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Comments 30951 to 31000:
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scaddenp at 05:30 AM on 14 March 20152015 SkS Weekly News Roundup #11A
Bill - on time scales of one to two hundred years, isostacy doesnt figure much in the calculation.
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PluviAL at 04:56 AM on 14 March 2015So what did-in the dinosaurs? A murder mystery…
One of the funnest, most informative, article I have read here; moving first graphic;).
Such a broad perspective brings up two questions 1) Is there a periodicity to asteroid "storms"? It'd be kind of like we have shooting star storms, but for different causes. 2) Does climate affect volcanism and seismicity?
The argument here is that volcanism affects climate, but the other seems just as likely to me through GIA, it just conjecture on my part, but the science seems to be moving in that direction.
Thus we could have feedback mechanisms between, cosmic periods, volcanism, climate change, back to volcanism, then climate change again. I call this idea, complex medium waves (CMW), because the period may be affected by chemical changes in the lithosphere, thus magma chemistry and flow characteristics. This may take tens of thousands of years, so it may fit well in this argument.
It is just conjecture on my part because I have no education, and little study along those lines, but I am very curious to know more. This story is very helpful, especially with the rich sources. Nice work.
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It's the sun
Dan Pangburn - "...further discussion is useless." I'm afraid I would have to agree.
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Dan Pangburn at 03:53 AM on 14 March 2015It's the sun
KR - To see the effect that TSI has on temperature requires the time-integral of TSI. Without even that trivial science skill, further discussion is useless.
Moderator Response:[PS] By all means feel free to link to or post what you mean by a "time integral of TSI". Be sure to do the same for the CO2 forcing.
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wili at 03:15 AM on 14 March 2015Scientists link Arctic warming to intense summer heatwaves in the northern hemisphere
"A decline in summer storminess is consistent with model projections of the impacts of a warming Arctic"
Could someone explain why this would be the case?
It seems counterintuitive to me, but then I am often surprised by how my idiot intuition leads me astray when making assumptions about how climate works. :-/
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wili at 03:07 AM on 14 March 20152015 SkS Weekly News Roundup #11A
curiouspa, besides following JH's advise, consider that seasons still exist. Then think somemore. In particular, consider what happens to the saltiness of the surface water around Antartcica after a bunch of that landbased ice sheet melts during the summer, and what are the likely, predictable consequences of that for ice extent during the next winter.
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billthefrog at 02:33 AM on 14 March 20152015 SkS Weekly News Roundup #11A
@ Tom Curtis #15
Hi Tom,
Yep, I realise there is a slight density difference between sea water and fresh water, with sea water being in the order of 2.5% - 3% more dense.
One needs to look closely at the figure of ~4 cms additional SLR that Prof Peter Noerdlinger is talking about. This, however, is not based solely on a total melt out of sea ice (i.e. ice that has formed at sea).
Instead, he has also included the contribution from ice shelves (ie ice that has formed on land and has subsequently flowed out onto the sea surface).
From figures available on Cryosphere Today, the annual average area of global sea ice (NH + SH) is 19 million sq kms. If one takes an average thickness at a reasonably generous 2 metres, and somehow smears this over the approx 360 million sq kms of ocean surface, that would give us an ice coating of just over 10.5 cms.
As the density of ice is around 92% of fresh water, this would in turn equate to a fresh water "film" of some 9.71 cms in depth floating on top of the denser sea water below. Comparing densities of fresh and salt water, the same mass of salt water would have been about 9.47 cms deep.
Obviously, the difference between these is only in the order of 2.5mm, and that's why I ignored this second (third?) order effect in my earlier response to curiouspa.
Ice shelves are a different matter all together, and I am somewhat surprised by the fact that they have been lumped together in this fashion. Massive chunks of ice coming down from the Jacobshavn Isbrae, from Petermann, Pine Island or Thwaites, or, more spectacularly from things like the Larssen B Shelf most assuredly do contribute to overall SLR.
cheers bill f
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CollinMaessen at 02:25 AM on 14 March 2015New Series: Science Communicators – Why We Love Communicating Science
Thanks everyone for the suggestions, I've added them to my notes. :)
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It's the sun
Dan Pangburn - If CO2 isn't the point of discussion (or rather, the relative influences of anthropogenic GHGs and the myth that 'it's the sun' responsible for all recent climate changes), then why did you bring it up? Particularly when your claim is so unsupported?
In the meantime, since we are concerned with changes in temperature, graphing those against changes in TSI is entirely appropriate to investigate correlations.
