Why doesn't the southern hemisphere have much more extreme climate
than the northern hemisphere?  In summer the southern hemisphere is 2M
miles closer to the sun and in winter it's 2M miles further away

Hello abook and thank you for your question.

It's all to do with the tilt of the Earth, and not with the distance
of the Earth from the sun.

"The seasons have nothing to do with how far the Earth is from the
Sun.  If this were the case, it would be hotter in the northern
hemisphere during January as opposed to July.  Instead, the seasons
are caused by the Earth being tilted on its axis by 23.5 degrees. 
Here's how it works"

"The Earth has an elliptical orbit around our Sun.  This being said,
the Earth is at its closest point distance wise to the Sun in January
(called the Perihelion) and the furthest in July (the Aphelion).  But
this distance change is not great enough to cause any substantial
difference in our climate.  This is why the Earth's 23.5 degree tilt
is all important in changing our seasons.  Near June 21st, the summer
solstice, the Earth is tilted such that the Sun is positioned directly
over the Tropic of Cancer at 23.5 degrees north latitude.  This
situates the northern hemisphere in a more direct path of the Sun's
energy.  What this means is less sunlight gets scattered before
reaching the ground because it has less distance to travel through the
atmosphere.  In addition, the high sun angle produces long days.  The
opposite is true in the southern hemisphere, where the low sun angle
produces short days.  Furthermore, a large amount of the Sun's energy
is scattered before reaching the ground because the energy has to
travel through more of the atmosphere.  Therefore near June 21st, the
southern hemisphere is having its winter solstice because it "leans"
away from the Sun"
http://www.crh.noaa.gov/fsd/astro/season.htm

A similar question to yours was also asked and answered here:
http://answers.google.com/answers/threadview?id=286805

Thank you very much for your question.

Very best regards.

THX1138

Search strategy included:
"southern hemisphere" seasons
://www.google.com/search?hl=en&lr=&ie=UTF-8&as_qdr=all&q=%22southern+hemisphere%22+seasons

---

Request for Answer Clarification by abook-ga on 17 Jun 2004 09:38 PDT

The answerer has provided the conventional reply, but actually all he has 
answered is why winter and summer occur at all (axial tilt) in either 
hemisphere.  It cannot literally be true that distance from the sun is of no 
account; it may play no part in creating the seasons, but over 4% more 
thermal energy reaches the earth when it is 92M miles from the sun than when 
it is 94M miles away.  That this occurs in the southern summer is only 
coincidental, but the question remains: why (or probably more important, 
how) is this extra energy distributed so that no apparent difference occurs 
in the extremity of the seasons from hemisphere to hemisphere.  I suspect 
the answer lies in the formation of complex atmospheric patterns which serve 
to even out the effects of this additional thermal energy.  Atmpospheric 
effects are certainly of prime importance, since the hottest times of the 
year do not occur at the summer solstice (June 21 or December 21) but one to 
two months later, due to atmospherically mediated climatic patterns.

---

Clarification of Answer by thx1138-ga on 17 Jun 2004 10:33 PDT

Hello again abook.

The answer is not really the complex atmospheric patterns, it is the
fact that the southern hemisphere has more area of ocean than the
northern hemisphere, thus when the Earth is closer to the sun the
southern oceans absorb that extra energy more than the in the northern
hemisphere where there is more land area.

See:

"There is more land in the Northern Hemisphere, and more water bodies
in the Southern Hemisphere. Now, land has a much lower specific heat
capacity than water; in other words, water can hold a lot of heat
while land cannot. Hence, land gets heated up faster and also cools
faster than water. So, during summer, the greater amount of land in
the northern hemisphere gets heated up quicker, while in the southern
hemisphere, the water soaks a lot of heat and gets warmer by a much
lesser amount. In any case, the result is that northern summers are
hotter than the southern summers"
http://curious.astro.cornell.edu/question.php?number=180

also:

"Even though the difference between the earth?s perihelion and
aphelion distances is less than 3%. The amount of solar energy
striking the earth is 7% greater at perihelion (in January) than at
aphelion (in July). This would lead one to conclude that summer in the
southern hemisphere, which occurs at perihelion, is warmer than summer
in the northern hemisphere. This, however, is not the case. Most of
the land mass of the earth is concentrated in the northern hemisphere.
The southern hemisphere, by contrast, is 80% covered by water. Water
has the ability to absorb large amounts of heat. The additional solar
energy supplied by the sun at perihelion is absorbed by the large
bodies of water in the southern hemisphere. The result is that
temperatures are actually more moderate during summers in the southern
hemisphere. On Mars, which does not have any oceans to absorb heat,
the temperature fluctuations are much greater due to perihelion and
aphelion."
http://www.physics.isu.edu/~hackmart/astlbsol.pdf

and:

"But that's not the whole story. Earth is warmer overall in July due
to the unequal distribution of land on the planet. Oceans and
continents are not distributed evenly around the globe, so the summer
sun beating down on the extensive land in the Northern Hemisphere
raises the temperature more than it does in the Southern Hemisphere
six months later."
http://starbulletin.com/2002/07/07/business/brill.html

Very best regards

THX1138

I still don't know what happens to the extra 4% of thermal energy...