tag:blogger.com,1999:blog-2313427464944392482.post6064590628629557663..comments2024-03-25T05:30:23.847+11:00Comments on HotWhopper: Sea level rise commitment could already be very highSouhttp://www.blogger.com/profile/08818999735123752034noreply@blogger.comBlogger15125tag:blogger.com,1999:blog-2313427464944392482.post-682947379574921802017-01-26T00:26:35.978+11:002017-01-26T00:26:35.978+11:00Yes, I think BBD has it pretty right. The bipolar ...Yes, I think BBD has it pretty right. The bipolar seesaw (climate, not psychology, though that too) has been researched quite a bit.<br /><br />It's a hypothesis that seeks to explain why temperature shifts in the northern and southern hemispheres can get out of phase. <br /><br />Broecker, Wallace S. "Paleocean circulation during the last deglaciation: a bipolar seesaw?." Paleoceanography 13, no. 2 (1998): 119-121. (pdf <a href="http://onlinelibrary.wiley.com/doi/10.1029/97PA03707/pdf" rel="nofollow">here</a>)<br /><br />Severinghaus, Jeffrey P. "Climate change: Southern see-saw seen." Nature 457, no. 7233 (2009): 1093-1094. (pdf <a href="https://www.researchgate.net/profile/Jeff_Severinghaus/publication/237639534_Southern_see-saw_seen/links/545660740cf26d5090a95ece.pdf" rel="nofollow">here</a>)<br /><br />Barker, Stephen, and Paula Diz. "Timing of the descent into the last Ice Age determined by the bipolar seesaw." Paleoceanography 29, no. 6 (2014): 489-507. (<a href="http://onlinelibrary.wiley.com/doi/10.1002/2014PA002623/full" rel="nofollow">full text here</a>)<br /><br />I believe that's related to why scientists are concerned that parts of the northern hemisphere might cool with a slowing of the AMOC, as global warming kicks in.Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-4236054363433466782017-01-26T00:09:43.534+11:002017-01-26T00:09:43.534+11:00Thank you BBD. That makes sense. And it's a re...Thank you BBD. That makes sense. And it's a relief to tussle with understanding part of a climate system instead of politics.Fishpawnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-26167113982192790822017-01-25T00:01:33.557+11:002017-01-25T00:01:33.557+11:00Readers may be interested:
https://www.theguardia...Readers may be interested:<br /><br /><a href="https://www.theguardian.com/environment/2017/jan/20/top-climate-experts-give-their-advice-to-donald-trump" rel="nofollow">https://www.theguardian.com/environment/2017/jan/20/top-climate-experts-give-their-advice-to-donald-trump</a>Bernard J.https://www.blogger.com/profile/16299073166371273808noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-14857851784893185852017-01-24T21:43:35.783+11:002017-01-24T21:43:35.783+11:001. What does "thermal memory" mean when ...<i>1. What does "thermal memory" mean when you're talking about oceans?</i><br /><br />I *think* just that once a large body of water is warmed up it takes a very long time to cool down again, even with interhemispheric circulation taken into account. This has a knock-on effect in suppressing Antarctic sea ice which (a) reduces albedo and (b) allows ventilation of the Southern Ocean crucial to outgassing CO2 into the atmosphere. Both are of course positive feedbacks to the initial NH orbital (Milankovitch) forcing. So you get initial NH warming, then cooling as AMOC turned off followed by SH warming then *symmetrical* temperature increase as GHG feedbacks globalise the warming. <br /><br />So something like this:<br /><br />- NH summer insolation increases especially at high latitudes<br /><br />- Mid/high latitude NH temperature increase causes sufficient melt from NH ice sheets for freshwater flux to inhibit NADW formation and halt AMOC [THC fact sheet: http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html see fig. 2]<br /><br />- NH now *cools* as equatorial >>> poleward heat transport stops<br /><br />- With the NH ‘heat sink’ turned off, the SH *warms*, as it must<br /><br />- Deep water warming in SH ocean causes release of carbon to atmosphere. This positive feedback globalises and amplifies the warming<br /><br />- NH melt resumes, fully engaging strongly positive ice albedo feedback<br /><br />- Deglaciation accelerates until largely complete; MIS5e interglacial begins<br /><br />BBDhttps://www.blogger.com/profile/10687930416706386215noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-63797038470764314852017-01-24T13:16:32.677+11:002017-01-24T13:16:32.677+11:00If someone has a bit of time, HEEELP!!
