Skepticism vs Alarmism

In a previous post, I considered the rise of pseudo-skepticism in much of current contrarian movements. At the heart of pseudo-skepticism is using what is demonstrably wrong as justification for the rejection of known evidence and well-established science; in order to explain the fact that virtually all the evidence disagrees with you, you need a conspiracy to explain the contradictory evidence away. So "flat earthers" say that because "you can see too far" and "water seeks its level" the earth must be flat, and physics and geology and maps and common sense are all wrong. That means NASA must be doctoring photographs of the earth, air traffic is faked, and nobody has ever been to Antarctica. Most people are "sheeple" who are simply not skeptical enough to see through all the lies and evidence and data and common sense to know that everyone in authority is lying to us. This kind of thinking can only be sustained with a well-developed confirmation bias. That is, once you believe something (the earth is flat) you must select what you trust accordingly - accept what confirms your belief, then reject what contradicts it and use a conspiracy to explain way the contrary evidence.

But confirmation bias does not only affect contrarians and conspiracy theorists. All of us are susceptible to it. We can selectively read sources that confirm what we already believe, selectively reinterpret evidence to make it support what we believe, or selectively remember evidence that confirms what we already believe. Confirmation bias makes us less critical of what seems right to us, so we don't check up on these things or evaluate them with the same skepticism we may apply to what we believe to be false. In Peter Berger's terms, what conforms to our plausibility structures is not evaluated in the same way as what contradicts them. When we're assessing threats with this confirmation bias, this can lead to alarmism, where we exaggerate threats to make them more alarming than they actually are.

A couple years ago, I came across claims that a "blue ocean event" is a tipping point that, when crossed, would lead to catastrophic warming in just a few years. I was told climatologists were saying it will "crush humanity like a bug." The thinking behind this is that we are rapidly losing Arctic sea ice (which is true), and as we lose sea ice, more sunlight is absorbed by the oceans and less is reflected back towards space, producing a positive feedback that amplifies warming by diminishing albedo (also true). And during the process of melting sea ice, some fraction of the excess solar energy goes to melting the ice and turn it into water. That energy is causes the phase change from ice to water without increasing temperature (called latent heat), but when the ice is melted that energy can be used to increase temperatures (also true). Consequently, within a few years of having ice free Arctic summers, the world may experience a rapid warming of global temperatures in just a few years that will squash us all like bugs.

Huh?

There are two aspects to this proposed "tipping point, at least as I've read it described: 1) the decrease in albedo and 2) change from latent to sensible heat.

Ice Albedo

The shrinking of sea ice, without immediate mitigation, is very likely to cause a "blue ocean event" sometime this century, and it is certainly accompanied by a positive feedback as the oceans absorb more heat and reflect less. It may also affect cloud feedbacks in the Arctic, which may be either negative or positive. Some studies have attempted to quantify this. One in particular estimated that the loss of sea ice between 1979-2007 resulted in +0.1 W/m^2 increase in radiative forcing, while a future "realistic ice-free summer" scenario (ice free for 1 month) will result in about +0.3 W/m^2.[1] If we use a TCR of 2 C and an ECS of 3 C, that would translate into 0.16 C short term and 0.24 C long term. A year round ice free Arctic (which is not a realistic expectation) would lead to about +0.7 W/m^2 (about 0.56 C). Uncertainties remain significant, but this does not appear to threaten sudden and catastrophic warming that will squash us like bugs. It is, however, something that should be treated with serious concern.

Latent Heat

Of all the excess heat from AGW, about 93.4% goes to heating the oceans, 2.3% goes to heating the atmosphere and 2.1 goes to heating land. This leaves only about 2.2% to melt ice - 0.9% melts mountain glaciers, about 0.4% goes to melting the Greenland and Antarctic ice sheets, and about 0.8% to melting Arctic sea ice. So we're talking about a change affecting 0.8% of the excess heat entering the climate system. For a crude estimate of how much heat that is, if 2.3% of the excess heat produced 1.2 C warming of the atmosphere then the 0.8% of the excess heat melting Arctic sea ice would be the equivalent of an extra 0.3 C atmospheric warming. But that's not the full story, because when we experience ice free summers, much of that 0.8% will go to heating the oceans and causing evaporation (a phase change from water to water vapor) without changing the temperature of the atmosphere. Some of it will add to the heating of the atmosphere as well, but we are not expected to have ice free winters even this century, so this will not affect the entire year in the Arctic. But even as we approach ice free summers and then see the Arctic become ice free for longer portions of the year, the fraction of excess heat that changes from melting ice to heating the atmosphere is exceedingly small. And it's not a sudden change; it's a change that happens gradually with ice loss; it has been happening and will continue to happen until we achieve an ice-free Arctic all year, if that ever happens.

There may well be estimates of how much additional warming would be due to the complete loss of sea ice, but I would be surprised if it was more than 0.1 C. By far the dominant heat sink in the climate system is the oceans. That's where over 93% of excess heat in the climate system goes. In fact, one recent meta-analysis[2] of tipping points concluded that there is no tipping point associated with shrinking Arctic sea ice - it scales linearly with Arctic temperatures. So it seems reasonable to conclude that the notion of a "Blue Ocean Event" that will cause sudden catastrophic warming and squash us like bugs would fit the definition of "alarmism." 

Conclusion

As I've shared in other posts, tipping points ought to be seen as a serious threat that can exacerbate warming, and some of them may increase warming beyond model projections. However, given my research so far, none of these thresholds have serious threat to become a kind of "cliff" beyond catastrophic warming becomes inevitable and mitigation does no good. These reports of sudden, catastrophic warming from a blue ocean event appear to be exaggerating the effects of legitimate principles of physics, so it can pass through our filters and feed our confirmation bias if we do not take some time to evaluate the claims. And to be sure, alarmism from a lack of skepticism is not limited to proponents of AGW. I've seen many "alarmist" predictions of catastrophe from contrarians claiming that mitigation will end western civilization and result in the rise of either communism or fascism to global dominance. But genuine skeptics think critically about the reports they read, and they evaluate claims against the available evidence.

References:

[1] Hudson, S. R. (2011), Estimating the global radiative impact of the sea ice–albedo feedback in the Arctic, J. Geophys. Res., 116, D16102, doi:10.1029/2011JD015804.

[2] Wang, S., Foster, A., Lenz, E. A., Kessler, J. D., Stroeve, J. C., Anderson, L. O., et al. (2023). Mechanisms and impacts of Earth system tipping elements. Reviews of Geophysics, 61, e2021RG000757. https://doi.org/10.1029/2021RG000757