The Congressional Budget Office (CBO) claims that it is “strictly nonpartisan” and “conducts objective, impartial analysis.” After the release of the CBO’s most recent report, Potential Increases in Hurricane Damage in the United States: Implications for the Federal Budget, the CBO seems to have lost its objectivity and appears to be operating with an agenda.

There are at least two large problems with the CBO’s report. First, the CBO goes outside the consensus of climate science with the CBO’s estimates of hurricane frequency, which ignore the Intergovernmental Panel on Climate Change’s (IPCC) explicit statements about hurricane frequency. Second, instead of relying on academic literature for estimates of hurricane damages, the CBO relies on research that was apparently funded by Tom Steyer, Michael Bloomberg, and Hank Paulson, all of whom have been activists the in cause of anthropogenic global warming.

These breaches of the CBO’s commitment to objectivity and impartiality are so large the CBO should immediately withdraw this paper.

The CBO was warned last year that this report was outside the scientific mainstream

This report has been over a year in the making. The CBO sent Roger Pielke Jr. a copy of the report to review last year. Here’s what Pielke told the CBO:

My overall comment is that the report largely ignores the relevant peer reviewed literature and the IPCC [Intergovernmental Panel on Climate Change]. Instead it repackages the work of the Rhodium Group, which is based on RMS perspectives and contracted work with [hurricane expert Kerry] Emanuel, which stands in stark contrast to his published scientific work. Thus, the report is way out of step with the science on this topic and stands out as a huge outlier.

That is probably OK for the political group that put forward the Rhodium effort, but perhaps not for a government agency known for its high quality work. Either way, the report should clearly explain why it has chosen to focus on a single, outlier contracted report rather than the scientific literature.

Pielke’s comments were in response to a draft, but the final version continues to disregard what the IPCC has said on hurricane frequency over time. The CBO actually cited the IPCC for a couple of issues in this report, but the CBO did not cite the IPCC on the critical issue of the frequency of hurricanes.

The CBO Relies on Outliers Claims and not on Consensus Science for its Projections

The Intergovernmental Panel on Climate Change was created to produce reports that say what the consensus science is on climate change. The CBO, however, only refers to these reports when it is convenient and uses outlier reports to make the claim of larger climate damages.

The CBO refers to the IPCC for estimates of sea level rise (see page 7, 23, and 24) and global mean surface temperature (see page 24) but not on hurricane frequency in a warming world. That is a glaring omission given that the point of the paper is “potential increases in hurricane damage.”

Presumably, the reason that the CBO did not refer to the IPCC on the frequency of hurricanes is because the trend in hurricane frequency is not clear (i.e. no significant observed trends). Here are the IPCC’s exact words:

Current data sets indicate no significant observed trends in global tropical cyclone frequency over the past century and it remains uncertain whether any reported long-term increases in tropical cyclone frequency are robust, after accounting for past changes in observing capabilities (Knutson et al., 2010).

No robust trends in annual numbers of tropical storms, hurricanes and major hurricanes counts have been identified over the past 100 years in the North Atlantic basin.[1]

In summary, confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low.[2]

Specifically, with regard to hurricanes in the Atlantic, the IPCC finds that the numbers of tropical cyclones have probably not increased, but there has been an increase in storm intensity:

More recent assessments indicate that it is unlikely that annual numbers of tropical storms, hurricanes and major hurricanes counts have increased over the past 100 years in the North Atlantic basin. Evidence, however, is for a virtually certain increase in the frequency and intensity of the strongest tropical cyclones since the 1970s in that region.[3]

As for near-term (the next couple decades) projections for hurricanes in the Atlantic, the IPCC finds that there is low confidence in hurricane projections through the mid-21st century. The IPCC states:

Therefore, based on the limited literature available, the conflicting near-term projections in basins with more than one study, the large influence of internal variability, the lack of confidently detected/attributed changes in TC [tropical cyclone] activity (Chapter 10) and the conflicting projections for basin-wide TC frequency even at the end of the 21st century (Chapter 14), there is currently low confidence in basin-scale and global projections of trends in tropical cyclone frequency to the mid-21st century.

Therefore, there is low confidence in near-term TC intensity projections in all TC basins.[4]

As for long-term projections for hurricanes in the Atlantic (and the globe), the IPCC finds that there is low confidence in region-specific projections, but that it is more likely than not that there will be some increase in hurricane frequency in some basins. Specifically, the IPCC states:

Shorter term increases such as those observed in the Atlantic over the past 30 to 40 years appear to be robust and have been hypothesized to be related, in part, to regional external forcing by GHGs and aerosols, but the more steady century-scale trends that may be expected from CO2 forcing alone are much more difficult to assess given the data uncertainty in the available tropical cyclone records.

Although projections under 21st century greenhouse warming indicate that it is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged, concurrent with a likely increase in both global mean tropical cyclone maximum wind speed and rainfall rates, there is low confidence in region-specific projections of frequency and intensity. Still, based on high-resolution modelling studies, the frequency of the most intense storms, which are associated with particularly extensive physical effects, will more likely than not increase substantially in some basins under projected 21st century warming and there is medium confidence that tropical cyclone rainfall rates will increase in every affected region.[5]

In summary, there aren’t robust trends of increasing hurricane activity that would suggest greater activity in the future. In terms of future hurricane projections, these projections are based on climate models and even then there is “low confidence” in any changes through the mid-century. After mid-century, there is continued “low confidence” in any changes, however, the IPCC believes there “will more likely than not” be some changes, but the IPCC cannot project where those changes will be in the long term.

