Heat waves and tipping points

“What we’re seeing is climate impacts that scientists thought would accompany certain temperatures happening far more rapidly, with far more devastating effects than had been forecast,” said Dr Simon Nicholson of the Forum for Climate Engineering Assessment at American University.

“We didn’t think that the Arctic would crash by now, and yet it’s almost gone. We didn’t think we’d be seeing these wildfires in Australia and the United States and elsewhere with the frequency and severity that they’re being seen.

“Given that we’re at about 1 degree Celsius, we thought those were far-distant prospects. So 1.5C of warming above pre-industrial averages could turn out to be far more devastating than had been imagined when that target was set as the threshold for international action.”

Last month was the planet’s hottest June on record, and probably the hottest in about 12,000 years. This month is shaping up to be the hottest July, and there’s a good chance that August will also break the record, because the relentless upward creep of global heating is being supercharged by the return of the cyclical El Niño phenomenon in the eastern Pacific.

More than one-third of the US population was under extreme heat warnings this week, and the city of Phoenix had its record 19th successive day over 110°F (43.3C).

Southern Europe is the same from Spain to Turkey, with daytime temperatures in the low 40s and little relief at night. Europe, which keeps better records on this than the United States, counted 61,000 heat-related deaths last year. This year will be much higher.

In the southern hemisphere, El Niño could mean record bushfires in Australia by December. Worrisome, because they have just discovered the 2020 fires were big and hot enough to drive the smoke up into the stratosphere, where it started destroying ozone and expanding the ozone hole again.

Did I mention that there are still 500 wildfires burning in Canada?

Well, what did you think that “global heating” would be like? No surprises there, except that what the scientists thought would be happening around 2030 is happening now.

2029 or 2030 is when we were scheduled to breach the “aspirational” never-exceed level of 1.5C higher average global temperature if emissions continued on the current track. Now the World Meteorological Organisation is saying there’s a 66 percent chance global average temperature will exceed +1.5C at least once between now and 2027.

This means we will be getting into territory where the “tipping points” may be lurking.

Ever since 2015, we have been operating with two “never-exceeds”. The big, flashing red lights with sirens blaring are at +2C, because after that we would be crossing lots of tipping points: Arctic sea ice gone, Amazon forest turning into savannah, methane coming out of melting permafrost, lots of things causing rapid, unstoppable further warming.

But they also set the lower, “aspirational” never-exceed target of +1.5C because they were worried some of the tipping points might activate before +2C. “Aspirational” because even in 2015 it didn’t look very likely we would be able to cut our emissions that rapidly.

That’s what we are heading for right now, and the forecast is that we’ll be in zone for extremes past +1.5C until 2027. Then, if all goes well, the cooler La Niña will see global average temperature fall back to a new normal — say, +1.3C.

That would be nice. If we have been really efficient about reducing our emissions in the meantime (miracles do happen), we might not see +1.5C again until the early 2030s. But if we cross some tipping points in the next few years, they won’t go back to “normal” afterwards. Unfortunately, it doesn’t work like that.