Climate's star witness

Earth's changing climate has had a high profile during the last week or so. I've never seen so much press coverage, following the IPCC's Fifth Assessment Report. The BBC in the UK continued with its outmoded practice of giving equal time to warmists and contrarians. I'm glad my taxes are no longer funding this idiocy. We pay taxes here, however, where the new government is in denial of incontrovertible evidence.

The overwhelming conclusion drawn from the Report is that, to stop temperatures rising above the two-degree target that seeks to curb climate change, most known reserves of fossil fuels need to stay in the ground. Read the IPCC's headline statements.

In the Land Court in Brisbane, climate change had its moment, too. And what better proponent could it have had? David Karoly is Professor of Meteorology in the Faculty of Science at the University of Melbourne. He is a climate change expert and contributed to the IPCC's Fourth Assessment Report in 2007. Professor Karoly researches climate variability and climate change, including greenhouse climate change, ozone depletion in the stratosphere and climate variations resulting from the El Niño Southern Oscillation. He has recently studied the effects of climate change on weather extremes and how they impact human and natural systems.

Professor Karoly is articulate, meticulous and assured about his research, conclusions and published assessments of cumulative carbon dioxide emissions and the global warming response. When questioned by Alpha Coal's slick lawyer, he dealt deftly with being described as a 'vehement opponent of the expansion of the coal industry in Australia'; with his report (as an independent expert witness) being called a 'literary review', when in fact he was an author, contributor or reviewer of much of the material cited; when defending his statement that it was, and is, appropriate to consider a high-emission scenario for future climate change*; and when justifying his assessment that the Alpha coal mine would be a significant partial contributor to the future impacts of climate change in Queensland**. When it was suggested by the applicant in the case (Hancock Coal) that, because there is a substantial range of estimates, assumptions, calculations, results and models in calculating a carbon budget, the science of carbon budgets was 'far from certain', Professor Karoly declared that the relationship between cumulative carbon dioxide emissions and temperature responses was a 'high confidence' relationship based on much evidence.

I wish that Professor Karoly could pop up every time a climate change sceptic denies the scientific consensus about our warming world. He speaks with such authority and certainty of his claims that I would defy anyone to contradict his figures.

Emissions scenarios necessarily involve a range of difficult estimates and assumptions: the response of the climate to increased emissions; feedbacks in the carbon cycle; uncertainties about the impact of other pollutants in the atmosphere; and whether or not climate policy is implemented. Within modelling there are many possible futures with different greenhouse gas emission scenarios.

The role of climate policy in Australia is an even bigger unknown than it was a short while ago. There is still a commitment to a five per cent reduction (from 2000) in emissions by 2020: the current government has the same target as the previous one, only now there is a cap on expenditure in order to achieve that target. LNP environment policy is extremely vague at best: it includes 'green armies', tree planting and putting carbon back in soil, but none of these measures is up to the enormity of reducing Australia's huge emissions.

And I have low confidence that Tony Abbott will consult Australia's eminent climate scientists.

* Based on recently observed emissions of greenhouse gases that have followed the highest, or above the highest, emissions scenario used by the IPCC

** Based on the 600 billion tonnes of the remaining carbon emissions 'budgeted' so as not to exceed the globally agreed 2-degree warming