Institute of Advanced Studies

The Origin and Consequences of Dangerous Climate Change

by Andrew Glikson, Earth and Paleo-climate Scientist at the Australian National University, Research School of Earth Science and School of Archaeology and Anthropology

The anthropogenic release of over 300 billion tons of carbon into the atmosphere since 1750 has pushed maximum CO2 level by near-40 percent higher than its natural state of 280 parts per million (ppm).   

When combined with methane (CH4), the current CO2-equivalent level is near-450 ppm. Mean global temperature since the early 20th century rose by about 0.8 degrees Celsius, with a further 0.5 degrees C masked by emitted sulphur aerosols. The sensitivity of the Earth’s atmosphere to changes on this scale has been underestimated. Climate science defines the upper limit of the Antarctic ice sheet near 500 ppm CO2, about 3-4 degrees Celsius higher than present temperature, and of the west Antarctic and Greenland ice sheets at about 400 ppm CO2.

The current CO2 level of 387 ppm, rising at about 2 ppm/year, threatens a shift in the earth’s climate state toward conditions of 3 million years ago (mid-Pliocene: 2-3 degrees C higher than pre-industrial levels; 25+/-12 meters sea level rise). Manifestations of this trend include rapid melting of Arctic Sea ice, near-30 percent increase in Greenland ice summer melt area during 1978-2008, collapse of West Antarctic ice shelves, polar-ward migration of climate zones on the scale of several hundred kilometers, with consequent increase in the intensity of droughts in southern Australia.

Major climate change is already manifest around the world, including fires, hurricanes, floods, sea level rises, glaciers melt at river headwaters and ocean acidification. Due to the cumulative nature and the centuries-long residence time of CO2, reduction in carbon emissions needs to be accompanied by CO2 down-draw technologies, aimed at lowering atmospheric levels to below 350 ppm, as indicated by leading climate scientists. These methods need to include soil biochar enrichment, extensive planting of CO2-sequestering plants and chemical capture methods. Time is of the essence.

This lecture was  part of the symposium: “A Green ‘New Deal’? Confronting Climate Change and the Financial Crisis”  held on 18 September 2009 at the University Club, UWA.  http://www.ias.uwa.edu.au/conf/greendeal