Global warming of +10C is ====>!!NOT!!<==== a reasonable expectation (erratum et apologia)

[GliderGuider]

41. I've been pondering what temperature change I believe is realistic

Last edited Tue Nov 20, 2012, 01:46 PM - Edit history (1)

The biggest question is what happens in the next 30 years. We're on the steepest part of the global emissions curve so far. At the rate we've been increasing our emissions since 1985, they could rise over 60% to over 55 GtCO2/year by 2030, and potentially to 75 Gt/year by 2040. That would raise levels to over 500 ppm by 2040.

I just don't see us reining in our emissions substantially - if at all - before 2040. I think we might be able to slow the rise of CO2 levels starting in 2040 to 2050 based on a combination of panic-driven policy changes and global economic depression, so that we end the century at at around 700 ppm. That would imply a rise of about +5C by the end of the century.

If CO2 emissions then fell to zero in the first half of the 22nd century, we would probably see a rise to +12 by the end of that century. They would rise that high because of both the additional CO2 we would generate in the first half of the century, as well as the long feedback effects that Hansen et al think raise the final equilibrium climate sensitivity to +6C per doubling.

+12 C is bad, but if the action we take by 2050 isn't drastic enough, we won't be able to keep it to even that level. We are in a very, very serious box.