Considering the serious risk that Global Warming poses, I trust that Professor Mark Pagani will forgive my cut and paste from his recent research paper :-
“High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations”
Mark Pagani et al. 2009
“Data and modelling for the middle Pliocene (approximately 3 – 3.3 [Million years ago] Myr) indicate that the global mean temperature was 2.4 – 2.9 degrees C warmer than preindustrial conditions, and approximately 4 degrees C warmer during the early Pliocene (approximately 4 – 4.2 Myr). If changes in carbon dioxide and associated feedbacks were the primary agents forcing climate over these timescales, and estimates of global temperatures are correct, then our results imply a very high Earth-system climate sensitivity for the middle (3.3 Myr) to early (4.2 Myr) Pliocene ranging between 7.1 plus or minus 1.0 degrees C and 8.7 plus or minus 1.3 degrees C per CO2 doubling, and 9.6 plus or minus 1.4 degrees C per CO2 doubling, respectively. If only the minimum estimates are considered, Earth-system sensitivity is still substantially higher than the range of probable ‘fast-feedback’ climate sensitivity often discussed, and implies that the impact of global warming acts to promote other feedbacks that substantially magnify warming over longer timescales.”
Numbers, numbers, but what does it all mean ? Well, Climate projections for the short- to mid- term might not be so very different from the IPCC projections we have studied so far – but the long-term consequences could be rather more catastrophic.