General Motors has reduced carbon tailpipe emissions 5.2 percent in the past two years, the company announced in an annual sustainability report that presented its commitments for producing a greener fleet of vehicles in coming years.

The 5.2 percent rise came in 2013 as an improvement from a baseline of 2011-MY vehicles sold in that model year. GM reduced tailpipe emissions 2.3 percent in 2012. In 2013, the study monitored all GM vehicles on the road dating back to the 2011-MY.

In its sustainability report released May 18, GM also restated its goal to have 500,000 vehicles on the road by 2017 with some form of electrification, including battery-electric vehicles, gasoline-electric hybrids, and eAssist extended-range electric vehicles such as the Chevrolet Volt.

In 2013, GM counted 153,034 vehicles on the road with some form of electrification.

GM has also committed to doubling the number of U.S. models that can achieve 40 miles per gallon highway or better by 2017. In 2013, five Chevrolet models could achieve that goal, including the Cruze, Cruze Eco, Sonic, Sonic5, and Volt.

GM has also set two global goals for Europe and China, including reducing the average carbon tailpipe emissions of Opel/Vauxhall by 27 percent by 2021 and reducing carbon emissions of its China fleet by 28 percent by 2020. The China goal has been added this year.

In China, General Motors has introduced the Sail Springo EV in 2013 as its first battery-electric vehicle for that market. The Springo can recharge in seven hours from a 220-volt charging station.

To combat rising air pollution, the Chinese government has begun tightening its corporate fleet average emissions regulations. Its Phase III regulations cover the 2012 to 2015 model years. The more aggressive Phase IV regulations covering the 2016 to 2020 model years are now being developed.

For more information or to read GM's full sustainability report, click here.