08-08-2014, 09:25 PM
Regarding obliquity and planetary temperatures, some models indicate that global average temperatures drop with lower tilt. For example, in the following link:
http://physics.bd.psu.edu/faculty/willia...ja2003.pdf
Table 1 gives a range of different scenarios. Run "PRES0" with 0 tilt, present geography, present CO2 and levels lower average temperatures by about 3K. Shifting to a Sturtian glaciation-era geography drops temperatures a bit more.
Supporting discussion is on pages 10-12 and Figure 15, where it shows the ice caps - or glacial ice sheets - grow significantly at low tilts compared to Earth's actual obliquity.
Much cruder modeling also shows the same growth of ice caps and tundra for low tilts:
http://www.bbc.co.uk/blogs/legacy/23degr..._tilt.html
The issue seems to be that the low tilt leaves larger areas of the planet with permanently cool temperatures. Not necessarily freezing (e.g., Britain stuck at 7C year-round), but not something that encourages summer thawing because, y'know, there is no summer per se. Just permanently small air conditioning bills.
Are those two models incorrect in the growth of ice caps due to near-0 obliquity? If so, do you have any other, crunchy references showing the impact of low obliquity on planetary temperatures?
http://physics.bd.psu.edu/faculty/willia...ja2003.pdf
Table 1 gives a range of different scenarios. Run "PRES0" with 0 tilt, present geography, present CO2 and levels lower average temperatures by about 3K. Shifting to a Sturtian glaciation-era geography drops temperatures a bit more.
Supporting discussion is on pages 10-12 and Figure 15, where it shows the ice caps - or glacial ice sheets - grow significantly at low tilts compared to Earth's actual obliquity.
Much cruder modeling also shows the same growth of ice caps and tundra for low tilts:
http://www.bbc.co.uk/blogs/legacy/23degr..._tilt.html
The issue seems to be that the low tilt leaves larger areas of the planet with permanently cool temperatures. Not necessarily freezing (e.g., Britain stuck at 7C year-round), but not something that encourages summer thawing because, y'know, there is no summer per se. Just permanently small air conditioning bills.
Are those two models incorrect in the growth of ice caps due to near-0 obliquity? If so, do you have any other, crunchy references showing the impact of low obliquity on planetary temperatures?
Mike Miller, Materials Engineer
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"Everbody's always in favor of saving Hitler's brain, but when you put it in the body of a great white shark, oh, suddenly you've gone too far." -- Professor Farnsworth, Futurama
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"Everbody's always in favor of saving Hitler's brain, but when you put it in the body of a great white shark, oh, suddenly you've gone too far." -- Professor Farnsworth, Futurama