We're ruining Earth, scientists warn
Jo Chandler
January 27, 2007
DROUGHTS will be longer, flooding rains will be rarer but heavier. Cyclones will hit harder. Violent storms and extreme heatwaves will strike more frequently. Evaporation will suck up scarce inland water. Sea levels will creep up half a metre. Oceans will be so acidic that in some places shells and reefs will dissolve.
And humanity, not nature, will be to blame.
This is the assessment of the state of the planet according to what is possibly the most reviewed document in history.
Containing contributions from 2500 scientists, citing 6000 reports and reviewed by 750 experts operating under a United Nations banner, the first part of the report will be released on Friday after line-by-line consensus is reached on its conclusions.
The most important paragraph in the 1200-page report is the strength of the scientific statement on the question that has most inflamed climate change sceptics what is driving global warming according to internationally recognised climate expert Dr Graeme Pearman, a former CSIRO chief of atmospheric research.
"It makes a much stronger statement about unequivocal evidence of air and ocean temperature rises, of the melting of snow and ice and the raising of sea levels, and that the effect is from human activities," he said. The report says the human influence on climate is at least five times that of any natural variation of the sun.
"Everyone realises that climate has varied in the geological past for a number of reasons, and one of them is that the output of the sun is not constant," Dr Pearman said. "But this report looks seriously at the evidence for that being the cause of this current warming, and is quite strong that if there is a solar influence, it is only a small part."
Dr Pearman has just completed his own review of the draft fourth assessment of the Intergovernmental Panel on Climate Change. The report largely confirms findings outlined in the third assessment, in 2001, but improvements in the science have produced a more authoritative, and frequently bleaker, document to guide policymakers around the world.
The last report built projections mainly on the basis of two climate models; this paper cites results from 21 models. They allow new insight into processes such as how the carbon cycle and climate change interact.
"When you release carbon dioxide, how does it get cycled into the atmosphere, the oceans, and the living plants and animals of the earth? One of the unanimous agreements in this is that the efficiency with which the earth can take up carbon dioxide is likely to decrease in coming decades.
"That's something we didn't want to hear, because it means the carbon dioxide we release will stay with us. We are more sensitive to what we do than we thought we were in the past."
The report is not without good news. Concern that the cycle of deep-sea circulation was collapsing the scientific scenario that underpinned the film The Day After Tomorrow is eased by the findings. "The oceans are more stable and resistant to change than we thought," it says.
The report provides vital data on issues consuming policymakers around the world, including local questions such as water management, and whether agriculture should shift north to find water.
For Australia, the anticipated temperature rise hasn't changed, it's still the global mean 2.5 to 3.5 degrees this century, assuming the world proceeds on a "business-as-usual" course.
But the report has much more rigorous rainfall projections.
"Regarding the southern part of the country, all the models seem to be agreeing that there will be a poleward movement of the high-pressure belt that dominates Australia's dry climate," Dr Pearman said.
"It means that the westerly storm belts that bring winter rain to the southern parts of the country are going to be further south and less effective."
Extreme events are more of a certainty more heatwaves, broken by damaging deluges. What's not clear to scientists is the effect a warmer planet will have on the El Ninos that shape Australia's weather, "but we do know they will operate on a warmer and generally drier Australia".
The increasingly dry outlook in the south may fuel debate about capitalising on monsoon rains in the north.
But the report would suggest caution on that front, finding the rains may be fuelled by localised effects such as pollution insulating South-East Asia, exaggerating the temperature variation with northern Australia and feeding the monsoon cycle. If Asia addresses pollution in a meaningful way, the monsoonal rainfall patterns may wane.
The report is likely to put other policy areas on the agenda. "We're already talking about water and agriculture, but coastal development is certainly another issue. Sea levels are rising
possibly higher than we thought. We are still developing huge communities that are very close to sea level. We need to be very cautious about those strategies and how we handle them."
Many questions of most immediate concern will not be addressed in the section of the report released next week.
Two further documents, relating to impacts, and then focusing on what might be done about them, will be published in April and May.
WHAT THE DRAFT UN REPORT SAYS
■ It is more than 90 per cent certain that human activities have caused global warming.
■ Global temperatures will rise by 2 to 4.5 degrees.
■ Earth will be increasingly unable to absorb rising carbon dioxide.
■ Sea levels could rise by between 20cm and 60cm in the next 100 years, and will continue to rise for 1000 years.
■ Snow will vanish from all but the highest peaks.
■ More extreme, violent weather.
