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No change in weather extremes, just a moving of the goalposts


A PAPER from the Global Warming Policy Foundation says that a recent shift in methodology by the UN’s Intergovernmental Panel on Climate Change (IPCC) has led to misleading claims about increases in weather extremes. The review by physicist Dr Ralph Alexander finds that IPCC claims are largely unsupported by observational evidence.

Dr Alexander says: ‘On almost every kind of extreme weather, with the possible exception of heatwaves, the evidence for significant changes is scant. But the latest IPCC report has introduced novel “attribution” statistics and now insists that things are getting worse. It’s yet another case of scientists trying to scare the public into compliance . . . The mistaken belief that weather extremes are worsening because of climate change is more a perception, fostered by media coverage, than reality. The IPCC’s new statistical method is playing an unworthy part in bringing this sorry state of affairs to pass.’

This is the paper’s summary:

‘This paper compares empirical observations of extreme weather events with their coverage in the 2021 Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC). The conclusions of AR6 are contrasted with observational data described in recent research papers and reports, particularly in relation to droughts, tropical cyclones, heatwaves (including marine heatwaves) and cold extremes. The paper also covers major floods, tornadoes, wildfires and coral bleaching, with a short update of the discussion of disaster risk analysis in my report last year.

‘In a shift of its previous stance, the IPCC claims, for the first time, that climate change is now affecting many weather extremes all over the globe. While this is not true and contrary to the avail­able evidence, AR6 does follow earlier IPCC reports in not making any strong statements attribut­ing extreme weather to global warming.

‘The IPCC claim that agricultural and ecological droughts are increasing is wrong. Several re­cent research studies have confirmed the lack of any long-term trend in drought worldwide over at least a millennium, with no evidence that modern global warming has played any role so far.

‘AR6 links tropical cyclones (hurricanes, typhoons and tropical storms) to global warming with a statement that the proportion of major tropical cyclones has increased across the globe since 1980. Although this assertion appears to be correct, a 2021 study found that the observation mere­ly reflects improvements in measurement capabilities since 1970, and is unlikely to be a genuine climate trend. Hurricanes overall show a decreasing trend around the globe, and the frequency of landfalling hurricanes of any strength (Categories 1 through 5) has not changed for at least 50 years.

‘Claims of strengthened evidence for attribution of heatwaves to global warming, and their more frequent occurrence, can be questioned because data before 1950 is largely ignored in AR6. In the US, for which there are detailed heatwave records back to 1900, a quite different picture emerges. The Hadley temperature compilation, which underlies the IPCC position that heatwaves are on the rise globally, needs to be tested on the much larger US dataset to see if it can reproduce the US data profile. Furthermore, the modern heatwave trend in AR6 is artificially exaggerated because the 1950 start date used is in the middle of a 30-year period of global cooling, from 1940 to 1970.

‘There is no convincing empirical evidence for the AR6 declaration that the frequency of ma­rine heatwaves has doubled since the 1980s. Because sea-surface temperature data from the pre-satellite era was unreliable and sparse, earlier marine heatwaves were likely missed. And the mag­nitudes of current marine heatwaves are most likely overestimated due to uncertainties in the marine datasets.

‘A statement in AR6 that cold extremes have become less frequent and severe is also wrong. Observational evidence shows that cold extremes are increasing and may have become more se­vere, a fact even acknowledged by the IPCC’s sister UN agency, the World Meteorological Organisa­tion (WMO).

‘And, although AR6 wrongly states that coral bleaching and mortality events have increased in recent decades, the report fails to note that such phenomena are not new. There is empirical evidence for bleaching of Australia’s Great Barrier Reef dating back to 1575, long before modern global warming began. This is another example of the IPCC’s neglect of history.

‘Wisely, AR6 does not change the IPCC’s previous position on floods, tornadoes or wildfires. But its conclusions about droughts, tropical cyclones, heatwaves and cold extremes cannot be justi­fied by actual observations.’

The GWPF invited the Royal Society and the Met Office to review this paper, and to submit a response to be published as an appendix to it. No reply was received.

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Paul Homewood
Paul Homewood
Paul Homewood is a former accountant who blogs about climate change at Not a Lot of People Know That

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