Transcript Global Warming

Global Warming
Or Climate Hysteria?
The Long View
• The Earth has
•
repeatedly
experienced climate
change throughout its
long history
The Phanerozoic Eon
is characterized by
fluctuations between
“Greenhouse” and
“Icehouse” climates.
Greenhouse World
• Cretaceous
•
•
•
Period was one
of significant
warmth.
Tropical
temperatures not
much different.
Much warmer at
poles – no ice!
Current models
cannot duplicate
these conditions.
The Great Cooling
• The bottom
The Eocene
Climatic Optimum
water of the
ocean has
cooled
gradually –
but
dramatically
over the
past 100
million
years.
The Eocene Climatic Optimum
• Tropical fossils found
•
•
at high latitude.
Fossil forest sites on
Axel Heiberg Island,
NWT, Canada
Turtles, Crocodiles
and other fauna
excavated from
nearby Ellesmere
Island
The Eocene Climatic Optimum
• Tropical fossils found
•
•
at high latitude.
Fossil forest sites on
Axel Heiberg Island,
NWT, Canada
Turtles, Crocodiles
and other fauna
excavated from
nearby Ellesmere
Island
The Eocene Climatic Optimum
• Birches, laurels, tulip trees, metasequoia, and
other deciduous tree species lived happily at
83N, where six months of darkness prevailed!
Ocean Circulation
• Some researchers
•
•
believe that ocean
circulation holds key
to long-term changes
Continental drift
allowed circumpolar
flow around
Antarctica in the
Miocene
Renewed glaciers in
Antarctica
Sea Level Changes
• Sea level
Our most
recent ice
ages
has also
been much
higher
throughout
“recent”
Earth
history
Rapid Changes Can Also Happen!
• Paleocene-Eocene Thermal Maximum (PETM)
Paleocene-Eocene Thermal
Maximum
• Ocean
responded
within 10,000
years.
• Caused by
sudden release
of methane(?)
from the
continental
shelf (??)
• Back to
“normal” within
100,000 years
Earth Today: The Ice Ages
• We live in an
•
“icehouse” period
that has been
around for the last
~1 million years.
Typified by short
warm interglacials
and then long
declines into
glacial episodes.
What causes these cycles?
• Changes in the
Earth’s orbital
parameters
(Milankovitch cycles).
– Distance to the sun
– Precession of the
Earth’s axis
– Changing of angle of
inclination
• These don’t work all
that well, but no one
has a better idea!