Gag order on the EPA

[Odin]

(01-26-2017, 03:51 PM)X_4AD_84 Wrote:

(01-26-2017, 08:05 AM)Odin Wrote:

(01-25-2017, 05:37 PM)X_4AD_84 Wrote:

(01-25-2017, 05:24 PM)Odin Wrote:

(01-25-2017, 04:14 PM)Galen Wrote: As I look back over geological time scales at the carbon dioxide levels and temperature I discover something very interesting.  First is that carbon dioxide levels have been much higher than they are now for much of the last 600 million years. Second the earth's average temperature has varied over that time from 10 to 25 degrees Celsius.

Unless the paleontologists are just making shit up then I am forced to conclude that carbon dioxide levels are not going to turn the earth into Venus because that never happened with much higher levels in the distant past.  This is exactly what I would expect from a system that has been stable for geological time scales.  If there was a positive feedback mechanism where carbon dioxide then it should have been triggered when carbon dioxide levels were greater than 3000 ppm.  Since we are here this clearly did not happen.

Nobody had said that the Earth risks becoming Venus, the absolute worst case scenario is driving CO2 levels high enough to shift the Earth back into a hot-house climate with no ice caps. If you don't see how devastating that would be to human civilization and the biosphere (because it will be happening much faster than it ever happened naturally) there is no point trying to reason with you.

The actual worst case scenario would probably be matching the previous interglacial in terms of sea level stand.

So far that does not appear to be likely. The rate of sea level rise is not currently enough to hit that level. Broad brush, the rise curve is still a decaying exponential which makes sense given how much of the continental ice has already retreated since the most recent glacial advance. What is really surprising is that the apparent amount of heat and work now in the oceans is estimated to be roughly the same as it was this far into the last interglacial. That sort of result seems to point to some mode that might be different than it was during the past interglacial, preserving more of the ice than was the case at a similar point back then. It may actually be an anthropogenic effect, perhaps the Asian Brown Cloud or some such. Now countering that (above and beyond GHGs) is the impact of soot. It may be that soot has more of an impact on sea ice than it does on serious glacial masses. Lots to learn still on this topic.

As far as I know the consensus among climatologists is that if CO2 levels exceed 550ppm there is nothing stopping the climate from flipping over into the hot-house mode due to all the positive feedback loops. It will take several thousand years for all the ice to melt, but melt it all will.

During the last interglacial, most of the continental ice was gone from the Northern Hemisphere, there was much thawing of perma frost, and the Arctic was free of sea ice every summer. There can be some debate about how high CO2 not to mention other GHGs got at the time. Nonetheless, there was no hot house. I don't even know what that term means. I suppose to some adherents that means going into something like the Carboniferous. That would be pretty tough given how much the mixture of major gases has changed, and the fact that the Equatorial Current can't circle the globe now due to the wall of The Americas and the near wall of SE Asia, India and Africa. The next opportunity for that sort of regime is hundreds of millions of years in the future.

I meant ALL the ice, even in Antarctica. The Earth shifts back and forth between two stable states, the hot-house world when the poles are ice-free and the deep oceans are warm and low in oxygen, and the ice-house world, where there is ice at the poles and the deep oceans are cold and oxygenated. Our current ice-house phase began at the end of the Eocene when the Antarctic ice sheet began to form.

The Carboniferous and early Permian was actually an ice-house world like our own, with a massive ice sheet at the south pole, and glacial-interglacial cycles exposing and then inundating the tropical lowland forests that became the great coal beds of Appalachia and Western Europe, the CO2 levels dropped to 300ppm at the end of the Carboniferous.