Greenland warming of 1920-1930 and 1995-2005 Geophysical Research Letters, 33, L11707, 13 June 2006, doi:10.1029/2006GL026510. http://www.agu.org/pubs/crossref/2006/2006GL026510.shtml |
Petr Chylek
Los Alamos National Laboratory, Space and Remote Sensing Sciences, Los Alamos,
New Mexico, USA
M. K. Dubey
Los Alamos National Laboratory, Earth and Environmental Sciences, Los Alamos,
New Mexico, USA
G. Lesins
Department of Physics and Atmospheric Science, Dalhousie University, Halifax,
Nova Scotia, Canada
Received 10 April 2006; accepted 9 May 2006; published 13 June 2006.
extracts from this paper: (from CCNet, Benny Peiser)
Abstract:
We provide an analysis of Greenland temperature records to compare the
current (1995-2005) warming period with the previous (1920-1930) Greenland
warming. We find that the current Greenland warming is not unprecedented in
recent Greenland history. Temperature increases in the two warming periods are
of a similar magnitude, however, the rate of warming in 1920-1930 was about 50%
higher than that in 1995 - 2005.
[...]
5. Discussion and Conclusion
[14] We have analyzed temperature time series from available Greenland locations
and we have found that:
[15] i) The years 1995 to 2005 have been characterized by generally increasing
temperatures at the Greenland coastal stations. The year 2003 was extremely warm
on the southeastern coast of Greenland. The average annual temperature and the
average summer temperature for 2003 at Ammassalik was a record high since 1895.
The years 2004 and 2005 were closer to normal being well below temperatures
reached in 1930s and 1940s (Figure 2).
Although the annual average temperatures and the average summer temperatures at
Godthab Nuuk, representing the southwestern coast, were also increasing during
the 1995-2005 period, they stayed generally below the values typical for the
1920-1940 period.
[16] ii) The 1955 to 2005 averages of the summer temperatures and the
temperatures of the warmest month at both Godthaab Nuuk and Ammassalik are
significantly lower than the corresponding averages for the previous 50 years
(1905-1955). The summers at both the southwestern and the southeastern coast of
Greenland were significantly colder within the 1955-2005 period compared to the
1905-1955 years.
[17] iii) Although the last decade of 1995-2005 was relatively warm, almost
all decades within 1915 to 1965 were even warmer at both the
southwestern (Godthab Nuuk) and the southeastern (Ammassalik) coasts of
Greenland.
[18] iv) The Greenland warming of the 1995-2005 period
is similar to the warming of 1920-1930, although the rate of temperature
increase was by about 50% higher during the 1920-1930 warming period.
[19] v) There are significant differences between the global temperature and the
Greenland temperature records within the 1881-2005 period. While all the decadal
averages of the post-1955 global temperature are higher (warmer climate) than
the pre-1955 average, almost all post-1955 temperature averages at Greenland
stations are lower (colder climate) than the pre-1955 temperature average.
[20] An important question is to what extent can the current (1995-2005)
temperature increase in Greenland coastal regions be interpreted as evidence of
man-induced global warming? Although there has been a considerable temperature
increase during the last decade (1995 to 2005) a
similar increase and at a faster rate occurred during the early part of the 20th
century (1920 to 1930) when carbon dioxide or other greenhouse gases could not
be a cause. The Greenland warming of 1920 to
1930 demonstrates that a high concentration of carbon dioxide and other
greenhouse gases is not a necessary condition for period of warming to arise.
The observed 1995-2005 temperature increase seems to be within a natural
variability of Greenland climate. A general increase in solar activity [Scafetta
and West, 2006] since 1990s can be a contributing factor as well as the sea
surface temperature changes of tropical ocean [Hoerling et al., 2001].
[21] The glacier acceleration observed during the 1996-2005 period [Rignot and
Kanagaratnam, 2006] has probably occurred previously. There should have been the
same or more extensive acceleration during the 1920-1930 warming as well as
during the Medieval Warm period in Greenland [Dahl-Jensen et al., 1998;
DeMenocal et al., 2000] when Greenland temperatures were generally higher than
today. The total Greenland mass seems to be stable or slightly growing [Zwally
et al., 2005].
[22] To summarize, we find no direct evidence to
support the claims that the Greenland ice sheet is melting due to increased
temperature caused by increased atmospheric concentration of carbon dioxide. The
rate of warming from 1995 to 2005 was in fact lower than the warming that
occurred from 1920 to 1930. The temperature trend during the next ten
years may be a decisive factor in a possible detection of an anthropogenic part
of climate signal over area of the Greenland ice sheet.
Copyright 2006, American Geophysical Union.