Desperately Searching For Climate Warming In China, Alaska And Canada
By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(Translated, edited by P Gosselin)
In mid October 2013 a temperature reconstruction of the last 250 years based on tree rings from northeast China appeared in the journal of Palaeogeography, Palaeoclimatology, Palaeoecology. Recorded were the values for the time period of May-June, i.e. late spring and early summer.
Northeast China cooler than 100 years ago
A Chinese team of scientists led by Yu Liu discovered that the temperatures in the pre-industrial time from 1745-1900 was rather stable. But since the beginning of the 20th century, the temperatures in the region of study began to cool. As a result today the region is about 1°C colder than it was 100 years ago.
Figure 1: Development of the May-June temperatures in Northeast China since 1745. A cooling trend began in 1900. Source: Liu et al. 2013.
Alaska has cooled over the last decade
Now let’s take a look at Alaska. How have temperatures there developed over the last years and decades? The Arctic is supposedly warming up faster and faster and we are all supposed to be in a state of alarm over this. But a look at the temperature curve of the last 60 years delivers a surprise (Figure 2). Already at the end of the 1970s temperatures were surging upwards and stayed at a high level until 2005. But since then the curve has fallen dramatically. Alaska has been only cooling for the last 8 years. The temperature development there is closely coupled to the Pacific Decadal Oscillation (PDO).
Figure 2: Temperature development of Alaska for the last 60 years. Source: The Alaska Climate Research Center.
USA is not warming
Moreover some scientists are now wondering why many rivers on the US west coast have been cooling significantly over the last few years. What could the cause of this be, especially at a time when things are supposed to be getting warmer? Also the temperature development for the USA for the last 110 years is showing a puzzling trend: Somehow over the long-term it just hasn’t gotten warmer? Already back in the 1930s and 40s it was just as warm as it is today (Figure 3).
Figure 3: Temperature development of the der USA based on USHCN data.
Canadian British Columbia was warmer in the 1940s
Also some interesting findings about the temperature history in Canadian British Columbia have become known. Based on tree-rings, scientists have reconstructed the temperature development for the last 800 years for the summer months of June/July (Figure 4). Here it can be observed that the 1940s were warmer than today. Also in the earlier centuries there were phases when it was warmer than today.
Figure 4: Temperature development for the last 800 years based on tree rings. Source: Pitman & Smith 2012.