The researchers said the culprits are plants which apparently produce about 10 to 30 percent of the annual methane found in the atmosphere.
Scientists measured the amount of methane released by plants and found it increases with rising temperatures and exposure to sunlight.
They say their finding is important in understanding the link between global warming and a rise in greenhouse gases.
At the same time, a study published in the British weekly science journal Nature claims that global warming has wiped out two-thirds of species of unique frogs that inhabit the cloud forests of Central America.
The study claims 67 percent of the 110 varieties of harlequin frog, along with the golden toad, have disappeared from tropical America in the past 20 years.
The authors point the finger at a fungus called Batrachochytrium
dendrobatidis that grows on the frog's skin and eventually slays the amphibian.
Outbreaks of the fungus are clearly linked to man-made global warming, said the authors, led by Alan Pounds of the Monteverde Cloud Forest Preserve in Costa Rica.
Of the world's 1,856 known amphibian species, 427 are listed as critically endangered, including 122 species that are possibly extinct.
Also a study published this week in the British journal Biology
Letters warns of the knock-on impact of climate shifts on whale populations.
British scientists looked at population numbers among southern right whales.
Their estimates, dating back 30 years, looked at individually identifiable whales spotted at their breeding grounds off the coast of Argentina in the Southwest Atlantic.
Breeding success was strongly linked with occurrences of El Nino, the disruptive buildup of warm water in the Western Pacific, which in turn had an impact on krill, the whales' staple food, in the Southern Ocean.