Regarding the oceans, both Rob and I have agreed that GHGs have little effect on how the oceans absorb SW radiation - but you seem to be missing the physics where GHG changes greatly affect how the oceans lose that energy, causing a forcing imbalance and therefore warming the oceans.
Climate temperatures are a balance between incoming energy gain and outgoing loss scaled by the Stephan-Boltzmann relationship, and changes in a balance can come from a finger on either side of the scales.
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macoles at 00:37 AM on 14 March 2015So what did-in the dinosaurs? A murder mystery…
Thanks howardlee, can't wait to tell my science loving 11 year old daughter about this great example of scientific process in action.
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Dan Pangburn at 00:35 AM on 14 March 2015It's the sun
Rob - I agree and restate: Atmospheric CO2 increasing from 3 parts in 10,000 to 4 parts in 10,000 can not significantly change the rate that the oceans absorb sunlight.
KR - The effect of CO2 is not the point of discussion here.
Temperature change, in degrees K, multiplied by the effect thermal capacitance (thermal inertia?), in Joule sec/m/m/K results in units Joule sec/m/m.
Forcing is in Joule/m/m.
My only point here is that it is misleading to compare these on the same graph. The correct comparison is between the temperature change and the time-integral of the net (you can call it total) forcing.
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CBDunkerson at 00:08 AM on 14 March 20152015 SkS Weekly News Roundup #11A
In terms of global ice changes I think looking at the rough percentages helps;
- Antarctic land ice: 90%, decreasing
- Greenland land ice: 9%, decreasing
- All other ice: 1%, decreasing
So yes, it is possible to find examples where ice is increasing (e.g. Antarctic sea ice & individual glaciers), but those are a subset of 1% of the planet's total ice... and even that 1% is overall in decline.
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howardlee at 22:36 PM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Ranyl - basically yes! The late Cretaceous, before the eruptions, was quite cool, with some suggestion there was even ephemeral ice in Antarctica. But the climate was overall warmer than the 20th century and CO2 levels higher. Ocean currents were also different as Antarctica was still connected to South America and Australia. So there were important differences between then and now, but the fundamentals of rapid greenhouse gas emissions and pollution leading to abrupt climate change, acidification and environmental disaster are the same.
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wili at 22:20 PM on 13 March 20152015 SkS Weekly News Roundup #11A
What should we make of the FOUR cyclones now swirling around the Western Pacivic and over Australia? Pam just hit cat 5 status.
Elsewhere: http://www.bbc.com/news/world-africa-31862881
"Angola floods kill at least 35 children and 27 adults".
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Tom Curtis at 21:25 PM on 13 March 20152015 SkS Weekly News Roundup #11A
billthefrog @14, melting of sea ice does raise sea level. The reason is that the ice, being fresh, is less dense than the salt water on which it floats. As a result, it floats higher than it would if floating in fresh water. The difference in the amount of ice above water between the ice floating and salt water and equivalent ice floating on fresh water is excess volume that contributes to sea level rise. The total melting of all sea ice including floating ice shelves would raise sea level by about 4 cm. (Paper)
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billthefrog at 20:17 PM on 13 March 20152015 SkS Weekly News Roundup #11A
@ scaddenp
As you well know, there is also the matter of isostacy to consider - especially at the local level. It is a standard (great white?) con trick to talk about there being a drop in measured MSL at such-and-such a place, and present this as a supposed counter argument to concerns over sea level rise.
In many areas that, until the geologically recent past, were covered by the Fenno-Scandian or Laurentide Ice Sheets, the crust is still physically rebounding following the loss of giga tonnes (terra tonnes?) of ice since the days of the last glacial maximum.
What I don't know* is whether or not isostacy has any overall meaningful impact on global sea level. Any ideas? (*That sentence should really have commenced... "Amongst the unimaginably vast number of things I don't know, is whether...)
@ curiouspa #
" ... Is the loss of Arctic sea ice a direct contibutor to sea level rise? ..."
I you look up "Archimede's Principle", especially the corollary regarding a body that is floating on a fluid, you should be easily able to work the answer out for yourself.
cheers bill f
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ranyl at 20:16 PM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Thanks Howardleevery thorough,interesting to read and insightful.
And very scarey!
Aren't we putting something like 3xmega eruption ratesof CO2, not to mention, SO2, CFC's for ozone, and a wholehostofother very toxic stuff into the world ecosystem and all at a rate imagineably quickly and from a low CO2 start (meanign CO2 input has more warming potential)..
