Garnaut: greenhouse science is “beyond reasonable doubt”

Ross Garnaut’s careful appraisal of climate science finds that evidence supporting decisive action has strengthened over the past three years. [22 March 2011 | Peter Boyer]

The capacity Hobart audience turning out earlier this month to hear Professor Ross Garnaut on the current state of climate change science was testament to our crying need for a mature, measured assessment of what’s happening.

VIGIL FOR THE CLIMATE: an Earth Hour gathering in St David’s Park, Hobart, 26 March 2011. Photo Lorraine Perrins.

VIGIL FOR THE CLIMATE: Gathering for Earth Hour in St David’s Park, Hobart, 26 March 2011. Photo Lorraine Perrins.

After missing the round of Garnaut presentations when his review did the rounds in 2008, this month Tasmanians finally got to hear in person the man who’s been central to Australia’s policy response to human-induced warming.

Garnaut’s original study in 2007-08 was marked by the meticulous care with which he disassembled, analysed and re-packaged the mass of information around the science and impact of climate change.

Last September Julia Gillard asked him to revise his report in the lead-up to a carbon pricing scheme, expected to begin next year. He’s now delivered six of his eight update papers, which besides science cover global emissions and policies, rural land use, carbon pricing, new technology and the electricity sector. He will deliver his full report late in May.

Garnaut’s science assessment has attracted attention not just from proponents of strong mitigation action but also those opposed to any action.  Because scientific research underlies all such action around the world, it’s a natural target for intense scrutiny and strident criticism.

There was no sign of any negative feelings about mainstream climate science in the Hobart meeting, which gave Garnaut respectful silence as he described how he had reached his present conclusion that the case for decisive emissions-cutting action is now stronger than ever.

Garnaut is not a scientist, but an economist and former diplomat who rose to prominence for some ground-breaking work in the 1980s on the economic rise of China. He began his climate work, he said, “with no strong views and no more than a common knowledge of climate change science.”

He set out to understand all sides of the arguments around global warming. “Having examined the sceptical responses and the responses to them in the mainstream science, the end point was an increase in personal confidence in the mainstream science.”

It was “an awful reality”, Garnaut said, that the evidence brought forward since 2008 offered no realistic hope that his 2008 review overestimated climate change risks. Observation and research since then “have confirmed and strengthened the propositions of the mainstream science”.

Dr Susan Wijffels, Oceans Theme Leader for the CSIRO’s Marine and Atmospheric Research Division and on co-Chair of the international Argo ocean monitoring program, discusses with Prof. Garnaut how Argo floats are used to obtain information about our oceans. (Left—Peter Boyer). PHOTO COURTESY CRAIG MACAULAY, CSIRO

Dr Susan Wijffels, Oceans Theme Leader for the CSIRO’s Marine and Atmospheric Research Division and on co-Chair of the international Argo ocean monitoring program, discusses with Prof. Garnaut how Argo floats are used to gather data about our oceans. (Left—Peter Boyer) PHOTO COURTESY CRAIG MACAULAY, CSIRO

His personal position — absent from the formal report — had shifted since 2007, he said. Then, the degree of certainty he attributed to the main propositions of science was in terms of civil law’s balance of probabilities. Now, it was “closer to the criminal law requirements of beyond reasonable doubt”.

Garnaut’s summary of the past three years of science included the following findings:

• Particles (aerosols) in the atmosphere will be reduced in coming decades. Because these have the effect of lowering temperatures, their absence will add to warming.

• The three major global temperature data sets show a “statistically significant” accelerating upward trend, with no evidence of any weakness in more recent years.

• Current sea level rise is considerably above the average rate for the 20th century. Satellite data shows increasing loss of land-based Greenland and Antarctic ice, with some credible analysis showing consequent sea-level rises as high as 1.9 m by 2100.

• A warming, more acid Coral Sea puts the Great Barrier Reef at “high risk” of being reduced to “an algae-dominated ecosystem”.

• Unchecked global emission levels would increase Australia’s exposure to extreme events, with Sydney experiencing extreme sea-level events 10,000 times more often by 2100 (meaning that today’s 100-year events would be happening every three or four days). Recent studies have linked a warming atmosphere with increased incidence of extreme rainfall events.

• While future rainfall can’t be precisely determined, most models project a general pattern of wetter conditions in tropical Australia and a drying of the southern part of the continent. The southern part of Western Australia is expected to be especially hard hit by water loss.

• Research shows species and ecosystems already responding to warming, including southward movement of flying foxes and sea urchins and earlier plant flowering and emergence of butterflies.

Garnaut warned of “severe consequences” if the world’s nations accepted a long-term greenhouse gas target level above 450 parts per million, but science had confirmed that it was “worthwhile” to pursue an initial target level of 450 parts per million.

If Garnaut needed confirmation that his work carried weight, he wouldn’t have had to look beyond the response to his science paper by Liberal Senator Nick Minchin. Such angry vitriol is a sure sign you’re making a mark.

• In his latest update paper, released last week, Garnaut advocated “economy-wide pricing of carbon” because it was the cheapest way to cut emissions. He said an emissions trading scheme, initially with a fixed (and rising) price of between $20 and $30 a tonne (a carbon tax), was “the best instrument for long-term emissions reductions”.

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