Trends and tipping point in the climate system:
Portents for the 21st century
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.
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