If we have any ancestors they really are going to wonder..
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scaddenp at 13:33 PM on 13 March 20152015 SkS Weekly News Roundup #11A
"uncertain at this point why." which should be understood as multiple factors at play with uncertainty over which ones are the most important, as opposed to "havent a clue what's going on".
Actual sources of sealevel rise are land ice loss, thermal expansion and land water storage change. ( see here for article on this). I dont think it is totally accurate to say sea ice change makes no difference but it is miniscule compared to the others.
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One Planet Only Forever at 11:31 AM on 13 March 20152015 SkS Weekly News Roundup #11A
Jim Hunt@6,
Thanks for the link to the extra information.
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curiouspa at 11:30 AM on 13 March 20152015 SkS Weekly News Roundup #11A
scaddenp-thanks.
I looked over links provided. Consensus seems to be that overall Antarctic ice on land is decreasing based on loss of thickness. Sea ice is increasing a little, and uncertain at this point why.
One statement I saw "when land ice melts and flows into the oceans global sea levels rise on average; when sea ice melts sea levels do not change measurably"
Does that imply that expected sea level rise is mainly from land ice loss, such as Greenland ice loss in the Arctic? Is the loss of Arctic sea ice a direct contibutor to sea level rise, or only secondarily thru loss of albedo and resultant ocean warming?
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Tom Curtis at 10:58 AM on 13 March 20152015 SkS Weekly News Roundup #11A
curiouspa @8, the gain in Antarctic sea ice is less than the loss in Antarctic land ice in terms of volume. The loss in Arctic land plus sea ice is greater than the loss in Antarctic land plus sea ice, a fact partly due to the fact that the Arctic has warmed more than the Antarctic (for well known reasons the explanation of which is partly explaineded by scaddenp @9). The Southern Ocean has been warming so that the Antarctic sea ice has grown even though the water on which it floats has been warming. That is due to the fact that:
1) increased rainfall due to the warming has resulted in fresher surface water, that freezes at a higher temperature; and
2) increased windspeed due to warming results in ice being pushed further north before it melts, with the open water created by the export of ice refreezing because it is further south.
Your intuition that "... if both poles were heated about the same amount, both would lose a similar amount of ice" is, therefore, incorrect (quite aside from the fact that the Arctic has been heated more).
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howardlee at 10:47 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Villabollo - I don't know that the atmosphere in the Cretaceous was thicker (assuming you mean height of the atmosphere, rather than density) - perhaps someone else can chime in. The height of the troposphere - the layer with sufficient density to make a difference to the asteroid - is about 7-20km. An asteroid travelling at cosmic speeds of about 30,000mph (48,000kph) would travel through that in about 1.5 seconds. Even if the height of the troposphere was higher I doubt it would make much difference.
If you feel like an amusing exploration of this theme check out this "What if" post
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howardlee at 10:21 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
ubrew12 - great minds think alike, so they already looked into the idea that Chicxulub triggered the eruptions ("antipodeal focusing"), but no. Adrian Jones looked into that in his recent paper and concluded that earlier work was correct in establishing that India was in the wrong place at that point in its continental drift. The forces in rock opposite a Chicxulub impact are also apparently not quite enough to fracture rock. If they coincided with an area primed for an eruption anyway they might just set it off, but otherwise not.
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Same Ordinary Fool at 09:29 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
To me this is as momentous a geological mystery as the story of Continental Drift. Then there were many different arguments from various fields, though they all led to one conclusion, that was eventually observed - in the spreading sea floor under the Atlantic ocean. The dinosaur whodunit is more traditional, with multiple suspects.
It's inevitable that geological research will be done more with lab coats and a little less with boots on the ground. That's where the answers lie. But to this observer part of the appeal of geology was its simplicity, that resulted in part from the greater unknowns. Just following fossils and formations, looking for an informative outcrop. And what's on top is younger.
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q41019573 at 08:44 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Amazing, interesting, informative, educational, and I'm 67. Thank you very much.
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scaddenp at 08:34 AM on 13 March 20152015 SkS Weekly News Roundup #11A
curiouspa - please see the link I provided on Antarctica sea ice for why Antarctica sea ice is expanding - it is paradoxical on first glance because sea temps are rising. However for overall Antarctic ice loss see here. Measurement is done with GRACE satellite or from height of ice sheet. As to assymetry between poles consider:
South pole is on land at around 2000m altitude - North pole in sea as is most of Arctic ice with exception of Greenland.
