BP Statistical Review of World Energy 2014, which was released earlier this week. It is a wonderful resource, kudos to BP.
The graph above shows the carbon intensity of global energy consumption from 1965 to 2013. Specifically, it shows the amount of carbon emissions (in tons) for every "ton of oil equivalent" consumed in the global economy. Thus, the consumption data includes both carbon intensive sources of energy (coal, gas, oil) and also the less carbon intensive sources (hydro, wind, solar, nuclear, etc.).
The graph shows that global energy consumption decarbonized at a remarkably steady rate from 1965 to the late 1990s. Since then, global energy consumption has become slightly more carbon intensive. In 2013 the carbon intensity of global energy consumption was just about the same as it was in 1991. Since 1999, this metric of carbon intensity has increased by 1.5%. The graph indicates that in the 21st century, whatever gains are being made by low carbon energy technologies, they continue to be equaled or even outpaced by continuing gains in fossil fuels.
To place this analysis in perspective: Cutting global carbon dioxide emissions by 50% (just to pick a round number) while increasing global energy consumption by 50% (another round number) implies a carbon intensity of 0.25 tons carbon per ton of oil equivalent.
For those wanting to explore a little deeper into why this analysis matters for how we might think about climate policies, have a look at this paper in PDF.