Andre said:
... global temperature and Earth reflection (albedo) have a very high correlation but the actual temperature reaction to changes in reflection is much less (0,6 deg C instead of 2,8 deg C) showing incredible climate stability to changes in forcing.
Correct me if I am wrong, but it would seem to me that the sign (+ or -) of this correlation must depend upon the temperature. For example,
(Case 1+):
If Earth were a little colder, then a slight farther drop in temperature would increase the snow cover and the albedo, thus tending to decrease the temperature farther as more solar heat is reflected back to space. This is:
A POSITIVE feed back system driving to colder conditions, perhaps even an ice age.
(Case 2-):
If, however, Earth were a little warmer, a slight increase in temperature would increase the percentage of cloud cover (assuming it is not already 100% as is the fact for Earth today) and increase the albedo, again reflecting more solar heating back into space. This tends to lessen the temperature rise (compared to that which would occur on a "dry planet.") This is:
A NEGATIVE feed back system tending to maintain stability despite changes in the conditions imposed.
Now you no doubt understand that 1+ and 2- indicates the type of feedback. Currently the "averaged Earth" seem to be in Case 2- as she resists rather surprisingly well all sorts of natural and man made efforts to radical change her temperature. If Earth were in Case 1+ even slight disturbances would grow as positive feed back system are unstable (until the saturate and become neutral stability in some new state, Case S. - For example if Earth were cold enough to initially be in Case 1+ this stable state, Case S, might be when all the oceans have frozen over. This state is sometimes called "Snow ball Earth" so "S" can be associated with that name or "stable.")
Now let us recognize that Real Earth is not "averaged Earth" but has two hemispheres in different seasons or temperature ranges. Very interesting results are possible (AND WOULD OCCUR) if Earth were not in essentially a circular orbit. For example, it is entirely possible that the Northern Hemisphere is locked in a permanent ice age (Case 1+ --> Case S) while the Southern Hemisphere remains in Case 2- state. I discuss this in detail in Chapters 5 & 6 of my book,
Dark Visitor, which I rarely mention it, but when I do, I always tell that the web site under my name, not only explains why I wrote this physics text in the form of a cosmic disaster story and gives details about the physic hidden in the story, etc, but also how to read it for free.
The basic idea of
Dark Visitor (reflected in this name) is that a small black hole quickly passing by the solar system will perturb the orbits of the planets by a gravitational impulse. This impulse will make them all have more elliptical orbits but not change their rotation axis. These small black holes, like most stars, typically occur in pairs.* They are more common than all the existing stars. In
Dark Visitor, one of 2.2 solar masses misses Earth by 12 AU** and change Earth's orbit to one of 378 days with eccentricity, e = 0.836 instead of the current e = 0.171.
The new "e" of Earth is less than the current "e" of Mars and an extra 13 days in the year would not seem to be a big deal, but it is. As bad luck would have it, Earth’s new apogee (1.108AU) occurs in the middle of the North's summer (makes less summer heating) and perigee (0.937AU) during northern winters provides more solar heating in winter. - That would seem to be great improvement, but it is a terrible curse! Climate is complex. (Andre probably agrees with that.) The really big snowfalls always occur in relative mild winter weather, not when it is bitterly cold. (Too little water vapor in the air.)
While the North is in winter, the South is in summer and at perigee, 0.063AU closer to the sun. Southern hemisphere is mainly ocean and it evaporates in Case 2- conditions so does not get too much hotter than currently but the cloud cover is 100% all summer long, and also 100% to a relatively high northern latitude. This continuous winter cloud cover in the mild winter conditions causes approximately two feet of snow to fall every day in Washington DC, for an winter total of 77 feet, the first year after the
Dark Visitor has passed, but the North is in Case 1+ so snow increases each year. Reason for Case 1+ conditions is the mild or almost cold summers do not melt all the snow that fell the prior winter.
In ten years, (approximately) the ocean levels have dropped enough to make all existing ports useless, and that is just the start of the cosmic disaster. In 100 years, the advancing ice sheet covers Miami and Washington DC is under more than 100 feet of ice. Many lives are lost in the Southern Hemisphere also because every summer evening for several hours, torrential rains fall and all the major cities are destroyed, but it is still possible to grow rice and humanity survives in the south. This ice age differs from all prior ones in that it is permanent and only present in Northern Hemisphere. (I live in Brazil - so I timed the passage of the
Dark Visitor in the computer code to make this so - only the Northern Hemisphere is uninhabitable.) Most people think that cold winters cause ice ages, but as discussed in greater detail in Chapters 5 & 6 they can be caused by warmer winters and colder summers that fail to melt all the ice, first only at high latitudes, but an ice sheet rapidly grows for that part of Earth in Case 1+ conditions.
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*The first of a pair of gravitationally-bound, small black holes (cores of first generation star pair) may have passed in the late 1920s. Neptune, the most distant Planet known at the time was perturbed, and the search for why led to the discovery of Pluto, which was for many years thought to be several times larger than Earth because that much mass is required to make the observed perturbation. It is now know than Pluto is smaller than the moon, which leaves open the question as to what did happen in the late 1920s. (A Dark Visitor passing? First of a pair?)
** Much more probable than the "direct hit", usually assumed in cosmic horror stories. As the black hole does not reflecting sun light, you can not see it coming. Some day it will come, but it is not likely to be passing in late 2007 or early 2008 as assumed in
Dark Visitor (Based on the slight perturbation observed now in Pluto's orbit.)
