At his AGU Tyndall Lecture: Raymond Pierrehumbert calls SRM geoengineering ideas "crazy", and "barking mad"

[David Lewis]

 AND, he added: "the modelling technology is not even up to doing this adequately despite what some aggressive proponents of geoengineering say". 

Raymond made his comments on geoengineering during the Q&A after his talk.  The full text of his geoengineering remarks, which occur starting around minute 54 and 50 seconds of the AGU 2012 Tyndall Lecture which streams from that link, follow:

""I see lots [ of geoengineering ideas ] that are feasible but they all terrify me.  Let me clarify a bit.  

Some people refer to schemes for taking CO2 out of the atmosphere, or sequestering CO2 as a form of geoengineering.  Those I find relatively benign because they [ aim to ] put the climate system back in the state that it was in before we started to mess with it.  

The feasible geoengineering things, feasible - technologically feasible - things, that scare me terribly, are the crazy ideas to make artificial volcanoes and put sulphate aerosols into the stratosphere.   And the reason I think those are barking mad is that CO2 will continue influencing the climate out for 10,000 years.  You have to renew the aerosol forcing every two years or so.  So you are assuming that somehow, society will stay together for the next 10,000 years and be able to jam up these extra aerosols, every two years or so... longer than there have been human civilizations practically.  And if you ever stop then the aerosols go away in a couple of years and then you are hit with the full force of global warming in a time scale that is determined just by the ocean relaxation time.  Unfortunately I think these sulphate aerosol injections are probably economically feasible.  You don't have to inject too much up there but it puts the world in a state that I call the Damocles World.  Its like the sword of Damocles which is the radiative forcing of CO2 just waiting to clobber you any time someone stops putting up these aerosols.  

And in addition we don't actually know enough about  aerosol formation and about response of models to aerosols to begin doing this kind of fine tuning to even figure out how much we should put up there.  There's some very good work by Leslie Gray at Oxford that shows how actually the modelling technology is not even up to doing this adequately despite what some aggressive proponents of geoengineering say".   

[Ken Caldeira]

I am a fan of Ray Pierrehumbert and his work, and agree with him 99% of the time.

In this case, I believe he misspoke when he implied that the set of "aggressive proponents of geoengineering" who say "the modeling technology is ... up to doing this adequately" is non-empty (where "this" presumably refers to "planning an imminent deployment").

First of all, there are very few proponents of geoengineering. (Perhaps, John Nissen and a few others fall into this category.)  In contrast, there are many proponents of geoengineering research.

I leave it to the reader to decide who is or is not aggressive.

I don't know any serious scientist who has said that existing models provide a sound basis for deployment of a solar geoengineering system.

Most climate modelers who investigate geoengineering proposals are pretty careful to put statements in their papers such as the following from Ban-Weiss and Caldeira (2010):

from Abstract:

It is important to note that this idealized study represents a first attempt at optimizing the engineering of climate using a general circulation model; uncertainties are high and not all processes that are important in reality are modeled.

and the final two paragraphs of the Discussion section:

This study treats geoengineering as an optimization problem. We present idealized results from a global climate model. We focus on scientific results and make no prescriptive statements. However, attempts to intervene in the climate system present a wide range of serious environmental and socio-political risks [2, 18–22], a thorough discussion of which is beyond the scope of this study. Further, the model used here does not include many factors that are important in reality (e.g., socio-political consequences, chemical consequences such as changes in stratospheric ozone, ocean circulation changes, aerosol transport and microphysics). For example, failure to reduce CO2 emissions will cause oceans to further acidify with potentially catastrophic consequences for ecosystems such as coral reefs [23]. Furthermore, the perception of a technical fix to the climate problem could result in increased emissions with greater long-term environmental damage. Decisions over testing or deployment of climate intervention systems could result in political or military conflict.

The main goal of this letter is to outline a new methodological approach. Previously, researchers have simulated interventions in the climate system and investigated what climate changes would result. Here, we specify climate objectives and investigate what climate interventions would meet those objectives most closely. It is important to note that the climate model used is much simpler than reality and predictions from individual models certainly do not provide a sound basis for action.

Best,

Ken

PS. By the way, I gave a lecture at AGU on ocean acidification right after Ray's talk. It is available on YouTube here:  https://www.youtube.com/watch?v=Pfz2l29aX9c  The talk is titled "Ocean Acidification: Adaptive Challenge or Extinction Threat?"

_______________
Ken Caldeira

Carnegie Institution for Science 

Dept of Global Ecology

260 Panama Street, Stanford, CA 94305 USA

+1 650 704 7212 kcal...@carnegiescience.edu

http://dge.stanford.edu/labs/caldeiralab  @kencaldeira

Our YouTube videos

The Great Climate Experiment: How far can we push the planet?  

Geophysical Limits to Global Wind Power

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From: "David Lewis" <jrando...@gmail.com>
To: geoengi...@googlegroups.com
Sent: Saturday, December 8, 2012 6:47:50 PM
Subject: [geo] At his AGU Tyndall Lecture:  Raymond Pierrehumbert calls SRM geoengineering ideas "crazy", and "barking mad"

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