The Right CO2 Reduction Target for a Soft Landing?

<<DRAFT; 081011>>. Much confusion and fuzzy-headed thinking surrounds the topic of climate change CO2 reduction targets. A lot of it is generated by the IPCC modeling scenarios relating CO2 concentrations in parts per million (ppm) to average surface temperature increases, and the IPCC recommendation of the 2 degree increase (Celsius) target and its associated CO2 concentration of 450 ppm.

Unfortunately, that scenario, according to the IPCC's own modeling has only a 50 percent chance of being achieved, with a high chance of being exceeded. Under the IPCC modeling and scientific consensus, exceeding 450 ppm pushes the climate system into highly likely catastrophic effects. Thus, the 2 degree target is not a prudent public policy and planning target. Complicating matters are some assumptions of linear increases in temperature and others that subsequent assessment has concluded indicate that the IPCC modeling is highly conservative.

A more prudent public policy target would be the IPCC's 1 degree scenario, limiting CO2 concentrations to 350 ppm, as described by Lester Brown and the Earth Policy Institute, as follows:

. . .  cutting net carbon dioxide (CO2) emissions 80 percent by 2020. This would keep atmospheric CO2 levels from exceeding 400 parts per million (ppm), up only modestly from 386 ppm in 2008. 2

This sets the stage for reducing CO2 concentrations to the 350 ppm that James Hansen and other climate scientists think is needed to avoid runaway climate change. It will also help keep future temperature rise to a minimum. Such a basic economic restructuring in time to avoid catastrophic climate disruption will be challenging, but how can we face the next generation if we do not try? 3

See Also: Will Tarsands be Game Over for Averting Catastrophic Climate Change? 

Climate Change Links:

• World Watch Institute Climate Change Reference Guide

• James Hansen, Target Atmospheric CO2-Where Should Humanity Aim

• Lester Brown, Plan B--Mobilizing to Save Civilization, Chapter 4: Stabilizing Climate

• IPCC targets lead to (at least) 54% odds of catastrophic climate change

• Mainstream Emissions Targets are Insufficient

• James Hansen, Paleoclimate Implications for Human-Made Climate Change

• Scientific American, IPCC Modelling Proves too Conservative with CO2 Reduction Targets Insufficient