An important Dutch-, US-, Austria– and Japan-authored paper by D.P. van Vuuren and 14 colleagues entitled “The representative concentration pathways: an overview”, Climatic Change, 109: 5-31, 2011: http://nldr.library.ucar.edu/repository/assets/osgc/OSGC-000-000-010-874.pdf estimates that (among other things) world GDP outcomes for various “representative concentration pathways” (RCPs) ranging from RCP2.6 (the most aggressive climate change action) to RCP8.5 (business as usual) are vastly better with strong climate change action. Importantly, the improved world GDP outcome for the best scenario, RCP2.6, was apparent from 2000 onwards and by 2100 is over $100 trillion (2000 dollars) better than for the worst, BAU scenario, RCP8.5.
Jeff Spross, “Report: the more carbon emissions we cut, the better the world economy does”, Climate Progress, 27 August 2013: http://thinkprogress.org/climate/2013/08/27/2530391/carbon-cut-better-economy/ has summarized the findings of D.P. van Vuuren: “The graph below [CO2 versus time for scenarios RCP2.6 to RCP8.5; Fig. 6 in van Vuuren et al., 2011] . shows the concentration of carbon in the atmosphere in parts per million (ppm) under four different RCP scenarios. The RCP2.6 (the green line) features the most aggressive reduction in carbon emissions by the global community, which stabilizes the carbon concentration around 450 ppm and then slowly brings it down. The RCP8.5 (the blue line) shows us blasting nearly all the way to 1,000 ppm by 2100, which is what we’re likely to do if we continue business as usual… Now look at this graph [GDP versus time for scenarios RCP2.6 to RCP8.5; Fig. 2 in van Vuuren et al., 2011] . That’s the wealth the planet will produce as modeled under the four RCPs. Needless to say, it doesn’t bode well for the claim that aggressively cutting carbon emissions will wreck the economy… By the end of the century, the global economy would be well over $100 trillion larger under the most ambitious policies to reduce carbon emissions, versus the business-as-usual scenario. There’s a reason for this. Climate change means more droughts and altered rain patterns, leading to greater food insecurity. It means constricted freshwater supplies and heat waves, putting more strain on the infrastructure of cities and communities. It means less water to help run power stations and manufacturing processes, and altered river flows that can render shipping lanes useless. It means stronger storms and extreme weather that cause more damage, and it even means new and larger climate areas diseases can travel in. Add it all up, and it means a lot of damage to the economy. The RCP2.6 is the course of action most likely to keep us under two degrees Celsius of warming — the threshold above which climate change becomes really dangerous according to most scientists. But the RCP8.5 is the scenario most likely to get us near five degrees Celsius of warming, an outcome summed up by David Roberts of Grist as “hell on earth. Worse, the IPCC reports [the Assessment Report 5, AR5, is due out soon] are consensus documents between many players. That leads them to be conservative in their climate projections.”
For related information see the following useful websites: “Cut Carbon Emissions 80% by 2020”: https://sites.google.com/site/cutcarbonemissions80by2020/ ; “100% renewable energy by 2020”: https://sites.google.com/site/100renewableenergyby2020/ ; “2011 climate change course”: https://sites.google.com/site/300orgsite/2011-climate-change-course ; and “300.org – return atmosphere CO2 to 300 ppm”, 300.org: http://sites.google.com/site/300orgsite/300-org---return-atmosphere-co2-to-300-ppm .