From global freezing to global scorching


The term global warming is inadequate since the actual
cycling in the last 450 million years has ranged hot to cold
extremes.

The hottest average temperature during this long period was about
22°C, 7°C hotter than now, and the lowest average about 8°C lower than
now.

So it is better to use at least three measures, cold-moderate-hot. In
polar ice caps existed with the first two, not with the latter. We
are in the moderate climate period right now but for most of the last
several million years it has been between cool and cold. The moderate
periods have been recently relatively brief.

The problem is that even if the sun's radiance never changed,
the earth's temperature could range between hot and cold
depending on the CO2 content and depending only on that.

Without CO2 earth would have an average temperature of -20°C.

Iceball earth (look it up). Ice right down to the equator, the
oceans nearly frozen solid, with only the thermal vents
keeping life alive.

But since the earth has water, it did not become as hot as Venus, even
though both planets started off with the same amount of CO2 (about 70
atmospheres). Venus because of its dense cloud cover actually now
receives less sunlight at the surface than the earth in spite of Venus
being closer to the sun. So forget how close it is to the sun.

One does not anticipate the earth becoming as hot as Venus or even
having average temperatures above 22°C in the next several hundred
million years. Eventually this will occur since the sun will
progressively put out more energy. In fact, based on a 10% increase
per one billion years, the sun should be putting out 5% more energy
than 450 million years ago. So if it were only the sun, the earth
would be warmer now than then.

Current projections are that it will be cool enough for the earth to
support life for perhaps a billion more years, in that sense earth is
in its middle age from the standpoint of supporting complex life. The
atmosphere requires oxygen (not too much, about what is has now) and
CO2 (for photosynthesis) to support complex life as we know it.

But the earth's current cold-moderate cycling is exceptional
when viewed over the last 450 million years. The atmospheric
CO2 is now still low (well below 1000 ppm) although higher
than anytime in the last 650,000 years, perhaps much
longer, having cycled between 200-300 ppm, with the temperature
variations being severe (8°C) and the climate differences radical.
Nobody would like to see the return of the Northern Hemisphere ice
sheets and if the temperature were headed down we might even chose a
policy of releasing more CO2 into the atmosphere and/or black dusting
the ice sheets so that the albedo would change and the sun's heat
absorbed.

Nor would one want it very much warmer on the average than now (we
even currently run our air conditioners too much in the summer).
Recognize a good thing when you have it. Moderation is all things,
especially the climate.

We are now at the point where it behooves us to estimate
much much heating will occur at various CO2 levels if they increase.

We do have geological records to look at. We know that other factors
are at work in influencing both local and global climates. The earth
precesses, and winter becomes summer every 5000 or so years. The earth
is on slightly elliptical path around the sun, the solar constant
effectively varies by couple of % during the year, the short term
sunspot cycle does not change the constant much (0.1%) but other
changes occur which may influence cloud formation. But mostly the CO2
is in the driver's seat right now.

The last hot period was during the Eocene (50 million years ago)
during which the CO2 content was around perhaps greater than 1100 ppm
(four times preindustrial concentrations),

There were no ice caps, there was a one period of rapid change
generating the Paleocene-Eocene Thermal Maximum (PETM). "The period
was marked by a rapid rise in greenhouse gases that heated Earth by
roughly 9° F (5° C), in less than 10,000 years. The climate warming
caused widespread changes including mass extinction in the world's
oceans due to acidification and shifts of plant communities due to
changes in rainfall."

See figure-
http://en.wikipedia.org/wiki/Image:65_Myr_Climate_Change.png

Any rapid rise in CO2 is probably due to volcanic releases although
catastrophic release of methane is another possibility. In fact some
95% of what was previously CO2 in the atmosphere is locked up in
sedimentary limestone. By subduction, these formations release CO2
when they get carried lower and encounter magma. This subduction is
caused by tectonic plate collisions which drive one or the other
plates lower. The earth is still energy dynamic even though the
internal heat being generated by the decomposition is a quarter it was
in the early life of the earth.`The continents will continue to move
around an in 250 million years will fuse again into the same kind of
super continent that existed 200 million years ago. But for right
now, man is the CO2 generator but otherwise volcanic emissions will
have to occur if the CO2 is to be high enough to prevent freezing.

