Today was a big day at the U.S. National Academy of Sciences (“NAS”). The Academy released two important climate reports, each dealing with one of two categories of global countermeasures for the effects of dumping unprecedented amounts of carbon dioxide into Earth’s atmosphere.
The first report, Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration, deals with ways of removing carbon dioxide from production, and binding it or burying it in a way that it will be stable for millennia. Removing carbon dioxide at this scale is hard, very expensive, and the engineering of these technologies is rudimentary. It would be much easier to do if carbon dioxide and other greenhouse gas emissions were zeroed first. In any case, it is an option if people of Earth fail to redirect their appetite for fossil fuel energy soon enough to zero carbon sources, even if there are serious questions regarding how such a massive program would be set up, run, and paid for. Note you cannot impose a Carbon Tax on Carbon which is no longer being consumed.
The second report, Climate Intervention: Reflecting Sunlight to Cool Earth, is of greater interest because of it’s high danger. We do not know the consequences of doing this kind of thing. The experiment has never been done. Once started it essentially cannot be stopped, unless a system of carbon dioxide removal were first constructed. It cannot be stopped because, otherwise, the effects of radiative forcing from accumulated carbon dioxide would be pressed on the planet suddenly, a shock with unknown consequences. The other reason this is dangerous is because it is much cheaper than carbon dioxide removal, the technology is within grasp, and may in fact be cheaper than kicking the fossil fuel habit.
Professor Ray Pierrehumbert, whose work I’ve often linked from this blog, and whose textbook and lab notes are outstanding, is a co-author of both reports. He’s also written an article about them at Slate. Quoting a key part of that article, titled “Barking mad”, and thus reprising comments from Ray’s lecture at the AGU Fall Meeting in 2012:
The take-home message is that it is not possible to use albedo modification to counteract peak CO2-induced warming without maintaining the climate intervention without interruption for millennia. At least, that’s the case unless we learn how to actively suck CO2 out of the atmosphere. The problem of millennial commitment makes it exceedingly imprudent to count on albedo modification to get and keep us out of a climate emergency. Absent effective CO2-removal techniques, albedo modification cannot be seen as a temporary measure that can give us time to get our act together to eliminate CO2 emissions. And if at any point albedo modification actions are ceased abruptly, the world would be faced with the rapid release of a century or more of pent-up warming.
(By the way, that lecture, regarding “successful predictions” is linked below. I like the posing of the problem, as a statistician who often builds models which are very difficult to test well.)
The place where Ray speaks to albedo modification is here: https://www.youtube.com/watch?v=RICBu_P8JWI#t=3279, although I recommend the entire lecture, because it is a great summary.
Given the tendency for people and economies to take the easiest, cheapest, short term way out, albedo modification remains a significant threat, one of the tempting consequences of our continued addiction. Ray considers the ethical implications, in his article at Slate.
One of his points of summary there is:
So yes, albedo hacking is still barking mad, but people are often driven to do barking mad things out of desperation, and we are heading to the breaking point now with our continued fossil fuel binge. But if it comes to albedo hacking, the result won’t be pretty.
Update, 10th February 2015, 16:51 ET
Update, 11th February 2015, 08:37 ET
The New York Times should actually read the reports on climate hacking before commenting on them. The spin of plausibility of these options is completely amazing, not even mentioning their costs and downsides, simply that these might exist! Shabby, Times, very shabby.