A study conducted by the UCS in 2013 showed that transportation accounted for more than half of the carbon monoxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into the air in the US. Globally, the situation is similar, with minor variations according to sector. According to the IPCC Fifth Assessment Report (2014), industry accounted for 21% of total greenhouse gas emissions, electricity and heat production for another 25%, and transportation accounted for 14%.