tag:blogger.com,1999:blog-1367053740188758246.post3014532873081120852..comments2023-06-21T00:39:34.443-07:00Comments on Dosbat: Something Wicked This Way Comes.Chris Reynoldshttp://www.blogger.com/profile/16843133350978717556noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-1367053740188758246.post-40177538455164874502012-12-15T00:05:45.475-08:002012-12-15T00:05:45.475-08:00There's a good Wikipedia page here:
http://en....There's a good Wikipedia page here:<br />http://en.wikipedia.org/wiki/Azolla_eventChris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-33207282235177466252012-12-14T23:52:28.861-08:002012-12-14T23:52:28.861-08:00Remig,
The anoxia that occurred during the PETM w...Remig,<br /><br />The anoxia that occurred during the PETM was in certain ocean basins and restricted to the deep ocean. Hence the losses of benthic foraminifera.<br /><br />For casual readers:<br />During the PETM the Arctic was almost a closed ocean. http://en.wikipedia.org/wiki/File:Early_Eocene_Arctic_basin.PNG<br />Given that Azolla is a freshwater plant, the closed nature of the ocean allowed freshwater input to create a freshwater cap on which the Azolla could grow, this growth is hypothesised to have reduced atmospheric CO2, the plants consumed CO2, lived and died, and sequestered carbon on the ocean bottom.<br /><br />That's an interesting point that hadn't occurred to me. The Azolla hypothesis suggests that the impacts of the PETM were limited by Azolla. So an event possibly closer to the Great Dying (End Permian) could have occurred without rapid draw down.<br /><br />I'm not persuaded right now. After the PETM CO2 levels were over 3000ppm. I seriously doubt we have enough carbon to hit such levels. So the absolute warming would be less, and ocean stratification (leading to anoxia) would be less - as that process is linked to temperature and buoyancy of water. Although... with colder oceans at depth, perhaps less of an absolute warming would be needed to make a warm cap over the ocean and shut down vertical mixing/ventilation of the oceans. Were that to happen, that alone would lead to an effective increase in CO2 as sequestration in the deeps would cease.<br /><br />I need to think about your point. Thanks.Chris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-89799743006582204142012-12-14T14:06:18.695-08:002012-12-14T14:06:18.695-08:00Actually the PETM may have been somewhat of a dud ...Actually the PETM may have been somewhat of a dud in NOT triggering a far more disastrous event, global ocean anoxia. Anoxia events result eventually in mass eruptions of hydrogen sulfide and are thought to be the cause of major extinctions. CO2 is thought to cause anoxia events when carbonate compensation is overwhelmed. The peculiar arrangements of continents around the Arctic at the time may have allowed the Azolla event to follow the PETM and clear the CO2 before an anoxia event could trigger. Unfortunately, those arrangements no longer hold.remighttps://www.blogger.com/profile/03983426765894995013noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-3287404316147328502012-12-13T12:11:57.824-08:002012-12-13T12:11:57.824-08:00Anonymous,
No need to apologise for spotting mist...Anonymous,<br /><br />No need to apologise for spotting mistakes, and thanks for spotting them.<br /><br />Terry/Tracker,<br /><br />I'll try to post tonight, but am not quite happy with it right now. I've had a post on hold since before I was ill about Arctic temperatures from a certain lake that escaped the glaciations, I can't recall the name right now - you'll see why when I post. I've expanded the post to cover other work.<br /><br />The short answer - during HTM about 1 to 2 degC above 20th century temperatures, we'll soon be past that, in Autumn we already probably are. But there were also Arctic super interglacials that were up to 5 degC warmer than preindustrial in the Arctic. <br /><br />My point is that at such times there was no methane cataclysm, no massive and persistent d13C excursion. What d13C excursions there have been were shortlived, using Sexton's reasoning they were probably from shifts of carbon around the earth, not injections of extraneous carbon, such as from methane hydrate.<br /><br />Oceanic methane hydrate, and land permafrost melt, will have played a role in the super interglacials. But it didn't cause a global cataclysm demanding more meddling in the climate (geo-engineering). <br /><br />I intend to post against geo-engineering in due course. I think it's foolish and dangerous.Chris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-87730335084588612632012-12-13T07:23:33.811-08:002012-12-13T07:23:33.811-08:00Chris
Very nice synopsis - I still have to wade t...Chris<br /><br />Very nice synopsis - I still have to wade through all the links.<br /><br />I wonder if you've taken into account the length of time that the ESAS has been inundated when comparing where we're heading to the HTM. <br />I'm not entirely convinced that the Arctic as a whole during the HTM was much warmer than what we're now experiencing. I know the CAA had warmer periods as did Greenland but my recollection is that when one area was very warm other areas were relatively cooler.<br /><br />If you have any links indicating Arctic wide temps during HTM I'd appreciate it<br /><br />TerryTerryhttps://www.blogger.com/profile/03779255589971268555noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-8111870244646035842012-12-12T14:39:08.311-08:002012-12-12T14:39:08.311-08:00"It didn't happen during the Holocene Opt..."It didn't happen during the Holocene Optimum, some 5000 years ago, nor was there a massive outgassing of methane."<br /><br />It'd like to understand this period a lot better than I do. Can you recommend anything to read about it?