10 degrees warmer in the Jurassic?

 

 

http://www.scotese.com/climate.htm

The vostok ice core data only covers the last 500 thousand years, but what about the last 500 million years?  This site has a little graph that shows Earth was 10 degrees C warmer than it is now during most of the Triassic, Jurassic, and Cretaceous periods.  It's based on a model of plate tectonics and assumptions about the conditions under which certain kinds of rocks form.   It assumes Laterite,  Bauxite, Glendonite, and Kaolinite form in warm conditions while Tillite, Dropstone, and Glendonite form in cool conditions.  So it can sort of map out the latitudes at which tropical regions existed in different time periods and extrapolate the global mean temperature from that.   According to this website there have been several periods of millions of years when there was no polar ice at all, based on analysis of sedimentary rocks.

Can any of you debunk that stuff?  If it's true then global warming doesn't seem that bad.  New Orleans and Miami are still screwed eventually, but "runaway global warming" is far off.   If it's true there appears to be a very strong negative feedback that prevents the global mean temperatrue rising above 22C.   I've been trying to think of what it could be, and came up with three possibilites:

 1. Higher temperatures make rocks erode and dissolve faster.  Greenhouse gasses could be sequestered by being combined with components of those rocks.

2. Change in meteorological patterns increases the albedo of tropical regions.

3. Ozone decreases due to stratospheric cooling, allowing more transmittance around the peak of the 310K black body radiation curve.

 

 

The wikipedia article on the author doesn't have much:  http://en.wikipedia.org/wiki/Christopher_Scotese

 

Also, I found a graph of carbon dioxide over millions of years:

http://www.globalwarmingart.com/images/7/76/Phanerozoic_Carbon_Dioxide.png

 According to that, CO2 levels were around 2000ppm during that period, over 5 times their present level of 385ppm.    Do any of you find evidence to the contrary?

MarineGunrock says...

Hear hear. Global warming is bullshit. Climate change, on the other hand, may very well be real. Sure, all that shit we're pumping into the air can't be good, but it's not the cause.

I wouldn't own a pickup just because gas is $4 a gallon.

swampgirl says...

I know.. it stays parked in the garage most of the time. When gas peaked over 4 bucks here, it took about 90 bucks to fill it up.

It's a really pretty Titan. Now we take turns over my little econo Versa that you made fun of once

Last year a dealer was begging us to trade it in when I was shopping for my little car.... now I doubt he'd want it. No one is buying them now days.

jwray says...

Even if all this is true it doesn't acquit CO2 emissions from possibly hastening the return to the next 22C plateau (during which there would be no polar ice caps). Residents of low-lying coastal areas need to move inland before that happens but it may be hundreds or thousands of years.

blankfist says...

I'm curious why the chart shows the temperature being warmer at the K-T Boundary. The whole reason the Earth experienced a rise in mammals during the Tertiary period is because of the extremely cold weather.

According to the reading I've done, the dinosaurs died because things got very, very cold at the end of the Cretaceous Period when a meteorite hit the Earth. Ash and debris was sent up into the atmosphere, blocking the sun, causing these extremely cold temperatures. Dinosaurs were ectotherms, so they warmed their bodies using heat from outside of them, most commonly the sun. Mammals are Endothermic, obviously, so they can raise their metabolic rate to generate heat internally without outside sources of heat. Thus, the rise of the mammals.

So, why would the chart show the temperature being warm? Very odd.

jwray says...

The sudden coldness caused by atmospheric debris from an astroid impact would only last a few decades. That's barely a blip on the radar in the chart's time scale, but enough to cause many extinctions. Each vertical pixel in that chart is over half a million years. There is no way particulate debris from an astroid could stay in the atmosphere that long.

Doc_M says...

It's a shame, but Al Gore had completely ruined the discussion by releasing that completely bullshit movie. And I don't think you'll find a scientist on the planet that stands behind that piece of garbage and if they do, they should have their tenure revoked.

blankfist says...

Good point, jwray. Not sure why that didn't occur to me. Still, doesn't it seem as if that blackout of the sun (for however long it lasted) would've had a significant impact on the climate? Maybe not. I'm not a scientist, so I would be speaking from ignorance.

swampgirl says...

>> ^jwray:
Even if all this is true it doesn't acquit CO2 emissions from possibly hastening the return to the next 22C plateau (during which there would be no polar ice caps). Residents of low-lying coastal areas need to move inland before that happens but it may be hundreds or thousands of years.



So I shouldn't go for that downtown Charleston property I've always dreamed about retiring in eh?

Doc_M says...

Gwiz donsn't like me

My harshly worded comment was only meant to highlight the fact that not only does politician, Al Gore not know what he's talking about but that it is in his interest that Global Warming be a catastrophic and deadly problem and that he has devastated the discussion of the topic by publishing a popular movie that is not supported by science. He was not honest and he published downright lies in that movie. It was counterproductive for the environmental/climate-change movement. He did more damage than he did help.

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