Ext User(BONZ0)
26-02-2007, 11:53 AM
In the study of Overpeck et al. (1997), who combined paleoclimatic
records from lake and marine sediments, trees and glaciers to develop a
400-year history of circum-Arctic surface
air temperature.
From this record they determined that the most dramatic
warming of the last four centuries (1.5°C) occurred between 1840 and 1955,
over which period the air's CO2 concentration rose by 28 ppm. Then, from
1955 to the end of the record (about 1990), the mean circum-Arctic air
temperature actually declined by 0.4°C, while the air's CO2 concentration
rose by 41 ppm.
On the basis of these observations, we calculate that over
the first 115 years of warming, when the air's CO2 concentration rose by an
average of 0.24 ppm/year, air temperature rose by an average of
0.013°C/year; while over the final 35 years of the record, when the air's
CO2 content rose at a mean rate of 1.17 ppm/year (nearly five times the rate
at which it had risen in the prior perio! d), air temperature actually
decreased, at a mean rate of change (0.011°C/year) that was nearly the same
as the rate at which it had previously risen.
Hence, it is abundantly clear from this analysis of air temperature behavior
in the Arctic (where CO2
effects are supposed to be most evident and first detectable) that whatever
effect the increase in the air's CO2 content might have had on earth's
surface air temperature over the period of study was totally overpowered by
the simultaneous effect of whatever changes may have occurred in whatever is
the chief determinant of climate change on earth.
With directly-measured temperatures,
as opposed to the
reconstructed temperatures used by Overpeck et al., focusing on the study of
Polyakov et al. (2003), who derived a surface air temperature history that
stretches from 1875 to 2000 based on measurements made at 75 land stations
and a number of drifting buoys located poleward of 62°N latitude.
From 1875 to about 1917, the surface air temperature of this huge northern
region rose
hardly at all; but then it took off like a rocket, climbing 1.7°C in just 20
years to reach a peak in 1937 that has yet to be eclipsed.
During this 20-year period of rapidly rising air temperature, the
atmosphere's CO2
concentration rose by a mere 8 ppm. But then, over the next six decades,
when the air's CO2 concentration rose by approximately 55 ppm or nearly
seven times more than it did throughout the 20-year period of dramatic
warming that had preceded it, the air temperature of the region poleward of
62! °N latitude experienced no net warming and, in fact, may have actually
cooled a bit.
In light of these results, it is difficult to claim
much about the strength of the warming power of the 75-ppm increase in the
air's CO2 concentration that occurred from 1875 to 2000
References:
Overpeck, J., Hughen, K., Hardy, D., Bradley, R., Case,
R., Douglas, M., Finney, B., Gajewski, K., Jacoby, G., Jennings, A.,
Lamoureux, S., Lasca, A., MacDonald, G., Moore, J., Retelle, M., Smith, S.,
Wolfe, A. and Zielinski, G. 1997. Arctic environmental change of the last
four centuries. Science
Polyakov, I.V., Bekryaev, R.V., Alekseev, G.V., Bhatt, U.S., Colony, R.L.,
Johnson, M.A., Maskshtas, A.P.
and Walsh, D. 2003. Variability and trends of air temperature and pressure
in the maritime Arctic, 1875-2000. Journal of Climate 16: 2067-2077.
Steig, E.J., Grootes, P.M. and Stuiver, M. 1994. Seasonal precipitation
timing and ice core records. Science 266: 1885-1886.
Stuiver, M., Grootes, P.M. and
Braziunas, T.F. 1995. The GISP2 18O climate record of the past 16,500 years
and the role of the sun, ocean and volcanoes. Quaternary Research 44:
341-354.
White, J.W.C., Barlow, L.K., Fisher, D., Grootes, P.M., Jouzel, J.,
Johnsen, S.J., Stuiver, M. and Clausen, H.B. 1997. The climate signal in the
stable isotopes of snow from Summit, Greenland: Results of comparisons with
modern climate observations. Journal of Geophysical Research 102:
26,425-26,439.
