Thursday 26 Nov 2020 | 01:12 | SYDNEY
Thursday 26 Nov 2020 | 01:12 | SYDNEY

Climate scientists too optimistic?

7 December 2007 11:06

Guest blogger:  Dr Sarah Potter, a post-doctoral fellow working on infectious disease policy for The George Institute for International Health. She is currently preparing a Policy Brief on global climate change and infectious disease for the Lowy Institute.

Thursday’s Bali Climate Declaration, from more than 200 international climate scientists, asserts that to keep below 2°C warming, global emissions must start to decline in the next 10-15 years.  We will need to cut emissions at least 50% below their 1990 levels by 2050, and in the long run we have to stabilise substantially below 450ppm CO2 equilibrium. No one wants to cry wolf (the general doom-saying that accompanied SARS and Avian Influenza comes to mind), but this would seem to be a slightly optimistic framing of the IPCC’s most recent findings. 

Referring to Table SPM.6 of the IPCC Summary for Policymakers of the fourth assessment report (AR4), it would actually appear that unless we can achieve these goals in a much shorter timeframe – roughly half that indicated in the declaration — we are already committed to a temperature increase of between 2 and 2.4°C. An increase of this magnitude is seen by many experts as a threshold, or tipping point, and is expected to cause the loss of the Great Barrier Reef through coral bleaching, the loss of numerous low-lying Pacific islands through increased flooding and rising sea levels, not to mention many hundreds of thousands of excess deaths.

It is just as well that Australia has now (as of Monday) pledged to reduce greenhouse gas emissions. Even with the best of intentions, there remains the real possibility that due to unforseen positive feedback loops or changes in the ocean’s capacity to store CO2, we will be unable to mitigate greenhouse gas emissions sufficiently to restrict global warming below this tipping point. As Neville Nicholls (IPCC lead author for the AR4 Working Group 1) explains in his response to the Bali Climate Declaration on the Australian Science Media Centre website, the time has definitely come to act.