The current concentration of carbon dioxide in the
atmosphere is of 370 parts per million (ppm). Scientific models indicate that 450
ppm CO2e is the maximum tolerable concentration in order to prevent the rise of
global temperatures from exceeding 2 degrees Celsius in comparison with
pre-industrial levels. According to the Intergovernmental Panel on Climate Change (IPCC) and the United Nation Framework Convention on Climate Change (UNFCCC), this is the limit to which we should aim for, in order to avoid disastrous consequences of climate change.
However, according to the Stern Review, the stocks of
hydrocarbons that are profitable to extract, under current policies, are more
than enough to increase the levels of greenhouse-gas (GHG) in the atmosphere well
beyond 750ppm CO2e, with very dangerous consequences to the climate system, the
society, and the economy.
Without strong coordinated international action to
limit GHG emissions, the concentration in the atmosphere will easily exceed
450ppm CO2e, the scenario that gives a 50% chance of avoiding the worst effects
of climate change.
Even the Stern Review analysis of the economics of
climate change recommends aiming for stabilisation somewhere within the range 450
- 550ppm CO2e. Higher levels would substantially increase the risks of very harmful
impacts, while reducing the costs of mitigation by comparatively little. On the
other hand, the above mentioned review states that aiming to lower concentrations would impose very high mitigation costs
in the short term with small gains, and might not even be feasible given the
past delays of the international community in taking strong action against
climate change.
Global coordinated action to prevent the world from
going beyond the 450 ppm CO2e is needed urgently. It matters a great deal.
Sources:
UNFCCC, http://unfccc.int/
"STERN REVIEW: The Economics of Climate
Change" available at http://webarchive.nationalarchives.gov.uk/+/http:/www.hm-treasury.gov.uk/sternreview_index.htm
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