In May 2013, it was reported that readings for CO 2 taken at the world's primary benchmark site in Mauna Loa surpassed 400 ppm . According to professor Brian Hoskins , this is likely the first time CO 2 levels have been this high for about million years.   Monthly global CO 2 concentrations exceeded 400 ppm in March 2015, probably for the first time in several million years.  On 12 November 2015, NASA scientists reported that human-made carbon dioxide continues to increase above levels not seen in hundreds of thousands of years; currently, about half of the carbon dioxide released from the burning of fossil fuels is not absorbed by vegetation and the oceans and remains in the atmosphere. 
The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide CO 2 , which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive. Other greenhouse gases include, but are not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and chlorofluorocarbons.
The case for natural climate change I also present an analysis of the Pacific Decadal Oscillation which shows that most climate change might well be the result of….the climate system itself! Because small, chaotic fluctuations in atmospheric and oceanic circulation systems can cause small changes in global average cloudiness, this is all that is necessary to cause climate change. You don’t need the sun, or any other ‘external’ influence (although these are also possible…but for now I’ll let others work on that). It is simply what the climate system does. This is actually quite easy for meteorologists to believe, since we understand how complex weather processes are. Your local TV meteorologist is probably a closet ‘skeptic’ regarding mankind’s influence on climate.