So I recently asked Benny Peiser what would convince him of an anthropogenic influence on climate. Peiser, as you may know, is not a climate scientist but a social anthropologist and a dedicated climate skeptic. He is the author of CC-Net, an email list that leans strongly against AGW.
Here's what Peiser told me:
I think that the release of anthropogenic greenhouse gases into theatmosphere has an influence on the climate. However, I don't think this in itself is the big issue in the climate debates. What remains largely uncertain is the extent of the warming effect of increased levels ofI'm not sure why Peiser needs evidence of accelerated warming, as opposed to just linear warming. I've asked him about a paper that finds an acceleration of sea-level rise, in New Zealand, and will report back what he says.
I'm an empiricist at heart. I look for clear observational evidence that would indicate a signal of accelerated warming or extraordinary environmental impacts that have been predicted. What I am looking for is a significant and continuous decadal warming trend as predicted by the IPCC
(0.2-0.7 degree C) or a significant acceleration of sea level rise. The real problem, however, is that even if these signals were to be detected in the near future, we would still don't know what the best policy response would be.