Uno-Verhandlungen: Deutschland verspricht Milliarden für globalen Klimaschutz

"Claim: Ice cores show that during earlier periods in the Earth's history, rises in carbon dioxide followed increases in temperature, and therefore the current rise in greenhouse gas concentrations has not caused the recent increase in global average temperature.

Misrepresentation: It is well established that analyses of ice core from Antarctic show that local temperature rises during the transition from glacial to interglacial periods, which are triggered by regular fluctuations in the Earth's orbit (and hence its distance from the Sun), were followed some time later by increases in the local average concentration of atmospheric carbon dioxide by up to 100 parts per million. However, the conclusion drawn in the programme that this means the recent rise on concentrations of carbon dioxide and other greenhouse gases could not be responsible for the recent increase in global average temperature is counter to the evidence presented in the scientific peer-reviewed literature.

In particular the programme misrepresented the contents of a paper by Nicolas Caillon and co-authors which was published in the journal 'Science' in March 2003. The paper by Caillon and co-authors examined the timing of changes in atmospheric carbon dioxide and temperatures during the Termination III deglaciation event about 240,000 years ago. The authors found that "[t]he sequence of events during Termination III suggests that the CO2 increase lagged Antarctic deglacial warming by 800+/-200 years and preceded the Northern Hemisphere deglaciation".

The programme presented a graph to illustrate the results of the work by Caillon and co-authors (to whom it was directly attributed), but which appeared nowhere within the paper. This graph was presented in support of the argument that rises in the atmospheric concentration of carbon dioxide are the result of, rather than the cause of, increases in temperature. However, Caillon and his co-authors concluded in their paper that "the situation at Termination III differs from the recent anthropogenic CO2 increase", noting that "the recent CO2 increase has clearly been imposed first".

In fact, the paper suggested that a fluctuation in the Earth's orbit initiated the increase in surface temperatures in Antarctica, and was followed by a gradual warming of the oceans, which released substantial volumes of carbon dioxide (the volume of carbon dioxide dissolved in sea water decreases with increasing temperature). It also indicated that the carbon dioxide released by the oceans added to the warming of the atmosphere, and contributed to the deglaciation of the Northern Hemisphere. The paper stated that the sequence of events during Termination III is "still in full agreement with the idea that CO2 plays, through its greenhouse effect, a key role in amplifying the initial orbital forcing".

A paper by Urs Siegenthaler and co-authors, published in the journal 'Science' in 2005, described evidence from the Dome C Antarctic ice core for lags of 800, 1600 and 2800 years between deglaciations at terminations V to VII and rises in the atmospheric concentration of carbon dioxide, respectively. However, the programme failed to point out that the record of temperature increases followed by rises in carbon dioxide concentration, which are described in the papers by Caillon and co-authors and Siegenthaler and co-authors, all relate to episodes of deglaciation. The last deglaciation on Earth occurred 12,000 years ago, but the current rise in carbon dioxide and other greenhouse gases, such as methane and nitrous oxide, started during the Industrial Revolution in the 18th century ie more than 11,000 years after the last deglaciation.

Furthermore, the programme failed to point out that the rise in temperature and carbon dioxide levels during Termination III occurred over a period of about 5000 years, much longer than the period since the start of the recent rises in temperature and gas concentrations in the 18th century. It also failed to acknowledge the findings of the paper by Siegenthaler and co-authors that "the atmospheric concentration of CO2 did not exceed 300 ppmv [parts per million by volume] for the last 650,000 years before the preindustrial era". As the IPCC Third Assessment Report in 2001 pointed out, the scientific evidence shows that the atmospheric concentration of carbon dioxide prior to the Industrial Revolution was 280+/-10 parts per million, and has risen continuously ever since, reaching 377 parts per million in 2006 ie the atmospheric concentration of carbon dioxide has risen in the last 250 years to a level today that is 25 per cent higher than the maximum recorded during a period of at least 650,000 years before the Industrial Revolution.

The programme clearly misrepresented the conclusions of the paper by Caillon and his co-authors, as well as the evidence that the recent increase in global average temperature is following a rise in the atmospheric concentrations of greenhouse gases."