Jan Esper of Johannes Gutenberg University Mainz in Germany and his collaborators were able to assembled a record of tree rings that is unprecedented in its continuity and consistency. These data came from the trunks of young and long-dead Scots pines at 17 sites in northern Finland and Sweden. Examining this database in a new way allowed them to identify the effects of small variations in Earth's orbit about the Sun on the climate. These small variations are the result of Earth's gravitational interactions with Jupiter and Saturn and are believed to be responsible for the ice ages. But, the researchers believe these small variations are also responsible for a cooling period of the last 2000 years. The data show that Scandinavia cooled from about 138 BC to about AD 1900 before it began warming again.
Of course, climate change deniers are jumping on this as proof that the current changes in our climate are not manmade. They want to claim that the current changes are just naturally occurring variations and that this tree ring data supports that conclusion. (Let's ignore how the denialists like to claim there is no change in the climate. Why are they trying to explain the changes if they think there are no changes?)
This is actually bad news for the denialists' claims and is another example of the only way you can reject manmade global climate change is to reject science. This research shows supports other work showing we are in a naturally occurring cooling cycle. The denialists, when they admit there is global climate change, say that the climate goes through naturally occurring cycles. This is correct. What is not correct is the belief we are in a naturally occurring warming cycle. The fact is, we are in a naturally occurring cooling cycle.
Just imagine how much worse off we are going to be when we really do enter a naturally occurring warming cycle.