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scaddenp at 10:36 AM on 13 May 2015GHG emission mitigation solutions - a challenge for the Right?
Interesting article http://www.vox.com/2015/5/12/8588273/the-arguments-that-convinced-this-libertarian-to-support-a-carbon-tax
on what convinced a liberatarian and his solution.
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wili at 23:38 PM on 12 May 20152015 SkS Weekly Digest #19
Good points, utr. If events alone could sway people's minds, states like Oklahoma and Texas, which have been through harrowing droughts recently, should be in the forefront of climate awareness.
But as it is, they host some of the most backward thinking people and senators in the Union.
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SirCharles at 23:22 PM on 12 May 2015Ice loss in west Antarctica is speeding up
Also => Sea Level Rising Faster. Ice Loss Speeding Up.
Moderator Response:[RH] Resized video. Please try to keep the image width to 500px as anything above that breaks the page formatting for this website.
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Tom Curtis at 22:16 PM on 12 May 2015Climate's changed before
skeptic123 @463, looking at the Vostock data another way, I examined in detail each of the four transitions from inter-glacial to glacial in the Vostock data. From each such transition, I determined the minimum interval for the transition, calculated as the time from the most recent relevant datapoint above -2 C to the time of the first datapoint following which was below -4 C. The relevant intervals were, from oldest to newest:
3426 years (average rate of decline = -0.006 C per decade)
4399 years (average rate of decline = -0.005 C per decade)
2654 years (average rate of decline = - 0.008 C per decade)
2028 years (average rate of decline = -0.01 C per decade)
(Note: the rates of decline are for a regional temperature value. Global values would be about half that.)
No matter how many times you repeat the quote, the data does not support it. Further, science proceeds by evidence, not by out of context quotation (which is rather the mark of pseudoscience).
Now, it is possible that the scientists who made that claim define an "ice age" as any period with a temperature anomaly less than x, where x is -0.5, or -0.1, or some other arbitrary value. It is also possible that they consider temperatures of x + 0.5 C as "a warm climate". In that case, what they say is true, trivial, and so vague without the specification that that is how they interpret their words, and a specification of x as to be useless. If you want to use the quote, it is therefore incumbent on you to find out the exact interpretation the authors give to the words.
Absent that effort, however, it remains that the data directly contradicts the claim supposedly based upon it. So, if you are not prepared to make the effort to provide the context of the quote on whose authority you rest, it is incumbent on you to follow the data. Failure to do so simply demonstrates that you accept data only if you think it supports your position. Worse, it shows that you present data that in fact falsifies your position as supporting it, and refuse to acknowledge the detailed examination that shows that the data refutes your position. Again, those are the hallmarks of pseudoscience.
Long experience has shown that debating with pseudoscientists is completely unprofitable in that their positions are not based on reason and evidence, and therefore cannot be altered by either reason or evidence. I also think that the complete divorce of your opinions from actual data is sufficiently evident to any interested readers that I do not need to spell it out again. Consequently I will ignore your responses in future until such time that you start correcting your position based in the actual data.
Moderator Response:[JH] Your above comment is actually directed at skeptic1223.
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bozzza at 22:10 PM on 12 May 2015Antarctica is gaining ice
I am saying it makes the fight to have climate science recognised by the trolls more difficult, yes!
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Jim Hunt at 21:35 PM on 12 May 2015Antarctica is gaining ice
bozzza@391 - So you're seeking a punchy "elevator pitch" that addresses the misleading headlines of Nova et al.?
And/or suggesting that this article needs updating to include the 2014/15 numbers? -
Rob Painting at 19:47 PM on 12 May 2015The Carbon Bubble - Unburnable Fossil Fuels - Seminar and Discussion
Rolf - oxygen makes up about 21% of Earth's atmosphere and CO2 about 0.039%. Furthermore, we know life has flourished prior to the addition of fossil fuel CO2 to the atmosphere by humans so, if we could bring back to a pre-industrial level, there would be ample oxygen available for plant and animal life.
There's no need to worry about CCS other than that it is so far as useful as the tooth fairy and unicorns.
