[Reader-list] Fwd: Lynas impacts

[Nagraj Adve]

I generally avoid sending prognosis about climate change impacts, not
least because they may seem far off and unreal. But there's a couple
of things about Lynas' piece below. One, his book Six Degrees is based
on published literature. Two, in impact after impact over the last few
years, reality has moved faster than the modelled prognosis.
Three, there was casual talk and media reporting of the Earth warming
by 3-4 degrees around the time of Copenhagen. Those who talk so
casually about warming should read this below. It's short.
Naga



Climate change explained: the impact of temperature rises 05 May 09

Written for the Guardian, 14 April 2009. A slightly updated precis of
Six Degrees

Less than 2C
Arctic sea icecap disappears, leaving polar bears homeless and
changing the Earth’s energy balance dramatically as reflective ice is
replaced during summer months by darker sea surface. Now expected by
2030 or even earlier.

Tropical coral reefs suffer severe and repeated bleaching episodes due
to hotter ocean waters, killing off most coral and delivering a hammer
blow to marine biodiversity.

Droughts spread through the sub-tropics, accompanied by heatwaves and
intense wildfires. Worst-hit are the Mediterranean, the south-west
United States, southern Africa and Australia.

2C-3C
Summer heatwaves such as that in Europe in 2003, which killed 30,000
people, become annual events. Extreme heat sees temperatures reaching
the low 40s Celsius in southern England.

Amazon rainforest crosses a “tipping point” where extreme heat and
lower rainfall makes the forest unviable – much of it burns and is
replaced by desert and savannah.

Dissolved CO2 turns the oceans increasingly acidic, destroying
remaining coral reefs and wiping out many species of plankton which
are the basis of the marine food chain. Several metres of sea level
rise is now inevitable as the Greenland ice sheet disappears.

3C-4C
Glacier and snow-melt in the world’s mountain chains depletes
freshwater flows to downstream cities and agricultural land. Most
affected are California, Peru, Pakistan and China. Global food
production is under threat as key breadbaskets in Europe, Asia and the
United States suffer drought, and heatwaves outstrip the tolerance of
crops.

The Gulf Stream current declines significantly. Cooling in Europe is
unlikely due to global warming, but oceanic changes alter weather
patterns and lead to higher than average sea level rise in the eastern
US and UK.

4C-5C
Another tipping point sees massive amounts of methane – a potent
greenhouse gas – released by melting Siberian permafrost, further
boosting global warming. Much human habitation in southern Europe,
north Africa, the Middle East and other sub-tropical areas is rendered
unviable due to excessive heat and drought. The focus of civilisation
moves towards the poles, where temperatures remain cool enough for
crops, and rainfall – albeit with severe floods – persists. All sea
ice is gone from both poles; mountain glaciers are gone from the
Andes, Alps and Rockies.

5C-6C
Global average temperatures are now hotter than for 50m years. The
Arctic region sees temperatures rise much higher than average – up to
20C – meaning the entire Arctic is now ice-free all year round. Most
of the topics, sub-tropics and even lower mid-latitudes are too hot to
be inhabitable. Sea level rise is now sufficiently rapid that coastal
cities across the world are largely abandoned.

6C and above
Danger of “runaway warming”, perhaps spurred by release of oceanic
methane hydrates. Could the surface of the Earth become like Venus,
entirely uninhabitable? Most sea life is dead. Human refuges now
confined entirely to highland areas and the polar regions. Human
population is drastically reduced. Perhaps 90% of species become
extinct, rivalling the worst mass extinctions in the Earth’s 4.5
billion-year history.