By Evan Vega
Long before modern modeling, William Gray dominated the field of hurricane forecasting, establishing a gold standard at Colorado State University that produced dozens of elite meteorologists. However, the pioneer’s later career shifted toward a contentious rivalry with the scientific consensus, as he leveraged his professional prestige to predict a global cooling period. A new forensic analysis by North Denver News, titled The Colorado Denialist, evaluates Gray’s climate claims against the observational record, finding that his most specific prediction—that cooling would persist through 2025-2030—has been contradicted by the warmest decade in recorded history.
A scientist revising a forecast is not a scandal; revision is the work.
The three claims that survive the audit are set out on what he got right.
Gray argued for years — loudly, and while the confident public line ran the other way — that you cannot get from a warmer ocean to more hurricanes by arithmetic, and that historical storm counts are contaminated by changes in how storms were observed.
NOAA’s Geophysical Fluid Dynamics Laboratory, in its most recent revision, concludes that the historical Atlantic hurricane data “do not provide compelling evidence” for a substantial greenhouse-driven century-scale increase in tropical storm or hurricane frequency, and that “most modeling studies project a decrease (or little change) in the global frequency of all tropical cyclones combined.” That is Gray’s position, reached by the institution he spent his later years arguing with.
The same assessment projects, with medium-to-high confidence, that rainfall rates increase, that average intensity increases, and that the proportion of storms reaching Category 4 or 5 increases. Rapid intensification is also projected to rise. Fewer storms, each one wetter and stronger, arriving on top of a higher sea level, is not a smaller problem.
Gray’s emphasis on multidecadal Atlantic variability also holds up, with the qualification that aerosols and greenhouse forcing are now understood to contribute to what he treated as purely internal. The Sahel is the clearest case: he tied a warm North Atlantic to wetter Sahel summers and the rains did partly recover, but the recovery is uneven east to west and the literature attributes it to a mixture of Atlantic and Indian Ocean temperatures, aerosols, greenhouse forcing and internal variability. He saw the pattern early. He was too certain about its cause.
The dated forecasts are set out in full, with the temperature record behind them, on the forecast page of the dossier.
Gray did something most participants in this argument never do: he made claims precise enough to be killed by data, and then he put dates on them. Collected in one place, the dated forecasts show a prediction being reissued rather than tested.
Every one of those start dates has passed. None was followed by cooling. The 2012 claim — that a weak cooling had been under way since about 2000 — describes a period that contains the eleven warmest years on record.
A scientist revising a forecast is not a scandal; revision is the work. What the record shows is that every revision pushed the cooling further out, and the 2012 paper does not say the earlier forecasts were wrong.
Gray’s own arithmetic is reproduced step by step on the sensitivity page; his water-vapour claim and his ocean-circulation argument have their own pages.
Gray’s climate position reduces to one figure, and to his credit he published the arithmetic behind it rather than asserting it. In the 2012 paper he takes the direct warming from a doubling of carbon dioxide and halves it, to about 0.5 °C. Where climate models find a strongly positive water-vapour and cloud feedback worth around 2 °C, he argues the feedback runs the other way, at about −0.2 °C. The result, in his words, is “only about 0.3°C, which is only about one-tenth of the global warming projected by nearly all of the recent GCM climate simulations.”
The IPCC’s Sixth Assessment Report gives a best estimate for equilibrium climate sensitivity of 3 °C, with a likely range of 2.5 to 4 °C, and assesses a value below 1.5 °C as effectively ruled out — a conclusion drawn from process understanding, the historical record, palaeoclimate evidence and emergent constraints together, not from models alone.
The step that fails is the first one. Standard radiative physics gives roughly 1 °C of surface warming for doubled carbon dioxide with water-vapour feedback left out entirely. Gray’s halving of that term is where the factor of ten begins, and reviewers at the time traced it to the way he balanced top-of-atmosphere forcing against changes in evaporation. It is an energy budget that does not close, not a difference of opinion about clouds.
This report began from a supplied review document carrying 37 references. Checking it against primary sources changed five things, four of which were errors that would otherwise have been published, and one of which was unfair to Gray. All are set out in full on the dossier’s corrections and limits page, and every document this report rests on is listed on its sources and method page.
Two cooling forecasts were dropped. The review built its central argument on Gray forecasts dated 1996, 2009 and 2012, and footnoted all three to a single reference: Gray’s curriculum vitae, a document that cannot carry a forecast wording. The 1996 forecast could not be found — not in his publication list, and not in catalogues that record individual newspaper interviews he gave. The 2009 forecast could not be sourced to Gray at all; its pairing of a 2001 start with a 2030 horizon corresponds to work published by other researchers that year. Neither is used here.
One number was corrected downward, against the story. The review credited Atlantic seasonal outlooks with 40 to 60 per cent skill in August, citing a 2017 review chapter. That chapter contains no such table: it reports qualitative bands and a single pair of percentages, skill rising from 3 per cent in the preceding December to 29 per cent in early August.
One criticism was corrected in Gray’s favour. He is commonly said to have confused relative humidity with specific humidity. He did not: his paper claims a reduction in both in the upper troposphere, with a table of observed changes behind it. That is a cleaner empirical claim than the one he is usually accused of making, and it is the one that satellite records contradict.
Two further claims in the review — a characterisation of the peer-review record, and an account of a National Science Foundation proposal review — could not be verified and are reported as unverified rather than asserted.
Part of the Verified Series: Read the previous investigation
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