to the left hand side of this diagram – the countries whose emissions are
two, three, or four times the world average. Countries that are most able
to pay. Countries like Britain and the USA, for example.

Historical responsibility for climate impact

If we assume that the climate has been damaged by human activity, and
that someone needs to fix it, who should pay? Some people say “the
polluter should pay.” The preceding pictures showed who’s doing the
polluting today. But it isn’t the rate of CO2 pollution that matters, it’s
the cumulative total emissions; much of the emitted carbon dioxide (about
one third of it) will hang around in the atmosphere for at least 50 or 100
years. If we accept the ethical idea that “the polluter should pay” then
we should ask how big is each country’s historical footprint. The next
picture shows each country’s cumulative emissions of CO2, expressed as
an average emission rate over the period 1880–2004.

Average pollution rate

Congratulations, Britain! The UK has made it onto the winners’ podium.
We may be only an average European country today, but in the table of
historical emitters, per capita, we are second only to the USA.

OK, that’s enough ethics. What do scientists reckon needs to be done,
to avoid a risk of giving the earth a 2°C temperature rise (2°C being the
rise above which they predict lots of bad consequences)? The consensus
is clear. We need to get off our fossil fuel habit, and we need to do so
fast. Some countries, including Britain, have committed to at least a 60%
reduction in greenhouse-gas emissions by 2050, but it must be emphasized
that 60% cuts, radical though they are, are unlikely to cut the mustard. If
the world’s emissions were gradually reduced by 60% by 2050, climate sci-