Climate Change Checkup

If you have the misfortune to follow the dreary climate change business, you’ll know that one of the fine points is which long-term emissions forecast to plug into your model. Never mind the accuracy of the models for now—even a good model is vulnerable to the age-old GIGO problem—”garbage in, garbage out.” In climate model forecasting, if you have an absurd emissions forecast, you’ll get absurd (but headline-grabbing) results.

People who follow this subject have long known that the emissions forecast that generates most of the scary headlines of the last few years is known as RCP 8.5 (short for “Representative Concentration Pathways”—never use plain language when you can use forbidding jargon), and most experts agree that its very high emissions forecast is bunk.

Holman Jenkins wrote cogently about it today in the Wall Street Journal. If you don’t have a subscription, here’s some of the relevant part:

The RCP 8.5 scenario was born to give modelers a high-emissions scenario to play with, and how it came to be embraced despite being at odds with every real-world indicator concerning the expected course of future emissions.

In a simple model of the world, authority figures say absurd and false things, and the media calls them out. The reverse happened this time, with the climate crowd reacting to the media’s botched coverage of the Fourth National Climate Assessment in 2018, itself a strained compilation of extreme worst-case scenarios that still couldn’t deliver the desired global meltdown. . .

To this day, the print edition of the New York Times has never mentioned RCP 8.5, the unsupported emissions scenario on which so many of its climate jeremiads rest.

The Washington Post has used it twice, once to say it portended a climate disaster and more recently to suggest its falling out of favor didn’t mean the climate wasn’t headed for disaster.

If you’re into the technical literature, here’s one of the recent articles in Environmental Research Letters that spells out what’s wrong with the alarmist emissions forecasts:

IPCC baseline scenarios have over-projected CO2 emissions and economic growth

Recent (post-2005) trends and energy outlook projections (to 2040) of global CO2 emissions are substantially lower than projected by baseline scenarios used in the IPCC’s Fifth (AR5) and Sixth (AR6) Assessment Reports, and are well off-track from widely-cited high-emission marker scenarios such as RCP8.5. We show that this divergence owes largely to per-capita GDP and carbon intensity growth slower than projected in baseline scenarios. The gap between observed and projected carbon intensity is very likely to continue to increase throughout the 21st century due to the implausible assumptions high-emission scenarios make about future fossil-fuel expansion.

Chaser, from Roger Pielke, Jr—remember how we always hear about how hurricanes are increasing in frequency and strength? Well:

A Remarkable Decline in Landfalling Hurricanes

Since 1945, the number of hurricanes that make landfall has declined by about a third. . .

Last week a paper published in Science concluded that worldwide, “To date, there has been no firm evidence of global trends of the frequency of tropical cyclones with maximum wind speed above the hurricane-force wind (64 knots) at landfall.” That finding, which confirms our work, was based on data since 1982. But what happens when we take a look further back in time? What we find might surprise you. . .

In fact, the overall number of landfalling hurricanes has decreased dramatically since the 1940s, while the number of major hurricane landfalls has shown no trend.

Responses