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I found this study by reading the blog at AccuWeather.com. If you are interested in climate, then you should spend time reading what the meteorologists over there have to say.
A study by 3 researchers and published in the Journal of Geophysical Research has concluded that the weather variations (both increases and decreases) are the result of natural climate processes. They find that the Southern Oscillation is a key indicator of changing global atmospheric temperatures seven months later.
The paper is titled “Influence of the Southern Oscillation on tropospheric temperature” and following is the abstract:
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 20°S and 20°N. 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.
So once again, we are in a situation where one researcher says that humans are to blame and another says that it is all natural.
Following are selected excerpts in Farm Weekly which is the article that AccuWeather referenced:
Australia, El Nino, emissions, ENSO, IPCC, ocean, Pacific Ocean, satellite, scientists, solar, solar activity, temperature, tropics, weather
The findings follow research released earlier this month by US scientists which shows that maximum solar activity and its aftermath have impacts on earth that resemble La Niña and El Niño events in the tropical Pacific Ocean.
In a statement to the media, lead author John McLean said that when climate modellers could not accurately determine historical temperatures “they added a ‘human influence’ to their models”.
“This paper shows that the missing component was the El Niño-Southern Oscillation (ENSO),” Mr McLean said.
“The IPCC acknowledges in its 4th Assessment Report that ENSO conditions cannot be predicted more than about 12 months ahead so until that situation improves projected global temperatures are likely to be quite inaccurate.”
The group says that 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.
“We have shown that internal global climate-system variability accounts for at least 70 per cent of the observed global climate variation over the past half-century,” Associate Professor de Freitas said.
Climate researchers have long been aware that ENSO events influence global temperature, for example, causing a high temperature spike in 1998 and a subsequent fall as conditions moved to La Niña.
Professor Bob Carter, one of four scientists who recently assisted Senator Steve Fielding in questioning the justification for the proposed Australian emissions trading scheme, says that this paper has significant consequences for public climate policy.
“Our paper confirms what many scientists already know: which is that no scientific justification exists for emissions regulation, and that, irrespective of the severity of the cuts proposed, an emissions trading scheme will exert no measurable effect on future climate.”