By Richard Black
Environment correspondent, BBC News website
You might think that you know the answer, having heard, seen and read numerous counter-blasts aimed at the Intergovernmental Panel on Climate Change (IPCC) over the course of this year, as the three components of its landmark climate assessment were published.
Despite having reported on climate change for more than a decade, I realised at the beginning of the year that I was not entirely sure.
On a sceptic's blog I would read "global warming isn't happening". Then I would read an op-ed saying "warming is happening but it's entirely natural". Later, someone would tell me "it is happening, it is caused by greenhouse gases, but the effect is so small it won't matter".
Either there was a genuine divergence in the views of the sceptical science community, I concluded, or their analyses were somehow getting scrambled in transmission through blogs, newsletters, and the mainstream media.
Their arguments sway the political approaches of some important countries, notably the US, which in turn influence the global discussions on whether to do anything about rising CO2 levels.
So I decided I had better try to find out.
Into the ether
The best approach seemed to be the simplest - just ask them. But first I had to define who I meant by "them".
Rather than choosing a group of people myself, I decided to use a group which had already been compiled by sceptics' organisations.
In April 2006, a group of 61 self-styled "accredited experts in climate and related scientific disciplines" wrote an open letter to Canada's newly elected prime minister, Stephen Harper, asking his government to initiate hearings into the scientific foundations of the nation's climate change plan.
The letter, complete with a list of signatories, was published in Canada's Financial Post newspaper.
Many, though not all, of the signatories were indeed scientists active in fields relating to climate science. And the group was large enough to suggest I might receive a workable number of replies.
So I compiled a questionnaire about their views on climate change science, with a dose of politics thrown in, and mailed it out.
I cannot guarantee that all 61 received it; I was unable to obtain contact details for one person, and was less than certain that I had correct details for three of the others.
On the other hand, I was fairly sure that the questionnaire would be spread through the blogosphere and - what should we call it? - the emailosphere? - which turned out to be so.
I went into this exercise not completely knowing what to expect; I guessed I would receive a wide variety of responses, and I was right.
Fourteen of the group filled in the questionnaire, in varying degrees of detail; another 11 replied without filling it in.
Of these, some sent links to articles explaining their position. Some replied with academic papers, for which I am grateful, especially to Doug Hoyt who mailed a number of references that I had not previously seen.
Some said this was a worthwhile exercise. Some, in circulated emails, said the opposite, in terms which were sometimes so frank that others of the group apologised on their behalf.
Down to details
Nine agreed that atmospheric levels of greenhouse gases such as carbon dioxide, methane and nitrous oxide had risen over the last century, with two saying decidedly that levels had not risen. Eight said that human factors were principally driving the rise.
Twelve of the fourteen agreed that in principle, rising greenhouse gas concentrations should increase temperatures.
But eight cited the Sun as the principal factor behind the observed temperature increase.
And nine said the "urban heat island" effect - where progressive urbanisation around weather stations has increased the amount of heat generated locally - had affected the record of historical temperatures.
Eleven believed rising greenhouse gas concentrations would not result in "dangerous" climate change, and 12 said it would be unwise for the global community to restrain production of carbon dioxide and the other relevant gases, with several suggesting that such restraint would bring economic disruption.
There was general disdain for the Kyoto Protocol, with respondents split roughly equally between saying it was the wrong approach to an important issue, and a meaningless exercise because there was no point in trying to curb emissions.
There was general agreement, too, that computer models which try to project the climate of the future are unreliable. Several respondents said the climate system was inherently unpredictable and therefore impossible to model in a computer.
The other questions produced sets of responses which I could not boil down into anything approaching a consensus view.
I do not think that anyone would take this exercise as a comprehensive assessment of the views of climate sceptics, which is probably an impossible task.
They are a disparate community, and if you put any two together they would surely disagree on some aspect of the science - just as would any two researchers you picked out from any discipline.
The IPCC and many of the world's climate scientists would, of course, profoundly disagree with the conclusions evidenced by this small group, and I have linked to some articles which detail some of the science behind their disagreement.
This exercise would not be complete without discussing some of the non-scientific comments and responses to my mailout, which represent a window into the suspicion, indignation and politicisation surrounding climate science today.
That, though, is for later in the week.