In the ongoing global warming debate there is often a significant difference between the perception of what is going on with the Earth’s climate when compared to what is actually going on. There is no greater example of this than the summer temperatures in the Northern Hemisphere. Since summer has arrived (in practice at least) I am going to spend the summer going over recent research that shows that the modern period is not having unusually high summer temperatures.
The normal perception is that the summer temperatures are going to increase until they are much, much hotter than they have been in who knows how long. The reality is not even close to that perception. A recent study (Yi, Yu, 2011) is probably the highest resolution reconstruction using temperature and precipitation records from the region and then correlating to tree-ring data to create a high resolution reconstruction of the summer temperatures for North-Central China.
While I understand that tree-ring reconstructions have a bad name to many, in my observations that problem really only applies to one group of people. Others somehow manage to get results that seem reasonable and this group is no exception.
The reconstruction covers the period from 1470-2002 AD so it is useful even to the modern day and there is a good overlap with the available summer data from the CRU.
This reconstruction shows a clear periodic cycle that is evident on a 50-100 year scale. The average summer temperatures can easily vary by 0.5 °C from one period to another. The really interesting result is the 1930′s. This was the period known in the United States as the Dust Bowl for it’s very hot summers and China shows the same result. The modern period has nothing on the temperatures from that period.
This can be compared directly to the CRU summer (June-Aug) temperatures for the period from 1850-2002. They show very, similar temperatures for the end of the period, but the differences for the 1930′s are astounding.
For all intents and purposes the CRU data misses the warm period that took place from 1920-1945. It doesn’t exist at all. Meanwhile, China was experiencing the warmest period in 500 years, but they are told that the modern temperatures are unprecedented. It would seem that the conclusion of global warming needs to review the data a little better.
Despite the perpetual media coverage, it is clear that the peak of the modern warming cycle for the summer months took place 70-80 years ago. It should be noted that the United States set the all time temperature record for 50% of the states back in the 1930′s. That China also experienced it’s warmest summers in the same decade should be no surprise.