Ancient humans 'altered' climate

Humans were influencing the climate long before the Industrial Revolution, new research suggests. Levels of methane rose steadily in the atmosphere in the first millennium, according to an analysis of gases trapped in ice beneath Antarctica. Much of the greenhouse gas came from huge fires lit by humans as they cleared land for settlements and farming, researchers report in Science.

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http://news.bbc.co.uk/1/hi/sci/tech/4219818.stm