 We still need to study nature’s contribution to trend
Recent studies by the Hadley Climate Research Center (UK), the Japan
Meteorological Agency, the National Oceanic and Atmospheric
Administration, the University of East Anglia (UK) and the University
of Alabama Huntsville show clearly that the rising trend of global
average temperature stopped in 2000-2001. Further, NASA data shows that
warming in the southern hemisphere has stopped, and that ocean
temperatures also have stopped rising.
The global average temperature had been rising until about
2000-2001. The International Panel for Climate Change (IPCC) and many
scientists hypothesize rising temperatures were mostly caused by the
greenhouse effect of carbon dioxide (CO2), and they predicted further
temperature increases after 2000. It was natural to assume that CO2 was
responsible for the rise, because CO2 molecules in the atmosphere tend
to reflect back the infrared radiation to the ground, preventing
cooling (the greenhouse effect) and also because CO2 concentrations
have been rapidly increasing since 1946. But, this hypothesis on the
cause of global warming is just one of several.
Unfortunately, many scientists appear to forget that weather and
climate also are controlled by nature, as we witness weather changes
every day and climate changes in longer terms. During the last several
years, I have suggested that it is important to identify the natural
effects and subtract them from the temperature changes. Only then can
we be sure of the man-made contributions. This suggestion brought me
the dubious honor of being designated “Alaska’s most famous climate
change skeptic.”
The stopping of the rise in global average temperature after
2000-2001 indicates that the hypothesis and prediction made by the IPCC
need serious revision. I have been suggesting during the last several
years that there are at least two natural components that cause
long-term climate changes.
The first is the recovery (namely, warming) from the Little Ice Age,
which occured approximately 1800-1850. The other is what we call the
multi-decadal oscillation. In the recent past, this component had a
positive gradient (warming) from 1910 to 1940, a negative gradient
(cooling — many Fairbanksans remember the very cold winters in the
1960s) from 1940 to 1975, and then again a positive gradient (warming —
many Fairbanksans have enjoyed the comfortable winters of the last few
decades or so) from 1975 to about 2000. The multi-decadal oscillation
peaked around 2000, and a negative trend began at that time.
The second component has a large amplitude and can overwhelm the
first, and I believe that this is the reason for the stopping of the
temperature rise. Since CO2 has only a positive effect, the new trend
indicates that natural changes are greater than the CO2 effect, as I
have stated during the last several years.
Future changes in global temperature depend on the combination of
both the recovery from the Little Ice Age (positive) and the
multi-decadal oscillation (both positive and negative). We have an
urgent need to learn more about these natural changes to aid us in
predicting future changes.
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