Over at Watts Up With That, Andy May provides a fascinating graph of Greenland temperatures over the last 4,000 years.
There are some interesting things to note:
- The climate cycles periodically and regularly.
- The current warming began back in 1750.
- The current warming began before the Industrial Age and before CO2 levels rising.
- Our current temperatures are no where near what they were in the past.
- SUVs did not cause these temperature fluctuations.
This average temperature reconstruction shows a steady decline in temperature since the Minoan Warm Period, interrupted by +-120 year cycles of warm and cold. Don’t take the apparent 120 year cyclicity too seriously all of the data was smoothed with a 100 year moving average filter. After the end of the coldest period, the Little Ice Age, the Modern Warm Period begins and temperatures rise to those seen in the Roman Warm Period. The Modern Warm Period is equivalent to the Medieval Warm Period within the margin of error. We need to be careful because we are comparing actual measurements to averaged proxies. When proxies are averaged all high and low temperatures are dampened. In particular, the Medieval Warm Period is somewhat smeared and dampened due to the Vinther record. The Vinther Medieval Warm Period peak is earlier than the Kobashi and Alley peaks. Major volcanic eruptions fit this timeline reasonably well. Rabaul is noted at 540AD. Others are Thera-Santorini in 1600 BC and Tambora in 1815. The HadCRUT 4.4 point shown with a red star is an average of several HADCRUT4 surface temperature grid points in the Greenland area thought to be comparable to the Greenland average temperature.