Global warming view under attack

22:39, Aug 04 2009

A storm has broken out over research saying human activities are not the main factor behind climate change.

The two-year study published in last week's American Geophysical Union's Journal of Geophysical Research by Auckland University climate scientist Chris de Freitas, academic Bob Carter, of James Cook University, Townsville, and Melbourne scientist John McLean concludes that in the past 50 years the average global temperature in the lowest layer of the atmosphere has risen and fallen in agreement with El Nino or La Nina conditions, and not because of increasing greenhouse-gas levels.

De Freitas said yesterday he had received congratulatory messages from overseas about the peer-reviewed research.

However, he was expecting a backlash this week from those who believed greenhouse gases were responsible for climate change.

"The topic is so political, so that if anything comes in that appears to rock the orthodox boat ...," he said.

New Zealand climate change scientists are already criticising the paper, questioning the data and the conclusions.

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National Institute of Water and Atmospheric Research (Niwa) principal climate scientist James Renwick said the international science community would be working on responses.

"This one's not going to go away in a hurry," he said.

"Regardless of what is actually said, one thing that bugs me is this is going to be held up by the standard climate change sceptics saying, `Oh, this has been published and demonstrates global warming is rubbish', and it doesn't demonstrate that at all."

New Zealand climate change scientist Jim Salinger said there was little new in the conclusions on the impact of El Nino-Southern Oscillation (Enso), which would not change the way most people thought about climate change.

"Others have done work showing that after increases in greenhouse gases the Enso is the next most important factor in variability. So their result doesn't surprise me."

De Freitas said the research had found about 80 per cent of temperature change was caused by atmospheric circulation.

"We are not saying there are not other things. Carbon dioxide (CO2) could be one of those many things affecting climate but, if it is, I don't think it's a very big one. The paper is quiet clear we don't tread on the CO2 ground at all.

"We have used three sets of data to make sure we are not chasing shadows in the dark satellite data, which only began in 1979, but is highly accurate; radiosonde balloon data from earlier than that; and surface temperatures back to 1961."

Renwick said he had talked about the paper with Niwa colleagues and their concerns were with the data and the conclusion.

"They have used their favourite versions of the radiosonde data and don't discuss the possible issues with some of the radiosonde and satellite data," Renwick said.

"They try and confuse the year-to-year variation and they have deliberately taken out the trend in their analysis.

`It's the conclusion section in the last part, the things they say they don't support them with anything they have in the paper.

"They strike me as being questionable at best not based on anything that's been shown.

"It is a real surprise it got through the peer review."

The Press