The Blanket Effect is intended for others to learn about weather modification and its related subjects in an easy to understand way. Started in 2005, this blog is a work in progress as the technology advances

November 5, 2007

50/50 Gulf Stream Collapse?

(We present excerpts from a research paper submitted to the 2005 United Nations Climate Control Conference, (PDF) Included is a loose 'translation' following each section for those of us who are put off by technical terms. The conclusions drawn in the 'translation' are solely of The Blanket Effect Editor's and do not represent the original authors' statements.)

Assessing the Risk of a Collapse of the
Atlantic Thermohaline Circulation

Michael E. Schlesinger 1, Jianjun Yin 1, Gary Yohe 2,
Natalia G. Andronova 1, Sergey Malyshev 3, Bin Li 1

1. Climate Research Group, Department of Atmospheric Sciences, University of Illinois at Urbana-
2. Department of Economics, Wesleyan University
3. Department of Ecology and Evolutionary Biology, Princeton University


In this paper we summarize work performed by the Climate Research Group within the Department of Atmospheric Sciences at the University of Illinois at Urbana-Champaign (UIUC) and colleagues on simulating and understanding the Atlantic thermohaline circulation (THC) (wikipedia).

We have used our uncoupled ocean general circulation model (OGCM) and our coupled atmosphere-ocean general circulation model (AOGCM) to simulate the present-day THC and how it would behave in response to the addition of freshwater to the North Atlantic Ocean.

(translation: In this paper we summarize work involving simulating and understanding the Gulf Stream circulation 'pump'. We have used our two models to simulate the present-day Gulf Stream and to see how it would behave if a lot of freshwater were added to the North Atlantic Ocean)

We have found that the THC shuts down ‘irreversibly’ in the uncoupled OGCM but ‘reversibly’ in the coupled AOGCM, the latter because of a negative feedback that cannot exist in the uncoupled OGCM.

We have represented this wide range of behavior of the THC with an extended and simplified version of the original simple model that gave rise to the concern about the THC shutdown.

(translation: We have found that the Gulf Stream shuts down irreversibly in one model but is reversible in the second model)

We have used this simple model of the THC together with the DICE-99 integrated assessment model to estimate the likelihood of a THC shutdown between now and 2205, both without and with the policy intervention of a carbon tax on fossil fuels.
(translation: We used the two models to estimate the likelihood of a Gulf Stream shutdown between now and 2205 A.D., both with and without the policy intervention of a proposed carbon tax on fossil fuels.

We find that absent any climate policy, there is a greater than 50% likelihood of a THC collapse. This likelihood can be reduced by the policy intervention, but still exceeds 25%.
(translation: Without any climate policy, there is more than a 50% likelihood of a Gulf Stream collapse. However, with policy intervention, the chances can be reduced to around 25%)

It would therefore seem that the risk of a THC collapse is unacceptably large and that measures over and above the policy intervention of a carbon tax should be given serious consideration.
(image below from
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