Regards
BONZ0
"Skepticism is the first step toward truth" Denis Diderot philosopher
records from lake and marine sediments, trees and glaciers to develop a
400-year history of circum-Arctic surface
air temperature.
From this record they determined that the most dramatic
warming of the last four centuries (1.5°C) occurred between 1840 and 1955,
over which period the air's CO2 concentration rose by 28 ppm. Then, from
1955 to the end of the record (about 1990), the mean circum-Arctic air
temperature actually declined by 0.4°C, while the air's CO2 concentration
rose by 41 ppm.
On the basis of these observations, we calculate that over
the first 115 years of warming, when the air's CO2 concentration rose by an
average of 0.24 ppm/year, air temperature rose by an average of
0.013°C/year; while over the final 35 years of the record, when the air's
CO2 content rose at a mean rate of 1.17 ppm/year (nearly five times the rate
at which it had risen in the prior perio! d), air temperature actually
decreased, at a mean rate of change (0.011°C/year) that was nearly the same
as the rate at which it had previously risen.
Hence, it is abundantly clear from this analysis of air temperature behavior
in the Arctic (where CO2
effects are supposed to be most evident and first detectable) that whatever
effect the increase in the air's CO2 content might have had on earth's
surface air temperature over the period of study was totally overpowered by
the simultaneous effect of whatever changes may have occurred in whatever is
the chief determinant of climate change on earth.
With directly-measured temperatures,
as opposed to the
reconstructed temperatures used by Overpeck et al., focusing on the study of
Polyakov et al. (2003), who derived a surface air temperature history that
stretches from 1875 to 2000 based on measurements made at 75 land stations
and a number of drifting buoys located poleward of 62°N latitude.
From 1875 to about 1917, the surface air temperature of this huge northern
region rose
hardly at all; but then it took off like a rocket, climbing 1.7°C in just 20
years to reach a peak in 1937 that has yet to be eclipsed.
During this 20-year period of rapidly rising air temperature, the
atmosphere's CO2
concentration rose by a mere 8 ppm. But then, over the next six decades,
when the air's CO2 concentration rose by approximately 55 ppm or nearly
seven times more than it did throughout the 20-year period of dramatic
warming that had preceded it, the air temperature of the region poleward of
62! °N latitude experienced no net warming and, in fact, may have actually
cooled a bit.
In light of these results, it is difficult to claim
much about the strength of the warming power of the 75-ppm increase in the
air's CO2 concentration that occurred from 1875 to 2000
References:
Overpeck, J., Hughen, K., Hardy, D., Bradley, R., Case,
R., Douglas, M., Finney, B., Gajewski, K., Jacoby, G., Jennings, A.,
Lamoureux, S., Lasca, A., MacDonald, G., Moore, J., Retelle, M., Smith, S.,
Wolfe, A. and Zielinski, G. 1997. Arctic environmental change of the last
four centuries. Science
Polyakov, I.V., Bekryaev, R.V., Alekseev, G.V., Bhatt, U.S., Colony, R.L.,
Johnson, M.A., Maskshtas, A.P.
and Walsh, D. 2003. Variability and trends of air temperature and pressure
in the maritime Arctic, 1875-2000. Journal of Climate 16: 2067-2077.
Steig, E.J., Grootes, P.M. and Stuiver, M. 1994. Seasonal precipitation
timing and ice core records. Science 266: 1885-1886.
Stuiver, M., Grootes, P.M. and
Braziunas, T.F. 1995. The GISP2 18O climate record of the past 16,500 years
and the role of the sun, ocean and volcanoes. Quaternary Research 44:
341-354.
White, J.W.C., Barlow, L.K., Fisher, D., Grootes, P.M., Jouzel, J.,
Johnsen, S.J., Stuiver, M. and Clausen, H.B. 1997. The climate signal in the
stable isotopes of snow from Summit, Greenland: Results of comparisons with
modern climate observations. Journal of Geophysical Research 102:
26,425-26,439.
Regards
BONZ0
"Skepticism is the first step toward truth" Denis Diderot philosopher