Further, the Medieval warm period was certainly not warmer than it is today. If you focus on limited data sets you could naively conclude that global temperatures were warmer during this period. This type of conclusion does not survive scientific scrutiny but seems to have been well established in denialist literature.

Mann(2009) Used more than 1000 tree-ring, ice core, coral, sediment and other assorted proxy records spanning both hemispheres to construct a global map of temperature change over the past 1500 years. If you were ever curious enough to look at the reconstructed surface temperature maps of the two periods you would see that the medieval warm period was not a global phenomenon like it is today. Global temperatures are higher today than any time in the last 1500 years.

gizmo_2655 wrote on Dec 16^th, 2011 at 12:09pm:


Here Bob Carter claims that rate of temperature change per century over the last 5000 year lies somewhere between +/- 2.5C per century. I don't
believe he provides an average rate of temperature change or a standard deviation. The average rate of
change would be something like +0.1C per century, which has been the average rate of warming since the end of the last ice age. Our current rate of warming is 1.5C per century and rising. Which is well above average but well within Bob's "geological envelope of
change."

Bob's argument is that we have experienced this rate of change before and it is well within the natural envelope of change. If Bob is using Greenland ice cores as his proxy for global temperature, his envelope of change will be stretched, as regional changes can be more dramatic than global ones. He also ignores the huge body of scientific work that has been done identifying the drivers that have caused the increases in temperature that he identifies as being similar to our own. Currently the only driver that can satisfactorily explain our current period of global warming is the increase in atmospheric CO2. It is why 97% of climate scientists accept AGW.

I'm still interested in where your initial rate of change measure comes from. Bob may have quoted another study somewhere else? If it is a measure Bob has created, I'd be very worried of it's accuracy considering the flaws in his treatment of other data and the almost certain likelihood that it would not have been peer reviewed.

The mid Holocene period, roughly 6,000 years ago, was generally warmer than today, but only in summer and only in the northern hemisphere. This astronomical climate forcing mechanism cannot be responsible for the warming over the last 100 years.

BatteriesNotIncluded wrote on Dec 18^th, 2011 at 3:56pm:


It's called a thermometer.

BatteriesNotIncluded wrote on Dec 19^th, 2011 at 8:53pm:


And get ready for a BIIIIG glass of 'coolaid'...

gizmo_2655 wrote on Dec 18^th, 2011 at 11:32pm:


Did Huang and Pollack conclude that the MWP was worldwide. Averaging out the other proxies suggests an entirely different conclusion.