2011-06-13 11:26:30Literature on past climate change trends
John Cook

john@skepticalscience...
121.222.9.229

Got this email:

I need your help with some information. I'm sure it's out there but it seems buried in all the other data.
The idea of human induced climate change is predicated on our influence on the environment exceeding natural variations in the climate. Given the natural climatic variations over history, how does the current variations in environmental changes compare to the historical norms. In other words, is the variability we are witnessing today happening faster than the historical variations (happening over decades rather than hundreds or even thousands of years) and what is the evidence supporting this.
I recognize the undo influence of mega volcanic eruptions and meteor strikes but see those as abberations.

I would answer that the idea of human induced CCC is not predicated on unprecedented warming trends but all the lines of evidence of increased greenhouse warming. But could anyone point me in the direction of papers that quantify past climate change trends and how they compare to the current 0.16C per decade?

2011-06-13 12:24:19
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.37

Offhand, this is the only one I can think of, but it's for CO2:

http://www.sciencedaily.com/releases/2011/06/110605132433.htm

2011-06-13 12:49:35
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.10.161

Almost have the PETM post ready. Probably finish it tonight.

I did run across a paper that put the current warming into context over the Pleistocene, but bugger if I can find it (thought I saved a copy). Anyway there's this paper covering the Amazon: 48,000 Years of Climate and Forest Change in a Biodiversity Hot Spot - Bush 2004  - the rate of warming in the last 48,000 years is about 1°C per millenium, in that region. The is no evidence of more abrupt warming in the paleo-data. The average rate of warming in the Amazon, since the 1970's. has been .26°C per decade! . I realize the tropical forests are warming faster than the global average though.

I reckon you have taken the best approach anyway. 

2011-06-13 12:55:51
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.10.161

Oh, and there's this one too: Millennial-scale temperature variations in North America during the Holocene - Viau 2006

"A mean continental July temperature reconstruction based on pollen records from across North America quantifies temperature variations of several timescales for the past 14,000 cal yr BP. In North America, temperatures increased nearly 4C during the late glacial, reaching maximum values between 6000 and 3000 cal yr BP, after which mean July temperatures decreased. Superimposed on this orbital-scale trend are millennial-scale temperature variations that appear coherent in structure and frequency with highresolution ice, marine and other terrestrial paleoclimate records of the Holocene. During the Holocene, climate in North America appears to have varied periodically every 1100 years rather than the 1500 year cycle found during the last glacial period. Coherence at frequencies between 900 and 1100 years between land, ice, and ocean records suggests a common forcing associated with widespread surface impacts during the Holocene. These results provide important insight to the global warming debate, as the observed twentieth century temperature increase appears unprecedented compared to our mean North American temperature reconstruction of the past 14,000 years."

2011-06-13 14:53:08
Ari Jokimäki

arijmaki@yahoo...
192.100.112.211

Papers on natural variability or perhaps papers on GHG role in historical climate changes? Other possibly relevant lists are found here under "paleoclimate".

2011-06-13 16:05:05Thanks, guys, just sent this response
John Cook

john@skepticalscience...
121.222.9.229

I could wait for more responses but his email is burning a hole in my in-box and I wanted to clear it out. So I borrowed from your responses and sent this:

Well, first of all, the idea of human induced climate change is not dependent on current warming being unprecedented. It's based on the many lines of evidence indicating an increased greenhouse effect due to rising CO2. In other words, our CO2 emissions are causing much heat to be trapped - this extra heat is driving climate change. There are a multitude of independent observations that demonstrate this - http://sks.to/agw

The forcing (eg – change in planet’s energy balance) due to rising CO2 levels is very significant – quite unusual in our Earth’s history. Hence the warming is unusual. The paper Millennial-scale temperature variations in North America during the Holocene - Viau 2006 finds the observed twentieth century temperature increase in the Northern Hemisphere appears unprecedented compared to temperature reconstruction over the past 14,000 years.

A paper covering the Amazon, 48,000 Years of Climate and Forest Change in a Biodiversity Hot Spot - Bush 2004, finds the rate of warming in the last 48,000 years is about 1°C per millenium, in that region. The average rate of warming in the Amazon, since the 1970's. has been .26°C per decade!

If you’d like to dig deeper, I’d suggest the excellent AGW Observer website which has pages on Papers on natural variability or perhaps papers on GHG role in historical climate changes? Other possibly relevant lists are found here under "paleoclimate".

2011-06-14 04:35:52comment
Robert Way

robert_way19@hotmail...
134.153.162.53

Rob,

I know Viau really well actually. Have the data for it and such. They don't do trends in the paper but there has been work done. There will be a new reconstruction from them soon using more pollen data and comparing the LIA and MWP to present. Will let you know when I get word of it.



Actually John,
On this topic I know the way to do this... It is really interesting and I could privately tell you results and methods etc... but because it hasn't even been submitted yet I am hesistant to post it on the forum. That being said it is the subject of a paper that a colleague is working on and hopefully it will be submitted soon for publication. This study would be very helpful for our purposes.