Boy, the timing is almost perfect.
On Saturday, the U.N. Intergovernental Panel on Climate Change told us that the world is going to end.
Opening with a sweeping statement directed at climate change skeptics, the summary declares that climate systems have already begun to change.
Unless action is taken, human activity could lead to "abrupt and irreversible changes" that would make the planet unrecognizable.
Just a couple days earlier, this report was released to the public. This is the summary with emphasis added:
Historical data provide a baseline for judging how anomalous recent temperature changes are and for assessing the degree to which organisms are likely to be adversely affected by current or future warming. Climate histories are commonly reconstructed from a variety of sources, including ice cores, tree rings, and sediment. Tree-ring data, being the most abundant for recent centuries, tend to dominate reconstructions. There are reasons to believe that tree ring data may not properly capture long-term climate changes. In this study, eighteen 2000-year-long series were obtained that were not based on tree ring data. Data in each series were smoothed with a 30-year running mean. All data were then converted to anomalies by subtracting the mean of each series from that series. The overall mean series was then computed by simple averaging. The mean time series shows quite coherent structure. The mean series shows the Medieval Warm Period (MWP) and Little Ice Age (LIA) quite clearly, with the MWP being approximately 0.3°C warmer than 20th century values at these eighteen sites.
The guys over at Climate Audit have been looking into tree ring data (you can read the discussion on this report here) recently and it's certainly looking possible that tree rings are not accurate or useful when it comes to doing climate studies. Rain maybe, but temperatures, not so much.
So, remember, the Earth's warmer than ever because of all our cars -- except that the Medieval Warm Period was warmer.
I blame Medieval cows.