This experiment adds a fully interactive sulphur cycle to the model used in the climateprediction.net experiment. This helps us to identify the effects of sulphate aerosol on the global climate system and the sensitivity of the model to perturbing sulphur cycle parameters
For this experiment, an extra 2 phases are added to the 3 phase experiment 1. In one extra phase, the sulphate emissions will be changed to those expected in 2005, and in the other both sulphate and carbon dioxide are changed. In addition, the sulphate emissions typical of 1985 are included in the first 3 phases. This experiment was available for download for a limited period of time, just like the thermohaline experiment we ran in 2004.
Why do we want to include sulphate aerosol in our models?
Sulphates act to scatter solar radiation and reduce the amount of solar energy reaching the surface. The reduction in solar radiation cools the surface and reduces the warming effect caused by greenhouse gases. So a prediction of the climate in the 21st century needs to contain the effects of sulphate aerosol otherwise the warming trend may be overestimated – the so-called ‘global dimming’ effect.
From this experiment we hoped to achieve a better understanding of the range of uncertainty in climate models due to the parameters in the sulphur cycle. This information was then be used in climateprediction.net experiments 2 & 3.
D. Ackerley, E.J. Highwood & D.J. Frame (2009) Quantifying the effects of perturbing the physics of an interactive sulfur scheme using an ensemble of GCMs on the climateprediction.net platform, Journal of Geophysical Research Atmospheres, 114.