No time to lose as climate change turns for worse

Canberra Times
Monday 27/7/2009 Page: 9

Urgency is the key in the transformation to a low-carbon future, Will Steffen writes

The carbon pollution reduction scheme to control Australia's emissions of carbon dioxide continues its long and tortuous road towards approval and implementation. Even more challenges await in December in Copenhagen, when the global community gathers to come to grips with climate change in earnest. Meanwhile, science is painting a clearer picture of the risks that lie ahead if the Copenhagen negotiations fail and human-driven climate change is allowed to continue unabated over the coming decades. In a word, the message from science to the negotiators is "urgency".

In many ways the climate system is now moving faster than we had thought likely a decade ago, and faster than the middle-of-the-range climate model projections suggest. For example, the rate of accumulation of carbon dioxide in the atmosphere has increased since 2000 because of growth in the global economy and the relative weakening of the natural processes that absorb carbon dioxide from the atmosphere.

Warming of the ocean, which absorbs the vast majority of the extra heat at the Earth's surface because of increasing greenhouse gases in the atmosphere, has also increased over the past few decades. Ocean heat content has risen particularly sharply since the late 1990s. Sea-level rise, in part caused by the thermal expansion of warming ocean water, has also increased in rate, from 1.6mm a year in the 1961-2003 period to 3.1mm a year in the 1993-2003 period. The higher rate has continued unabated through to the most recent measurements to 2008.

The world's ice realms are also changing rapidly. Arctic sea ice is being lost at a rate faster than any model has predicted. In the past 15 years the Greenland ice sheet has gone from being in balance - the rate of melting and disintegration being balanced by the accumulation of snow in the interior - to a net loss of about 200 cubic kilometres a year.

More recently, the Antarctic ice sheets have also shown net losses in mass. Global air temperature, too, is rising as expected. Despite considerable year-to-year and even decadal variability, the long-term trend is unmistakably upwards. Thirteen of the 14 warmest years ever recorded since the instrumental record began about 1850 have occurred since 1995.

The rate at which the world's climate is now shifting towards a warmer future carries significant risks for contemporary society, and especially for Australia. Of all of the world's industrialised countries, Australia is probably the most vulnerable to the consequences of climate change, or "climate disruption" as it is increasingly called.

The sea level is expected to rise by an additional 50cm to a metre by 2100 relative to 1990; levels somewhat more than lm high cannot be ruled out. A sea-level rise of "only" 50cm would already increase the frequency of flooding events associated with high tides and storm surges by 100-fold at many places along Australia's coastline.

Increasing absorption of carbon dioxide by the ocean is increasing its acidity, which, coupled with rising sea surface temperature, is stressing corals. The Great Barrier Reef, the world's largest coral-dominated ecosystem, may well be largely converted to algae beds by the second half of the century.

The health and wellbeing of Australians are directly threatened by global warming. Temperature related extreme events, such as the Melbourne heat wave earlier this year, have become more likely with global warming. So have "megafires" of the type that swept across Victoria in February and damaged Canberra in 2003.

With the Murray-Darling Basin in the grip of a severe, multi-year drought, the threat to water resources in south-east Australia looms large. As the evidence strengthens for a climate change drought link, so do the risks for the most agriculturally productive and populous parts of the country.

The severity of these doom-and-gloom projections, of course, assumes that human-driven emissions of greenhouse gases will continue unabated for several decades at least. Much has been written about the perceived high costs of reducing greenhouse gas emissions, thus contributing to inaction and to a possible realisation of these doom-and- gloom projections.

However, the prevailing economic thought globally has shifted strongly The costs of inaction far outweigh costs of abatement. Delaying action means more severe climate change with escalating adaptation and impacts costs. Delay also locks in carbon-emitting infrastructure such as coal-fired power plants and makes emission reductions in future mach more costly.

The news from the engineering community is even better. Society already has many technologies, such as a suite of renewable energy systems, that can quickly and effectively reduce greenhouse gas emissions. Their costs are dropping rapidly and novel approaches such as "smart grids" are facilitating their deployment.

The challenge of climate change is indeed complex-spanning science, technology, economics, public policy, history, psychology, systems analysis and much more. The broad knowledge base required to meet the challenge is expanding rapidly, giving hope that society is approaching a turning point in the transformation to a low-carbon future. But there is no time to lose in getting to that turning point.

Professor Will Steffen is the director of the ANU Climate Institute Australia (www.anu.edu.au/climatechange) which is holding its first open day today.