Negative news reports about climate change are not affecting public opinion on the issue, but then positive reports aren't as well, suggesting the public is losing interest, researchers say.

Researchers from Princeton University and the University of Oxford in Britain, analyzing Google Trends for Internet searches on climate change, say worldwide attention on the subject has been on the decline since 2007.

They looked at searches for "climate change" and also "global warming," and determined media coverage of the issues resulted in only short-lived increases in public awareness or interest, which never translated to long-term Internet search activity for the terms.

The researchers focused mainly on two widely reported stories concerning climate change.

The first was a hacking of emails of a Climate Research Unit at Britain's University of East Anglia in 2009, revealing what climate skeptics claimed was a campaign to quash dissenting scientific views on human-caused climate change.

Dubbed "climategate," the accusation proved baseless as investigation found no evidence of any scientific misconduct.

The second event covered by the media was the discovery, also in 2009, of an error contained in a report by the United Nations Intergovernmental Panel on Climate Change that supposedly overestimated the speed at which glaciers in the Himalayan mountains would melt.

The Princeton and Oxford researchers specifically charted Internet searches in the period surrounding the two events, finding the trending search dropped from an initial peak by almost half every 6 days and had mostly petered out by 22 days after the stories broke.

"The search volume quickly returns to the same level as before the incident," Oxford researcher Greg Goldsmith said. "This suggests no long-term change in the level of climate change skepticism."

"We found that intense media coverage of an event such as 'climategate' was followed by bursts of public interest, but these bursts were short-lived."

Media coverage that causes great concern among scientists on both sides of the climate change debate seems to have slight effect on the public consciousness of the issue, the researchers conclude in their report on their study, published in the journal Environmental Research Letters.

There may be a fatigue factor at work, the researchers suggest, causing a loss of interest among even those who have been passionate about the issue.

"If public interest in climate change is falling, it may be more difficult to muster public concern to address climate change," study author William Anderegg of Princeton's Environmental Institute said. "This long-term trend of declining interest is worrying and something I hope we can address soon."