Cold Winter, Hot Winter

For Americans living in the eastern half of the country, this winter seemed quite cold, and for some states winter temperature was indeed colder than average (average defined by the period from 1895 to the present). Those states are shaded light blue in the following map. Shaded in light pink are states whose winter was hotter than average, orange for the states with a winter much hotter than average, and in deep red are the states that have just been through their hottest winter on record (graph courtesy of Climate at a Glance).

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Global Warming has Accelerated

My paper with Stefan Rahmstorf showing that global warming has accelerated was published in Geophysical Research Letters today. The main result is that global warming is NOT proceeding at the same old rate it has been since 1975. It’s going faster.

The Guardian has a good article about it. It points out that our estimate is faster than that of other experts, and quotes some of them who express caveats. Honestly, I agree with most of their caveats — I think that the rate over the last 10 years is quite high but isn’t likely to sustain for very long. The truly important point is what we and (almost) all seem to agree on: that the warming rate really has increased. The latest year’s data — which didn’t make it into our study — only strengthens that conclusion.

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Global Temperature Update

Now that 2025 is complete, several organizations have published year-end results for an important measure of climate change: the Global Mean Surface Temperature anomaly. These include NASA (the Goddard Institute for Space Studies), HadCRU (the Hadley Centre/Climate Research Unit in the U.K.) and ERA5 (reanalysis data from C3S, the Copernicus Climate Change Service in Europe).

I’ve transformed their numbers to “warming since pre-industrial times,” which is what we seek to keep below 2°C, and here is a graph of yearly average temperature since 1850 for HadCRU, since 1880 for NASA, and since 1940 for ERA5:

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Trump: Delusional and Stupid

Three things stand out about Donald Trump’s hour-long speech at the United Nations. First, he hurled a lot of insults, including insulting the United Nations, all while telling representatives of most of the world’s nations that their countries were on the road to failure. Second, he spent a lot of time (a lot!!) bragging about himself while claiming he wasn’t bragging about himself. Third, when it comes to climate change he went full denial.

He called climate change “the greatest con job ever perpetrated on the world,” and said “All of these predictions made by the United Nations and many others, often for bad reasons were wrong. They were made by stupid people …” But he declared his love for fossil fuels of all kinds, proudly informing us that he has “a little standing order in the White House. Never use the word coal, only use the words clean, beautiful coal.

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Hit and Run

The “climate working group” (CWG), the gang of five which produced the climate report for the Department of Energy, has been dissolved. The report will not be changed in response to the many criticisms received, because the climate working group is no longer working.

According to a spokesperson from DoE,


“DOE determined that the draft report and the public comments it solicited achieved the purpose of the CWG, namely to catalyze broader discussion about the certainties and uncertainties of current climate science,” a DOE spokesperson said. “We will continue to engage in the debate in favor of a more science-based and less ideological conversation around climate science.”

What follows is my opinion:

The statement from the DoE spokeperson is partly true and mostly a lie. Yes it achieved the purpose of the DoE. No, that purpose wasn’t to “catalyze broader discussion.” No, they are not in favor of a more science-based and less ideological conversation about climate science — just the opposite.

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How Bonferroni goes wrong

Having declared (in the last post) that in a recent study of sea level data from locations around the world the Bonferroni correction is not an acceptable procedure, I thought it might be a good idea to show how that comes to be.

First, a very simple example. We test data from location “A” for acceleration of sea level rise, and get a p-value of 0.042. That’s less than our critical test value 0.05, so we declare “acceleration is statistically significant.” Another team tests data from location “B” (a different location), getting a p-value of 0.046. This too is less than 0.05, so they too declare statistical significance. Along comes someone who says there were two tests done, so applying the Bonferroni correction requires a modified critical value of 0.05/2 = 0.025. Neither p-value is lower than that, so neither location shows statistically significant acceleration — despite the fact that as individual tests, they both do.

The Bonferroni correction can lead you astray.
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Bad Science on Sea Level

In a recent report about climate change from the U.S. Department of Energy (DoE), the authors state that “U.S. tide gauge measurements reveal no obvious acceleration beyond the historical average rate of sea level rise.” This is false. Judith Curry has defended this statement by pointing to Voortman & DeVos (2025), who analyze tide gauge data and state that


“Statistical tests were run on all selected datasets, taking acceleration of sea level rise as a hypothesis. In both datasets, approximately 95% of the suitable locations show no statistically significant acceleration of the rate of sea level rise.”

This too is false, and I believe I know how they came to this mistaken conclusion.


Consider the tide gauge record from Cedar Key, Florida (yearly values from PSMSL, the Permanent Service for Mean Sea Level) from 1950 to the present:

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Sea Level Rise in the U.S.A.

I’ve already blogged about the lame treatment of sea level in the new DOE report. It has attracted some attention from those who want to know how the Trump administration is butchering climate science. But — unlike the authors of the DOE report — it seems my readers also want to know what’s really happening to sea level along the coasts of the USA.

If global sea level is accelerting (and it is), then it’s no surprise we see statistically significant acceleration on the east coast and Gulf coast of the U.S., by why not on the west coast?

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I tested for recent acceleration at U.S. tide gauge stations by fitting a quadratic to the data since 1970. It’s not the best test, but it’s simple and I think it’s a good one. It raises the question, what is the average acceleration since 1970 of global sea level? I took the tide gauge reconstruction from Frederikse et al. and fit a quadratic to its data since 1970, which estimates the average rate of global sea level acceleration since 1970 to be 0.083 ± 0.024 mm/yr/yr (95% CI).

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U.S. Government makes old lies new again

A report from the U.S. Dept. of Energy (DOE) (an official U.S. government report) tells us that

U.S. tide gauge measurements reveal no obvious acceleration beyond the historical average rate of sea level rise.

It’s one of the main points of chapter 7 (Changes in Sea Level). But the DOE report is not the origin of this particular falsehood. For instance …

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Sea Level Rise in NYC

In response to my last post, a reader asked


Please evaluate their Fig. 7.6 graph of the 30 year trailing rate of Battery sea level rise. The author’s comment is that “NOAA’s projection is remarkable — as shown in Figure 7.6, it would require a dramatic acceleration beyond anything observed since the early 20th century.”

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My evaluation: for the purpose of giving the wrong impression, it’s a very clever graph for at least two reasons.

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