Combustion of fossil fuels accounts for about 5% or so of the total release of CO2 into the atmosphere per year. Natural processes release and absorb many times that per year.
This is one of the dumbest 'arguments' of the anthropocentric truthers and bible throwers.
The natural process is a carbon
circulation. Combustion of fossil fuels takes carbon out of the ground and transfers it into the ocean and the atmosphere.
It is not a circulation but a pump which over time slowly puts more and more carbon into the ground from out of the air. This is why the long term carbon graphs show carbon as constantly decreasing at a steady rate over millions of years. The amount we've taken out and put back into the air is a fraction of what was put into the ground over just the past 100M years.
In fact, this removal was/is a problem. Without mankind's intervention, atmospheric carbon would have dropped below the level require for photosynthesis in not too far into the future (geologically speaking, I think the forecast was ~10M years). It is very accurate to say that without the industrial era life on the earth would have run into issues.
One of the founders of Green Peace has a great discussion on this. He argues that we should be trying to extract carbon out of the ground to reverse this process and ensure a buffer, and shows how in the big picture we'd still be a levels which are historically low for the earth.
The reality is mankind will probably only develop the technology to extract enough carbon to get the earth back to where it was 100M years ago, which in the big picture is not much. Nuclear/wind/solar will be much cheaper alternatives after that because most of the carbon is just too difficult or uneconomical to get to.
Edit:
http://news.heartland.org/newspaper-article/2015/03/20/why-i-am-climate-change-skepticHuman Emissions Saved Planet
Over the past 150 million years, carbon dioxide had been drawn down steadily (by plants) from about 3,000 parts per million to about 280 parts per million before the Industrial Revolution. If this trend continued, the carbon dioxide level would have become too low to support life on Earth. Human fossil fuel use and clearing land for crops have boosted carbon dioxide from its lowest level in the history of the Earth back to 400 parts per million today.
At 400 parts per million, all our food crops, forests, and natural ecosystems are still on a starvation diet for carbon dioxide. The optimum level of carbon dioxide for plant growth, given enough water and nutrients, is about 1,500 parts per million, nearly four times higher than today. Greenhouse growers inject carbon-dioxide to increase yields. Farms and forests will produce more if carbon-dioxide keeps rising.
We have no proof increased carbon dioxide is responsible for the earths slight warming over the past 300 years. There has been no significant warming for 18 years while we have emitted 25 per cent of all the carbon dioxide ever emitted. Carbon dioxide is vital for life on Earth and plants would like more of it. Which should we emphasize to our children?