This is the latest instalment in a continuing series of posts on the (mostly bad) arguments that contrarians make against global warming. A list of earlier parts in the series can be found at the bottom of this post.
Claim: Natural CO2 emissions far outweigh our own.
Fact: This claim is true but misleading. Before the Industrial Revolution, natural emissions of 698 Gt/yr were balanced by natural absorptions of 698 Gt/yr (neglecting volcanic emissions, which make no significant difference on human timescales):
Human emissions are indeed much lower than natural emissions (for 2000-2008, 28.1 Gt/yr from fossil fuels and 5.3 Gt/yr from land use change), but they are not balanced by natural absorption, so the CO2 has been building up in the atmosphere: Continue reading