There are very few scientists today who are prepared to state categorically that man is primarily responsible for global warming. This is a marked change from 10, or even 5, years ago. The reason for this sea change is pretty obvious - even as the global atmospheric carbon dioxide has continued to rise (passing through 400ppm earlier this year), average global temperature increases have stalled. Since 1998 there has been no statistically significant increase in global temperatures. Even the grandfather of AGW*, former Nasa scientist James Hansen, admits “the five-year mean global temperature has been flat for a decade.”
Of course, Hansen and others who have made their reputations (and in the case of Gore and many others, their fortunes) out of this end-of-times global hysteria aren't yet prepared to admit they are wrong, instead trying to explain away the global warming pause with fanciful theories such as China's smog (i.e. atmospheric carbon is apparently both the cause of the warming and the lack of it - as claimed in the Economist article linked above).
Some climate scientists such as the authors of this paper claim that Hansen et al have got the cause and effect wrong - carbon dioxide levels in the atmosphere follow temperature changes, not cause them. Others such as Dr Syun-Ichi Akasofu of University of Alaska and Dr Murry Salby of Macquarie University state that global temperature patterns are entirely consistent with the recovery from the Little Ice Age around 1600 and long-term cyclical trends such as the multi-decadal oscillation.
The politicians and crony capitalists like Gore who have prospered from the global warming business are not easily deterred, however. President Obama has cynically joined the envangelical, suddenly discovering climate change in his second inauguration address and in Britain, energy secretary Ed Davey continues to push the party line in a vain attempt to justify some of the highest energy prices in the world that cause misery and deaths every winter.
The cause for rational debate is not helped by studies like this recently published by Cook et al, which attempts to bolster the hoary old argument that 97% of scientific papers on the subject endorse AGW. As prominent sceptical commentator Anthony Watts shows here a straw poll of the scientists whose papers were categorised as pro-AGW say their work has been mis-represented by the study's authors.
The real scientific consensus is as follows:
- Global temperatures have increased modestly (about 1 degree in total) since the mid-19th Century
- Atmospheric carbon dioxide levels are increasing on average around 3% per year, although the rate of change varies considerably by season (more in summer) and geographical location (more in highly vegetated areas and less in populated areas)
- Mankind's carbon emissions roughly equate to the level of increase in atmospheric carbon dioxide but the increases are poorly correlated to seasonal (mankind's emissions are higher in winter) and geographical (more in populated areas) changes
- There is an increasingly poor correlation between average global temperature and atmospheric carbon levels.
It seems to me the climate change lobby don't know when to concede defeat. In years to come I am sure we will look back on the whole AGW scare as nothing more than a load of hot air.
* Anthropogenic (i.e. human-caused) Global Warming