Pre-industrial rise in greenhouse gases had natural and anthropogenic causes

For years scientists have intensely argued over whether increases of potent methane gas concentrations in the atmosphere -- from about 5,000 years ago to the start of the industrial revolution -- were triggered by natural causes or human activities. A new study suggests the increase in methane likely was caused by both. A new study, published Friday in the journal Science, suggests the increase in methane likely was caused by both.http://feeds.sciencedaily.com/~r/sciencedaily/~3/I...