QuatreHiead, on 30 June 2012 - 10:53 AM, said:
......even if we went to an ideal environmentally friendly society today, how long before the level of global climate change returns to more like what we observed 20 years ago or something?
Backing up climate change? Don't find that discussed much. Just working at stabilizing it a degree or two or three © warmer is usually what's mentioned.
From what I gather, somewhere between several decades and never to actually reverse climate change.
First, depends on whether or not a climate/greenhouse gas "tipping point" has been reached. If it has, then feedback processes will continue raising greenhouse atmospheric gas concentrations even if we quit burning fossil fuels. If, for instance, there is enough ongoing methane release in the Arctic from thawing permafrost and thawing methane hydrates then the addition of that methane, a strong greenhouse gas, would offset reduction of fossil fuel CO2. Then more warming, yet more thawing methane, more warming, etc. Opinions are divided on how close such a tipping point might be. Some people apparently think we've already gone past, but I don't think the professional climate change scientists are prepared to say so.
Several decades to several centuries is a common answer, I think.
Looking at what IPCC had to say several years ago in
http://www.ipcc.ch/p...n/faq-10-3.html in figure 1a it shows expected atmospheric CO2 concentrations under several scenarios. If human fossil fuel CO2 is
eliminated: "Complete elimination of CO
2 emissions is estimated to lead to a slow decrease in atmospheric CO
2 of about 40 ppm over the 21st century. "
So, let's see, we're at 396 ppm now(
http://www.esrl.noaa...md/ccgg/trends/ ), stop fossil fuel CO2 altogether, get CO2 level back down to 356 ppm bt 2100, 356 looks about like a 1995 level (
http://www.esrl.noaa...rends/#mlo_full ). Throw in a decade or two of climate system inertia, so get back to 1995 climate by roughly 2112 if we stop fossil fuel CO2 emissions completely this year.
Suddenly stopping fossil fuel use altogether isn't reasonable. I have seen plans for getting down to 10% of current use by 2050 that I think are feasable. A feasable plan and an executed plan sure aren't the same though.