Geoscience Reference
In-Depth Information
Introduction
The most logical approach to the climate change problem would be to significantly cut
GHG emissions. At the moment, many countries are developing very rapidly and thus
global emissions are expanding at a faster and faster rate. So how much do we need to cut
emissions by? As we have seen in previous chapters, scientists feel that 2°C is the tipping
point, when almost all people in the world become losers from climate change. So limiting
climate change to 2°C seems to be the logical thing to do. Especially as the Stern Report in
2007 suggested the cost of adapting to a low-carbon economy now would be about 1‒3 per
cent of world GDP compared to costs of at least 20 per cent world GDP if we do nothing.
To try to limit climate change to 2°C we need to understand how much carbon dioxide and
other GHGs this represents.
Figure 30
shows the probability of temperature changes based
on different amounts of atmospheric carbon dioxide. Even at the lowest level of 450 parts
per million (ppm), there is at least a 40 per cent chance that climate change will be above
2°C. Remember that at the moment we are already at 400 ppm and increasing at over 2
ppm per year so that 2°C limit could be reached in less than 25 years. We face a huge chal-
lenge if we are to contain climate change to this limit, and the only way we will do that is
by an international treaty backed up with efficient regional and national policies.
