28 percent of US carbon emissions in 2011 were from transportation including cars:  http://www.epa.gov/climatechange/ghgemissions/sources.html

The US is responsible for 17% of world carbon emissions although the US has less than 5% of the world’s population.

http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions

http://en.wikipedia.org/wiki/List_of_countries_by_population

To avert a massive species die off that could threaten human survival, human beings must dramatically reduce carbon emissions.  Carbon emissions and total atmospheric concentration are currently increasing every year.  Government and industry are not doing anything serious to avoid this disaster.

http://350.org/about/science/

http://co2now.org/