... interesting article... here is a segment
http://wattsupwiththat.com/2014/03/29/when-did-anthropogenic-global-warming-begin/#more-106553
However, there is not compelling evidence that anthropogenic CO2 was sufficient to influence Earthâs temperatures prior to 1950, i.e. âClimate model simulations that consider only natural solar variability and volcanic aerosols since 1750âomitting observed increases in greenhouse gasesâare able to fit the observations of global temperatures only up until about 1950.â NASA Earth Observatory âThe observed global warming of the past century occurred primarily in two distinct 20 year periods, from 1925 to 1944 and from 1978 to the present. While the latter warming is often attributed to a human-induced increase of greenhouse gases, causes of the earlier warming are less clear since this period precedes the time of strongest increases in human-induced greenhouse gas (radiative) forcing.â NASA Geophysical Fluid Dynamics Laboratory / Delworth et al., 2000 âInternal climate variability is primarily responsible for the early 20th century warming from 1904 to 1944 and the subsequent cooling from 1944 to 1976.â Scripps / Ring et al., 2012: âThere exist reasonable explanations, which are consistent with natural forcing contributing significantly to the warming from 1850 to 1950â³. EPA
So how to clear up this confusion? Letâs take a look at the dataâ¦