Scientific reticence

Something unexpected happened to temperatures in 2023. How will scientists react?

In the chart above, the bars represent confidence intervals, the red dots are the predicted temperatures, and the blue dots are the actual temperatures. 2023 was the hottest year on earth for a long stretch. It was also a much warmer year than scientists predicted it would be.  

The chart shows that 1992 was also an anomalous year. That year scientists' expectations were confounded by the eruption of Mount Pinatubo in the Philippines, which belched forth a huge quantity of "short-lived planet-cooling aerosols," according to Zeke Hausfather. To be sure, there was a volcano eruption in 2022 that shot water vapor into the atmosphere (which would produce warming temperatures), but it had a small climate impact and may, on balance, have actually cooled the earth (because the eruption produced aerosols as well).

So the stunning warmth of 2023 can't be explained by a volcano. Something important and more fundamental happened that is not reflected in standard climate models. 

We know that the earth is getting generally darker, as sea ice retreats—remember that picture of extraordinarily low sea ice around Antarctica last fall?

That means less heat is being reflected back into space. We also know that cloud-cover and aerosol particles are thinning. The signal being sent by the year 2023 is that these changes may be happening more quickly than widely-used climate models assume. 

That's what Dr. James Hansen, who's been sticking his neck out since the 1980s, is saying. Hansen predicted this week that we'll be seeing sustained temperatures 1.6-1.7ºC above pre-industrial numbers by May of 2024. He says increasing ice melt at the poles is being driven along more quickly than the standard models predict, resulting in not only a darker earth but also injecting freshwater into layers of the ocean. That ice melt, he believes, is wreaking havoc with the global conveyor belt of currents on which civilization has depended for thousands of years. And it is also poised to trigger incredibly rapid sea level rise in the second half of this century.

Hansen wrote about these ice melt dynamics in a paper he says was "blackballed by the IPCC" because it disagreed with the IPCC's views about threats to ocean circulation and large volumes of sea level rise. And a recent paper of his arguing that IPCC sea level rise models were too conservative and failed to adequately incorporate several factors—including the climate's sensitivity to feedback effects and the reduction in shipping-related pollution—was pooh-poohed by other scientists who said that Hansen's work was "very much out of the mainstream."  

Well, given what actually happened in 2023, maybe the mainstream needs to think more broadly.

This past week, I talked to oceanographer John Englander of the Rising Seas Institute, who famously took Bret Stephens to visit Greenland. Englander's book, Moving to Higher Ground, is required reading if you're interested in sea level rise. Englander has been working on this issue for years. 

Englander told me that Hansen had written early papers about scientific reticence. Look at this one, from Hansen in 2007: 

I suggest that a ‘scientific reticence’ is inhibiting the communication of a threat of a potentially large sea level rise. Delay is dangerous because of system inertias that could create a situation with future sea level changes out of our control. I argue for calling together a panel of scientific leaders to hear evidence and issue a prompt plain-written report on current understanding of the sea level change issue.

Culture is everything. Scientists are naturally cautious, and we want them to be because objective skepticism is the point of what they do. Cautious scientists do better in attracting funding and promotions. But when it comes to ice sheet instability and sea level rise, Hansen argued in 2007, "there is a danger in excessive caution." He goes on: "We may rue reticence," he says, particularly as changes accelerate and become exponential. We'll lose the ability to plan.

If rapid ice mass loss means thousands of cities are at profound risk of being inundated in a matter of decades, wouldn't you want policymakers to know this and do something about it? 

It may be that scientists are going after Hansen because he is pointing out that we're probably already committed to more than 1.5ºC of heating and will soon sail through 2º—and they want the globe to keep fighting to lower emissions. This makes sense, in a way. These mainstream scientists want the clear message to get out that sharply reducing emissions is necessary, right now. Hansen seems to think that we're farther down the slippery slope already, and that seems defeatist to the mainstream.

The trouble is that the globe has a second problem, one that has to be worked on at the same time: Seas are going to rise very quickly and people will need to be helped in huge numbers to survive this ongoing, chaotic, cataclysmic, physical transition. Encouraging more people to buy electric cars won't make a difference to that problem. But, as Englander told me this past week, "People don't want to look at a dark situation if there's not a simple solution."

Now there's an anomaly and its name is 2023. Maybe when 2024 is also an anomaly we'll see scientific consensus swing toward something a bit braver. In the meantime, follow Jim Hansen as the heat accelerates. He's usually right.