All the talk since yesterday is about the new Jan Esper et al paper: Orbital forcing of tree-ring data published by Nature Climate Change. Press release here.
The main focus of the paper is the modest long-term 0.3°C cooling per thousand years that has taken place over the last 2000 years, likely due to Earth’s orbital factors. Unfortunately the authors did not go into the cause of the wide and obvious temperature variations occuring over the period. The press release quotes the authors:
We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low,” says Esper. “Such findings are also significant with regard to climate policy, as they will influence the way today’s climate changes are seen in context of historical warm periods.”
That sure blows out of the water Al Gore’s AIT con-job claim that the Medieval Warm Period was a just minor negligible event, doesn’t it?
Yet, it’s a pity Esper et al did not go into why temperatures 1000 years ago were as high as today’s and why temperatures of the past varied so widely.
There are some fascinating points about the curve that others will surely look into:
1. 20th century rise is not unusual
The abrupt temperature rise near the end of the 20th century is not unusual. Similar or even greater rises occurred around 1500AD, 1150AD, 700AD, 300AD and 100BC.
2. No correlation with CO2
Recall that CO2 was more or less steady at 280 ppm before starting its sharp climb 150 years ago. Yet, the smoothed temperature curves over a range of almost 2°C and the annual measurements range over 6°C! This completely contradicts the old storyline that climate had been more or less stable before man started emitting CO2. Clearly an array of powerful natural factors are at play here.
3. Natural cycles are clearly visible
The 1000-year solar cycle is clearly visible, and strongly suggests that there’s much more to solar forcing than total solar irradiation. There has to be a solar amplification mechanism, such as the one put forth by Svensmark, which, by the way, is gaining support from a growing body of scientific evidence. Of course there are some quacks who may suggest cyclic volcansim.
4. IPCC under-estimated natural trends
The press release states: “Our results suggest that the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia.” That also can be interpreted as: The IPCC likely over-estimates the short-term warming of CO2.
Looking at the 2000-year chart above, it certainly wouldn’t take a
rocket climate scientist to reach that conclusion.
The CO2 global warming theory has just lost another leg.