In addition to environmental and health costs at home, China's dependence on coal is cause for concern on a global scale. Due in large part to the emissions caused by burning coal, China is now the number one producer of carbon dioxide, responsible for a full quarter of the world's CO2 output.[40] According to a recent study, "even if American emissions were to suddenly disappear tomorrow, world emissions would be back at the same level within four years as a result of China’s growth alone."[41] The country has taken steps towards battling climate change by pledging to cut its carbon intensity (the amount of CO2 produced per dollar of economic output) by about 40 per cent by 2020, compared to 2005 levels.[40] Reuters reports that "emissions and coal consumption will continue to rise through the 2020s, even though at a slower rate, barring a major intervention including a shift to cleaner burning gas from coal" - in other words, "meeting the carbon intensity target will require a significant change in trajectory for carbon emissions and coal consumption."[42] To that end, China has announced a plan to invest 2.3 trillion yuan ($376 billion) through 2015 in energy saving and carbon emission-reduction projects.[42]