Reuters: The global economic downturn could cut greenhouse gas emissions by as much as 50 percent, a scientist said on Thursday at the Congress on Climate Change. Terry Barker, director of the Center for Climate Change Mitigation Research at Cambridge University, said the recession could cause a reduction in carbon emissions by 2012 bigger than the estimated 35 percent cut in the 1929-1932 Great Depression. “My top-of-the-head prediction is it would go down as much as 40 to 50 percent …