The '''anthropogenic global warming theory''' is one of several explanations for the 1.5 degrees F of warming<ref>[http://www.cru.uea.ac.uk/cru/info/warming/ Climatic Research Unit Sheet #1]</ref> of the earth's surface recorded since the middle of the 19th century. | The '''anthropogenic global warming theory''' is one of several explanations for the 1.5 degrees F of warming<ref>[http://www.cru.uea.ac.uk/cru/info/warming/ Climatic Research Unit Sheet #1]</ref> of the earth's surface recorded since the middle of the 19th century. |