<< The first thing that you learn in a science degree is that all scientists should be 'skeptics' >>

Fair enough Stezza.

<< Climate scientists should start with the theory that human activity does not 'contribute ' to climate change, and then attempt to prove this theory wrong. >>

No, no. They should start from the neutral position of having an open mind on whether or not human activity has a significant influence. That is, from a position of being skeptical about both positions.

So they shouldn’t become AGW ‘alarmists’ or ‘denialists’ unless they are sure of their position.

However, if they remain skeptics, they should most definitely err on the side of caution, that human activity could be causing dangerous climate change. And therefore they should be taking basically the same position as the alarmists or AGW advocates and fight for a major change away from our fossil fuel fuelled energy regime and towards renewable energy, and other greenhouse gas emission-reducing measures.

The alarmists/advocates and the skeptics should be aligned!! It should only be hardened denialists that are in the do-nothing business-as-usual camp!

This appears to be the least vitriolic forum on AGW yet, as much as the author tries to stir emotion.

Maybe AGW really has run its course.

Perhaps PM Rudd will debate Tony Abbott .. and pigs will fly.

Good article, Geoff Davies. However, it seems to me that most of the so-called climate "skeptics" here at OLO have invested far too much bluster and bile in denialism for a measured and reasonable argument like yours to have any chance of enlightening them.

Even in the face of the trenchant climate delusionism that we see here all too often, it's probably worth real scientists like you reiterating the science as often as possible. At least when the crap hits the fan, those of the denialists masquerading as skeptics who are still alive won't be able to say they weren't told.

without doubt the climate has changed. Is it natural or man made?

I suggest an experiment, would all the man made beleivers, in order to capture carbon, put a plastic bag over their heads. This would reduce the amount of carbon dioxide in the air we breath.

I do not accept the idea of AGW because I think that there are far too many holes in the science. One example among many concerns the origin and residence time of CO2 in the air. What follows here is the Abstract from a paper by Tom Segalstadt, Associated professor of Resource and Environmental Geology, University of Oslo.
'In a paper recently published in the international peer reviewed journal "Energy and Fuels" Dr. Robert Essenhigh (2009) Professor of Energy conversion at The Ohio State University, addresses the residence time (RT) of anthropogenic CO2 in the air. He finds that the RT for bulk atmospheric CO2, the molecule 12CO2 is about 5 years, in good agreement with other cited sources (Segalstad 1998), while the RT for the trace molecule 14CO2 is about 16 years. Both of these residence times are much shorter than what is claimed by the IPCC. The rising concentration of atmospheric CO2 in the last century is not consistent with the supply from anthropogenic sources. Such anthropogenic sources account for less than 5% of the present atmosphere, compared to the major input/output from natural souces(about 95%). Hence anthropogenic CO2 is too small to be a significant or relevant factor in the global warming process, particularly when comparing with the far more potent greenhouse gas water vapour. The rising atmospheric CO2 is the outcome of rising temperatures rather than vice versa. Correspondingly, Dr Essenhogh concludes that the politically driven target of capture and sequestration of carbon from combustion would be a major and pointless waste of physical and financial resources'

I do not necessarily have to accept Segalstad's views, but at least I must consider them. It is untrue to say that the 'science is settled' for it clearly is not.

And if you want a really big problem that really does unarguably exist try human population growth!

Any scientist worth their salt is a sceptic.To accuse Tony Abbott or anyone who wants to see the whole truth of being a denalist, equated with holocaust deniars,is adhominen of the lowest order.

The science is not settled,and carbon derivatives traded by the Global corporates will not reduce CO2 one iota.