Nature, not man, responsible for recent global warming

Now the cat is put among the pigeons.

Research recently completed by two Kiwis and an Aussie reveals that natural forces are the dominant influence on climate. They say little or none of the late 20th century global warming and cooling can be attributed to human activity.

John McLean, Chris de Freitas and Bob Carter published their paper, “Influence of the Southern Oscillation on tropospheric temperature”, in the prestigious Journal of Geophysical Research on July 23, 2009.

“The surge in global temperatures since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean that made warming El Niño conditions more likely than they were over the previous 30 years and cooling La Niña conditions less likely” says co-author de Freitas, quoted at Climate Depot.

“We have shown that internal global climate-system variability accounts for at least 80% of the observed global climate variation over the past half-century. It may even be more if the period of influence of major volcanoes can be more clearly identified and the corresponding data excluded from the analysis.”

That’s all for now; more later.

UPDATE: 24 July 2009, 23:59

This is one of those (apparently) rare things in the climate debate: a peer-reviewed paper that casts doubt on the theory of strong anthropogenic global warming. Here’s hoping the alarmists note this new paper and grant it the respect it deserves without heaping the authors with ad hominem insults, though I’m not holding my breath. Please note that by ‘respect’ I mean refuting it with observation and reason, not hyperbole and obfuscation.


J. D. McLean, C. R. de Freitas, and R. M. Carter
Received 16 December 2008; revised 23 March 2009; accepted 14 May 2009; published 23 July 2009.

Time series for the Southern Oscillation Index (SOI) and global tropospheric
temperature anomalies (GTTA) are compared for the 1958–2008 period. GTTA are
represented by data from satellite microwave sensing units (MSU) for the period
1980–2008 and from radiosondes (RATPAC) for 1958–2008. After the removal from the
data set of short periods of temperature perturbation that relate to near-equator volcanic
eruption, we use derivatives to document the presence of a 5- to 7-month delayed close
relationship between SOI and GTTA. Change in SOI accounts for 72% of the variance
in GTTA for the 29-year-long MSU record and 68% of the variance in GTTA for the
longer 50-year RATPAC record. Because El Niño Southern Oscillation is known to
exercise a particularly strong influence in the tropics, we also compared the SOI with
tropical temperature anomalies between 20S and 20N. The results showed that SOI
accounted for 81% of the variance in tropospheric temperature anomalies in the tropics.
Overall the results suggest that the Southern Oscillation exercises a consistently dominant
influence on mean global temperature, with a maximum effect in the tropics, except
for periods when equatorial volcanism causes ad hoc cooling. That mean global
tropospheric temperature has for the last 50 years fallen and risen in close accord with
the SOI of 5–7 months earlier shows the potential of natural forcing mechanisms to
account for most of the temperature variation.

Citation: McLean, J. D., C. R. de Freitas, and R. M. Carter (2009), Influence of the Southern Oscillation on tropospheric temperature, J. Geophys. Res., 114, D14104, doi:10.1029/2008JD011637.

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