The more I talk with people about their attitudes towards and feelings about climate change, the more I have discovered that many (perhaps most) well-educated and socially-engaged people have only a somewhat vague idea of the nature, scale and likely timing of the various kinds of dangers we face on our current path. And so, when I came across
this summary from Joe Romm, I immediately thought that many of my readers might find it a useful resource to peruse, bookmark, reflect upon and share with others. If you are not really sure what impacts mainstream scientific research currently considers likely from a middle of the road business as usual scenario (i.e. not worst case), then
this post lays out many of the key issues in an accessible way.
The figure included above is from
MIT research from 2009 and shows the likelihood of different temperature outcomes based on two broad scenarios. On the left is business as usual. This is not the worst case and does not include slow feedbacks. On the right is a world where we take aggressive global action to reduce carbon emissions. The temperatures are the average global difference between the world in 1990 and in 2100. Since most other discussions used pre-industrial temperatures as a baseline and the world had already warmed by about 0.5ºC by 1990, then this needs to be added to the numbers to compare with other publications. My main criticism of the image is in the choice of colour. A rise of 3.5-4.5ºC above pre-industrial temperatures can in no sense be understood as reassuringly green. Such a change in the space of a century would be unlikely to be compatible with industrial civilisation as we know it or the possibility of feeding anything like the 9-10 billion people projected to be around by then.