CSIRO submission to the Prime Ministers Emission Trading Task force - to stay below 2 degrees C we need to keep below 375-550ppm CO2e - We are already at 430ppm CO2e in Earth's atmosphere

Table produced by Philip Sutton from The Greenleap Strategic Institute.
Modified with comment by Adrian Whitehead from Zero Emissions Network.

The table below is largely based on material from the Stern Report p 195

Stern Review, chapter 8 "The Challenge of Stabilisation"

Stern Review final report

The table below shows a range of risks associated with increasing concentrations of atmospheric greenhouse gases (GHG) listed in carbon equivalents (the total concentrations of GHG from all sources and expressed as ppm of carbon dioxide. Note this give us a figure of around 430ppm rather than 380ppm for just CO2).

The earth has already experienced a 0.8ºC rise above pre-industrial levels, with a further 0.5ºC or more 'built in' due to previous releases of GHG and the buffering effects of the ocean. Of critical concern is the level of GHG at which ocean acidification occurs, and the tipping point for a runaway climate change event is reached.

Currently there is debate around what rise in temperature will trigger a runaway climate event. James Lovelock suggests we have already passed it, while others such as George Monbiot say a 2ºC above pre-industrial levels will create a environmental tipping point. There seems to be a growing consensus that a 4ºC rise will cause a runaway climate change event.

If we conservatively accept the 4ºC rise as the point for a runaway climate change event, the Hadley Centre already gives a greater than 1% chance of reaching this temperature with the current levels of GHG in the atmosphere. Would you fly on a plane with a 1% chance of catastrophic failure?

From this analysis we conclude that we must immediately reduce the levels of atmospheric GHG to lower the risk of catastrophic climate change.

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Table Notes:

Temperatures shown are increases above pre-industrial levels. Temperature probability data in the range (400 - 550 ppm and 2ºC - 5ºC is from Stern Review 2006, Box 8.1, Part III, p. 195. The clusters of four percentages are probabilities generated by a range of models that have, from left to right: (a) the highest estimates, (b) The Hadley Centre ensemble (more recent and towards the higher end), (c) the IPCC TAR 2001 ensemble, and (d) the lowest probabilities. The probabilities for a 1.5ºC warming at 400 ppm CO2e has been taken from Azar and Rodhe (1997). The acidity rating (for oceans) is from Ken Caldeira, Carnegie Institution, Stanford (pers. comm.) According to Prof. Danny Harvey, University of Toronto, the current (late 2006) level of carbon dioxide equivalent is ~490 ppm (Note: Jim Hansen of NASA thinks that the Stern climate projections are too sensitive (Pers. Comm.)

Jim Hansen from NASA's Goddard Institute writes of a previous climatic event that resulted in ice sheet collapse and one metre sea level rise every 20 years. Read here.

"A. Paleoclimate data indicate that ice sheet collapse can be catastrophic. For example, in Meltwater Pulse 1A, about 14,000 years ago, sea level went up about 20 meters in 400 years, an average rate of 1 meter every 20 years. There are numerous other cases in the record of rapid sea level rise of many meters"

Jim Hansen NASA Climatology: Ice Melting will be both Sea and Temperature Trigger
"Third, because CO2 is already near the dangerous level, steps must be taken to 'draw down' atmospheric CO2. Farming and forestry practices that enhance carbon retention and storage in the soil and biosphere must be supported. In addition, burning biofuels in power plants with carbon capture and sequestration can draw down atmospheric CO2 , in effect putting anthropogenic CO2 back underground where it came from. CO2 sequestered beneath ocean sediments is inherently stable , and other safe geologic sites may also be available."