Climate change down to nature
Nature, not mankind, is responsible for recent climate change, new research shows.
The two-year study by three Australasian scientists was published yesterday in the American Geophysical Union's Journal of Geophysical Research and casts doubt on the widely accepted view that human activities are responsible for recent global warming.
Auckland University climate scientist Chris de Freitas, James Cook University (Townsville) academic Bob Carter and Melbourne scientist John McLean found little or none of the late 20th century warming trend could be attributed to humans.
Their research said that in the past 50 years the average global temperature in the lowest layer of the atmosphere had fallen and risen in close agreement with El Nino or La Nina conditions.
A strong relationship between the southern oscillation index, which brought an El Nino in its negative phase and a La Nina when positive, had been a major temperature influence since continuous records of lower-atmosphere temperatures began in 1958, the paper said.
In 2007, the Intergovernmental Panel on Climate Change (IPCC) said global surface temperatures had increased by 0.74 degrees Celsius, plus or minus 0.18C, between 1906 and 2005, and that 11 of the 12 warmest years on record were in the 12 years before 2007.
The panel found that rising levels of greenhouse gases from human activity were responsible for much of that increase.
Computer models projected that global surface temperatures would possibly rise a further 1.1C to 6.4C during the 21st century, the IPCC said.
De Freitas said the research would cause a stir in the scientific and environmental communities.
The paper had been peer-reviewed over six months and accepted by a top academic journal.
"This will have an effect. This is scientific research, not an opinion," de Freitas said.
"There will be people who will be forced to correct me, no doubt, but that is what science is all about it's all about robust debate."