As we must have North Pole Summer Ice to have a “safe” climate system due to its ability to reflect large amounts of Sunlight, it means that “safe” levels of CO2 in the atmosphere lie somewhere between 300 and 325 ppm CO2. Unfortunately we are not sure exactly where that is, so the “safe” target / goal for CO2 concentrations is 300 ppm or below.
“Safe” Climate = 300 ppm CO2 or below
Now knowing this, you can see how ridiculous all the proposals to stabilise our Greenhouse gases at levels higher than today are.
James Hansen suggests that we have only decades to return to a “safe” level of greenhouse gases or we will run the risk of passing points of “no return” for a number of critical global warming positive feedback mechanisms.
James has proposed an interim target of 350 ppm CO2 and the closure of the coal industry, the latter of which he mentions in a recent letter to Kevin Rudd.
“Prime Minister Rudd, we cannot avert our eyes from the basic fossil fuel facts, or the consequences for life on our planet of ignoring these fossil fuel facts. If we continue to build coal-fired power plants without carbon capture, we will lock in future climate disasters associated with passing climate tipping points. We must solve the coal problem now.”
James Hansen letter to Kevin Rudd 27 March 2008
Unfortunately people have already begun to misinterpret Hansen’s call for an interim target and are confusing this with a “safe” target. Please don’t do the same, as 350 ppm CO2 is as much of a death sentence for the planet as 400, 450, 550, 650 etc.
1. http://www.columbia.edu/~jeh1/2008/TargetCO2_20080407.pdf
2. http://www.columbia.edu/~jeh1/RoyalCollPhyscns_Jan08.pdf