If you think the title of this post is a reference to the ongoing discussion about the Whiteman, Hope, and Wadhams piece in Nature about the economic impacts of a 50 billion ton methane release from the Arctic (see Climate science: Vast costs of Arctic change), a.k.a. the “$60 trillion” debate, here’s the good news: It isn’t.
The bad news is that I’m going to try to jump start a discussion about another finding, one that is literally the most terrifying thing I’ve read in the more than 10 years I’ve been studying climate and energy issues. It’s a paper that should be causing considerable turmoil, yet has appeared and all but disappeared without so much as an online peep. Before I dive into this, I would beg you not to succumb to the temptation of “single study syndrome”, i.e. placing undue emphasis on a single research finding. It could well be that the paper mentioned below will be rejected as a flawed outlier and not accepted as part of the scientific consensus in time. It’s also possible that it will go down in history as a landmark finding that helped to reveal the true urgency of this mess we’ve created. If there are follow-on publications that support this finding or include other factors (explained below) that show it was optimistic(!), then those would certainly earn the title of most terrifying climate finding and explain the “so far” part of this post’s title.
Enough foreplay. The paper is If anthropogenic CO2 emissions cease, will atmospheric CO2 concentration continue to increase?. The abstract (emphasis added):
If anthropogenic CO2 emissions were to suddenly cease, the evolution of the atmospheric CO2 concentration would depend on the magnitude and sign of natural carbon sources and sinks. Experiments using Earth system models indicate that overall carbon sinks dominate, such that upon cessation of anthropogenic emissions, atmospheric CO2 levels decrease over time. However, these models have typically neglected the permafrost carbon pool, which has the potential to introduce an additional terrestrial source of carbon to the atmosphere. Here we use the University of Victoria Earth System Climate Model (UVic ESCM), which has recently been expanded to include permafrost carbon stocks and exchanges with the atmosphere. In a scenario of zeroed CO2 and sulphate aerosol emissions, we assess whether the warming induced by specified constant concentrations of non-CO2 greenhouse gases could slow the CO2 decline following zero emissions, or even reverse this trend and cause CO2 to increase over time. We find that a radiative forcing from non-CO2 gases of approximately 0.6 W m−2 results in a near balance of CO2 emissions from the terrestrial biosphere and uptake of CO2 by the oceans, resulting in near-constant atmospheric CO2 concentrations for at least a century after emissions are eliminated. At higher values of non-CO2 radiative forcing, CO2 concentrations increase over time, regardless of when emissions cease during the 21st century. Given that the present-day radiative forcing from non-CO2 greenhouse gases is about 0.95 W m−2, our results suggest that if we were to eliminate all CO2 and aerosols emissions without also decreasing non-CO2 greenhouse gas emissions, CO2 levels would increase over time, resulting in a small increase in climate warming associated with this positive permafrost carbon feedback.
If you’re seeing this for the first time and aren’t a climate scientist, I suspect it will take a few minutes for the implications of this study to crystallize in your mind. While that’s happening, let me offer some thoughts while you ponder this in background mode, and we can do a cognitive docking maneuver in a few paragraphs.
The scenario modeled in this paper is essentially the most utopian dream of environmentalists: The immediate and complete cessation of fossil fuel burning, worldwide. The overwhelming assumption by every environmentalist I’ve ever communicated with about emissions and public policy is that such dramatic action would be ideal from a climate standpoint — “there’s no emissions like no emissions” — but has zero chance of happening for all the obvious reasons of short-term human and economic impact, infrastructure lock-in, political corruption, etc. Further, people assume (again, in my experience) that such a fantasy scenario would be more than enough to avoid climate armageddon, so we still have a place to stand somewhere between our disastrous business-as-usual path and utopia where we’ll be “safe” if we come up with a schedule of carbon emissions reductions, such as the endlessly mentioned 80% reduction from 1990 levels by 2050, or some other formulation that keeps us from exceeding the roughly 485 billion tons of CO2 remaining on our “carbon budget”.
The problem is that almost no one talks about the really big picture, taking into account Arctic permafrost, methane hydrates, albedo flip, and aerosol whiplash. Even this study doesn’t hit all those points; it seems, based on the abstract, to include the permafrost carbon and aerosol whiplash but not methane hydrates. I don’t know what, if anything, it says about albedo flip.
Even without including those Brobdingnagian methane hydrate deposits (the subject you’re relieved I’m not talking about, I would remind you) the result is that if we zero out CO2 and aerosol emissions and don’t make major cuts to non-CO2 greenhouse gases then not only will we see continued warming due our current thermal disequilibrium, a.k.a. the warming “in the pipeline” scientists have been talking about for decades, but feedbacks will ensure that the level of CO2 in the atmosphere will continue to rise. In other words, this paper is saying that we’ve already passed the mother of all tipping points.
Does anyone here think that we can approach a complete fossil fuel cessation and a simultaneous major cut to non-CO2 greenhouse gas emissions?
Does anyone here think that falling short of that extreme goal — especially at a time when worldwide CO2 emissions are still rising — will do anything other than make our situation considerably worse?
Does anyone here think that this paper is describing anything short of a runaway effect that could only be stopped by geoengineering?
UT grad student images water system beneath Antartic Glacier (Hint: It’s as big as the US state of Florida.)
 Please don’t leap to the conclusion that I reject or disagree with anything the authors of that piece said.
 The 485 number is based on the 565 billion tons figure mentioned in the Do the Math video, which I’ve updated to account for emissions since the end of 2010. And yes, you should watch Do the Math, even if you’ve seen it already:
 More formally “Arctic amplification”, albedo flip refers to the increased warming from the loss of ice and snow in the Arctic region. Open ocean and bare land absorb much more sunlight than do snow and ice, which means considerable additional warming during the Northern Hemisphere summer.
 Aerosol whiplash refers to perhaps the nastiest part of our climate mess, what James Hansen has called our “Faustian bargain with coal”. Aerosol emissions, largely from power plants, have a fairly strong cooling effect because they reflect sunlight. The problem is that as reduce our aerosol emissions the atmospheric level of aerosols will decrease in weeks to months, vastly quicker than would the atmospheric level of CO2 if/when we cut those emissions. We’re already cutting aerosols, as the EU has been aggressively installing scrubbers on power plants, with the US playing catch up. China is now getting very serious about curtailing their aerosol emissions, in an effort to improve local air quality. For the purposes of this posting, the thing to keep in mind is that if we end coal burning we also end aerosol emissions, which means the CO2 already in the atmosphere stays around essentially forever in human planning terms while we lose the benefit of the aerosols very quickly and suffer a jump in warming. Hence the whiplash.
 I’m sure experts could/would add other items to this list of factors for a “big umbrella” assessment of our climate situation, such as changes in ocean and atmosphere currents. I’ve only included those that are major factors according to the current scientific consensus, as best I understand it.