AGW: human activity increseas CO2
increased CO2 => increases temperature
CAGW: Catastrophic Anthropogenic Global Warming
human activity increases CO2
increased CO2 => increases temperature
positive climate feedback mechanisms => magnified warming
It is that last item where the controversy lies. Climate models all have a parameter that represents the climate sensitivity which predicts the way the climate responds to changes to input.
If you believe that the sensitivity is high, then small changes to the input (via CO2 warming, for example) lead to large changes in the system and catastrophic results.
If you believe the sensitivity is low, then small changes to the input do not have catastrophic outcomes.
There has been considerable news of late that observations of temperature changes over the last 15-20 years do not match the predictions over the same time period of the models using a high climate sensitivity values.
For most conservatives it is. Even in this thread we have people claiming it's all just a natural cycle.
>There has been considerable news of late that observations of temperature changes over the last 15-20 years do not match the predictions over the same time period of the models using a high climate sensitivity values.
New papers that suggested slightly lower sensitivity gave figures that were still within the range put forward in the last IPCC report, and still suggested sensitivities high enough to cause serious and damaging climate change unless emissions are reduced.
Climate is a noisy system, you can't measure significant change in global surface temperature in only 15 years. You should take the time to go and look at the actual temperature data to get a feel for how noisy it is[1]. Short term cycles like ENSO -- that we currently have no real ability to predict -- have a far greater impact on surface temperatures over those time scales[2]. It just so happens that the last 15 years or so have seen a dominance of la Niña years (which correlate with cooler surface temperatures) for reasons we don't really understand; it could just be random or possibly ENSO could have been affected by climate change.
The only people talking about a "pause" are conservative pundits and climate change deniers. It shows weaknesses in the models, but nobody was claiming that the models were accurate for short timescales or that we have the complete picture a at all. There are still huge gaps in our understanding, but that is hardly a cause for celebration.
So it's like if you're not disputing smoking is bad for health, but you're saying it's not "catastrophically" bad?
It's like the sooner one stops smoking, the less chance he has for a "catastrophic" lung cancer; it's not like when you smoke 10K cigarettes you sure won't get cancer but if you smoke 20K you sure do.
Of course, different people call "catastrophe" different things, but the analogy is quite apt here. There is no "catastrophe" coming, in the sense of a sudden disaster. We can stop any time, and the sooner we stop, the better overall result (and less costly) will be.
You are assuming that the climate system can be modeled via linear mechanisms, that human caused changes are more significant (from a climate modeling standpoint) than natural variations, and that the costs of modifying human behavior (e.g. more expensive energy via renewables vs coal) are less than the costs of adjusting to a changing climate.
My biggest frustration with the CAGW adherents is that they don't assign any cost to their proposed mediation policies. Often their cures are worse than the disease.
CAGW is used as a justification for all sorts of increases in government power, which by itself is probably more dangerous than even the worst scenarios promulgated by CAGW supporters.
