gizmo_2655 wrote on Dec 16
th, 2011 at 12:09pm:
MOTR wrote on Dec 16
th, 2011 at 11:54am:
You are missing my point, gizmo. I am interested in checking a statement you quoted as fact.
...but it doesn't really change the fact that the rate of change is still well within the normal range that's been found in geological and ice core samplings......it's usually between 0.5C and 1.5C per century.....(+/- 0.2C)
I asked you where this was established and you referred me to Carter and Plimer. It obviously didnt come from Plimer and the only paper from Carter that relates to climate change, does not investigate ice core samples.
It came from a talk Bob Carter made several years ago....It's on video somewhere on the net.....I might have a link to it, but I'm not sure...
Ahh..I found it...
http://www.youtube.com/watch?v=uh20cnLwCiw&feature=player_embedded#!Look at about 11 minutes in...
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.
He chooses to disconnect the facts that it is warmer than it has ever been in the Holocene period (our current interglacial period) and
the rate of change is statistically high. 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.
But it isn't warmer now than it's ever been in the Holocene...
Even within 'recent' history (the last 2000 years) there have been times when it was warmer than now...
And there've been at least 4 or 5 other periods when the temperature was above the current temperatures in the last 10,000 years...
Should I mention the Roman Warm Period, and the Medieval Warm Period (when the Vikings grew crops in Greenland, which was ice free???)