Well no one ever thinks that action only is warranted IF it is occuring IF AGW costs more than merely adapting and IF those costs aren't outclassed by the benifits. Then we should do something about it seriously rather that just progress towards NON fossil fuel energy generation.
Imagine if it were the other way and we had global cooling( which we are likely to have for the next 30 years) look what happens to countries under consistant snowy conditions. By comparison to a 59-90 cm sea level rise over the next 90 years , which is another thing peple struggle to get is that 90 years is a long time for people to think "ooh that sea is getting a bit closer isn't it?"
time lags.................. the killer of all the costs of AGW.
