The report finds that in many cases the risks associated with climate change are more serious than previously thought. Furthermore, says the report, different models suggest that delaying action would require greater action later for the same temperature target and that even a delay of 5 years could be significant. If action to reduce emissions is delayed by 20 years, rates of emission reduction may need to be 3 to 7 times greater to meet the same temperature target, the study finds.
The book also suggests that given current energy use predictions the world will, in the absence of urgent and strenuous mitigation actions in the next 20 years, almost certainly be committed to a temperature rise of between about 0.5oC and 2.0oC relative to today by 2050.
However, technological options for significantly reducing emissions over the long-term already exist using a portfolio of options whose costs are likely to be smaller than previously considered, the report says. Multi-gas strategies, emission trading, optimal timing and strong technology development, diffusion and trading are all required to keep costs of low-level stabilisation relatively low. Inclusion of technological learning in models also suggests that projected costs of such reductions can be reduced by over half. Nonetheless, demonstrated energy efficiency improvements under the present market system in industrialised countries are not enough to offset increases in demand caused by economic growth in developing countries, says the book, although some developing countries have shown much higher improvement rates over certain periods. Efficiency improvements and alternative energy supply such as nuclear and renewables are of priority for developing countries to contribute their share to the effort of stabilisation, the book concludes, adding: “Major investment is needed now in both mitigation and adaptation. The first is essential to minimise future impacts and the latter is essential to cope with impacts which cannot be avoided in the near to medium-term."
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