Emily Murgatroyd | July 29, 2008 By Emily Murgatroyd ??? Tuesday, July 29, 2008 - 10:05 Heidi Cullen, climate expert and correspondent for The Weather Channel and formerly a scientist at the National Center for Atmospheric Research in Boulder, Colorado explains why scientists are so sure that our burning of oil, coal, natural gas and other fossil fuels is causing a disruption in the earth's climat