Climate Change Predictions: What Went Wrong?

As egg-on-face moments go, it was a double-yolker. Last week a group of climate scientists published a paper that admitted the estimates of global warming used for years to torture the world’s conscience and justify massive spending on non-carbon energy sources were, er, wrong. The admission was overdue acknowledgment of something that has been obvious for years.

Being wrong is not a criminal offence, especially in science, where in the long run almost everything turns out to be wrong, but the global warmers have adopted such a high-and-mighty tone to anyone who questions them that for sceptics this was pure joy.

The world may still be doomed, but it is not quite as doomed as the climatologists have repeatedly told us.

The admission was overdue acknowledgment of something that has been obvious for years. Despite the climate models predicting rapidly rising temperatures, between 1998 and 2013 temperatures barely rose at all. This was a pause, not a change in the underlying trend, the scientists and the Intergovernmental Panel on Climate Change insisted. Global warming was still going on, even when it wasn’t.

The pause hadn’t been predicted by the computer models, but admitting that wasn’t really an option. Anxiety needed to be ramped up in order to achieve international agreement on cutting carbon emissions. That was achieved — at the cost of browbeating doubters — and the Paris agreement struck in 2016 committed signatories to limit warming to 1.5C above pre-industrial levels.

It couldn’t actually be done, the scientists said. To keep warming below 1.5C, total emissions from 2015 onwards could not amount to more than 70 gigatonnes of carbon — seven years’ worth at current emission rates.

Last week’s paper in Nature Geoscience recalculates that as 200 gigatonnes, or 240 gigatonnes if great efforts are also made to reduce other global-warming gases such as nitrous oxide and methane.

So instead of seven years, we’ve got 20, or maybe 24. The task has gone from impossible to very difficult, said one of the paper’s authors, Joeri Rogelj.

Another author, Myles Allan of Oxford, told The Times: “We haven’t seen that rapid acceleration in warming after 2000 that we see in the models. We haven’t seen that in the observations.”

Allan’s defence of the models, however, was peculiar. He said that they had been assembled a decade ago, so it wasn’t surprising they had deviated from reality. Yet these are the very same models used to make predictions for 50 or 100 years ahead which have saddled taxpayers with huge costs to pay for alternative energy sources. Anybody who doubted their predictive power was labelled an unscientific dolt, a “climate denier” fit to be listed with the Flat Earthers.

As long as there have been computer models, there have been inaccurate forecasts. In the early 1970s the Club of Rome published The Limits to Growth, an extrapolation of population, pollution and resource depletion that concluded that the world was heading for imminent catastrophe. It sold more than 16m copies. I keep one on my shelves to remind me of the folly of Malthusian predictions.

Today the world is richer, cleaner, and better-fed than it was in 1972, while the Club of Rome is forgotten. It still exists, headquartered in Winterthur, Switzerland, which must be nice.