CO2 levels in
the atmosphere
were higher
than today
for the first
4 billion years
of Earth’s
4.5 billion year
history.
Modern life formed
in the past 540 million
years.
During the Eocene
Thermal Maximum,
temperature was likely
higher than at any time
in the past
550 million years,
while CO2 had been
on a downward track
for 100 million years.
We have been in a major
cooling period since the
Eocene Thermal Maximum,
50 million years ago.
The Earth was an average
of +16 degrees C. warmer then,
mainly at higher latitudes.
The entire planet
was ice-free.
The Arctic and Antarctica
were covered in forests.
The ancestors of every
species on Earth today
survived through what
may have been the
warmest time in the
history of life.
Glaciers began to form
in Antarctica 30 million
years ago, and in the
northern hemisphere
3 million years ago.
Today, even in our
interglacial "Holocene"
period, of the Pleistocene
Ice age, we have one
of the coldest climates
in Earth’s long history.
Antarctic ice cores show
in the past 800,000 years
there have been regular
100,000 year cycles,
including only
10,000 to 15,000
warm years out of
every 100,000 years,
called interglacials.
These 100,000 year
"Milankovitch cycles"
are linked to
the eccentricity of
the Earth’s orbit and
its axial tilt, which affect
the amount of incoming
solar energy.
The Milankovitch cycles
are far more likely to cause
a change in temperature,
than a change in CO2.
And a change in
the temperature
would cause a change
in atmospheric CO2,
due to outgassing of CO2
from the oceans, during
warmer times, and
absorption of CO2
by the oceans,
during colder periods.
CO2 peaks lagged
temperature peaks
by an average
of 800 years,
during the
most recent
400,000-year period.
That would mean
temperature
changes
CAUSED
CO2 level
changes.
A cause always
comes before
an effect.
20,000 years ago
was the peak of the
last major glaciation.
At that time, there was
3.3 kilometres (2 miles)
of ice on top of what is
now the city of Montreal.
95% to 100%
of Canada
was covered by
a sheet of ice.
If the Milankovitch cycle
continues to prevail,
this will happen again,
gradually, during the
next 80,000 years.
Could warming
from CO2 emissions
prevent another
glaciation ?
I assume
any warming
will have a
positive effect.
At the height
of the last glaciation,
20,000 years ago,
sea level was about
120 meters (400 feet)
lower than it is today.
By 7,000 years ago,
all low-altitude and
mid-latitude glaciers
had melted.
During the Holocene
Thermal Optimum,
from 9,000 to 5,000
years ago, the Sahara
was green.
Temperature has risen
at a slow rate in Central
England since 1700.
Not from human
CO2 emissions
-- they were not
relevant until 1900,
and not important
until 1950.
CO2 emissions
began a much faster
rise after 1950,
yet there was
no global warming
before 1975.
Earth is 'greening'
as higher levels of CO2,
due to human emissions
from the use of fossil fuels,
promote increased plant
growth around the world.
If humans had not begun
to unlock some of the
carbon stored underground,
as coal oil and natural gas,
life on Earth would have
been starved of CO2
and plants would have
begunn to die off in
one or two million years.
if the Earth were
considered to be
24 hours old,
we were at
38 seconds
to midnight
when we
reversed
the declining
CO2 trend.
That trend would have
eventually caused
the death of all plants,
and all life, on our planet.