Low-ball Climate Assessments

“At 3 degrees of warming, the risk of extreme weather events could increase fivefold by century’s end. Flooding from sea-level rise and heavier rainstorms could cause four times as much economic damage worldwide as they do today.”
— NYT on the 2022 IPCC report.

Century’s end? At 3 degrees of global warming? That is downplaying what the data says has already happened in the 21st century with just 1.1 degrees of overheating.

The big five types of extreme weather are where a >3x surge has been sustained, more like a sudden climate flip than a “black swan” event in an otherwise stable climate regime. (“Severe” here means more than $1b damage per episode, corrected for inflation.)

Figure 2. The annual number of severe windstorms in inland U.S. surged to 6x baseline in 2008, with a 10x peak in 2020. This category includes high winds, severe tornado swarms, derechos, and hailstorms — but severe (>$1b damages) hurricanes are in a category of their own, and they stayed flat until a jump in 2020.

1. In 2008, the annual number of severe inland-US wind­storms began to occur at six times (6x) their 1980–2007 baseline rate.

2. Similarly, US severe fire weather (hot, dry, windy) was 4x baseline after 2006.

3. Severe US inland floods (again, omitting hurricanes) were 3x baseline after 2010.

Two less frequent types of extreme weather showed >3x increased brutality because some episodes lasted much longer, a different type of measure than the usual peak temperature or peak wind strength.

4. In Gulf Stream territory, tropical cyclones (TCs, aka hurricanes) stalled with major effect in 2002, 2017, and 2018.

5. A mega heatwave struck Europe in 2003 (70,000 deaths in about a month), causing much talk of a black swan event unlikely to be seen again in our lifetimes. A second mega struck Russia in 2010 (56,000 deaths). Both mega’s were preceded by a springtime drought prior to the blocking event.

Furthermore, all five surges began when global warming had paused between 2001 and 2013 (Figure 3). They were consequences of prior warming, not of further rise.

Figure 3. Global mean surface temperature (not shown) is a mix of three parts land to seven parts sea surface temperature. The warming pause is best seen in the less noisy SST record. SST has been slid up about 9˚C so that its curve overlaps Land Temperatures about 1976. The ups and downs move together from 1950 to 1984. From 1985 to 2001, land temperature rose 4x faster than sea surface temperature.

Stopping warming per se is not enough. Repairing the climate with actual cooling should be our target — and that has a long lead time, making this a climate emergency.

Figure 4. To merely counter the annual GHG emissions would require sinking -46 GtCO2/yr.

Once starving countries start invading their neighbors’ food supply, or the global economy tanks, international cooperation will become difficult. How will civilization repair climate when trapped on a slippery slope?

Reference links at CO2Foundation.org and WilliamCalvin.org.



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William H. Calvin

William H. Calvin

President, CO2Foundation.org. Professor emeritus, University of Washington School of Medicine in Seattle. Author, many books on brains, human evolution, climate