Trends and tipping point in the climate system:
Portents for the 21st century
Andrew Glikson
Earth and Palaeoclimate science
Australian National University
Mass extinctions in the history of Earth occurred when the atmosphere-ocean-land carbon and oxygen cycles, on which the biosphere depends, have been perturbed at rates to which species could not adapt. Rising atmospheric greenhouse gas levels above 330 ppm CO2 at rates of ~2 ppm/year and mean temperature rise of ~0.016oC/year since 1975-1976 are driving the fastest climate change trend recorded since about 34 million years ago, representing a critical climate threshold leading into uncharted territory and threatening the biosphere and human civilization. It is suggested the arrest of carbon emissions may not be sufficient to halt the current trend, except if accompanied with global efforts at down-draw of atmospheric CO2 using a range of bio-sequestration, organic and chemical methods.
Read the entire report here.
Get real
"driving the fastest climate change trend recorded since about 34 million years ago" Andrew, mammoth carcases thawing in the Siberian permafrost (and still edible,) were discovered years ago with sedges still in their mouths. Spring vegetables. The climate change froze them instantly and in terms of the age of life on earth, a second ago. Think again. Mark you I noticed you did say "trend". I'm not a sceptic but I abhor half-science.
Iteration on my part but nevertheless, the Vikings settled Greenland a thousand odd years ago in a brief climatic optimum that only lasted 100 or so years. 300 years ago ice fairs were held on the Thames and a permafrost existed in parts of the UK. We simply don't know enough about this stuff yet.