Ocean cooling geoengineering project

This experiment uses exactly the same setup as the Seasonal Attribution Experiment but instead looks at the effect of a sudden artificial cooling of the ocean surface.

Motivation

On the one hand people are becoming increasingly concerned about climate change caused by human emissions of greenhouse gases, but on the other hand they are also realising both that a lot of greenhouse gases have already been emitted and that reducing future emissions substantially could be quite difficult. One idea for how to deal with this is to actively cool the ocean surface, supposedly to “natural” temperatures.

For instance, James Lovelock, of Gaia fame, and Chris Rapley, director of the Science Museum in London, have proposed inserting large vertical pipes in the ocean which would passively use the energy of waves to force cool water to rise from the deep ocean to the surface, thereby cooling the surface. (It could also get more carbon dioxide to be absorbed from the atmosphere and stored in the the deep ocean, but we will only worry about the cooling effect here.) This experiment will examine the effects of any method that would cool the ocean surface but leave other conditions the same. Will inland areas be cooled? Will rainfall change?

Method

This new experiment consists of two components. The first is a set of simulations of the year 2000 (actually March 2000 to April 2001) using the actual conditions experienced in year 2000. These conditions include observed values of the atmospheric concentrations of greenhouse gases and other gases and aerosols, as well as observed ocean surface temperatures and sea ice coverage. Simulations differ in the initial weather state set for midnight on 1 March 2000, such that each simulation gives an example of what the weather could have been like in year 2000. Altogether, these simulations give an estimate of the climate for that year. These simulations were completed as part of the Seasonal Attribution Experiment.

The second component involves re-running these simulations, but with ocean surface temperatures cooled (and sea ice extent expanded) according to an estimate of what year 2000 conditions would have been had we not been emitting greenhouse gases (note this is not quite “natural” because we would still have been doing other things, like emitting sulphate aerosols). These ocean conditions were estimated as part of the “non-industrial” component of the Seasonal Attribution Experiment. (We will use only only one of the 40 estimates used in that experiment though, the one with the pattern estimated from the HadCM3 model and the amplitude as the 6th decile estimate based on a comparison of that pattern with the observed record.) Note though that unlike those “non-industrial” simulations, these simulations will use the true observed greenhouse gas concentrations.

Status

• Some simulations used in this experiment were run previously under the Seasonal Attribution Experiment.
• The first simulation dedicated to this experiment was started on 11 December 2008.
• The final simulation was started on 11 March 2009. Thanks to all who volunteered their computers!
• This experiment will enter the analysis phase when all simulations are completed.