Richard Tol Inserts His Outdated Conclusions

My last post discussed how it appears Richard Tol abused the IPCC process to dramatically rewrite material in order to promote his views as the IPCC’s views while removing information and references. Today I’m going to show additional details which make the revisions even more suspect.

Before I get to that, I want to take a moment to point out one issue has been resolved. This all began when Bob ward said a new section had been added to the chapter Richard Tol helped head. Tol responded to this claim by saying:

In fact, that section was moved from Chapter 19 to Chapter 10. As far as I am aware, Mr Ward did not raise this concern with the IPCC. He was informed no later than 2 April 2014 that the text was moved rather than added.

However, Tol has since acknowledged the text was not merely moved but was completely revised. Specifically, he says:

The comments on the Second Order Draft called for a complete revision, so that’s what was done.

I don’t agree any comments “called for a complete revision.” Regardless, Tol has acknowledged the text was revised as I claimed. It’s good to have that point resolved even if we have no explanation as to why Tol gave a mendacious response to Ward on this issue.

With that point settled, it’s worth examining the revision the section underwent in more detail. Specifically, I want to examine the first two sentences of the section:

Since AR4, four new estimates of the global aggregate impact on human welfare of moderate climate change were published (Bosello et al., 2012; Maddison and Rehdanz, 2011; Roson and van der Mensbrugghe, 2012), including two estimates for warming greater than 3°C. Estimates agree on the size of the impact (small relative to economic growth) but disagree on the sign (Figure 10-1).

The first couple times I read these sentences I thought they both referred to the same thing. The first sentence talks about “new estimates.” The second sentence talks about what “[e]stimates” show. One could be forgiven for thinking the two sentences refer to the same thing. They don’t.

The second sentence begins with “[e]stimates” instead of “these estimates” for a very specific reason. The claim estimates “disagree on the sign” of the impact is not true for the “four new estimates” the first sentence refers to. This can be seen by examining Figure 10-1:

AR5-10-1

The caption tells us “estimates published since IPCC AR5 are highlighted as diamonds” (AR5 is a typo meant to be AR4). All four diamonds in this figure are negative. There are only two dots which are positive. We can find out what papers they belong to by looking at the referenced Table 10.B.1:

AR5-10-B-1

There are 20 impact estimates in this table. Seventeen are negative. One is zero. Two are positive. The positive ones are:

(Mendelsohn et al. 2000)a 		0.1 
(Tol 2002) 				2.3

Both of which came about over a decade ago.

Each IPCC assessment report is supposed to tell the reader what has been learned since the last report. This section pretends to by referring to estimates made since the last report. It then immediately switches focus to a conclusion supported solely by work from over a decade ago, giving no information about what the new estimates show. The next sentence is even more telling:

Climate change may be beneficial for moderate climate change but turn negative for greater warming.

This is almost an exact copy of the position Richard Tol has repeatedly advanced. He’s published multiple papers making this claim, such as this one (which contains a table nearly identical to 10.B.1), and the claim has gotten him a healthy amount of media attention. It’s telling the claim showed up only after the section was completely revised to fit in the chapter Tol helped head.

As though that wasn’t telling enough, one of the two outdated estimates this conclusion rests upon is one published in a paper by Tol (2002). The other estimate is barely positive, and it has a footnote. Suspicious people will have already checked that footnote and seen:

a Results aggregated by (Tol 2013).

Which shows the positive impact is one Tol himself calculated based upon Mendelsohn’s work.


The two sentences referring to benefits of global warming, a core component of Richard Tol’s proposed worldview, rest entirely upon calculations Tol did on data from over a decade ago. These outdated estimates are given a prominent position, completely supplanting all more recent estimates. In doing so, they take up half of a paragraph in a section which has only two paragraphs.

Not only was all data from the last decade ignored in a way which favors Tol’s proposed worldview, two figures were deleted and replaced by a table and figure which can be found in Tol’s published work.

It’s difficult to see how anyone could justify this.

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