December 8, 2009
Climate claims fail science test
THE UN Climate Change Summit started this week in Copenhagen with far more dissent than its organisers hoped for from two extremes of the climate change debate
We had the "grandfather of climate change", James Hansen, describing the proceedings as counter-productive and "a farce", while the chief Saudi Arabian negotiator to the summit, Mohammed al-Sabban, doubts the current science and suggests there is no longer any point in seeking agreement to reduce emissions.
It is therefore certain that the global political debate on managing carbon emissions and climate change will continue well beyond the Copenhagen summit. It is to be hoped that the scientific debate is also permitted to continue.
Results released this year suggest that the degree of scientific certainty falls short of that desirable before we set binding targets and dollar values on carbon emissions. Indeed, Tim Flannery, chairman of the Copenhagen Climate Council admitted that: "We can't pretend we have perfect knowledge: we don't."
This is a refreshingly honest comment when contrasted with some of the statements in the hacked emails of the Climatic Research Unit, UK, made by leading British and US climate scientists, who were caught with their fingers on the "delete button" when faced with climate data that failed to agree with their computer models.
Meanwhile two recent results published by top scientists cast doubt on the Intergovernmental Panel on Climate Change's theory about the link between atmospheric carbon dioxide and global warming. These are of of significance because whereas the climate models used by the IPCC rely on software to represent a large number of highly complex Earth processes, these results are equivalent to experimental observations on the Earth itself.
Paul Pearson of Cardiff University and his international team achieved a breakthrough recently, published four weeks ago in arguably the world's top scientific journal, Nature.
They unravelled records of atmosphere, temperature and ice-cap formation 33.6 million years ago, when the Earth cooled from a greenhouse without ice caps, into something quite similar to our present day.
These results from "Laboratory Earth" have a particular advantage: we can see what happened after the event for two million years.
With today's records we see changes in atmospheric CO2 and temperature over 50 years and seek to project what will happen in the future.
Pearson's work contains a couple of remarkable results.
First the greenhouse atmosphere pre-cooling contained a CO2 concentration of 900 parts per million by volume, or more than three times that of the Earth in pre-industrial days.
We can't be sure what triggered the Earth to cool despite, or because of, its changing green-house atmospheric blanket, but once it did, cycles of ice cap formation and glaciation commenced, apparently governed by the same variations in the Earth's orbit that govern the ice ages of the past million years.
Second, while the cooling of the Earth took place over a time-span of around 200,000 years, the atmospheric CO2 first dropped in association with the cooling, then rose to around 1100ppmv and remained high for 200,000 years while the Earth cooled further and remained in its new ice ages cycle.
We can compare these huge swings (both up and down) in atmospheric CO2 with current computer-modelled estimates of climate sensitivity by the IPCC which suggest that a doubling of CO2 relative to pre-industrial
times will produce a temperature increase of 2.5C to 4C.
If the Earth started a cycle of ice ages 33.6 million years ago while having its very carbon-rich atmosphere, and if the Earth showed cycles of ice-age activity when atmospheric CO2 was four times the level that it was in humankind's pre-industrial times, what new information must we incorporate into our present climate models?
Another key parameter in climate modelling is the warming amplification associated with increasing CO2 in our atmosphere.
This amplification factor is generally believed to be greater than one, giving rise to an understanding that increases in atmospheric CO2 amplify warming (a positive feedback in the physical process), and the IPCC has quantified this to deliver the finding that most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in man-made greenhouse gas concentrations.
However since the IPCC's fourth report, our Laboratory Earth has also delivered new data on this CO2-induced amplification factor.
The tool for the study in this instance is recent satellite-based temperature data now extending over 30 years.
Building on a methodology published 15 years ago in Nature, climatologist and NASA medallist John Christy and colleague David Douglass studied global temperature impacts of volcanic activity and ocean-atmospheric oscillations (the "El Nino" effect) and separated these from global temperature trends over the past 28 years.
The result of their analysis is a CO2-induced amplification factor close to one, which has implications clearly at odds with the earlier IPCC position.
The result was published this year in the peer-reviewed journal Energy and Environment and the paper has not yet been challenged in the scientific literature.
What this means is that the IPCC model for climate sensitivity is not supported by experimental observation on ancient ice ages and recent satellite data.
So are we justified in concluding that the concentration of atmospheric CO2 is not the only or major driver of current climate change? And if so, how should we re-shape our ETS legislation?
I don't know the answer to these questions, but as Nobel prize winning physicist Richard Feynman observed: "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."
Michael Asten is a professorial fellow in the school of geosciences at Monash University, Melbourne.