WASHINGTON – Less than two months before a key international conference on curbing climate change, a major U.S. poll has found a sharp drop in public concern about global warming.

According to the survey by the Pew Research Centre for the People & the Press, 65 percent of the public believes that warming constitutes either a “very serious” (35 percent) or “somewhat serious” (30 percent) problem, down from 79 percent in July 2006 and from 73 percent just 18 months ago.

The survey also recorded a sharp drop in the percentage of the public that believes that “there is solid evidence the Earth is warming” – down from 71 percent in April, 2008, to 57 percent – and in the percentage that believes global warming is caused primarily by human activity – from 47 percent to 36 percent over the same period.

The survey of 1,500 adult respondents comes was released just six weeks before the U.N. Climate Change Conference in Copenhagen where the representatives of 192 nations will gather to hash out the basic principles of a treaty to curb global emissions of greenhouse gases that virtually all climate and atmospheric scientists agree constitute the major cause of global warming.