HadCRUT3 shows a huge heat wave coinciding with World War Two in the forties. That is just off the left end of their curve and rises higher than their chosen zero point line. While in my opinion that WW II rise is entirely imaginary their reason for excluding it is obviously a desire to draw a straight line. To go back to 1940 instead of 1950 would entirely spoil their chance of showing a relentless temperature rise graphically. But all the temperatures above 1980 are cooked by being raised up. To see how it is done look at Figure 16 in my book (Figure 24 in 2nd. ed.) which compares HadCRUT3 with satellite temperature measurements. The ENSO oscillations – El Nino peaks and La Nina valleys – become clearly observable at that resolution.

It turns out that they have made all the valleys very shallow and by that trick given their curve an upward slope. The El Nino peaks match quite well with satellites at first but when later it does not work they simply raise the entire curve. By the time 21st century arrives HadCRUT3 is floating happily a tenth of a degree above the satellite temperature curve. You can even see how they doctored it by looking at the 1998 super El Nino on their own graph. That is the last high peak on the right side. The two valleys that flank it are at greatly different heights while in the satellite record both sides of that same super El Nino are even. They are not the only ones who do it – NOAA is worse – but you will have to read about it yourself.

Thank’s for the comment.
I fear “precession” has a bigger impact on our climat changes than estimated. This is an element on the long term, were humans have no experience.

Precession alone is powerful enough to drive a 20,000 year cycle wherein the Sahara alternates between a lush, wet land with three giant interconnected lakes and the desert we see today.

Precession, of course, is but one of three orbital eccentricities collectively known as Milankovitch cycles. These cycles are clearly the primary drivers of climate change on the scale of roughly 100,000 years, 40,000 years and 20,000 years.

But, many make the mistake of thinking about these cycles as being binary in nature. These cycles play out on a continuum and the interplay of these cycles is constantly altering our climate.

I hope that helped.

Click here for some more basic climate change science.

Has anybody ever thought about the “presession” [?? ed note] of the earth’s axis? It changes very slowly and must have an inpact on the earth’s global temperature in the very long term.