This is a brief follow-up piece to my Chemistry World article about the CLOUD experiment going on at CERN. One of the interesting things I realised while researching the article is that although we know quite a lot about how human activity might be warming the globe, we know a huge amount less about how we might be cooling it.
The IPCC report for policy makers (free to view pdf) illustrates this clearly. On page four you can see the error bars showing the uncertainty associated with each forcing factor. It shows we know a lot about how CFCs, green house gases and ozone affect global climate but where aerosols are concerned we are very uncertain; as Jasper Kirkby says “the error bars are huge!” I just thought this was a really interesting point to make. And given the poor understanding of aerosols in cloud formation that CLOUD has laid bare, this should probably now be a real focus of research. Kirkby also explains some of the facts himself in this lecture (the first six minutes give a good background).