While pensioners on talkback debate the impact of a mooted carbon tax on their household budget, Julia Gillard wears out her shoe leather, and Tont Abbott sniffs another dead fish, another kind of carbon conference has been rolling out.

Over the past three days, Australian and international experts have gathered at Melbourne University to consider “Four degrees or more: Australia in a hot world”.  In opening the conference, keynote speaker Professor Hans Joachim Schellnhuber, director of the Potsdam Institute, and former climate adviser to the German Chancellor and the EU, asked rhetorically: “What is the difference between two degrees (of temperature increase) and four degrees ?” His answer was concise. “The difference,” he said, “is human civilisation”.

Previously, in March 2009, Schellnhuber had told the Copenhagen science conference that in a four-degree warmer world the population “… carrying capacity estimates (are) below 1 billion people”.  Little wonder that the notion that humans might reasonably adapt to a four-degree warmer world seems absurd. Professor Tony McMichael, a world-leading authority on the impacts of climate change on human health, told the conference that “if we were to move to a world that was four five, six or seven degrees warmer, I think that what we imagine to be our adaptive strategies will become irrelevant.”

One reason is not just the world would be significantly hotter on average, but the extremes would be beyond the experience of most people and most nations.

So how hot will hot be? One answer comes from Andreas Sterl and 10 colleagues from the Royal Netherlands Meteorological Institute and the Institute for Marine and Atmospheric Research at Utrecht University. In “When can we expect extremely high surface temperatures?”, they ask how extreme would temperatures be at end of this century if the global average temperature were to increase by 3.5 degrees by 2100 compared to 2000.

And 3.5 degrees warmer than 2000 is where we are presently heading. If all the commitments made by governments around the world to reduce greenhouse gas were honoured, and that is all, then temperatures by 2100 would likely be about four degrees warmer than 1900, or about 3.4 degrees warmer than at the start of the 21st century.

Sterl and his team project what the hottest that could be expected in a 100-in-a-hundred-year event, known at a T100 value. Or to be precise, “the annual-maximum 2m-temperature that on average occurs once in 100 years” (temperature two metres above the surface). Statistically, such an event may not happen in a 100 years, but it may also happen more than once, as we saw last summer in a series of  “100-in-a-hundred-year” rain and flood events in eastern Australia.

Sterl’s findings are displayed on the map. The deep-red colouring most of Australia is the range between 48 and 52 degrees. The remainder in deep orange is 44-48 degrees. By way of comparison, Australia highest recorded temperature was 50.7 degrees on January 2, 1960 at Oodnadatta, South Australia. Extreme heatwaves across southern Australia during late January/early February 2009 set a Melbourne maximum temperature record of 46.4 degrees, and a state maximum temperature records for Victoria of 48.8 degrees at Hopetoun, and drove the Black Saturday bushfires, which were the worst on record.

As the authors note, “According to this figure, temperature extremes reach values around 50 degrees in large parts of the area equatorward of 30 degrees. This includes heavily populated areas like India and the Middle East … projected T100 values far exceed 40 degrees in Southern Europe, the US Mid-West by 2090-2100 and even reach 50 degrees in north-eastern India  and most of Australia. Such levels receive much too little attention in the current climate change discussion, given the potentially large implications.”

Prof David Karoly of Melbourne University, in addressing future fire risk in Australia at Oxford’s “4 Degrees and Beyond” conference in September 2009, concluded: “We are unleashing hell on Australia.”

In Melbourne this week, that message was reaffirmed in an array of evidence from many of the leading researchers in their fields.

Peter Fray

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Peter Fray
Editor-in-chief of Crikey