The anti-science Democrats and left-wing greens absolutely hate the Medieval Warming Period (MWP), due to its invalidation of the modern CO2 global warming-climate change hypothesis - no matter their extraordinarily lame corrupted/bogus attempts to prove otherwise, the objective empirical evidence continues to confirm the MWP was an uniquely extended warm era
(click on image to enlarge, image source)
In another fascinating exposé of climate science flim-flam produced by yet another group of academia climate-quacks, Steve McIntyre has the adjacent chart embedded in his article.
This chart represents a 5,000 year span of temperature variation in the Arctic region (Ellesmere Island) per peer-reviewed research . To add context, we superimposed the atmospheric CO2 levels (mauve curve) from the last 2,000 years.
Several very obvious conclusions can be drawn that gut claims by anti-science alarmists and quacks:
1. Climate change is a science-proven constant.
2. Periods of global warming and global cooling happen frequently
3. The Medieval and Roman periods were warmer than the modern era
4. Temperatures changed regardless of CO2 levels
5. CO2, be it natural or human, is not the globe's "thermostat"
Finally, per the HockeySchtick blog, it is known that the essentially barren Ellesmere Island had temperatures some 2 to 3 degrees higher than current temps, despite the gigantic CO2 emissions of our modern consumer/industrial era.
Additional climate-history and peer-reviewed postings. More historical temperature charts.