Climate change is not a theory, a speculation or a conspiracy
by environmentalists. Even the most hardened climate change
deniers have realised that they can no longer credibly deny
its existence or claim that it doesn't have anthropogenic
( man made ) origin. All they can argue about is the scale
of its effects.
Imagine you are about to board a plane. On one side of the
path through the airport are hundreds and hundreds of aircraft
scientists. They are a bit shy and nerdy and don't shout too
loud - but, having checked each others sums most carefully
- they are saying that there is a 95% chance that your aircraft
will crash. Opposite them, scientists of other disciplines
shout loudly and persuasively that the aircraft is OK. It
may be a bit broken but it will all be OK. Would you fly?
You are on our one planet. Hundreds of climate scientists
have carefully checked each others working and have collectively
concluded that warming of the climate system is happening,
that it is caused by man made greenhouse gasses and that the
earth is going to warm by something between 1.1 and 6.4 degrees
C by 2100. Opposite them, another group shouts that the world
is just a bit broken but will be OK. You cant get off
the plane this time though. You have nowhere to go. There
is only one earth. We have to fix the problem.
The IPCC creates reports based on the consensus view of hundreds
of peer reviewed climate science papers from all round the
world. This approach tends to smooth out the predictions and
ends up assuming that the relationship between greenhouse
gasses and temperature are basically linear. If we add so
many million tons of CO2 then the temperature will go up this
much. From this they create the predictions above for 2100.
This suggests that there is time to act. There are, however,
rogue systems which are likely to upset this assumption. These
are known as forcings. Balances between the forces involved
in maintaining the earths temperature which, once they
start to change, could make things happen much faster than
the reports suggest.
Ice cover in the arctic is one of these. Summer ice reflects
the sun's energy back into space and keeps the arctic ocean
cool - but global warming has reduced the area of summer ice
and replaced it with dark, energy absorbing, sea. The sea
warms. The next year there is less summer ice. The sea warms
more. A positive feedback mechanism creating additional warming
over a period - until there is no more summer ice.
Arctic tundra is another. Thousands of square kilometres
of frozen marshland, permafrost, made up of layers of vegetation
laid down over hundreds of thousands of years. As climate
change warms the soil, the frozen vegetation thaws and starts
to decompose - giving off the greenhouse gasses carbon dioxide
and methane. Potentially in huge quantities. Methane is of
particular concern as it has at least twenty times the warming
effect of the same amount of CO2 released. So, once again,
global warming thaws the tundra. The tundra gives off methane.
The methane causes more global warming. More tundra thaws.
More methane. More warming