Tuesday, May 10, 2011

Aerosol evolution: two scenarios

This is a post inspired by SteveF's work at Lucia's blog here:


The above table from excel uses (I hope) SteveF's method to look at the evolution of aerosol forcings over time. In his simple analysis of equilibrium climate sensitivity, SteveF looked at the situation now and worked out what aerosol forcing would have to be if forcing caused an increase of .4207 degrees per watt per square metre and if forcing caused an increase of .81 degrees per square metre (and another higher scenario).

I have extended his analysis to cover the period 1970 to 2010. One of the thing that I noted in the comments to that thread was that the aerosol forcings under the higher sensitivity scenario are currently the same as they were after the Mount Pinatubo eruption. This seems unlikely. More reasonable is the lower sensitivity scenario, in which current sensitivity is about half of that after Mount Pinatubo erupted.

One interesting fact is that under the higher sensitivity scenario there is quite an upward trend over time in aerosol forcings. This does to some extent seem reasonable, imo, as the increase in CO2 emissions is directly associated with an increase in sulphur emissions. In fact, the correlation between well mixed greenhouse gas (WMGHG) forcings is high (r^2 value of 0.81). This makes sense to me.

Still not sure what it all means, but it is interesting to play with. :)

And I have realised that I may have missed one important component: solar forcings. I will check into that.

*Done a little checking. SteveF seems to simply use one value, but that could be because he is only looking at one year - he might change that value for each year.

*Re correlation, the lowest value for a statistically significant correlation, ignoring possible autocorrelation, which is relatively small, is 0.55 degrees per watt per square metre.

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