Normally CO2 is naturally removed by weathering and photosynthesis,
the latter is presently nearly at a steady state, biological release
of CO2 (by oxidative rotting) into the atmosphere is about equal to
the photosynthetic uptake. The big changes in CO2 content during the
glacier-interglacier periods are due to ocean water absorption (with
cooling) and release (by heating). This CO2 reservoir doee fix CO2 as
does weathering or photosynthesis.

By the end of the Carboniferous (300 million years ago),
photosynthesis alone had sent the CO2 levels to very low values,
biomass build-up had occurred and this eventually resulted in the
formation of coal. This near exhaustion of CO2 changed the climate
radically changes from hot to cold. It remained cold for 10s of
millions of years until CO2 was released into the
atmosphere and the temperatures sent up again to the hot level.

"Average global temperatures in the Early Carboniferous Period were
hot- approximately 20° C (68° F). However, cooling during the Middle
Carboniferous reduced average global temperatures to about 12° C (54°
F). This is comparable to the average global temperature on Earth
today"

"Similarly, atmospheric concentrations of carbon dioxide (CO2) in the
Early Carboniferous Period were approximately 1500 ppm (parts per
million), but by the Middle Carboniferous had declined to about 350
ppm -- comparable to average CO2 concentrations today!"

"Earth's atmosphere today contains about 380 ppm CO2 (0.038%).
Compared to former geologic times, our present atmosphere, like the
Late Carboniferous atmosphere, is CO2- impoverished! In the last 600
million years of Earth's history only the Carboniferous Period and our
present age, the Quaternary Period, have witnessed CO2 levels less
than 400 ppm."

That indicates that if atmospheric CO2 goes above 1000 the earth's
average temperature will rise up to near the 22°C "limit". This is
always why current estimates of temperature increases are "only"
a couple degrees if the CO2 concentration rises "only" another 200 ppm
or so. For any increase in global temperatures we sill see larger
increases in the Northern Hemisphere than near the equator. The
climates will shift and a number of species will become rapidly
extinct. Other plant and animal life will eventually replace
them but not in our lifetimes.

Insects will benefit more than man. We might best give up our
carnivore habits and become insectivores. Fly soup, anyone?












In fact some 95% of what was previously CO2 in the atmosphere is
locked up in sedimentary
limestone. By subduction, these formations release CO2 when they get
carried lower and encounter magma. This subduction is caused
by tectonic plate collisions which drive one or the other plates
lower.
The earth is still energy dynamic even though the internal heat being
generated by the decomposition is a quarter it was in the early life
of
the earth.`The continents will continue to move around an in 250
million
years will fuse again into the same kind of super continent that
existed
200 million years ago. But for right now, man is the CO2 generator
but otherwise volcanic emissions will have to occur if the CO2 is to
be high enough to prevent freezing.

Normally CO2 is naturally removed by weathering and photosynthesis,
the latter is presently nearly at a steady state, biological release
of CO2 (by oxidative rotting) into the atmosphere is about equal to
the photosynthetic uptake. The big changes in CO2 content during the
glacier-interglacier periods are due to ocean water absorption
(with cooling) and release (by heating). This CO2 reservoir doee
fix CO2 as does weathering or photosynthesis.

By the end of the Carboniferous (300 million years ago),
photosynthesis alone had sent the CO2 levels to very low values,
biomass build-up had occurred and this eventually resulted in the
formation of coal. This near exhaustion of CO2 changed the climate
radically changes from hot to cold. It remained cold for 10s of
millions of years until CO2 was released into the
atmosphere and the temperatures sent up again to the hot level.

