There's another silly article by someone called Andy May at WUWT, claiming that because the slope of a temperature chart went up in the early twentieth century, and has been going up again and again and again, CO2 can't be causing global warming. Andy May wrote:
It is very hard to claim that mostly natural forces caused the warming from 1910 to 1945 and mostly man-made forces caused the similar warming from 1975 to 2009. The simplest explanation, given the data before us, is that the natural forces were the same in the two periods. That being said and accepting that man does have some influence on climate today with his CO2 and methane emissions, it seems more likely that our influence is in the 22% to 25% range. “More than half” is not credible to this observer.No, it's not hard to claim that at all.
Andy's committed a logical fallacy of personal incredulity. The temperature goes up when there's a positive forcing or when a negative forcing disappears. The forcings can be different yet still have the same effect. In the early 20th century the negative forcing from volcanic activity disappeared, and the solar forcing got a bit stronger. In the second half of the twentieth century it was virtually all human forcing, primarily CO2.
Andy's article was almost too dumb to comment on. What I will write about is a comment by Don Easterbrook. He wrote:
August 23, 2016 at 1:35 pm
As I (and a number of others) pointed out years ago, the 1915-1945 warming is almost identical to the 1979-2000+ warming, clearing showing that you don’t need any CO2 increase at all to get that kind of warming. And it is no coincidence that both periods correspond to warm PDO periods. A nearly identical situation occurred in the preceding century–a warm period from about 1850 to 1880, followed by a cool period from 1880 to 1915, similar to the 1945 to 1977 cool period (before it was erased by NASA and NOAA).
So the question became, how long have these 25-30 years alternating warm/cool periods been going on? I plotted up the GISP2 oxygen isotope measurements of Stuiver and Grootes for the past 500 years and found a pattern of regularly alternating warm/cool periods with an average duration of 27 years (you can find this curve in several of my publications–just google my name to find them).
This regularly repeating pattern of warm/cool periods of 25-30 years, long before CO2 entered the picture, shows that these climate changes have nothing at all to do with CO2 . And because the past is the key to the future–we can extrapolate this ongoing pattern into the future (which I did in 1999 when I predicted global cooling for the first two decades of this century). The so-called ‘pause’ in recent global warming is not a pause at all, it’s just a continuation of the same pattern that has been going on for 500 years.
I don't know about GISP2, however globally there's not been any 25-30 years of alternating warm/cool periods lately. Look at the chart below. You can shift the slider across if it helps - it's around 30 years wide. So that's why Don's extrapolations into the future turned out to be woefully wrong.