A recent article in the UK highlights a University of Manchester study that has calculated that a mere 10% increase in the amount of green space in built-up centers would reduce urban surface temperatures by as much as 4°C. Depending on your estimate of temperature sensitivity to carbon and your view of future population and economic growth, in the consensus view this is somewhere between 75 and 200 years of warming.
Now while the result itself probably indicates why climate models are not super-reliable, the concept illustrates why adaptation (limiting the impacts of emissions-driven warming) is generally so much more cost-effective than mitigation (reducing emissions) as a way to deal with climate risk. I don’t need a huge econometrics model to tell me that adding 10% to park space in London has got to be a lot cheaper the costs to everyone who lives and works in London of forcing a restructuring of the conomy to reduce emissions by 50%.