Ice has
been melting
on our planet
for about
20,000 years.
I tell people here in Michigan
that my property was under
a mile of ice 20,000 years
ago, and sometimes that
makes them realize
global warming has been
with us for a long time !
The melting ice
has already raised
sea level by 400 feet.
But no more
than 0.5 feet,
of the 400 foot total,
could have been caused
by greenhouse warming.
Global warming
has affected the Arctic
more than any other
part of our planet.
Greenhouse gases
would be expected
to most affect
both poles.
But Arctic ice
is floating ice,
so melting does not
raise the sea level.
Antarctica ice
won't melt
because the
temperature there
is below freezing,
even in the summer.
And that wouldn't change
if the global temperature
rose two degrees C,
or even four degrees C. !
What's left to melt,
that could affect
sea level ?
Mainly Greenland.
The average
Greenland
ice thickness
is 2135 meters,
or 7000 ft.
Greenland has
2,850,000 km3
of ice.
All of it would
have to melt
to raise sea level
by 7 meters.
But that won't happen !
In the interior of Greenland,
only the very top of the ice
melts in the summer.
The vast majority
of Greenland’s ice
never comes close
to reaching
temperatures
above freezing.
Summer in Greenland
is roughly two months long.
Temperatures in the other
ten months of the year
are below -10 degrees C.
The two months of summer
are not enough time to melt
much Greenland ice.
Increasing the average
global temperature by
+2 degrees C,
or even by
+4 degrees C.,
would not be enough
to make the Greenland
interior go above freezing,
because of the elevation.
Also, the weight of the
Greenland ice has depressed
the interior of the continent
into a bowl shape, that will
disrupt drainage of the
melting glaciers into
the ocean.
The interior summit
of Greenland is
two miles above sea level,
with a temperature range
of -26 degrees C in winter
to 0 degrees C. in summer.
The Summit station,
in inland Greenland,
barely gets above
0 degrees C.
in the summer.
Greenland has been
losing ice mass
over last 20 years.
But there was less ice
at the end of the 1930s
in Greenland,
than there is today.