There are many likely effects of climate change: positive and negative, economic and ecological, humanitarian and financial. And if you aggregate them all, the overall effect is positive today — and likely to stay positive until around 2080.Best of all, this is the result of a review of all the literature. So this is the fabled "consensus". The science that is, apparently, "settled". The Speccie quite properly notes that the results have a degree of scientific and economic uncertainty in them. But there is the rub:
You can choose not to believe the studies Prof Tol has collated. Or you can say the net benefit is small (which it is), you can argue that the benefits have accrued more to rich countries than poor countries (which is true) or you can emphasise that after 2080 climate change would probably do net harm to the world (which may also be true). You can even say you do not trust the models involved (though they have proved more reliable than the temperature models). But what you cannot do is deny that this is the current consensus. If you wish to accept the consensus on temperature models, then you should accept the consensus on economic benefit.Or you could say nothing, cherry-pick your results, shout down your opponents, and carry on wasting public money keeping your organisation's budget up:
In exchange for [£1.8 trillion], we hope to lower the air temperature by about 0.005˚C — which will be undetectable by normal thermometers. The accepted consensus among economists is that every £100 spent fighting climate change brings £3 of benefit.