Here is how Hansen’s argument goes :
Chief instigator of climate change was earth orbital change, a very weak forcing.
Chief mechanisms of Pleistocene climate change are GHGs & ice sheet area, as feedbacks
Hansen says that ice ages are driven by very small changes in Earth’s orbit, which get massively multiplied by changes in greenhouse gases (i.e H2O and CO2.)
However, when talking about solar “forcings” the story is different. Hansen says that changes in the sun’s output are “too small” to have much effect on the climate.
So why doesn’t he believe in the same massive solar feedback as he claims for orbital cycles and small increases in CO2? Is feedback somehow prejudiced against the Sun?
One thing I’ve wondered. If the sun can have a grand minimum like the Maunder Minimum, can it have longer or stranger minimums?
Chief instigator of climate change was earth orbital change, a very weak forcing.
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BWHAHAHAHAHAHAHAHAHAHAHA!!!!!
When orbital eccentricity is at its maximum, the difference between incoming solar insolation at perehelion and aphelion is as much as 30%. A “very weak” forcing indeed.
While it is true that overall solar insolation changes very little between glacial and inter-glacial periods, the seasonal and latitudinal variations are huge, and it is these which drive the Earth into and out of Ice Ages.
In terms of feedback, topographical changes associated with the growth and recession of ice sheets is, IMO, probably the primary cause (imagine raising New York to 10,000 ft above sea level and see how cold it gets – even during todays inter-glacial regime).
Rising and falling levels of CO2 have to be a secondary feedback since, before we came along, there is no known mechanism for causing large-scale changes in levels of atmospheric CO2 which are NOT TEMPERATURE RELATED.
The louder Dr. Hansen bangs the CO2 drum, the more idiotic he looks to those of us who have even a rudimentary knowledge of the Earth’s climate history….
How about the Siberian traps as a non-temp related release mechanism for CO2?
To stop climate change,
one must stop supernoval eruptions, solar flaring, sunspots, orbital
wobbles, meteorites, comets, life, mountain building, erosion, weathering,
sedimentation, continental drift, volcanoes, ocean currents, tides and ice
armadas
“Hansen says that changes in the sun’s output are “too small” to have much effect on the climate.”
Isn’t he specifically talking about current climate change? If so then the two thing are not mutually exclusive because small changes in Earth’s orbit could have cause change in the past – and almost certainly did.