Antarctica is isolated to some extent from rest of planet by circumpolar current and winds. Arctic weather is influenced by air masses from lower latitudes.
Ozone depletion also plays a part in Antarctic radiative balance.
Sea ice in Arctic is year round phenomena. Because sea ice is at lower latitudes in Antarctica, (higher latitudes are covered by land) most of it is completely melted out in summer.
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villabolo at 08:06 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Don't know if this is on topic but I've heard that the atmosphere may have been thicker during that epoch. If it were would that have made a difference? How would the atmosphere have been affected by such an impact?
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curiouspa at 07:14 AM on 13 March 20152015 SkS Weekly News Roundup #11A
For wili,
I think if both poles were heated about the same amount, both would lose a similar amount of ice. The Arctic would lose sea ice and the Antarctic would lose an equal amount of land and sea ice.
I'm not excluding that there can be variations with net overall global loss. I just want to know the facts-simply stated- is Antarctica gaining or losing ice? It may be there is overall loss of ice but increase in sea ice only. The only satellite data I can find is sea ice since 1979. Thanks.
Moderator Response:[JH] If you enter "Antarctica" into the SkS search box, you will find a wealth of information about what's going on there.
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scaddenp at 07:14 AM on 13 March 2015Measuring Earth's energy imbalance
Chpter 2 of IPCC AR5 discusses the measurement in 2.3.1. You might like to start with the references from there. I understand there are some difficulties with accuracy in the raw data though making it hard to get a precise measure of magnitude. ARGO data may be a more accurate way to get TOA imbalance.
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shoyemore at 06:43 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
I remember two articles in Scientific American in the 1980s explaining the rival theories. The Deccan Traps were advanced as the alternative to the asteroid. It was a little shocking to read a popular very media-friendly theory attacked. Over the years I assumed the volcano account had receded or been discounted. Great article.
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uncletimrob at 06:23 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Thank you! A most interesting article that takes me back to early undergraduate lectures nearly 4 decades ago. Another for the recommended reading list.
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bcglrofindel at 05:58 AM on 13 March 2015Measuring Earth's energy imbalance
I'm not sure where the right place to ask this is, so please redirect me if I'm in the wrong place. Does anyone know where I can track down the Top-Of-Atmosphere net energy/radiation data from CERES and prior to that ERBE? I've been looking and looking for an easy referencable observed energy balance graph covering the satellite era and can't seem to find them. I can find summaries of the overall trend for CERES, and pieces of ERBE from sometime in the 80's, but nothing by way of a simple graph. Surely with one of the express purposes of these satellites being to measure incoming and outgoing radiation somebody has put together a net radiation graphic of some form already somewhere? If I could be pointed in the right direction it'd be greatly appreciated.
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ubrew12 at 05:55 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
I'm not a scientist so am free to speculate: If you tunnel through Earth to the spot opposite the Chicxulub Crater, you will be in the Indian Ocean. Hmmm.
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howardlee at 05:29 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Yes there's a pretty strong pattern. I think the end-Ordovician is now perhaps the only exception of the phanerozoic, linked by some to the first spread of vascular plants causing CO2 reduction and Global Cooling, resulting in the Hirnantian Glaciation.
John Mason has a post due out soon on the Permian Mass Extinction - the most extreme example.
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wili at 05:17 AM on 13 March 2015So what did-in the dinosaurs? A murder mystery…
Thanks. I always find myself treating the end-Cretaceous extinction as the exception to the general rule that mass extinctions have been caused by GW, which was too bad, since it's the only mass extinction event that most people (think they) know something about.
Now I can just point to this article.
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Andy Skuce at 05:03 AM on 13 March 2015Consensus and geoengineering - how to convince people about global warming
I have been critical of Dan Kahan in a recent post here, but I think there's a lot of value in most of what he has written. I wrote a long post on SkS sometime ago that was broadly appreciative of his work. I think he is right to worry about getting more people, especially those on the political right in the USA, to accept the science. He's not alone in that.
Where I differ with him is that I see consensus (or information) messaging as part of a two-pronged approach, along with his cultural cognition stuff, whereas he seems convinced that consensus messaging is counter-productive. I think the study that Dana highlights in this post effectively removes that worry.
One irony is that the tone of some of Dan's informal remarks about consensus have themselves been rather harsh and they actually risk polarizing those of us who are trying to nudge public opinion in the direction of reality. If communicators are going to change the status quo, it's going to take all of us.
