The State of Paleoclimate Understanding
Posted by Jeff Id on April 9, 2013
In the huge amount of justified complaints made here about what I think of paleo-reconstructions, one detail is probably lost in the chaff.
I really wish I knew what historic temperatures were. You can’t read that much paleoclimate information and not want to know. Steve McIntyre clearly inspired my reading, and unfortunately the inspiration came through a wholly skeptical lens. In time it has turned out that the skeptical perspective of the statistics and data in paleoclimate were 100% justified.
With data so noisy, yet so full of potential revelations, scientists are also justified in their interest. As time has passed, I’ve grown to understand that there isn’t really any known solid way to divine the history of climate. We have enough clues to see past warmth and plenty of clues to show deep past ice ages, yet the trivial level of understanding of past temperature is quite distant from the equivocation-ridden certainty of present day scientific publications.
Ed Cook was no small player in the paleoclimate field. His own words have a ton of meaning for those who have enough understanding of the pervasive nuance in the field:
the results of this study will show that we can probably say a fair bit about <100 year extra-tropical NH temperature variability (at least as far as we believe the proxy estimates), but honestly know fuck-all about what the >100 year variability was like with any certainty (i.e. we know with certainty that we know fuck-all).
This statement is an absolute scientific truth to my understanding. There are multiple sentiments in it which have very solid meaning in interpreting these hockey stick plots. First, and most interesting for those of us who actually want to know the truth, dendros seem to have discovered a way to see short term climate variation a very long time ago. Variations on a scale of <100 years are also important because they give us some partial understanding of climate. Unfortunately, Ed and I disagree as to the certainty of the meaning of even these short term variations.
That known correlation in itself is extremely cool. Skeptics of dendro question the linearity of these fluctuations with respect to temperature, but the short-term fluctuations themselves are highly correlated in local regions. We can say that whatever was happening in climate to those regions, is measurable, and good plant growth years in one location were good plant growth years. Not exactly known temperature “climate”, but growth climate is still a very cool thing.
Ed Cook knows the difference between short and long term variations, and after performing tree ring standardizations as I have, you get an understanding of why the long term signals (trends) in dendro hockeysticks are not likely represented by the data. The math and physics simply don’t allow it. Long term temperature trends derrived from tree rings, are necessarily quite meaningless.
Paleoclimate is noisy, and little is truly known in my opinion. Better data is required, and despite the every-month premature conclusions from the experts, we shouldn’t lose site of the fact that once we discover the right proxy (or proxy combination), the math will not be the issue and finally we will know a true piece of our distant climate history.
Whatever we find out, that day when we finally know, will be an interesting day for me.