2009
Allen, Myles R., et al. "Warming caused by cumulative carbon emissions towards the trillionth tonne." Nature 458.7242 (2009): 1163-1166. (
link to article)
Matthews, H. Damon, et al. "The proportionality of global warming to cumulative carbon emissions." Nature 459.7248 (2009): 829-832. (link to article)