His basic premise is that, with the controls we are likely (not) to put in place, temperatures will rise 8*C in the temperate zones and 4*C in the tropics by 2100.  He notes the effect that particulate emissions are having at present in reducing solar heating and notes that it can and probably will disappear well before then.  I recall a PBS program, NOVA, I believe, that addressed the particulate emissions issue and made a comment this time last year.  Turned out poemless had written a diary on the subject the year before and I had been watching a re-run.  Most of the estimates I have seen predict 6C increases if we do little.  None of them, to my knowledge, include the present moderating effect of industrial haze on greenhouse temperature increases.

The rest of Lovelock's conclusions deal with his estimates of the impact of these changes.  I do not believe any "serious" person or organization has yet published an analysis of the impact of such changes on the carrying capacity of the planet.  I do recall a comment by asdf regarding the extenction of species as climate change proceeds faster than species can adapt.  Given our species' known aversion to bad news, I would be reluctant to write off Lovelock's analysis out of hand.  We do know that the Pentagon and the CIA are taking these issues seriously.

"It is not necessary to have hope in order to persevere."