Discussion paper: Climate response to imposed solar radiation reductions in high latitudes

[Ken Caldeira]

MacCracken, M. C., Shin, H.-J., Caldeira, K., and Ban-Weiss, G. A.: Climate response to imposed solar radiation reductions in high latitudes, Earth Syst. Dynam. Discuss., 3, 715-757, doi:10.5194/esdd-3-715-2012, 2012. 

Folks,

I am not a big fan of these discussion journals, but we have nevertheless submitted a manuscript to Earth System Dynamics Discussions.  You are invited to comment on this paper at  http://www.earth-syst-dynam-discuss.net/3/715/2012/esdd-3-715-2012.html  

The abstract is repeated below.

Best,

Ken

--------------------------------------

Earth Syst. Dynam. Discuss., 3, 715-757, 2012
www.earth-syst-dynam-discuss.net/3/715/2012/
doi:10.5194/esdd-3-715-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.

Climate response to imposed solar radiation reductions in high latitudes

M. C. MacCracken¹, H.-J. Shin^2,3, K. Caldeira², and G. A. Ban-Weiss^2,4
1Climate Institute, 900 17th St. NW, Suite 700, Washington, DC 20006, USA
²Carnegie Institution for Science, Deptartment of Global Ecology, 260 Panama Street, Stanford, CA 94305, USA
³Korea Institute of Atmospheric Prediction Systems, Systems Division/Model Validation Team 35 Boramae-ro 5-gil, Dongjak-gu, Seoul, 156-849, South Korea
⁴Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720, USA

 Abstract. Increasing concentrations of greenhouse gases are the primary contributor to the 0.8 °C increase in the global average temperature since the late 19th century, shortening cold seasons and lengthening warm seasons. The warming is amplified in polar regions, causing retreat of sea ice, snow cover, permafrost, mountain glaciers, and ice sheets, while also modifying mid-latitude weather, amplifying global sea level rise, and initiating high-latitude carbon feedbacks. Model simulations in which we reduced solar insolation over high latitudes not only cooled those regions, but also drew energy from lower latitudes, exerting a cooling influence over much of the hemisphere in which the reduction was imposed. Our simulations, which used the National Center for Atmospheric Research's CAM3.1 atmospheric model coupled to a slab ocean, indicated that, on a normalized basis, high-latitude reductions in absorbed solar radiation have a significantly larger cooling influence than equivalent solar reductions spread evenly over the Earth. This amplified influence occurred because high-latitude surface cooling preferentially increased sea ice fraction and, therefore, surface albedo, leading to a larger deficit in the radiation budget at the top of the atmosphere than from an equivalent global reduction in solar radiation. Reductions in incoming solar radiation in one polar region (either north or south) resulted in increased poleward energy transport during that hemisphere's cold season and shifted the Inter-Tropical Convergence Zone (ITCZ) away from that pole, whereas equivalent reductions in both polar regions tended to leave the ITCZ approximately in place. Together, these results suggest that, until emissions reductions are sufficient to limit the warming influence of greenhouse gas concentrations, polar reductions in solar radiation, if they can be efficiently and effectively implemented, might, because of fewer undesirable side effects than for global solar radiation reductions, be a preferred approach to limiting both high-latitude and global warming. 

_______________
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

Currently visiting  Institute for Advanced Sustainability Studies (IASS)  

and Potsdam Institute for Climate Impact Research (PIK) in Potsdam, Germany.

[Mike MacCracken]

Personally, I look forward to comments on our paper that has just been posted for discussion and think the idea of wider discussion of draft papers is a good idea (in addition to the normal review set of comments, which is also taking place).

The key point of the paper is start determining if there are ways in which application of SRM can be engineered to reduce its problematic aspects while still using the approach to address the most important impacts being caused by climate change, in this paper’s case, high latitude climate change, and perhaps do so in the nearer rather than the long term. Admittedly, calculations are idealized and implementation might well be challenging, but the question is whether we can optimize not just how the sulfate layer might be created or clouds brightened, but also about the distribution of the intervention and the objectives being pursued to find potentially more practical and workable approaches.

So, yes, comments would be welcomed.

Mike MacCracken

On 7/26/12 6:27 AM, "Ken Caldeira" <kcal...@carnegiescience.edu> wrote:

MacCracken, M. C., Shin, H.-J., Caldeira, K., and Ban-Weiss, G. A.: Climate response to imposed solar radiation reductions in high latitudes, Earth Syst. Dynam. Discuss., 3, 715-757, doi:10.5194/esdd-3-715-2012, 2012. 

Folks,

I am not a big fan of these discussion journals, but we have nevertheless submitted a manuscript to Earth System Dynamics Discussions.  You are invited to comment on this paper at  http://www.earth-syst-dynam-discuss.net/3/715/2012/esdd-3-715-2012.html  

The abstract is repeated below.

Best,

Ken

--------------------------------------

Earth Syst. Dynam. Discuss., 3, 715-757, 2012

www.earth-syst-dynam-discuss.net/3/715/2012/ <http://www.earth-syst-dynam-discuss.net/3/715/2012/>

doi:10.5194/esdd-3-715-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.

Climate response to imposed solar radiation reductions in high latitudes

M. C. MacCracken1, H.-J. Shin2,3, K. Caldeira2, and G. A. Ban-Weiss2,4
1Climate Institute, 900 17th St. NW, Suite 700, Washington, DC 20006, USA
2Carnegie Institution for Science, Deptartment of Global Ecology, 260 Panama Street, Stanford, CA 94305, USA
3Korea Institute of Atmospheric Prediction Systems, Systems Division/Model Validation Team 35 Boramae-ro 5-gil, Dongjak-gu, Seoul, 156-849, South Korea
4Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720, USA

 Abstract. Increasing concentrations of greenhouse gases are the primary contributor to the 0.8 °C increase in the global average temperature since the late 19th century, shortening cold seasons and lengthening warm seasons. The warming is amplified in polar regions, causing retreat of sea ice, snow cover, permafrost, mountain glaciers, and ice sheets, while also modifying mid-latitude weather, amplifying global sea level rise, and initiating high-latitude carbon feedbacks. Model simulations in which we reduced solar insolation over high latitudes not only cooled those regions, but also drew energy from lower latitudes, exerting a cooling influence over much of the hemisphere in which the reduction was imposed. Our simulations, which used the National Center for Atmospheric Research's CAM3.1 atmospheric model coupled to a slab ocean, indicated that, on a normalized basis, high-latitude reductions in absorbed solar radiation have a significantly larger cooling influence than equivalent solar reductions spread evenly over the Earth. This amplified influence occurred because high-latitude surface cooling preferentially increased sea ice fraction and, therefore, surface albedo, leading to a larger deficit in the radiation budget at the top of the atmosphere than from an equivalent global reduction in solar radiation. Reductions in incoming solar radiation in one polar region (either north or south) resulted in increased poleward energy transport during that hemisphere's cold season and shifted the Inter-Tropical Convergence Zone (ITCZ) away from that pole, whereas equivalent reductions in both polar regions tended to leave the ITCZ approximately in place. Together, these results suggest that, until emissions reductions are sufficient to limit the warming influence of greenhouse gas concentrations, polar reductions in solar radiation, if they can be efficiently and effectively implemented, might, because of fewer undesirable side effects than for global solar radiation reductions, be a preferred approach to limiting both high-latitude and global warming. 


_______________
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

Currently visiting  Institute for Advanced Sustainability Studies (IASS) <http://www.iass-potsdam.de/>   
and Potsdam Institute for Climate Impact Research (PIK) <http://www.pik-potsdam.de/>  in Potsdam, Germany.