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.
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.