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Monday, December 10, 2012

Graham Readfearn: Life At Four Degrees

by Graham Readfearn, ABC environment, ABC (Australia), December 10, 2012

With global climate change talks moving too slowly, scientists are now talking of a rise in global temperatures of four degrees. What would this mean for Australia?

Dead Horse Gap

With four degrees of temperature rise from climate change, scenes like this from the Australian Alps will be a thing of the past.Credit: Mike Banks (ABC Environment)

"AVERAGES ARE VERY MISLEADING," says Professor Lesley Hughes. "An average never killed anything."
Professor Hughes, one of Australia's Climate Commissioners, is talking about recent reports suggesting the world is heading for an average 4 °C of global warming by the end of this century.
Both the World Bank and the Global Carbon Project, an international group of scientists including members of CSIRO, have come to this conclusion based on the assumption that the world will do little to cut back on emissions of greenhouse gases mainly from burning fossil fuels and cutting down forests.
But what might a 4 °C Australia look and feel like?
To researchers and those members of the public engaged in the climate change issue, the idea of the world warming by 4 °C is an alarming prospect.
But there's also a common mistake of confusing the weather with the climate, which could leave some ambivalent over the thought of a temperature rise of 4 °C.
"Between six o'clock this morning and twelve o'clock today we will get at least a four degree difference in temperature. But that is of course misleading," says Hughes, a professor of ecology at Macquarie University who has been researching climate impacts for 20 years.
"What a shift in averages actually means is a shift in the extremes of what we experience. As temperatures shift two, three or four degrees we get proportionally larger shift in the days above 35 degrees."
In 2008, work by CSIRO found that if there was no action to cut global emissions, the number of days each year over 35 °C experienced in Australia's capital cities would jump dramatically.
For example, Darwin gets about 9 days a year over 35 °C but by 2070 this was projected to rise to 221 -- more than half the year would be above 35 °C. Melbourne would go from 9 to 21 days above 35 °C, and Sydney from 3 to 9.
"Roughly speaking, you can also translate each degree of temperature rise with about 150 kilometres shift from south to north. So 4 °C for Sydney is like having the climate which is currently 500 kilometres up the coast, or even further," says Hughes.
Impacts on our landscape, she says, would see coral reefs bleached, Alpine areas without snow and species failing to move quickly enough to stay in appropriate habitats. Species living 600 metres or more above sea level in Queensland's wet tropics would be at risk as those cooler, misty environments disappear altogether.
Professor Jean Palutikof, director of the government-funded National Climate Change Adaptation Research Facility, believes an Australia 4 °C warmer than today will be a very different place.
"It would just be too unpleasant to be out of doors," she says. "People would be living far more enclosed lives. It would be a heavily energy-dependent existence as you have to cool all of those spaces that you put people into.
"You would have to be running your air-conditioners as a matter of course. The huge challenge would be to lay our hands on the energy we would need to maintain our comfort levels."
Under four degrees many species would be extinct and one expects that for the Great Barrier Reef,
there's nothing good in a 4 °C rise. Our landscape will be impoverished and our well-being eroded.

Professor Palutikof, who previously led a technical team at the Intergovernmental Panel on Climate Change looking at impacts of climate change, adds that agriculture would need to be more mechanised to protect workers from heat. Bushfire risk would be a major threat.
Patterns of international trade would be different and pressures on food supplies would increase. "Global alliances will change," she says.
"Under four degrees many species would be extinct and one expects that for the Great Barrier Reef, there's nothing good in a 4 °C rise. Our landscape will be impoverished and our wellbeing eroded."
Tony McMichael, Professor of Population Health at the Australian National University, is currently writing a book chapter looking the health implications in an Australia that's 4 °C hotter.
In the chapter, McMichael highlights how heat waves in Melbourne and Adelaide in 2009 put "power supplies, morgue capacity and transport systems" under stress. In Adelaide, he writes how railway lines buckled under the heat and commercial refrigeration vans were hired as makeshift morgues.
He says: "It is intuitively obvious that more extremes of heat means more distress and more hospitalisations and deaths. Again it is important for us all to understand that this is not a simple incremental increase in risk but this will be a steep rise in risk as we approach the threshold capacity of human bodies to handle extra heat loads."
One study has suggested that if Australia's temperature increased by 4 °C, there would be 17,200 annual temperature-related deaths, up from 5,800 in 1990.

Scientists look seriously at 4 °C

The just-closed United Nations climate talks in Doha were framed around a hope that the world should avoid 2 °C of global warming -- considered to be a benchmark over which climate change becomes "dangerous."
But away from the UN conferences, scientists have been openly discussing the prospects of the world warming by 4 °C.
In 2009, a conference held in Oxford, England, and sponsored by Oxford University and the UK's Met Office discussed "4 degrees and beyond." In Melbourne last year, leading scientists met to discuss Australia in a 4 °C world.
McMichael says: "This is not a straightforward path for science to say with any certainty what will happen under extreme and somewhat unimaginable conditions.
He says the government delegates at Doha are basing their talks on out-of-date science published by the IPCC back in 2007.
"The science has moved on. Two degrees is a bit of a security blanket that they can cling to. In their commentary they believe it can be achieved by taking serious action either now or in 2020. Most of the science is saying that if we leave it that long then, as far as we can see, it will become an impossible task and we will be committed to temperatures higher than two degrees. Possibly as high as four, five or six degrees."
McMichael accepts that some scientists will be accused of being 'alarmist' -- especially given the dire consequences he says should be considered.
"There are very good orthodox scientists who cringe at the thought of trying to label as science, uncertain predictions of the distant future," he says.
"Now my view is that as a global community we have not faced this type of rapid escalation in generalised risk to life support systems before. It is not a 'wait and see' situation -- we have to do the best we can with current knowledge and theory to foresee the range of possibilities and to alert the public and policy makers to the fact that this is a range of possible.
"Of course no-one is saying that there is going to be an apocalypse, but it would be foolhardy to say that there is not going to be."
But Professor Hughes does see some hope of avoiding 4 °C even though she says the chances of avoiding 2 °C are "vanishingly small" -- a sentiment also shared by Palutikof.
"Because we understand what is causing it, we do have a chance to fix it," concludes Hughes.
"If the climate was changing in this rapid way and we knew that it was the fault of the Sun, then we would have no hope because we can't control that. But because we understand the basic physics of the greenhouse effect and we know where the greenhouse gases are coming from then we know we can fix it.
"In 50 years time, the notion that we were using coal as our main energy source will seem absolutely absurd. We are on the trajectory of change but the transition has to come an awful lot faster."

1 comment:

Redreamer said...

and once we get to 4 degree's C? then what? Suddenly all feedback loops stop? or it feeds into even higher global temperatures? A 4c world then leads to a 6c world etc..... this is what runaway climate change is going to look like..