This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.
According to the IPCC, 150 billion tonnes of carbon go into the atmosphere from natural processes every year. This is almost 30 times the amount of carbon humans emit. What difference will any reductions we try to do make?
This is quite true that the natural fluxes in the carbon cycle are much larger than anthropogenic emissions. But in the natural process, for roughly the last 10K years until the industrial revolution, every gigatonne of carbon going into the atmosphere was balanced by one coming out. What we have done is to alter only one side of this cycle. We put approximately 6 gigatonnes of carbon into the air but, unlike nature, we are not taking any out.
Thankfully, nature is actually compensating in part for our emissions, because only about half of the CO2 we are emitting is staying in the air. Nevertheless, since we began burning fossil fuels in earnest over 150 years ago, the atmospheric concentration that was relatively stable for the previous several thousand years has now risen by over 35%. So whatever the total amounts going in and out on their own, humans have clearly upset the pre-existing balance and altered significantly an important part of the climate system.
“Natural Emissions Dwarf Human’s” was first published here, where you can still find the original comment thread. This updated version is also posted on the Grist website, where additional comments can be found, though the author, Coby Beck, does not monitor or respond there.