What the CBO says about Changing Hurricane Frequency

Instead of citing the IPCC on what the science says about hurricane frequency, the CBO instead asserts without citation, “The effect of climate change on hurricanes is less certain, but scientists find that it could increase the frequency of hurricanes in the North Atlantic, particularly the most intense categories of hurricanes.”[6]

While it is certainly true that some scientists think that hurricanes could increase, the actual data do not say that we have observed such an outcome to date. The actual data “indicate no significant observed trends in global tropical cyclone frequency over the past century” as stated above.

The CBO later admits “Although scientists find that climate change will affect the conditions that give rise to hurricanes, significant uncertainty surrounds the ultimate effect of climate change on the frequency of hurricanes in the United States. That effect is unclear because of uncertainties…”[7]

Again, this is true—that uncertainty surrounds hurricane frequency—but instead of assuming the current hurricane frequency, the CBO assumes an increase in hurricane frequency by citing two scientists who believe hurricanes could increase in frequency. If the CBO had been objective and impartial, they would at the very least note what the IPCC and the climate data say about one of the key features of hurricane damages.

CBO Relies on Reports Apparently Funded by Tom Steyer et. al.

Besides omitting any reference to the scientific consensus on hurricane trends, the CBO also relies on damage functions from Risk Management Solutions (RMS). This is problematic for a number of reasons. First, as Pielke warned the CBO in 2015, “You will do better by relying on the academic literature for this information–see Bouwer literature review cited above–rather than the work of RMS, which has proven to be flawed on many occasions. They have a business interest in this topic.”[8]

While there is nothing wrong with having a business interest in a topic, the issue here is that for CBO to maintain its objectivity and impartiality, it is far better served by relying on the academic literature and the IPCC. While there is nothing wrong for a politically-minded group like the Center for American Progress, for example, to omit the work of the IPCC and instead rely on research that is an outlier, the CBO should stick to the scientific consensus.

This is especially true because of the source of RMS’s business interest in this topic? One of RMS’s business interests is money from Tom Steyer, Michael Bloomberg, and Hank Paulson. But first, here’s how the CBO report explains the use of the RMS information:

RMS has developed damage functions that translate U.S. hurricane occurrences into state-specific estimates of expected damage. A more detailed discussion of the damage functions and CBO’s assessment of their validity is provided in the working paper that accompanies this report. For a description of the RMS model, see Michael Delgado and others, “Technical Appendix: Detailed Sectoral Models,” in Trevor Houser and others, American Climate Prospectus: Economic Risks in the United States (Rhodium Group and Risk Management Solutions, October 2014), p. C-6,

The American Climate Prospectus, according to its website, “is the result of an independent assessment of the economic risks of climate change commissioned by the Risky Business Project.” The Risky Business Project was “founded by co-chairs Michael R. Bloomberg, Henry Paulson, and Tom Steyer.”

The fact that the CBO relied on work that was apparently funded by Tom Steyer, Michael Bloomberg, and Hank Paulson instead of relying on the academic literature once again calls into question the CBO’s objectivity and impartiality, especially given Steyer and Bloomberg’s outspoken positions on climate change.


The CBO has built a reputation on objective and impartial analysis. This report, however, is a very biased and deceptive document. The CBO fails to recognize what the scientific mainstream has to say about critical issues of the frequency of hurricanes and instead of relying on the academic literature for information about hurricane damages, the CBO instead relies on data funded by Tom Steyer, Bloomberg, and Paulson. If this paper came from the Center for American Progress, that would be one thing, but this paper fails the CBO’s stated standards for objectively and impartiality and should be immediately withdrawn.

[1] Intergovernmental Panel on Climate Change, Climate Change 2013: The Physical Science Basis, Chapter 2: Observations: Atmosphere and Surface, p. 216,

[2] Id. at 220.

[3] Id. at 216.

[4] Intergovernmental Panel on Climate Change, Climate Change 2013: The Physical Science Basis, Chapter 11: Near-term Climate Change: Projections and Predictability Observations, p. 992,

[5] Intergovernmental Panel on Climate Change, Climate Change 2013: The Physical Science Basis, Chapter 14: Climate Phenomena and their Relevance for Future Regional Climate, p. 1252,

[6] CBO at 2.

[7] CBO at 8.

[8] Roger Pielke Jr. comment on CBO draft of August 31, 2015, Also, it should be it should be noted than the Bouwer literature the Pielke cited is titled Projections of Future Extreme Weather Losses Under Changes in Climate and Exposure. The CBO actually cites this paper once in their working paper that accompanies this hurricane report, but only to say “Information on the elasticity of hurricane damage with respect to socioeconomic variables—that is, the percentage change in damage given a percentage change in population or per capita income—is limited.” Why this scientific literature review is not cited more often on the critical issue of damages again calls into the CBO’s lack of objectivity and impartiality.


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