Global GHG emissions by gas: 65% is from carbon dioxide fossil fuel use and Source: IPCC ... Global greenhouse gas emissions can also be broken down by the economic activities that lead to their production. Pie chart ... Together, these sources represent a large proportion of total global CO2 emissions. read more
Electricity and Heat Production (25% of 2010 global greenhouse gas emissions): The burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions. read more
As others have stated, far less than 1%, representing about 0.04% of the total atmosphere. At ground level that percentage is sufficient to completely render the atmosphere opaque to infrared radiation in and around 15 microns of wavelength. read more
Total carbon dioxide (CO2) contributions are reduced to 72.37% of all greenhouse gases (368,400 / 509,056)-- (ignoring water vapor). Also, from Table 2 (but not shown on graph): Anthropogenic (man-made) CO2 contributions drop to (11,880 / 509,056) or 2.33% of total of all greenhouse gases, (ignoring water vapor). read more