I just wrote this in reply to a comment on an earlier thread, but it got fairly long and I thought it might as well get a post of its own.
John Ham commented on my "Happy Blog Action Day for Climate" post, in quotes below - my responses are after each quoted bit.
JH: "You don't really mean to compare Venus' atmosphere with that of Earth do you?!"
me: Same laws of physics - a useful data point on the scale.
JH: "Of course a doubling of CO2 is likely to raise average temperatures here on Earth on the order of 1 degree C (that's a bad thing?),"
me: That's a GOOD thing? That's the question. So read IPCC AR4 wg2, and Mark Lynas' book Six Degrees: our future on a hotter planet LC#: QC981.8 .G56 L983 2008; ISBN: 9781426202131 -- because it's not just 1C - see below...
JH: "...but all the rest is poorly understood feedbacks, despite what the climate modelers tell you."
me: Not *that* poorly understood -- there is a whole body of scientific literature on feedbacks and the effective climate sensitivity to an initial forcing. The net gain from the combined feedbacks has to be more than zero to account for paleo/historical data and recent satellite results. Royer 2007 in Nature is a good recent entry: Royer 2007
A handy summary of results of over 60 studies estimating the sensitivity factor is at Barton Paul Levenson's climate pages
A detailed book is Understanding Climate Change Feedbacks from the Panel on Climate Change Feedbacks, Climate Research Committees, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, National Research Council of the National Academies.
LC call # QC981.8 .C5 U485 2003
Also readable online here (See box on p.19-20 for a good summary of feedbacks and gain in climate sensitivity.) Note: quite technical.
JH: "(They should get out more often so they stop confusing their models with reality.)"
me: They aren't *confusing* the models with reality - they test the models against data from the real world. The point of modeling is to improve our understanding of the behaviour of a complex system. They apply the laws of physics. They readily admit what their models do and don't cover, and what they can and can't replicate. I've been to guest lectures on campus by several top climatologists who refer to their modeling work, and it's clear to me they have their feet on the ground of hard data from the real world.
JH: "Or ocean acidification (a pretty scary term used to describe making the pH of the oceans slightly less alkaline than they currently are, if that were possible): a good look at ocean carbonate chemistry debunks that idea fairly quickly."
me: I've had a good look at ocean carbonate chemistry. There's a chapter on it in this nice 4-volume collection in our UofT science library:
Climate change : critical concepts in the environment
edited by Frank Chambers and Michael Ogle.
LC # QC981.8 .C5 C5144 2002
Note: quite technical
I also defer to the "alarmist" statement from 155 leading oceanographers in the 2009 Monaco Declaration.
JH: "Is this really how you propose to 'engage the denial'? "