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scaddenp at 04:57 AM on 13 March 20152015 SkS Weekly News Roundup #11A
curiouspa - You might want to look (and continue any discussion) on this thread. Short answer - Antarctia is losing ice but there is a statistically significant increase in the sea ice around it. Just dont fall for idea that this somehow offsets arctic ice loss (it is small by comparison and has little climate impact since it occurs in winter). In particular, you need to look at why these things are happening. The skeptic argument is that its getting warmer in arctic but cold in Antarctic so cant be CO2/anything to worry about. Not true.
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swampfoxh at 04:44 AM on 13 March 2015Consensus and geoengineering - how to convince people about global warming
I suspect (and probably hope) that the science community can probably appreciate that the "personas" in the US political power structure are as much a part of the problem as the fossil fuel industry and the average voter himself. On the one hand, President Obama, gives the appearance that he supports blocking the XL Pipeline while he opens up the Atlantic offshore drilling sites and certain Arctic continental shelf areas for drilling. But, I don't see the scientific community (the hard science guys) saying much of anything about this hypocrisy. Could it be that the great majorities of scientists are political liberals and deign to criticize this guy? KR's looking for getting things done and wants the science to point the way to sensible public policies, but unless the scientific community is prepared to ridicule the inappropriateness of the power structure's "wacko" decisionmaking on climate remedies, even good science will give us nothing to bite into. Massive population reduction, for example, is a sensible public policy if we are going to fix the climate problem. Total curtailment of global coal fired power plants is another. A permananet moratorium on global land clearing operations is yet another sensible public policy. The shutdown of global synthetic fertilizer producers is yet another. Shutting down the global internal combustion engine manufaturers, yet another. But, the recent US-EPA 30% reduction mandated for coal-fired power plants is not a sensible public policy when the science realizes that just this one category requires at least an 85% reduction in emissions and that should have happened 12 years ago!
I think I know what y'all are going to say about my doomsday scenario, but I want to hear it anyway, so, fire back. I have class tomorrow and I'd like to tell my students what you have to say. Thanks.
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Jim Hunt at 03:42 AM on 13 March 20152015 SkS Weekly News Roundup #11A
OPOF @2 - There are a range of Arctic sea ice metrics, which peak at different values on different dates. I've been covering a range of them today, to coincide with The Economist's Arctic Summit:
http://GreatWhiteCon.info/2015/03/some-statistics-for-the-2015-economist-arctic-summit/
The "15% extent" ones are currently at their lowest level for the date by a considerable margin. Cryosphere Today area is also at a record low today, but only just.
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Consensus and geoengineering - how to convince people about global warming
swampfoxh - I completely agree, hard-core deniers will never be convinced. And I think that single fact makes all the Kahan-style whinging about 'polarization' ineffective.
Is the goal to convince everyone, including those invested in not listening? Only if your sole question is "Can't we all just get along?". Or is it (IMO) more important to simply get things done, to minimize the damage from climate change? If the latter, then properly informing public opinion about the science and expert views, rather than vested disinformation, should at the very least point the way to sensible public policies.
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wili at 03:15 AM on 13 March 20152015 SkS Weekly News Roundup #11A
Here's the link to a pdf of the original study on failing carbon sinks.
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wili at 03:13 AM on 13 March 20152015 SkS Weekly News Roundup #11A
This seems like a pretty important development.
curiouspa, the north and south poles are polar opposites in more than one way--the Arctic is an ice-covered ocean (mostly) surrounded by continents; the Antarctic is an icesheet-covered continent surrounded by ocean.You tell _me_ what you think the result of heating each of these up a bit would likely be. No agenda...just a question.
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swampfoxh at 03:09 AM on 13 March 2015Consensus and geoengineering - how to convince people about global warming
I have a Masters Degree in Government. This, perhaps, qualifies me to teach "Global Warming: Proof or Politics", which I do bi-monthly here in west-central Virginia. I point this out because, although I read SkS "religiously" I find the science pretty baffling (which most of you "hard scientists" would not find surprising). But, I am often struck by the many comments on the subject of "how to convince the Deniers to 'buy' the science", a science which is very solid and, frankly, needs no additional "evidence" to get people off their butts and out into the street to solve this climate problem. So, instead of fulminating over how to get the deniers to "get with the program" we should be getting the rest of us (the most of us) to get on with the solutions. We know people believe in God without the slighest scientific evidence so why bother with such subjects? People will believe in God and other fairy tales long after we have fixed the climate problem, so let's put managers and policymakers into positions of political power that can do what needs to be done here and stop wasting time and dialog on BS.
