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Jim: You are on extent & Jaxa stopped delivering new data...
Stephen Hawking is a shining bright light in science. Maybe the most intelligent man these days. But even he can fail to do his homework - to collect enough data. So... imagine a world, where every bit of fossile carbon indeed was burned. And the oceans warmed up, released the sea-bed methane. Sounds decently bad. But a world like that, a carbon dioxide level of 1000 - 2000 ppm and an additional methane burst happened. And the thrilling thing is: It happened a time, when the world was not that different from our modern one. The sun had already our present power, the continents were lying at almost the right places, just India did not yet collide with Asia, and the Mediterranean sea was bigger. In the early Eocene this lead to the PETM (Paleocene Eeozene Temperature Maximum. Tropical polar sea coast with saltwater crocodiles (fossils...). There were no glaciers anywere in the world, even not in the densly forested antarctic mountains. There was an anoxic deep sea, and a subsequent deep sea life extinction event. But the climate then was stable. So it would be now. Indeed, this carbon boost was rapidely washed out of the athmosphere. A hot greenhus world means less radiation from the surface into space and more convection. Also the few changes to today made the eocene earth moist. The world was wet (and so it would be again). A wet and hot world is washing whole mountains into the sea in really short time. Many minerals are abundant which bind CO2 during this withering and sedimentation processes. During the Eocene the active volcanism of 100 Ma before was subsiding significantly. So the constant source of CO2. And in contrary the CO2 - binding withering thrieved. Addidionally significant amount of biological carbon was bound in deep sea sediments (hello crude oil). And this is now minus 250 years, continents drier (geology changes), CO2 sequestered by withering, a cold ice age climate in a short warmer intermediate phase. Today we are changing it. No volcanism, but humans. We are doing it way faster, what took dozens of Ma in former times, we are doing it in a few hundrets of years. We may walk directly into a modern PETM. Oh and this would change a lot 120m + sea level. completely tropical earth, no cold-loving ecosystem survives. But then the carbon is over, the withering dominates again. It may take a few Ma - but this geolocigal cycle is on cold now (and this lasts 100 - 200 Ma, when you look back to older events). Our CO2 will form sediments, and the earth will cool down to at least near ice age conditions again. What do you need for Venus? More solar power. A lot more. Right now - if CO2 ever fell below 100 ppm due to withering we would see a snowball earth again. We are way closer to a very cold earth than to a runaway greenhouse climate. Right now, the greenhause effect of water amplifies any change of conditions, but not to a runaway risk. With (a lot) more solar power this may change once. Despite clouds, water vapor is a strong greenhous gas, with more solar input an atmosphere of water vapor would be stable - and than this heat would crack the carbonates and add CO2. Likely we will not go completely venus in far, far future, we do not have enough carbonates to support a 90 bar atmosphere, it is (and was at the first days of earth) more a "Venus light" with some 20 bars or so (if I remember a paper right I read).
Toggle Commented Jun 2, 2016 on ASI 2016 update 1: both sides at Arctic Sea Ice
...that was also my first thinking reading the text (@ Gerrit). No way to increase stratospheric temperature by RISING air, and particularly not if it ogirin is from the cooler tropopause. But those mountains, deserts may play a role. higher mountains to the south, cold wintery deserts to the north, higher to the north the icy arctic. Behind the mountains, the pretty warm subtropical and tropical regions are shielded from sibirian cold air. But as this cold air moves south on other pathways, particularly in higher elevations (see the 500hPa pressure height) the pressure drops over the complete northern part of the northern hemisphere. What if you get once a disturbance riding into the Himalayan region? Suddently the polar front, the jet stream will bend, and the way is free for higher tropopause air masses to stream north, filling up the low pressure aloft. As this air mass is pushed now over the mountains it drops, warms (also in the Troposphere), exactly what happened several times this year. Than a warm layer is coating the very cold bottom arctic air mass, stabilizing the usual wind systems(increasing pressure, pushing out cold air on the bottom). But what happens in stratosphere, with that kind of massive falling winds in the troposphere, causing huge,and some of them standing, gravity waves? In some places that will cause the air to drop for thousands of merters, generating high tenperatures. Another effect is simply, that warmer, southern stratospheric air, pushed to the north by stratospheric lows and heights, will genrerate a HUGE temperature deviation, when replacing, the cold statospheric air in arctic winter... The only contra is the coriolis force, usually southern, warm stratospheric air cannot reach the pole. But with disturbances breaking those stratospheric jets, all of a sudden those muves are possible. And than air with 0°C moves into egions where normally you find -60°C... That is a huge deviation, and that will have influence downstream in the troposphere...
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Apr 25, 2013