<br /><br />TheTrackerhttps://www.blogger.com/profile/10011829472333355911noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-9943340845778780462012-12-12T13:22:04.387-08:002012-12-12T13:22:04.387-08:00I completely agree with the Tracker on the quality...I completely agree with the Tracker on the quality of this post, thank you very much, this will take me a long time to read and digest fully. <br /><br />two extremely minor editorial thingies to point out, right in the beginning, <br /><br />"... analogue for the current Anthropogenic Global Warming (AGW) is the Paleocene Eocene Thermal Maximum (AGW)..." I guess you want the abbreviation PETM in there; <br /><br />Fifth paragraph, " ... because of the high price making previously uneconomic sources unfeasible. ..." That should probably be "feasible". <br /><br />dont get me wrong, I know very well how this happens, I never noted all the typos in my last submission until after it was finally out, could have eaten my hat. This does in no way mean anything bad, only I first have to work through all the pdf´s behind it (for that another big thank you to you!!) Good to see you posting.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-70213844641824392982012-12-10T22:58:25.353-08:002012-12-10T22:58:25.353-08:00I don't see any of that as being a problem wit...I don't see any of that as being a problem with my numbers, it's more a problem with the politics. Yet in the public consciousness I still see dropping atmospheric levels to 350ppm or sticking to no more than 2degC as goals. What I'm arguing is it is too late to avoid dangerous climate change.<br /><br />"An "ice-free" Arctic means total collapse of the Earth systems."<br /><br />It didn't happen during the Holocene Optimum, some 5000 years ago, nor was there a massive outgassing of methane. The situation is serious, it doesn't need overstating.Chris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-17245871060354846272012-12-10T22:29:32.720-08:002012-12-10T22:29:32.720-08:00"The idea of stopping at 350ppm, or 2 degrees..."The idea of stopping at 350ppm, or 2 degrees, of staying in safe levels of AGW will be totally out of our hands within a matter of decades."<br /><br />Something very wrong with your numbers. I'll quote:<br /><br />The 2ºC "target" is a politically (not scientifically) set target from the European Union (EU) that goes back to the mid 1990s.<br /><br />Since then, although the weight of scientific evidence has increasingly shown that a globally averaged 2ºC temperature increase will be disastrous for humanity and much of life on Earth, the figure has stuck.<br /><br />A safe limit was established at +1ºC even before 1990 (Villach Conference, 1987). The Avoiding Dangerous Climate Change conference in Exeter (2005) arrived at a limit of 1ºC (although acknowledging that dangerous climate change for developing countries is below 1ºC).<br /><br />Many papers have been published over the years saying that 2ºC is too dangerous, and the precautionary weight of evidence is 1ºC to 1.5ºC. (These figures are now superseded by actual changes in the Arctic.)<br /><br />The EU now acknowledges that a 2ºC global warming is not safe.<br /><br />"[...] overall global annual mean surface temperature increase should not exceed 2°C above pre-industrial levels in order to limit high risks, including irreversible impacts of climate change; RECOGNISES that 2°C would already imply significant impacts on ecosystems and water resources. [...]" (2610th Council Meeting, Luxembourg, 14 October 2004)<br /><br />At a 2005 meeting in Buenos Aires, the European Union addressed the question of what is dangerous climate change under the United Nations Framework Convention on Climate Change (UNFCCC). They came to the conclusion that dangerous global warming lies between 1.0ºC to 1.5ºC, thereby giving a safe limit of 1ºC.<br /><br />The United Nations Environment Program (UNEP) has published a danger level of 1.5ºC based on 2007 IPCC data.<br /><br />But these new figures have not been noticed, and the 2 degree target remains virtually the only limit cited in mass media and many scientific media.<br /><br />The target that has been talked about in international negotiations for two degrees of warming is actually a prescription for long-term disaster. -- James Hansen<br /><br />Two degrees of warming will lead to an ice-free Arctic and sea-level rise in the tens of meters, Hansen told LiveScience.<br /><br />An "ice-free" Arctic means total collapse of the Earth systems. Yet 2ºC is still the "target" for negotiations. Clearly, this makes no sense at all, but was simply chosen as being politically expedient.<br /><br />And this:<br /><br />Between 1990 and 2011, global emissions of carbon dioxide have increased by 54 percent, and this is expected to jump to 58 percent based on projections for 2012. Humans will have released some 35.6 gigatons of greenhouse gases into the atmosphere in this year alone, with an average increase of 3.1 percent per year. That number was slightly lower in 2012, measuring 2.6 percent, though that was mainly due to the economic crisis, the paper says.<br /><br />According to the quotations above, there is zero possibility (or safety) in 2C. And 35.6 gigatons of greenhouse gases were released this year alone.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-13807648750739571642012-12-10T08:59:45.756-08:002012-12-10T08:59:45.756-08:00Thanks Tracker.
Sorry to give such a negative op...Thanks Tracker. <br /><br />Sorry to give such a negative opinion, but as you well know the situation tends to that.Chris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-41214340054137774662012-12-09T13:23:06.884-08:002012-12-09T13:23:06.884-08:00This is one of the best "where we are" p...This is one of the best "where we are" posts I've ever seen. So many great quotes. I'll probably be gushing about it over my way before long.<br /><br />Very, very well done.TheTrackerhttps://www.blogger.com/profile/10011829472333355911noreply@blogger.com