Washington - A prominent US sceptic of the human causes of climate change, Richard Muller, has reversed course and said on Tuesday that he now believes greenhouse gases are responsible for global warming.
“I was not expecting this, but as a scientist, I feel it is my duty to let the evidence change my mind,” said Muller, a professor of physics at the University of California, Berkeley.
Muller is part of a group of more than a dozen scientists on the Berkeley Earth Surface Temperature team studying how temperature changes may relate to human activity, or to natural events such as solar and volcanic activity.
The average temperature of the Earth’s land has risen 1.5ºC over the past 250 years and “the most straightforward explanation for this warming is human greenhouse gas emissions”, the team said in a report posted online.
The analysis goes 100 years further back than previous research and takes an even stronger stance than the UN intergovernmental panel on climate change which said in 2007 that “most” of the warming of the past 50 years could be attributed to human activity and that higher solar activity prior to 1956 might have fuelled some of the warming the Earth has experienced.
The Berkeley team’s analysis said: “The contribution of solar activity to global warming is negligible.”
It added that its finding did not rely on climate models, which critics say have the potential for inaccuracies.
Instead, the finding was based “simply on the close agreement between the shape of the observed temperature rise and the known greenhouse gas increase”.
Further research would factor in ocean temperatures, which were not included in the latest report, it said.