A new theory was advanced that global warming began 8,000 years ago when farmers began clearing forests for agriculture and grazing large herds of livestock, which led to higher carbon dioxide and methane levels; by A.D. 1700, human activity had raised the global temperature by .8 degrees Celsius, an increase roughly equal to that caused by industrial activity since then.
A new theory was advanced that global warming began 8,000 years ago when farmers began clearing forests for agriculture and grazing large herds of livestock, which led to higher carbon dioxide and methane levels; by A.D. 1700, human activity had raised the global temperature by .8 degrees Celsius, an increase roughly equal to that caused by industrial activity since then.