In a time when climate change is being used as a political and media football with no apparent agreement on what is causing it, or even if it is happening, how can we assess the truth?
The media is no help, since it tends to exaggerate for sensational effect. Scientific journals contain errors and untruths, and the way some scientists are funded means they may (unconsciously or otherwise) present a biased view in order to keep their funding or their jobs. The whole point of publishing scientific papers is to allow other scientists to repeat experiments or measurements. Sometimes later studies back up the initial published findings, and sometimes they do not.
So how can we decide if it's happening and what is causing it?
Firstly, a claim made by a single scientist, no matter how prominent, is almost worthless unless backed up by studies (plural). Secondly, claims made by scientists working for industries with a vested interest in climate change issues one way or another (such as those working for the coal and nuclear power industries) are also questionable because these scientists are being paid to express opinions that farour their industries.
Thirdly, there is little validity in assessing the situation by turning to the myriad sites on the Internet, many of which are written by people with a nice theory but little (or very selective) knowledge, and many others which quote scientific publications that have later been discredited. Sites such as Wikipedia (and Helium), while useful, are not reliable as sources of information since they are not written by scientists working in the field, and are not reviewed.
Perhaps the best source of information is the Intergovernmental Panel on Climate Change (IPCC), which sifts through all the global scientific and technical data and presents its findings in the form of reports and powerpoint presentations. It is said to be, if anything, too conservative, but it is not tied to any government, political party or industrial interest groups, and is open to all members of the United Nations. By reviewing and assessing all the data, this group is likely to present the most accurate, unbiased, and reliable information.
Their verdicts:
'We conclude that the variations and trends of the examined indicators consistently and very strongly support an increasing global surface temperature over at least the last century, although substantial shorter-term global and regional deviations from this warming trend are very likely to have occurred.'
'... the 20th century warming is highly unusual, even taking into account the large uncertainties in these reconstructions. The observed warming is inconsistent with model estimates of natural internal climate variability.'
'The observed warming in the latter half of the 20th century appears to be inconsistent with natural external (solar and volcanic) forcing of the climate system' and is 'inconsistent with natural forcing.'
And finally: 'Anthropogenic factors do provide an explanation of 20th century temperature change.'
As you can see, they don't go in for sensational headlines, but it is clear their verdicts are: 1)It's getting warmer, 2) The warming is not consistent with non-human causes, and 3)The warming is consistent with being the result of human activity.
References:
http://www.ipcc.ch/
http://www.grida.no/climate/ipcc_tar/wg1/093.htm
http://www.grida.no/climate/ipcc_tar/wg1/467.htm
http://environment.newscientist.com/channel/earth/climate-change/dn11637
http://www.realclimate.org/index.php/archives/2006/07/runaway-tipping-points-of-no-return/
