Chris de Freitas: Evidence must prevail

Greenpeace spokesperson Cindy Baker claims scepticism about global warming is a bad thing.

Her fixation with a majority view and "consensus science" suggests she believes that advancement of scientific understanding is a matter of voting.

Scientific authority is achieved over time, not granted by official declaration or voting.

In a lecture in 2004, author and scientist Michael Crichton said: "The work of science has nothing whatever to do with consensus. Consensus is the business of politics. The greatest scientists in history are great precisely because they broke with the consensus."

She goes on to attack those scientists who promote scepticism as agents funded by the fossil fuel industry. Using this logic, one must conclude that all funding contaminates all results.

No doubt Greenpeace has good intentions, but its message appears to be driven more by dogma and propaganda than science. The facts speak differently. Although no one yet has the full story on climate change, there are a few key issues which ultimately drive public opinion and on which alarmist dogma relies. There is evidence of global warming. The climate has warmed about 0.6C in the past 100 years, but most of that warming occurred prior to 1940, before the post World War II industrialisation that led to an increase in carbon dioxide emissions.

But warming does not confirm that carbon dioxide is causing it. Climate is always warming or cooling. There are natural variability theories of warming.

To support the argument that carbon dioxide is causing it, the evidence would have to distinguish between human-caused and natural warming. This has not been done.

Whatever the cause of the changes in the climate, none of it is unprecedented. During the Medieval Warm Period, from 900 to 1200 AD, the Vikings sailed in Arctic waters that are now permanent sea ice, and farmed in Greenland soil that is now frozen solid. This was followed by the Little Ice Age which ended around 1850.

"Predictions" of future climate come from mathematical climate models.

But these models have not been verified, so their output is merely conjecture and not capable of being the mainstay of policy.

It is an uncontroversial fact that the scientists who construct global climate models accept that they do not adequately handle key aspects of the climate system, such as the role of clouds and aspects of heat transfer in ocean circulation.

Water vapour dominates the greenhouse effect, and global-warming predictions are based heavily on how water vapour is likely to respond to increased carbon dioxide. But climate science is not yet capable of predicting this response.

Predictions from climate models are of little value until they are reliable. A climate model is just a hypothesis until there is empirical evidence that proves it is correct.

In a good deal of the literature on global warming, claims about the future state of climate are based solely on model results. These are often treated as factual and quoted as justification for the Kyoto Protocol.

Model predictions reflect only the belief of the modellers. But when models are presented to the public as predictive tools and a basis for public policy, the issue of social responsibility arises.

Adherence to the Kyoto Protocol will mean far-reaching industrial changes and billion-dollar decisions. Given that the financial stakes are extremely high, surely the validity of these models should be more carefully assessed. Compare this to businesses which must thoroughly audit their financial statements and forecasts.

The issue of carbon dioxide and the perceived risk of dangerous climate change has taken on life of its own because it suits so many agendas: air quality, consumption of finite resources, energy efficiency, reduced dependence on costly foreign oil, opposition to industrial growth, zeal of environmentalism, international economic competition, revenue generation from environmental taxes, ongoing supply of research funds.

The key question is: Which way forward?

Many global warming sceptics contend that liberal environmental agendas are behind alarming global-warming headlines; on the other hand, sceptics often bring policy agendas of their own.

Enlightened government leaders should not identify with either of these groups.

Sane and reasonable advice will come from climate scientists who do not indulge in doom-laden conjecture, but calmly continue their search for evidence that proves or disproves theories or hypotheses about possible human impacts on global climate.

These scientists are ever-willing to modify their views as new facts emerge. They know that, given a choice between alarmism and honesty, science must always choose honesty.

Perhaps this could be used as a platform to arrange a review of New Zealand's strategy on climate science research, the basis of claims government scientists make and current national climate policy.

Perhaps one constructive way forward is joining the Asia-Pacific Partnership on Clean Development and Climate (APP). Countries already APP members - United States, Australia, Japan, China, India and South Korea - account for most of the world's population and a large part of its industry.

The pact looks at how to develop technologies to reduce emissions rather than having specific reduction targets confined to small group of developed nations as is the case with Kyoto.

* Chris de Freitas is an Associate Professor in the School of Geography and Environmental Science at the University of Auckland.