(11) Provided global warming exists, what strong evidence exists against it being caused by humans? - Quora: "Over the period involved (since 1750), we need to look at what's changed. One major area of change is the amounts of some minor (<1000ppm) gases. Given our understanding of the physical behaviours of these gases, the main contributor is carbon dioxide (CO2), with some effect from methane (CH4), chlorofluorocarbons (CFCs) and nitrous oxide (N2O). So it's either these or what is happening is within natural variation. The vast bulk of science points to the former over the later. Scientists are looking for alternate theories. This shouldn't be confused with vested interests trying to sow doubt.
Going back beyond 1750 helps us understand how the biosphere works, but is not of direct relevance to the current situation.
Once it's accepted that CO2 is the cause, there is no doubt it's human caused. The carbon in the biosphere has different isotopic ratios to the carbon in fossil fuels. Recent measurement show the biosphere's isotopic ratios changing to reflect the introduced fossil carbons circulating into all corners of the biophere, via the carbon cycle." "
'via Blog this'
From Noel Kelly at Quora
Charles Sanders Peirce - Thinking in Threes