"......If someone has a bit of time, HEEELP!!<br /><br />"... the thermal memory of the seesaw response in the SH extratropics, likely associated with sea-ice retreat (27, 28)..."<br /><br />1. What does "thermal memory" mean when you're talking about oceans?<br /><br />2. I don't understand "seesaw response in the SH extratropics, likely associated with sea-ice retreat (27, 28)". <br />(a) On first reading I visualised heat sort of sloshing from pole to pole until it reached a stable state where the poles were about equally warmer than... than they were before the warming started?? But that would be a global seesaw, not a SH one - wouldn't it? - and would the heat still slosh if the AMOC has broken down?<br /><br />(b) Is, or was, there a hot/cool seesaw between the tropics and the Antarctic - mebbe because there's more ocean in the SH? What's the association between that and sea-ice (SH? NH? Both?) retreat and is it different from what's happening now? <br /><br />3. My present understanding, which I think fits with Steve Bloom's comments above, is that the take-home from this paper not so much about how warming is working through the oceans now as it about is about refining how the models handle warming. Fair enough?<br /><br />Thanks.fishpawnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-82929903965672861112017-01-23T13:22:42.319+11:002017-01-23T13:22:42.319+11:00TBC, this is the excitement William demands.TBC, this is the excitement William demands.Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-39109462381294245072017-01-23T13:20:06.468+11:002017-01-23T13:20:06.468+11:00That was the first point. The second one supports ...That was the first point. The second one supports Hoffman's view as stated to the Graun (as quoted by BBD above).<br /><br />Maybe the best way to put is that the same warming commitment can result in quite different rates of ice sheet melt/sea level rise if the pattern of the forcing differs. Delivery of warm water to the base of the ice sheets is literally the worst thing that can happen in that regard. Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-27578461501138777402017-01-23T12:10:35.740+11:002017-01-23T12:10:35.740+11:00That's a point. This paper was about that glob...That's a point. This paper was about that global temperatures back in the last interglacial may only have been what they are now. We are heading for hotter. A lot hotter if some people get their way.Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-51069483508893680572017-01-23T11:28:38.950+11:002017-01-23T11:28:38.950+11:00Consensus sea level rise estimate for 400-ppm cond...Consensus sea level rise estimate for 400-ppm conditions last seen in the mid-Piacenzian (~3 mya) is 24 meters. There is no reason o expect much different in our future, especially as we will be lucky to cap things off at 560 ppm (close to enough for complete ice sheet melt).<br /><br />For near-future non-equilibrium conditions, even the LIG is a poor guide. Forcing today is not forcing then, and most crucially it's not at all clear that the relatively warm water now being pushed onto the bases of the ice sheets had much of an analog then.<br /><br />Speaking of which, if people want an example of a key paper that was largely ignored (TBF in part because there were a lot of important ice sheet papers published last fall), <a href="https://earth.stanford.edu/news/studies-offer-new-glimpse-melting-under-antarctic-glaciers" rel="nofollow">here ya go</a>. Lead author pull-quote:<br /><br />"THIS IS A SHOCKING AMOUNT OF MELT FOR AN ICE SHELF TO EXPERIENCE."<br /><br />That was said in reference to:<br /><br />"Previous studies using other techniques estimated the average melting rates at the bottom of Dotson and Crosson ice shelves to be about 40 feet per year (12 meters per year). Using their direct radar measurements, the team found stunning rates of ice loss from the glaciers' undersides on the ocean sides of their grounding lines. The fastest-melting glacier, Smith, lost between 984 and 1,607 feet (300 and 490 meters) in thickness from 2002 to 2009 near its grounding line, or up to 230 feet per year (70 meters per year)."Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-27091617626361102212017-01-23T07:56:22.665+11:002017-01-23T07:56:22.665+11:00I live at 93m so we just have to prepare for the r...I live at 93m so we just have to prepare for the refugees. On a slightly more frivolous note, I have long suspected that ice sheets are melting faster than a lot of predictions suggested, based on almost no evidence BTW.jrkrideauhttps://www.blogger.com/profile/04869979887929067657noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-11413958066643896682017-01-23T06:38:21.566+11:002017-01-23T06:38:21.566+11:00Maybe not exciting for you William.
