Environmental Engineering Reference
In-Depth Information
North America, Europe and Japan that are even going to pay lip service
to going as far as an eighty percent emissions reduction. These nations
are the principal economic beneficiaries of the industrial revolution that
caused the GHG build-up. Developing countries will need some highly
convincing incentives to do likewise. China has recently overtaken the
US as the world's biggest GHG emitter: it is currently the biggest carbon
culprit, but as regards the current stock of GHGs that has built up in the
atmosphere over the period 1850-2000, China is responsible for only six
percent of emissions, compared to thirty percent for Europe.
An unflinching, rigorous analysis of the science would suggest that the
entire world's annual amount of new emissions is going to have to be cut
by
more than eighty percent
below today's level for emission levels, and
therefore the climate, to stabilize. Only this would bring emissions down
to less than five gigatonnes (Gt) of CO
2
e a year - the level that the planet's
soils, vegetation and oceans could naturally absorb. Earth's absorptive
capacity is not inconsiderable. The Stern report suggested that of the
2000Gt of CO
2
released into the atmosphere over the past two centuries
through human activities - chiefly the burning of fossil fuels, ploughing
land and cutting trees - sixty percent had been absorbed in the land and
sea, leaving 800Gts of CO
2
to accumulate in the atmosphere.
Getting a move on
There is a serious time-pressure for action. The longer the delay in cutting
the flow of new emissions, the higher the stock of emissions will rise, and
with it the temperature. “Every ten-year delay in achieving peak emissions
adds another 0.5˚C to the most likely temperature rise”, says Vicky Pope
of the UK Met Office. And, furthermore, it's important to remember that
peak emissions refers only to the point at which a decline in emissions
begins, not the point at which an eighty percent cut is achieved.
Unfortunately, there is evidence that rising temperatures weaken the
absorptive capacity of carbon sinks - the aforementioned soils, vegetation,
trees and oceans - mainly due to the carbon-absorbing vegetation dying
off during droughts. For instance, the very hot summer of 2003 in Europe
is believed to have turned the continent's terrestrial ecosystem from a
carbon sink into a carbon source. The CarboEurope research project,
funded by the European Commission, estimated that during July and
August 2003, 500m tonnes of carbon were released into the atmosphere
by Europe's fields and forests, around twice as much as the emissions from
fossil-fuel burning in Europe during the same period.
