A study by Horst-Joachim Ludecke, Rainer Link, and Friedrich-Karl Ewert of the European Institute for Climate and Energy cannot find a definite human influence on the temperature over the past century. It concludes that, at most, any human-caused warming is “marginal”.
In a peer-reviewed paper for the International Journal of Modern Physics, the trio write:
We evaluate to what extent the temperature rise in the past 100 years was a trend or a natural fluctuation and analyze 2249 worldwide monthly temperature records from GISS (NASA) …
The data document a strong urban heat island effect (UHI) and a warming with increasing station elevation. For the period 1906-2005, we evaluate a global warming of 0.58 0C as the mean for all records. This decreases to 0.41 0C if restricted to stations with a population of less than 1000 and below 800 meter above sea level. About a quarter of all the records for the 100-year period show a fall in temperatures.
Our hypothesis for the analysis is … that the observed temperature records are a combination of long-term correlated records with an additional trend, which is caused for instance by anthropogenic CO2, the UHI or other forcings. We apply the detrended fluctuation analysis (DFA) and evaluate Hurst exponents between 0.6 and 0.65 for the majority of stations… As a result, the probabilities that the observed temperature series are natural have values roughly between 40% and 90%, depending on the stations characteristics and the periods considered.
‘Natural’ means that we do not have within a defined confidence interval a definitely positive anthropogenic contribution and, therefore, only a marginal anthropogenic contribution can not be excluded.
Andrew Bolt April 07 2012 (12:05pm)