Sources affected by humans that are contributing to global warming are, among others, carbondioxide, methane (CH4), dinitrogenoxide (N2O), ozone (O3), chloride fluorcarbons and particles. CO2 contributes the most. (1) The Global Warming Potential (GWP) measures the total effect on global warming for a specific amount of gas. GWPs show that CH4 and N2O have respectively 21 and 320 times the effect CO2 has on global warming. Still the concentration of CO2, CH4 and N2O in the atmosphere are 380, 1.7 and 0.31 ppm, which makes CO2 the most important greenhouse gas. Around the 1960s the concentration of CO2 was not more than 320 ppm, and it is still increasing.
The emmisions of carbon caused by humans are approximately 7 billion tons per year. 2 billion tons are bound to the seabed, while 1-2 billion tons are caught by growing forrests. This leaves an increase of more than 3 billion tons of carbon per year in the atmosphere.
Sources (for this article, that is):
1. "Kjemi og miljølære" - Nils Chr. Boye
First: We should not underestimate the power of methane, coming from agriculture, ruined marshes & wetlands, thawing tundra and various underwater deposits (hydrates).
SvarSlettSecond: There's a simple equation that will prove our CO2 emissions are considerable higher than 7 billion tons.
We currently consume more than 80 million barrels of oil, each day. Using the following variables: 158 liters / barrel, 0.85 kg / liter, 2kg CO2 / kg oil we arrive at more than 20 million tons CO2, each day. This give more than 7 billion tons of CO2 annually, from oil alone.
Add in coal, gas and biomass (forest, jungle) as well as methane from thawing tundra etc, and we got a problem.
An article in New Scientist March 21st, 2009, listed our total emissions in 2008 at 26 billion tons.
A note:
My numbers are rounded or adjusted to be indisputable; for example, one get 2.2 - 2.4 kg CO2 per kg oil, and we produced close to 85 million barrels in 2008 and 2009. The density of crude oil also varies but is usually higher than 0.85 kg/liter.