In defense of Milankovitch by Gerard Roe

[Sunsettommy]

The Reference Frame

Tuesday, July 06, 2010

EXCERPT:

Just a month ago, I had some doubts about the validity of the Milankovitch theory because I had seen no truly convincing reconstructions. However, during our Nice retreat, Richard Lindzen told me - privately as well as in his talk - about the following 2006 paper by Gerard Roe:

In defense of Milankovitch, Geophysical Research Letters (backup), Vol. 33, L24703, doi:10.1029/2006GL027817, 2006 (full text PDF)

Just to remind you, the Milankovitch cycles are periodic astrophysical or orbital phenomena that were claimed by Milutin Milankovitch to explain the glaciation cycles - the ice ages and the interglacials. The idea is that these cycles change the amount of sunshine near the Arctic circle which was claimed by the Serbian scholar to be globally important.

LINK
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Inside the link several past mistakes were discovered and corrected that then produced stunning new evidential support of the Milankovitch theory.

[MostlyHarmless]

It's an interesting read, but Roe appears to accept that CO2 plays a significant role in climate. He is a luke-warmist, and while that doesn't destroy his argument per se, it colours it fairly strongly. A sceptic would come out rather more in favour of the influence of Milankovitch cycles.

[Sunsettommy]

Quote:Moreover, this model requires no lag to be adjusted and no significant CO2 forcing to be added if you want to reproduce the data very well. Roe explicitly mentions - even in the abstract - that CO2 is not needed; moreover, it's changes are lagging so they are (mostly) consequences, rather than causes, of the ice-volume and temperature changes.

Here Lubos seems to think Roe is actually downplaying the role of CO2 to being a follower,rather than a driver of the climate.

Roe's words:

Quote:Furthermore, variations in atmospheric CO2 appear to lag the
rate of change of global ice volume. This implies only a secondary role for CO2 -- a weaker radiative forcing on the ice sheets than summertime insolation -- in driving changes in global ice volume.

At any rate he does not give much support for CO2 anyway:

Quote:Atmospheric CO2 has also been suggested as driving
changes in global ice volume [e.g., Shackleton, 2000; Lea,
2004]. The concentration of CO2 varied between about 200
and 280 ppmv over the last several ice age cycles, and
caused approximately 2 Wm2 variations in surface longwave
radiation forcing.

Notice the tiny CO2 range over SEVERAL ICE AGES?

This chart alone using that very belief Alarmists has stated for a long time,that CO2 for thousands of years stayed around the 280 level until 1880's,when it starts going up.Shows how negligible if any the warm forcing or is it cold forcing capabilities.

Can anyone find it in the chart?

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