As everyone in the world knows by now, the U.N.'s IPCC, its Climategate scientists, other consensus-only "scientists", and the mainstream media have put all their money on the human CO2-horse that "causes" global warming. Unfortunately, the IPCC political agenda of proving human CO2 emissions are the cause of global warming and/or climate change has not proven terribly effective or convincing (google Copenhagen failure). Why?
The IPCC chose a pseudo, non-scientific approach that was unable to explain the actual real-world (non-model) physical science and the actual climate observable conditions since 1880, as this chart indicates -- human CO2 emissions are not a major, primary driver of temperatures, nor the climate. Instead, the IPCC science focus should be on solar, land-use and aerosol (soot, dust, etc.) forcings. The 5% increase in global temperatures is more likely due to black soot, solar/cosmic and land-use factors than CO2. (click on image to enlarge)
Note: The IPCC climate science assumes that all human CO2 emissions remain in the atmosphere for 100 to 200 years. The vast majority of peer-reviewed research finds, though, that human CO2 emissions remain in the atmosphere less than 10 years. The IPCC assumes this without any physical evidence and it has been a major reason why IPCC climate models have been absolute failures in predicting major climate trends, like the recent global cooling.
The adjacent chart shows the cumulative growth percentage in human fossil fuel CO2 emissions since 1880, versus the cumulative growth percentage for both the atmospheric CO2 levels and the NCDC global average temperature. If human CO2 has a global warming impact, it's not significant based on the actual evidence, i.e., human CO2 emissions have a low correlation with global temperature increases. (The 'Human CO2 Emissions' bar is based on assumption that total human fossil fuel CO2 emissions prior to 1880 was a cumulative 20 gigatons.)