New York  - Czech President Vaclav Klaus defended scientists and others who question the prevailing opinion on global warming late Sunday in New York, to open a conference of climate-change skeptics.

An outspoken critic of the United Nations and Western governments that hold the view that climate change is caused by human activity, Klaus has become the standardbearer for a group for scientists and organizations believing that natural forces are more likely behind whatever climate change might currently be underway.

"It's difficult to change their minds," Klaus told an audience of about 1,000 attendees at the New York Marriott Marquis hotel at Times Square. "They subscribe to the IPCC reports."

He denounced politicians for backing the UN Intergovernmental Panel on Climate Change (IPCC), business and industry leaders for profiting from the anti-climate change campaign and "irresponsible" scientists for rushing to the conclusion that extensive use of fossil fuels and other human activities hare causing global warming.

Klaus' position on climate change has been awkward for the European Union. The Czech Republic currently holds the six-month presidency of the EU, which has called for strong action to reduce emissions of the greenhouse gases believed to be causing global warming.

The IPCC reports issued last year found that Earth's temperatures have already reached crisis proportions and that human activities are key to driving them up with the release of carbon dioxide.

"They take climate change for granted," he said, complaining that his group of doubters has been branded "naive" by proponents of anti- climate change.

The 2009 International Conference on Climate Change is sponsored by the Chicago-based Heartland Institute and supported by close to 60 business and civil-society groups. (dpa)