"Average global temperatures in the Early Carboniferous Period were
hot- approximately 20° C (68° F). However, cooling during the Middle
Carboniferous reduced average global temperatures to about 12° C (54°
F). This is comparable to the average global temperature on Earth
today"

"Similarly, atmospheric concentrations of carbon dioxide (CO2) in the
Early Carboniferous Period were approximately 1500 ppm (parts per
million), but by the Middle Carboniferous had declined to about 350
ppm -- comparable to average CO2 concentrations today!"

"Earth's atmosphere today contains about 380 ppm CO2 (0.038%).
Compared to former geologic times, our present atmosphere, like the
Late Carboniferous atmosphere, is CO2- impoverished! In the last 600
million years of Earth's history only the Carboniferous Period and our
present age, the Quaternary Period, have witnessed CO2 levels less
than 400 ppm."

That indicates that if atmospheric CO2 goes above 1000 the earth's
average temperature will rise up to near the 22°C "limit". This is
always why current estimates of temperature increases are "only"
a couple degrees if the CO2 concentration rises "only" another 200
ppm
or so. For any increase in global temperatures we sill see larger
increases in the Northern Hemisphere than near the equator. The
climates will shift and a number of species will become rapidly
extinct. Other plant and animal life will eventually replace
them but not in our lifetimes.

Insects will benefit more than man. We might best give up our
carnivore habits and become insectivores. Fly soup, anyone?





In fact some 95% of what was previously CO2 in the atmosphere is
locked up in sedimentary
limestone. By subduction, these formations release CO2 when they get
carried lower and encounter magma. This subduction is caused
by tectonic plate collisions which drive one or the other plates
lower.
The earth is still energy dynamic even though the internal heat being
generated by the decomposition is a quarter it was in the early life
of
the earth.`The continents will continue to move around an in 250
million
years will fuse again into the same kind of super continent that
existed
200 million years ago. But for right now, man is the CO2 generator
but otherwise volcanic emissions will have to occur if the CO2 is to
be high enough to prevent freezing.

Normally CO2 is naturally removed by weathering and photosynthesis,
the latter is presently nearly at a steady state, biological release
of CO2
(by oxidative rotting) into the atmosphere is about equal to the
photosynthetic uptake. The big changes in CO2 content during
the glacier-interglacier periods are due to ocean water absorption
(with cooling) and release (by heating). This CO2 reservoir doee
fix CO2 as does weathering or photosynthesis.

By the end of the Carboniferous (300 million years ago),
photosynthesis alone had sent the CO2 levels to very low values,
biomass build-up had occurred and this eventually resulted in the
formation of coal. This near exhaustion of CO2 changed the climate
radically changes from hot to cold. It remained cold for 10s of
millions of years until CO2 was released into the
atmosphere and the temperatures sent up again to the hot level.

"Average global temperatures in the Early Carboniferous Period were
hot- approximately 20° C (68° F). However, cooling during the Middle
Carboniferous reduced average global temperatures to about 12° C (54°
F). This is comparable to the average global temperature on Earth
today"

"Similarly, atmospheric concentrations of carbon dioxide (CO2) in the
Early Carboniferous Period were approximately 1500 ppm (parts per
million), but by the Middle Carboniferous had declined to about 350
ppm -- comparable to average CO2 concentrations today!"

"Earth's atmosphere today contains about 380 ppm CO2 (0.038%).
Compared to former geologic times, our present atmosphere, like the
Late Carboniferous atmosphere, is CO2- impoverished! In the last 600
million years of Earth's history only the Carboniferous Period and our
present age, the Quaternary Period, have witnessed CO2 levels less
than 400 ppm."

That indicates that if atmospheric CO2 goes above 1000 the earth's
average temperature will rise up to near the 22°C "limit". This is
always why current estimates of temperature increases are "only"
a couple degrees if the CO2 concentration rises "only" another 200
ppm
or so. For any increase in global temperatures we sill see larger
increases in the Northern Hemisphere than near the equator. The
climates will shift and a number of species will become rapidly
extinct. Other plant and animal life will eventually replace
them but not in our lifetimes.

Insects will benefit more than man. We might best give up our
carnivore habits and become insectivores. Fly soup, anyone?

.