Horst-Joachim Lu ̈decke, Rainer Link, and Friedrich-Karl Ewert
EIKE, European Institute for Climate and Energy, published in International Journal of Modern PhysicsC, Vol. 22, No. 10, doi:10.1142/S0129183111016798 (2011), copyright World Scientific Publishing Company, www.worldscinet.com.
We evaluate to what extent the temperature rise in the past 100 years was a trend or a natural fluctuation and analyze 2249 world- wide monthly temperature records from GISS (NASA) with the 100-year period covering 1906-2005 and the two 50-year periods from 1906 to 1955 and 1956 to 2005. No global records are applied. 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 warm- ing 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.
As a result, the probabilities that the observed temperature series are natural have values roughly between 40% and 90%, depending on the sta- tions 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.
In this paper, we have used 2249 unadjusted monthly temperature records of 100 and 50 years in length and evaluated the temperature changes for the periods 1906-2005, 1906-1955, and 1956-2005. Our analysis was based exclusively on local records and applied DFA, Monte Carlo methods and synthetic records. The main results and conclusions are the following.
- a) The mean of all stations shows 0.58 0C global warming from 1906 to 2005. If we consider only those stations with a population of under 1000 and below 800 meter above sea level this figure drops to 0.41 0C and would probably decrease even further if we were to take into account the warm biases caused by the worldwide reduction in rural stations during the 1990s, by changes to the screens and their environments, and by the appearance of automatic observing systems.
- b) From 1906 to 2005, about a quarter of all records show falling temperatures. This in itself is an indication that the observed temperature series are pre- dominantly natural fluctuations. ’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 ex- cluded. We evaluated - with a confidence interval of 95% - the probability that the observed global warming from 1906 to 2005 was a natural fluctuation as lying between 40% and 70%, depending on the station’s characteristics. For the period of 1906 to 1955 the probabilities are arranged between 80% and 90% and for 1956 to 2005 between 60% and 70%.
d) The vast majority of temperature stations are found on land and in the northern hemisphere, and have Hurst exponent of α ≈ 0.63 in such loca- tions. However, two thirds of the Earth are covered with water, and the relatively few stations on islands or near oceans have higher Hurst exponent of α ≈ 0.7. Therefore, a real exponent for the entire Earth could be some- what higher than α ≈ 0.63. Records with higher exponents embody even higher probabilities for natural fluctuations.