda and a poor grasp of the issues, in the pocket of fossil fuel industries. A dangerous denier.

Koonin, however, is a theoretical physicist who served as Undersecretary for Science in President Obama’s Department of Energy and has extensive experience on climate science. Could he have an agenda that leads him to distort the science? Well, I know at least two Nobel prize economists who fits that description, and if it can happen in economics, it can happen in climate science. The best way to find out is to assess the arguments.

Koonin’s arguments

But first note: Koonin is not a “denier”. He confirms that the planet is getting warmer, and that greenhouse gas emissions due to human activity are contributing. He diverges from the consensus, however, in arguing that:

1. Human emissions play a relatively smaller role compared to other determinants of the climate, such as variations in solar activity, volcanic activity and fluctuations in the height and density of cloud coverage;

2. Climate models are unable to capture these other factors with sufficient precision; hence forecasts of how the climate will change – including due to human emissions – are subject to a very high degree of uncertainty;

3. While most of these uncertainties are recognized in the body of the official climate reports (the latest runs to 4,000 pages…), they are mostly ignored in the executive summaries in favor of simpler messages that get further simplified and dramatized by the media. Koonin documents this with quotes from the climate reports.

The mystery of the 1910-1940 global warming

A couple of examples from Koonin’s book:

  • The multiple models used for the IPCC (Intergovernmental Panel on Climate Change) studies differ significantly in their forecasts of the global average temperature: the difference in predictions across models is about 3°C; in other words the degree of uncertainty is larger than the 1-3°C temperature changes that these models try to explain and predict.

  • The models are unable to reproduce the significant increase in global temperature that occurred between 1910 and 1940, of a similar magnitude to that recorded between 1970 and now – and scientists are unable to explain why. This is a pretty damning indictment of the models, and to my knowledge it has not been refuted. The obvious implication: if these models cannot even replicate the past, why should we think they can predict the future?

Let’s focus on this last point for a moment. Here is the first picture in the Summary for Policymakers of the latest IPCC report:

The image to the left highlights the sharp increase in temperature between 1850 and 2020. Since the graph spans 2,000 years, it’s hard to see the detail in the more recent period, so let’s first take a look at this other chart, taken from

Here you can see that between 1910 and 1940 the global temperature rose by an amount comparable to the 1980-2020 rise (from -0.5 to + 0.2 vs from -0.1 to +0.6).

Now look again at the right-hand panel of the IPCC picture:

In the chart above I have highlighted the point Koonin makes: the model simulations including human activity (brown line) fail to explain the 1910-1940 rise in temperature (black line).

Extreme weather

Koonin provides a much more detailed critical assessment of the models, but let me turn to a few of his points that highlight the chasm between the media headlines and the reality:

  • There is no significant trend in the global number of cyclones or in the number of US hurricanes; and no scientific evidence that global warming causes more hurricanes.

  • We do not know whether floods and droughts have been increasing, decreasing or have remained stable in frequency. We simply do not know.

  • The highest temperatures in the US have not increased since 1900. (Though the coldest temperatures have gotten less cold.)

Koonin does agree that climate change is increasing the severity of forest fires in the Western US. His points above, though, stand in stark contrast to the media headlines and politicians’ claims that climate change is causing an increase in the frequency and severity of extreme climate events, including hurricanes, heat waves, and even the unusual cold wave that hit Texas earlier this year.

Is Koonin lying? I went looking for a second opinion – you will find it in Part II of this blog.

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