-
Posted by BOB WARD
- Posted on 5/15/2014 6:22:38 AM
Professor Tol appears to have made an attempt, albeit not entirely successful, to correct the errors in his 2009 paper with the publication by the ‘Journal of Economic Perspectives’ of ‘Correction and Update: The Economic Effects of Climate Change’.
However, for Nordhaus (2006), Tol (2014) makes an incomplete correction. The original paper by Tol (2009) cited Nordhaus (2006) as finding an impact of -0.9 per cent of GDP for warming of 2.5°C. In fact, Nordhaus (2006) provided estimates for a warming of 3.0°C. The additional material accompanying the Tol (2014) correction lists an estimate for Nordhaus (2006) for warming of 3.0°C. Sadly, Table 1 of the correction still wrongly lists Nordhaus (2006) as providing an estimate of impacts for warming of 2.5°C, alongside an estimate, not included in the original paper, of an impact of -1.1 per cent of GDP for a warming of 3.0°C.
Unfortunately, Table 1 of the Tol (2009) correction also lists the wrong value for Nordhaus (1994b), like the original paper.
In addition, the correction includes five further data from four studies, on top of the extra results from the two Nordhaus studies, listed in Table 1 and plotted in Figure 2. Disappointingly, not all of these data are correct. They include two estimates attributed to a paper by Roberto Roson and Dominique Van der Mensbrugghe on ‘Climate change and economic growth: impacts and interactions’, which was published in 2012 in the ‘International Journal of Sustainable Economy’. The Tol (2014) correction suggests that the estimates apply to a warming of 2.9°C and 5.4°C. In fact, the correct figures are 2.3°C and 4.8°C.
The Tol (2014) correction plots all 21 estimates, including the erroneous data, in Figure 2, and the least squares fit yields a very different result from Figure 1. The one data point, attributed to Tol (2002), which suggests significant net benefits from warming is shown to be an outlier and the least squares fit indicates no net benefit for any warming. This finding is highlighted in the text of the Tol (2014) correction, which states: "unlike the original curve (Tol 2009, Figure 1) in which there were net benefits of climate change associated with warming below about 2°C, in the corrected and updated curve (Figure 2), impacts are always negative, at least in expectation." This is an important revision.
The Tol (2014) correction also suggests that the updated Figure 2 shows "damages do not accelerate as fast for more pronounced warming", and cites extrapolated figures for warming of 5°C. However, this conclusion depends on the curve fitted to Figure 2, which is inaccurate because of the errors in the plotting of the data, particularly for Roson and Van der Mensbrugghe (2012).
I have drawn the attention of the ‘Journal of Economic Perspectives’ to the outstanding errors in the Tol (2014) correction and update, and again requested that it makes available the details of the aggregations of other authors’ work performed by Professor Tol.
However, for Nordhaus (2006), Tol (2014) makes an incomplete correction. The original paper by Tol (2009) cited Nordhaus (2006) as finding an impact of -0.9 per cent of GDP for warming of 2.5°C. In fact, Nordhaus (2006) provided estimates for a warming of 3.0°C. The additional material accompanying the Tol (2014) correction lists an estimate for Nordhaus (2006) for warming of 3.0°C. Sadly, Table 1 of the correction still wrongly lists Nordhaus (2006) as providing an estimate of impacts for warming of 2.5°C, alongside an estimate, not included in the original paper, of an impact of -1.1 per cent of GDP for a warming of 3.0°C.
Unfortunately, Table 1 of the Tol (2009) correction also lists the wrong value for Nordhaus (1994b), like the original paper.
In addition, the correction includes five further data from four studies, on top of the extra results from the two Nordhaus studies, listed in Table 1 and plotted in Figure 2. Disappointingly, not all of these data are correct. They include two estimates attributed to a paper by Roberto Roson and Dominique Van der Mensbrugghe on ‘Climate change and economic growth: impacts and interactions’, which was published in 2012 in the ‘International Journal of Sustainable Economy’. The Tol (2014) correction suggests that the estimates apply to a warming of 2.9°C and 5.4°C. In fact, the correct figures are 2.3°C and 4.8°C.
The Tol (2014) correction plots all 21 estimates, including the erroneous data, in Figure 2, and the least squares fit yields a very different result from Figure 1. The one data point, attributed to Tol (2002), which suggests significant net benefits from warming is shown to be an outlier and the least squares fit indicates no net benefit for any warming. This finding is highlighted in the text of the Tol (2014) correction, which states: "unlike the original curve (Tol 2009, Figure 1) in which there were net benefits of climate change associated with warming below about 2°C, in the corrected and updated curve (Figure 2), impacts are always negative, at least in expectation." This is an important revision.
The Tol (2014) correction also suggests that the updated Figure 2 shows "damages do not accelerate as fast for more pronounced warming", and cites extrapolated figures for warming of 5°C. However, this conclusion depends on the curve fitted to Figure 2, which is inaccurate because of the errors in the plotting of the data, particularly for Roson and Van der Mensbrugghe (2012).
I have drawn the attention of the ‘Journal of Economic Perspectives’ to the outstanding errors in the Tol (2014) correction and update, and again requested that it makes available the details of the aggregations of other authors’ work performed by Professor Tol.