Keine Klimakatastrophe !
07.05.2007 um 11:12This is an issue that is often misunderstood in the public sphere and media,so
it is worth spending some time to explain it and clarify it. At least three carefulice
core studies have shown that CO2 starts to rise about 800 years (600-1000 years)after
Antarctic temperature during glacial terminations. These terminations arepronounced
warming periods that mark the ends of the ice ages that happen every100,000 years or
so.
Does this prove that CO2 doesn't cause global warming? Theanswer is
no.
The reason has to do with the fact that the warmings take about5000 years to
be complete. The lag is only 800 years. All that the lag shows is thatCO2 did not cause
the first 800 years of warming, out of the 5000 year trend. Theother 4200 years of
warming could in fact have been caused by CO2, as far as we cantell from this ice core
data.
The 4200 years of warming make up about 5/6 ofthe total warming. So CO2
could have caused the last 5/6 of the warming, but could nothave caused the first 1/6 of
the warming.
It comes as no surprise that otherfactors besides CO2 affect
climate. Changes in the amount of summer sunshine, due tochanges in the Earth's orbit
around the sun that happen every 21,000 years, have longbeen known to affect the comings
and goings of ice ages. Atlantic ocean circulationslowdowns are thought to warm
Antarctica, also.
From studying all the availabledata (not just ice cores), the
probable sequence of events at a termination goessomething like this. Some (currently
unknown) process causes Antarctica and thesurrounding ocean to warm. This process also
causes CO2 to start rising, about 800years later. Then CO2 further warms the whole
planet, because of its heat-trappingproperties. This leads to even further CO2 release.
So CO2 during ice ages should bethought of as a "feedback", much like the feedback that
results from putting amicrophone too near to a loudspeaker.
In other words, CO2
does not initiate thewarmings, but acts as an amplifier once they are underway. From
model estimates, CO2(along with other greenhouse gases CH4 and N2O) causes about half of
the fullglacial-to-interglacial warming.
So, in summary, the lag of CO2behind
temperature doesn't tell us much about global warming. [But it may give us avery
interesting clue about why CO2 rises at the ends of ice ages. The 800-year lag isabout
the amount of time required to flush out the deep ocean through natural oceancurrents.
So CO2 might be stored in the deep ocean during ice ages, and then getreleased when the
climate warms.]
To read more about CO2 and ice cores, seeCaillon et al., 2003,
Science magazine
Guest Contributor: JeffSeveringhaus
Professor of
Geosciences
Scripps Institution ofOceanography
University of California, San
Diego.
Update May 2007: We have afuller exposition of this on a more recent
post.
it is worth spending some time to explain it and clarify it. At least three carefulice
core studies have shown that CO2 starts to rise about 800 years (600-1000 years)after
Antarctic temperature during glacial terminations. These terminations arepronounced
warming periods that mark the ends of the ice ages that happen every100,000 years or
so.
Does this prove that CO2 doesn't cause global warming? Theanswer is
no.
The reason has to do with the fact that the warmings take about5000 years to
be complete. The lag is only 800 years. All that the lag shows is thatCO2 did not cause
the first 800 years of warming, out of the 5000 year trend. Theother 4200 years of
warming could in fact have been caused by CO2, as far as we cantell from this ice core
data.
The 4200 years of warming make up about 5/6 ofthe total warming. So CO2
could have caused the last 5/6 of the warming, but could nothave caused the first 1/6 of
the warming.
It comes as no surprise that otherfactors besides CO2 affect
climate. Changes in the amount of summer sunshine, due tochanges in the Earth's orbit
around the sun that happen every 21,000 years, have longbeen known to affect the comings
and goings of ice ages. Atlantic ocean circulationslowdowns are thought to warm
Antarctica, also.
From studying all the availabledata (not just ice cores), the
probable sequence of events at a termination goessomething like this. Some (currently
unknown) process causes Antarctica and thesurrounding ocean to warm. This process also
causes CO2 to start rising, about 800years later. Then CO2 further warms the whole
planet, because of its heat-trappingproperties. This leads to even further CO2 release.
So CO2 during ice ages should bethought of as a "feedback", much like the feedback that
results from putting amicrophone too near to a loudspeaker.
In other words, CO2
does not initiate thewarmings, but acts as an amplifier once they are underway. From
model estimates, CO2(along with other greenhouse gases CH4 and N2O) causes about half of
the fullglacial-to-interglacial warming.
So, in summary, the lag of CO2behind
temperature doesn't tell us much about global warming. [But it may give us avery
interesting clue about why CO2 rises at the ends of ice ages. The 800-year lag isabout
the amount of time required to flush out the deep ocean through natural oceancurrents.
So CO2 might be stored in the deep ocean during ice ages, and then getreleased when the
climate warms.]
To read more about CO2 and ice cores, seeCaillon et al., 2003,
Science magazine
Guest Contributor: JeffSeveringhaus
Professor of
Geosciences
Scripps Institution ofOceanography
University of California, San
Diego.
Update May 2007: We have afuller exposition of this on a more recent
post.