Worst case scenarios 3: Climate change
The big threat to the worlds environment as a whole is global warming. The best-bet projections prepared by the International Panel on Climate Change suggest that, in the absence of substantial action to mitigate global warming, global temperatures would probably increase by about 1 degree C between now and 2050 and by a further 1 degree C between 2050 and 2100.
This ‘best estimate’ implies environmental damage on a scale sufficient to justify an urgenr response. Of most concern to Queenslanders is the likelihood that rising sea temperatures could cause large-scale bleaching of coral reefs (the process by which symbiotic microorganisms are expelled from corals, leading to the death of the coral). A recent study by Queensland University’s Centre for Marine Studies estimated that 95 per cent of the coral cover on the reef would be lost by 2050, even under conservative assumptions about the rate of global warming.
However, many opponents of action to mitigate global warming have pointed to the uncertainties that surround climate projections to argue that the IPCC estimates may be overstated. Under favourable assumptions about such things as the feedback between climate change and concentrations of water vapour, it is possible that the temperature change associated with global warming will be less than 1 degree C, and might be swamped by natural climatic cycles. There are even some scientists (mostly not experts in the relevant fields) who deny the reality of global warming altogether.
The problem with this optimistic view of things is that it is equally important to look at the possibility that things might be worse than we currently expect on the basis of available scientific knowledge. The worst-case scenarios typically involve some sort of ‘tipping point’, with large-scale melting of the Atlantic ice shelf or a sudden change in ocean currents. Such changes can produce positive feedback leading to rapid climate change. The worst case scenarios typically involve a temperature increase of 5 degrees C.
The best strategy in this case is that of the Kyoto protocol. The reductions in emissions proposed under Kyoto won’t be enough to prevent global warming. But they provide a starting point. If new evidence over the next decade shows that the problem is not as bad as we thought, measures to implement Kyoto will be like an insurance policy on which we have not made a claim. The alternative possibility, of doing nothing, then being confronted with the worst-case scenario will involve far greater economic and environmental costs.