Wednesday, October 17, 2012

16 years of non-Global warming?

You may seen articles and stuff about a supposed 16 year pause in global warming.   There's been all kinds of spin on both sides of the AGW debate.   Here is my take:

Visually speaking, yes the global surface temperature in September was virtually the same as the global temperature in early 1997.   Mathematically speaking, there is still a positive trend line between those two points, given all the monthly data points in between.   I prefer the graph below created here.

It shows the HADCRUT4 dataset from 1880 until now with trend lines shown in various periods.  As far as I am concerned, the true starting point of the current negative trend is 2002 (ie 10years and counting) at a rate that is similar to the trendline value from the mid-1940's to the late 70's and 1880 to 1910.   Note that among climate scientists, it is generally accepted that AGW supposedly began in the last half of the 20th Century.   As Judy Curry notes, skeptical arguments stem in part from the  "Failure of climate models to provide a consistent and convincing attribution argument for the warming from 1910-1940 and the plateau from the 1940′s to the 1970′s", ie what caused the warming in the early 20th century and what caused the cooling in the mid part?

I am not the only one who interprets the surface record this way.  See pgs 21 and 22 here.
Some would argue that the Global temperature is dominated by the oceans and in particular the ENSO.   I would argue that natural variations, including oceanic oscillations, account for the majority of the changes we have seen.

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