As awareness increases about impact of climate change there is a need for clear and simple information about the issues. Unfortunately the subject has become polarised into very extreme views, from outright denial to extreme pessimism.
To help newcomers to the field understand what could be going on, I offer this note:
Climate change deniers either claim that climate change is not happening at all (a very difficult position to hold as the evidence stacks up), or that it is a purely natural event that is nothing to do with man kind's use of fossil fuels. This position has had a lot of support from powerful lobby groups that have a vested interest in confusing the debate. Some supporters of this position can be very aggressive, attacking anyone with a different view.
There is a conventional view on climate change, represented by the International Panel on Climate Change (IPCC) that a majority of governments and most scientists accept, at least in public. This view describes climate change occurring over multiple decades, meaning that we still have time to keep using fossil fuels while we work out what to do next, while temperatures rise relatively slowly, sea-levels rise slowly (measured in millimetres per year), and that technical solutions will be found to solve the problems.
The problem with the conventional view is that the computer models it is based on tend to underestimate the rate and degree of change. The IPCC has been criticised for using research that is out of date, and not taking into account newly discovered factors such as arctic methane and the darkening of ice due to pollution. This has led to a number of prominent scientists breaking ranks and making predictions of an abrupt form of climate change that could produce serious consequences in a much shorter space of time (3-10 years) instead of the 50-100 years predicted by the conventional models.
The abrupt climate change models involves accelerating feedback loops that cause more rapid exponential change, and describe tipping points which, once passed, make it very difficult to reverse that change. Personally I am becoming more convinced by this viewpoint, there appears to be growing evidence that several tipping points have already been crossed. One of these is the melting of permafrost in the Arctic allowing methane (a powerful greenhouse gas) to escape in quantities that may accelerate climate change beyond man's ability to control.
There is an even more extreme position which abrupt climate change supporters can take, which is that of near-term human extinction. This claims that it's too late to stop runaway climate change taking the planet to a point where humans may be unable to survive, or where a large proportion of species go extict. I understand the arguments being made, but I see them as predictions based on extrapolations from models, rather than facts that have been scientifically proved. As those models are incomplete, I am reluctant to accept them as proof of the extinction hypothesis. Amongst supporters of this position ("Doomers") there are those who are almost as aggressive in support of their views as some of the Deniers.