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It's the sun
Dan Pangburn - "...my analysis has found that CO2 has no significant effect on climate..."
Then, with all due respect, your analysis is simply wrong.
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It's the sun
Dan Pangburn - Reality doesn't care about beliefs.
With respect to the significance of CO2 concentration changes, I suggest reading the CO2 is just a trace gas thread. Your statement sounds like an argument from incredulity.
Atmospheric GHGs (active in the IR) have very little effect on how the oceans absorb sunlight. But by warming the surface atmosphere, they have a significant effect on how fast the the oceans lose energy to the atmosphere, and hence create a forcing imbalance on the oceans themselves. See the discussion here.
"...you are destined to wonder why the average global temperature isn't increasing."
What? How can you possibly claim this? There are short term variations in atmospheric temperatures, but if you look at the global temperatures including the oceans, or even just examine a sufficiently long period for statistical significance in atmospheric temperatures, they are indeed increasing. That statement of yours is nonsense.
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curiouspa at 02:23 AM on 13 March 20152015 SkS Weekly News Roundup #11A
Just a question-no agenda. I hear various things. Is Antarctic ice increasing, decreasing, or staying the same. The article seems to be definitive that Arctic sea ice is decreasing.
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Rob Honeycutt at 01:58 AM on 13 March 2015It's the sun
Dan @1113... It's not a matter of "belief." You have to understand the physics involved. For one, atmospheric concentrations of CO2 don't affect incoming radiation that warms the ocean.
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Dan Pangburn at 01:30 AM on 13 March 2015It's the sun
KR - I don't believe that atmospheric CO2 increasing from 3 parts in 10,000 to 4 parts in 10,000 has significantly changed the way that the oceans absorb sunlight.
My only point in this discussion is, to be a meaningful comparison, the temperature change should be compared to the time-integral of the forcing instead of the forcing itself.
Tom - It is puzzling why you declare that my definition of forcing is bogus when I have not even defined forcing. I assumed that everyone knew what cosntituted a forcing. My understanding is no different from AR5 (except my analysis has found that CO2 has no significant effect on climate).
I HAVE defined 'break-even'.
If you cannot see that the energy change (which, when divided by effective thermal capacitance, is temperature change) is the time-integral of the energy change rate (AKA net forcing) this isn't going anywhere and you are destined to wonder why the average global temperature isn't increasing.
Moderator Response:[PS] And your analysis is published where? Time to show us some data I think. It is pretty hard to accept the word someone who cannot calculate the radiative effect from an increase in CO2 without some pretty convincing mathematical analysis including all definitions used.
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One Planet Only Forever at 00:19 AM on 13 March 20152015 SkS Weekly News Roundup #11A
Here are a few clarifying points regarding the first arcticle "Arctic sea ice dwindling toward record Winter low".
The image in the article from NSIDC does indeed show the ice extents well below the average maximum and below the +- 2% standard deviation shaded area. However, the maximum ice extent of 14.522 sq km appears to have occurred on Feb 26. Perhaps the article is referring to the extent on March 12 when the average line is at its maximum.
However, the NSIDC webpage the image can be found on also includes a Chartic Interactive Sea Ice Graph that allows the user to see graphs of all of the previous years. And many previous years reached their maximum extents well after March 12. And some years there were early rapid declines in Arctic extents that were followed by expansion to that later maximum.
A more important point is that the extent reported by NSIDC is for at least 15% sea ice coverage. Temporary currents or wind conditions could pack brocken up ice into a smaller areas that could expand when current or wind conditions change.
So, the current Artcic Sea Ice extent is indeed well below any previous values in the NSIDC set of reported years. However, a lot can change in a short time. And the most recent extents are not continuing the rapid decline.
Time will tell what the resulting summer minimum will be. It may even be that the winter maximum extent of 15% or greater sea ice will exceed the 14.522 sq km that was measured on Feb 26.
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wili at 21:20 PM on 12 March 20152015 SkS Weekly News Roundup #11A
Thanks again for these, especially "Friction means Antarctic glaciers more sensitive to climate change than we thought "
So is anyone putting this together with other recent findings of faster-than-expected movement of various icesheets to come up with new estimates for the range of possible levels of slr we may expect by the end of the century and beyond? It would seem to me that such a project would be most important for policy makers (and for anyone living anywhere near the ocean).
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