The author Akasofu explains his themes clear and comprehensively in the 54 pages long paper1 . Concerning the early Arctic warming, which is subject of this website, the abstract says:
- Two natural components of the presently progressing climate change are identified. The first one is an almost linear global temperature increase of about 0.5oC/100 years, which seems to have started in 18001850, at least one hundred years before 1946 when manmade CO2 in the atmosphere began to increase rapidly.
- The second one is oscillatory (positive/negative) changes, which are superposed on the linear change. One of them is the multi-decadal oscillation, which is a natural change. This particular natural change had a positive rate of change of about 0.15oC/10 years from about 1975 (positive from 1910 to 1940, negative from 1940 to 1975), and is thought by the IPCC to be a sure sign of the greenhouse effect of CO2.
Subsequently the author explains (p. 44):
- It is important to note that the temperature rise from 1910 to 1940 was as steep as the one that started in 1975; the range of change was also similar. Although the IPCC was interested only in the rise after 1975, they should have also paid serious attention to the temperature rise between 1910 and 1940 and should have tried to understand its cause before deciding that the rise after 1975 was mostly due to the effect of CO2.
The author concludes that it is not appropriate to conclude -a priori- that the 0,6oC rise is mostly due to human causes without carefully subtracting the contribution of natural changes.
This site welcomes the clear references to the ‘temperature rise between 1910 and 1940′, but wonders that little efforts have been made to highlight the role of the Arctic in this rise, as the rising rate was much higher in the Arctic as elsewhere (p. 34). After all, Prof. Akasofu is the Founding Director of the Int. Arctic Research Center of the University of Alaska Fairbanks, which adopted the slogan: “Reducing Uncertainty in Arctic Climate Change Prediction”2. Even if Akasofu regards the rise before 1940 as a natural change, arctic research should be interested to understand and to explain.
Here a new book and website may help:http://www.arctic-heats-up.com/. With the material and information presented, together with about 100 graphic figures in color, the climate change debate will be enhanced with astonishing new aspects. The book concludes that the early warming was caused and sustained over two decades by the West-Spitsbergen Current since winter 1918/19. This reflects recent observations concerning the rapid retreat of sea ice in the Arctic Ocean, particularly 2007, which “may be partly caused by the inflow of warm water into the Arctic Ocean” as mentioned with references by Akasofu (p.38). The new book focuses on the early warming from 1919 to 1940, but leave no doubt that the early event might be part of the situation even today, by mentioning e.g.:One needs only to consider the water renewal time for the Arctic Bottom water, which is a couple of dozen years in the Amundsen- and Nansen-Basin but more than 500 years in the Canada- and Makarov-Basin. (p. 41).
However the overriding effort should be a detailed understanding of the warming in the early 20th Century, and we fully agree with Prof. Akasufo statement: “Thus, it may be concluded that processes other than the CO2 effect have a greater influence on sea ice in the Arctic Ocean than the greenhouse effects of CO2. The Arctic Ocean is special in this respect.“(p.40)
1Online version 03/19/2009; S.I. Akasufo; “Two Natural Components of the Recent Climate Change: (1) The Recovery from the Little Ice Age (A Possible Cause of Global Warming) and (2) The Multi-decadal Oscillation (The Recent Halting of the Warming)”, at:http://people.iarc.uaf.edu/~sakasofu/little_ice_age.php
2See the Homepage logo at: http://www.iarc.uaf.edu/