You don't...Maybe not exciting for you William.<br /><br />You don't have to wait that long for the impacts. According to this 2014 article from John Church and Xuebin Zhang, in the Asia Pacific, regional sea-level rise will be generally noticeable before 2030 - so in about 13 years.<br /><br />https://theconversation.com/15-years-from-now-our-impact-on-regional-sea-level-will-be-clear-31821<br /><br />And it doesn't require SLR to be in the metres for it to cause problems. The impacts will probably start with storm surges coinciding with high tide.<br /><br />http://www.businessinsider.com.au/this-photo-of-a-swimming-pool-swept-away-from-a-multi-million-dollar-home-shows-the-power-of-sydneys-storms-2016-6<br /><br />Then all storm surges, then all high tides, ...<br /><br />But not all people living near the ocean have waterfront pools on Sydney's beaches. A lot of industrial land and cheap housing is built on coastal swamps and will need to remediated or moved. It only needs to be high enough to start seeping into the landfill and you only need one flooding event to do severe damage. Every lived in a house with wet floorboards? <br /><br />And a lot of agricultural produce in Asia comes from the large deltas which already suffering from encroaching salt water.<br />MikeHnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-7661421137617990422017-01-23T05:56:02.455+11:002017-01-23T05:56:02.455+11:00that isn't exciting.
From the Graun:
A cruci...<i>that isn't exciting.</i><br /><br />From the Graun:<br /><br /><i>A crucial unknown is the rate at which the ice sheets will melt in the future, and the latest findings do not have a direct bearing on this question, according to Jeremy Hoffman, a climate scientist at the Science Museum of Virginia and the paper’s lead author.<br /><br />During the LIG, warming occurred over more than 10,000 years, meaning that changes to the global ice sheets could happen in parallel. The current warming trend has occurred over decades, and it is not clear how far behind the melting of ice will lag....</i>BBDhttps://www.blogger.com/profile/10687930416706386215noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-53155042335204633622017-01-23T05:40:01.463+11:002017-01-23T05:40:01.463+11:00You're right, William, I only briefly mentione...You're right, William, I only briefly mentioned timescales in the quote:<br /><br /><i>He said that heating up the “depths of our vast oceans” to the point where sea levels reached that point would take thousands of years</i><br /><br />However the seas could rise by 1 to even possibly 2 metres (3 to 6 feet or so) over coming decades as I understand it, which would be quite exciting for those of us still around before the turn of this century. (Not me, but my great nieces and maybe even my nieces will see this).Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-47640944025733574222017-01-23T05:34:07.090+11:002017-01-23T05:34:07.090+11:00The timescales are important, and you're not r...The timescales are important, and you're not really addressing that. 6-9 m of SLR over 4kyr is 0.15 - 0.225 m / century and that isn't exciting.William M. Connolleyhttps://www.blogger.com/profile/05836299130680534926noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-85860154606454226262017-01-23T05:08:39.215+11:002017-01-23T05:08:39.215+11:00Regarding the quote, "Of course, in very basi...Regarding the quote, "Of course, in very basic terms, that suggests today’s sea surface temperatures are still within the range of natural variability, contradicting climate model-based nonsense about current values, while sea levels still have a ways to go to catch up to the past."<br /><br />I would like to add that, while natural in cause, the changes during glacial and interglacial periods are not simply natural variability, they're externally forced, as were the MCA and LIA. I too often see skeptics talking about these things as being natural variability when that's not exactly what it means.<br /><br />cabcAnonymousnoreply@blogger.com