The importance of response times for various climate strategies - Springer

[Andrew Lockley]

http://link.springer.com/article/10.1007/s10584-013-0769-5

If climate action becomes urgent: the importance of response times for various climate strategies

Detlef P. van Vuuren, Elke Stehfest

Abstract

Most deliberations on climate policy are based on a mitigation response that assumes a gradually increasing reduction over time. However, situations may occur where a more urgent response is needed. A key question for climate policy in general, but even more in the case a rapid response is needed, is: what are the characteristic response times of the response options, such as rapid mitigation or solar radiation management (SRM)? This paper explores this issue, which has not received a lot of attention yet, by looking into the role of both societal and physical response times. For mitigation, technological and economic inertia clearly limit reduction rates with considerable uncertainty corresponding to political inertia and societies’ ability to organize rapid mitigation action at what costs. The paper looks into a rapid emission reductions of 4–6 % annually. Reduction rates at the top end of this range (up to 6 %) could effectively reduce climate change, but only with a noticeable delay. Temperatures could be above those in the year of policy introduction for more than 70 years, with unknown consequences of overshoot. A strategy based on SRM is shown to have much shorter response times (up to decades), but introduces an important element of risk, such as ocean acidification and the risk of extreme temperature shifts in case action is halted. Above all, the paper highlights the role of response times in designing effective policy strategies implying that a better understanding of these crucial factors is required.

This article is part of a special issue on "Geoengineering Research and its Limitations" edited by Robert Wood, Stephen Gardiner, and Lauren Hartzell-Nichols.

[Mike MacCracken]

I continue to wonder how one can be so concerned about the warming that would occur at a supposed end of SRM and not be worried about the rapid onset of SRM if used in an emergency manner (not to mention that by the time of the emergency it may be too late to reverse (e.g., think about Greenland melting rate, could it be reversed?). As climate warms/changes, there is always some adaptation going on, so the thought of suddenly taking the global average temp down a degree C would likely lead to quite large disruptions and dislocations, just as would coming out of such a cooling. The disruption of going into SRM can be smoothed, and so could an exit (if we assume we have as much sense as needed to get agreement to start SRM), just as going in one could have a sudden change likely as disruptive as coming out if not managed well. So, why all the focus on the back end problem, without a similar concern at start-up?

Mike MacCracken

[John Latham]

Sorry if I'm missing a point, Mike, but - in principle - the transition
to full SRM deployment in the case of Marine Cloud Brightening
could be made at a selected rate and modified in a controllable
manner by adjusting the sea-water spray rate. Additional
flexibility is provided by varying the choices of the locations at which
sprayiing occurs. The same principles could be applied to sub-global MCB
geo-engineering, in the cases of coral reef protection and
weakening of hurricanes, via propitiously chosen surface water
cooling.
All Best, John.


John Latham
Address: P.O. Box 3000,MMM,NCAR,Boulder,CO 80307-3000
Email: lat...@ucar.edu or john.l...@manchester.ac.uk
Tel: (US-Work) 303-497-8182 or (US-Home) 303-444-2429
or (US-Cell) 303-882-0724 or (UK) 01928-730-002
http://www.mmm.ucar.edu/people/latham
________________________________________
From: geoengi...@googlegroups.com [geoengi...@googlegroups.com] on behalf of Mike MacCracken [mmac...@comcast.net]
Sent: 22 May 2013 03:17
To: Andrew Lockley; Geoengineering
Subject: Re: [geo] The importance of response times for various climate strategies - Springer

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[Mike MacCracken]

Hi John--I wholeheartedly agree that a gradual implementation could be done.
It seems to me, however, in many of the discussions, the application is
being talked about as an emergency application that could be done much more
rapidly than CO2 mitigation rather than as a gradual application. It is
those proposed cases that prompted my comment.

Best, Mike

[Fred Zimmerman]

It's somewhat academic since in all likelihood the most time-consuming element in the process will be the political deliberations necessary to reach agreement on action.  We're at 20 years and counting from Rio and we are still increasing emissions every year.

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Fred Zimmerman

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