Healthy soil and sustainable growing

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Four Degrees of Devastation
By Stephen Leahy
http://ipsnews.net/news.asp?idnews=48791

UXBRIDGE, Canada, Oct 9, 2009 (IPS) - The prospect of a four-degree Celsius 
rise in global average temperatures in 50 years is alarming - but not 
alarmist, climate scientists now believe.

Eighteen months ago, no one dared imagine humanity pushing the climate beyond 
an additional two degrees C of heating, but rising carbon emissions and 
inability to agree on cuts has meant science must now consider the previously 
unthinkable.

"Two degrees C is already gone as a target," said Chris West of the 
University of Oxford's UK Climate Impacts Programme.

"Four degrees C is definitely possible...This is the biggest challenge in our 
history," West told participants at the "4 Degrees and Beyond, International 
Climate Science Conference" at the University of Oxford last week.

A four-degree C overall increase means a world where temperatures will be two 
degrees warmer in some places, 12 degrees and more in others, making them 
uninhabitable.

It is a world with a one- to two-metre sea level rise by 2100, leaving 
hundreds of millions homeless. This will head to 12 metres in the coming 
centuries as the Greenland and Western Antarctic ice sheets melt, according 
to papers presented at the conference in Oxford.

Four degrees of warming would be hotter than any time in the last 30 million 
years, and it could happen as soon as 2060 to 2070.

"Political reality must be grounded in physical reality or it's completely 
useless," John Schellnhuber, director of the Potsdam Institute for Climate 
Impact Research, told the conference.

Schellnhuber recently briefed U.S. officials from the Barack Obama 
administration, but he says they chided him that his findings were "not 
grounded in political reality" and that "the [U.S.] Senate will never agree 
to this".

He had told them that the U.S. must reduce its emissions from its current 20 
tonnes of carbon per person average to zero tonnes per person by 2020 to have 
an even chance of stabilising the climate around two degrees C.

China's emissions must peak by 2020 and then go to zero by 2035 based on the 
current science, he added.

"Policymakers who agreed to a two-degree C goal at the G20 summit easily fool 
themselves about what emission cuts are needed," Schellnhuber said.

Even with a two-degree rise, most of the world's coral reefs will be lost, 
large portions of the ocean will become dead zones, mountain glaciers will 
largely vanish and many other ecosystems will be at risk, Schellnhuber 
warned. And there is the risk of reaching a tipping point where the warming 
rapidly accelerates.

The planet has already warmed 0.74 C over the past century and the warming is 
now increasing at a rate of 0.16 C per decade, according the 
Intergovernmental Panel on Climate Change (IPCC) 2007 report.

With 2008 emissions at the very top end of the IPCC's worst case estimates, 
it is time to look at what that may mean for the planet, said Richard Betts 
of the Climate Impacts research team at the Met Office Hadley Centre in 
London.

Continuing on the current high emissions path means average global 
temperatures would increase by 4.0 to 5.6 degrees by 2090. Brazil, much of 
Canada, parts of the U.S., Siberia and Central Europe would be eight degrees 
warmer than in the past 50 years, computer models show. Rainfall in the north 
will increase but wet tropics will become 20 percent drier.

The models are based on human emissions alone, and do not include 
heat-amplifying feedbacks from melting ice or changes in carbon sinks. When 
those are factored in, it moves the timetable forward so that "reaching four 
degrees by 2060 is a plausible, worst-case scenario" with the median being 
2070. By 2100, 5.5 degrees is possible, he said.

Few places would experience the global average temperature, Betts cautioned, 
noting that the computer models show the Arctic warming 15 degrees while many 
other regions of the world would experience 10 degrees of additional warming.

These scenarios do not include potential tipping points like the release of 
the 1.5 trillion tonnes of carbon in northern permafrost or the melting of 
undersea methane hydrates.

What would the world look like when it is four degrees warmer? It will likely 
mean one to two billion people will not have access to adequate fresh water 
because of the major shift in rainfall patterns, said Nigel Arnell, director 
of the Walker Institute for Climate Systems Research at the University of 
Reading in Britain.

Up to 15 percent of existing or potential cropland - and 40 percent in Africa 
- will become too dry and too hot for food production. While there might be 
some gains in northern areas like Canada and Russia, generally the soils 
there are not suitable for crops, he said.

Flooding will affect at least 500 million people because sea levels will rise 
more than one metre by 2100. The somewhat contentious issue of future sea 
level rise has been resolved with a new computer model that almost perfectly 
matches the historical changes in sea level since 1880, reported 
oceanographer Stefan Rahmstorf at Germany's Potsdam Institute for Climate 
Impact Research.

The new model projects sea level rise by 1.2 to 1.9 metres from 1990 levels 
by 2100, said Rahmstorf.

"We're expecting a really big sea level rise in the longer run," he said.

Even at two or three degrees of warming, sea level will inevitably rise many 
metres higher in the centuries to come. The main questions are how fast 
levels will increase, and whether vulnerable countries like Holland can build 
seawalls fast enough to keep up with the rising water levels and the 
extraordinary costs involved, he said.

In a four-degree warmer world, adaptation means "put your feet up and die" 
for many people in the world, Oxford's Chris West said bluntly. "In accepting 
the many alarming impacts, we see that it (a four-degree C increase) is not 
acceptable."

The climate negotiators heading to Copenhagen in December must accept the 
fact that the world's carbon emissions must eventually stop - and stop 
completely. There is no sustainable per capita carbon emission level because 
it is the total amount of carbon emitted that counts, explains Myles Allen of 
the Climate Dynamics group at University of Oxford's Atmospheric, Oceanic and 
Planetary Physics Department.

Carbon dioxide remains in the atmosphere for many centuries, which makes it 
the most important greenhouse gas to reduce and eliminate. The current focus 
on CO2 concentrations like 450 ppm or 350 ppm is the not the right approach 
since it is the total cumulative emissions that determine how warm the planet 
will get, Allen told the conference.

If climate negotiators only look at slowing rates of carbon emissions, then 
natural gas will be substituted for coal because it has half of the carbon - 
but the total amount of carbon in the atmosphere will continue to increase.