This is an extract from The Science of Climate Change — Questions and Answers, published by the Australian Academy of Science and distributed to members of parliament, every local government authority in Australia and every Australian high school, in August last year. Crikey will be running a series of extracts, including canvassing common myths.
No scientific conclusion can ever be absolutely certain.
However, a balanced assessment of the available evidence and prior knowledge allows us to attach levels of confidence to the findings of climate science.
There is a high degree of confidence in the broad conclusions of climate science.
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We are very confident of several fundamental conclusions about climate change: that human activities since the industrial revolution have sharply increased greenhouse gas concentrations; that these added gases have a warming effect; and that the Earth’s surface has indeed warmed since the Industrial Revolution. Therefore, we are very confident that human-induced global warming is a real phenomenon. Another important conclusion is supported unambiguously by all the evidence so far: “business as usual” emissions, with continuing high reliance on fossil fuels, will lead to a significantly warmer world.
Some aspects of climate science are still quite uncertain.
The exact amount of warming that will result from any particular trajectory for future greenhouse gas emissions cannot be projected precisely, because it depends on details of processes that reinforce or dampen disturbances to the climate system. Important processes involve clouds, water vapour, ocean circulations and natural influences on greenhouse gas levels in the atmosphere. However, future warming can be specified within plausible bounds, not only from climate models but also from interpretations of climate changes in the past. How climate change will affect individual regions is very hard to project in detail, particularly future changes in rainfall patterns, and such projections are highly uncertain. Neither can “tipping points” or rapid climate transitions be projected with any confidence, although they involve high risks should they occur. Uncertainty about future climate change works in both directions: there is a chance that climate change will be less severe than current best estimates, but there is also a roughly equal chance that it will be worse.
Despite the uncertainties, climate science has an important role to play in informing public policy on climate change.
Decisions on when and how to respond to climate change involve many factors that lie outside the realm of science, including ethical and economic considerations. An appropriate response will depend on value judgments and an assessment of the risks of various courses of action. Just as in any other sphere of human activity, decisions will need to be made before we have absolute certainty about the future.
The role of climate science is to inform these decisions by providing the best possible knowledge of climate outcomes and the consequences of alternative courses of action.
* The Australian Academy of Science, which represents Australia’s foremost scientists, provides scientific advice to policy makers and promotes excellence in Australian science, has devoted considerable resources to untangling the science of climate change and presenting it in a simple and easily understood format. The full report can be downloaded here.