This theory predicts (extremely accurately as it happens) that known variations in the orbit of the Earth bring us closer or move us further away from the sun creating really quite
small changes in insolation.
Small changes in insolation driven by changes in the Earth's orbit can push the planet into or out of an ice age through the planet's «climate feedback» mechanisms.
The small changes in insolation will cause earlier and more extensive spring melting of Arctic ice, and indeed less ice formation over winter because northern winters are now shorter and milder than they were in 1750, due to apsidal precession.
This is similar to the error they make when they claim that greenhouse gases can produce temperature increases 3 - 5 times that of the direct radiative effects of doubling CO2 (through the action of non-linear feedbacks), but deny
that small changes in insolation can produce effects that are much larger than can predicted from the original forcing.
Not exact matches
Changes in insolation are also thought to have arisen from
small variations
in solar irradiance, although both timing and magnitude of past solar radiation fluctuations are highly uncertain (see Chapters 2 and 6; Lean et al., 2002; Gray et al., 2005; Foukal et al., 2006).
The ice age orbital correlation is old knowledge; there all those years ago
in my high school geology text *, along with the observation that the
insolation change is way too
small to provide a simplistic explanation.
Re 37 Kevin McKinney — actually, orbitally - forced global annual average
changes in TOA solar
insolation are very
small (
in the case of Earth) and depend only on variations
in eccentricity (setting aside the idea that there is a plane of dust and the plane of the orbit has a significant effect that way — heard the idea awhile ago, not sure there's much to support it?).
Changes in eccentricity alone have limited impacts on insolation, due to the resulting very small changes in the distance between the Sun and the
Changes in eccentricity alone have limited impacts on
insolation, due to the resulting very
small changes in the distance between the Sun and the
changes in the distance between the Sun and the Earth.
There are Milankovitch cycles of around 21,000, 40,000, 100,000, and 400,000 years —
in the 100,000 year cycle involving orbital eccentricities the
change in insolation is much
smaller than with the 21,000 and 40,000 year cycles.
Small changes in northern summer
insolation can not
in itself transform the planet.
However, the
change in incoming solar radiation —
insolation — at this timescale is
small, and therefore difficult to reconcile with the amplitude of the glacial cycles.
To compare this with AGW, AR5 Table AII.2 yields an annual average year - round and global forcing increase averaged over the last 30 years of +0.026 Wm ^ -2 / year, many times higher than the part - year, part - globe CSI which is also a
small part of the
insolation changes over the last 1,000 years, an effect which is adjudged, with or without any omission, to be insignificant
in comparison to AGW.
Those for Summer and Winter are not, but the seasonal
change in insolation for those times of year is
small.
Much higher above I mentioned the possibility — but again the
change in insolation over the Holocene (even at 65N) is very
small.