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Being involved in the Garnaut Climate Change Review was certainly an interesting task and involved getting our hand on some of the latest data being generated by the other contributors to the projects. Uncertainty plays a big part of climate change and the work by Garnaut has at the very least frame further policy debate. By defining the targets for CO2 emissions (aim for at least 550ppm and if the world jumps on board then aim for 450ppm) policy makers now have a defined set of parameters to help compare alternative options.

The review explored a range of scenarios to deal with the uncertainty associated with what may actually occur from climate change. Just quickly climate change differs to seasonal variation (natural adjustments to the mean) as the whole distribution of outcomes that move to a new mean. In this case the new mean may have irreversible consequences and the full outcomes are ill defined. I have cherry picked the next two images from our report to highlight the impact from doing nothing about climate change (running the worst case study) and the benefits from mitigation and climate stabling at 550ppm (running what is expected to occur).

For the worst case we can see that the under the current technology we are using that irrigation is severely impacted by 2030 (approx 45% loss from base), by 2050 production is only 1/3 of the base and by 2100 irrigation is only opportunistic at best in the basin. The impact of the environment is far worse as within this situation and by 2050 around 5,400GL is used by irrigation and the Corrong (marked as flow to Sea in the results) gets about 900GL on avergae. Scarily enough this equates to the 2006/07 irrigation extractions and normal flows to the Coorong are around 5,000GL (I have not been able to fine the actual flow to Coorong) which puts the current drought into perspective.

Worst Case No Mitigation

The second image displays what may happen if we invest in mitigation to curb CO2 to 550ppm and the expected conditions are too occur. There is far less impact to the system and in fact it is highly likely that on-farm mitigation and research and development could cope with these changes. While the environment still takes a bit of a beating its still significantly better off.

Expected Outcomes with CO2 at 550

There are numerous permutations of what we could do to offset the environmental impacts (i.e. buying back water, further investment in salinity mitigation, redesigning the CAP, etc) and the impacts to agricultural production can be determined. The big policy question is how much of a trade-off between the environment and agricultural production to we want. These questions along with others will help frame some of the on-going work in RSMG.

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