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uncletimrob at 17:52 PM on 12 May 20152015 SkS Weekly Digest #19
@ Will. It will be interesting to see how "natural variabilty" (eg El Nino) is viewed in western Queensland which is already suffering a drought. My - admittedly limited with some friends who live in Roma - experience is that their political leanings prevent any discussion that the climate is changing and that these extended droughts may become the norm. I certainly feel their pain as their livelyhoods are destroyed, but dissociating politics from science is a hard one in a tough, unforgiving (climate wise) region.
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wili at 16:10 PM on 12 May 20152015 SkS Weekly Digest #19
BoM just called it: "the Bureau's ENSO Tracker has been raised to El Niño status"
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bozzza at 12:50 PM on 12 May 2015Antarctica is gaining ice
Ok, I was just saying the numbers look weird and I think that is worthy of considered comment as to why.. I haven't understood the meaning of statistical significance but as far as sea-ice area graphs of Antarctica are concerned the last few results seems to be worth talking about.
I get the mechanisms discussed but the real-politik of statistics and publicly inspired meaningful thresholds cannot go unanswered.
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Rolf Jander at 12:31 PM on 12 May 2015The Carbon Bubble - Unburnable Fossil Fuels - Seminar and Discussion
CCS worries me because CO2 is two thirds oxgen. CO2 in the air could eventually be used by plants and the oxygen returned to us. If it is locked away forever we have lost that oxygen and reduced the atmosphere as a whole. Let's just focused on reducing the production of co2.
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scaddenp at 12:15 PM on 12 May 2015Antarctica is gaining ice
I not entirely sure I understand your concern. As far as I can see, the article is comparing Winter Antarctica seaice (no climaticalogical effect because it happens when the sun isnt shining), versus Summer Arctic sea ice (where the loss is significant due to reduce albedo). The skeptic narrative is that northern hemisphere warming is more than matched by southern hemisphere cooling (sea ice as evidence). However the narrative fails because sea ice increase isnt due to SH cooling - the Antarctic is warming too. Its just that real situation is more complicated.
A better comparison is to compare the climatological effect from sea ice albedo between hemispheres. Tamino did that here - compare that with the rather deceptive approach at Nova.
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denisaf at 12:04 PM on 12 May 20152015 SkS Weekly Digest #19
Climatologists are obtaining copious amounts of evidence of unusual events such as icebergs melting, ocean currents changing, etc, etc. to be taken into account in models and in the logical arguments to arrive at a sound view of what is almost certainly happening, global atmospheric warming with associated ocean heating and acidification.
The unsubstantiated beliefs of deniers of irreversible, rapid climate change caused largely by the emissions from the combsution of fossil fuels are not making a contribution to the understanding that would help society to adopt mitigation measures. Are they proud of their malfeasance?
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bozzza at 10:19 AM on 12 May 2015Antarctica is gaining ice
I'm not denying the article is helpful in explaining that ozone depletion is causing wind increases and melting of land ice plus rain increases are freshening the Southern ocean changing the layers so that warm and cold waters don't mix like they once did... I'm simply saying the numbers look curious.
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MA Rodger at 04:52 AM on 12 May 2015Climate's changed before
skeptic1223@470.
"It doesn't directly," you write. Indeed it doesn't make that assertion at all.
Now you are asserting that "we know that 3 million years ago CO2 concentrations were the same as today's." You provide a quote from a livescience blog but is your assertion supported by this livescience blog? The answer is "no".
If you could be bothered to examine the Scripps posting referenced by your livescience blog, you will see that it talks of "The Pliocene is the geologic era between five million and three million years ago. ... It is trickier to estimate carbon dioxide levels before then(800kybp), but in 2009, one research team reported finding evidence of carbon dioxide levels ranging between 365 and 415 ppm roughly 4.5 million years ago." So this citation is actually a little early for our purpose and the range of CO2 level has mostly been left behind by today's anthropogenic emissions.
Perhaps you can find some support for your assertion elsewhere. But then do bear in mind the actual age we are interested in is the point that Arctic glaciation kicked off which I believe was 2.7Mybp. -
Jim Hunt at 03:33 AM on 12 May 2015Antarctica is gaining ice
In which case doesn't this very article answer your question in great detail?
If not you will need to elucidate in much greater detail!
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rocketeer at 02:21 AM on 12 May 20152015 SkS Weekly Digest #19
I find it amusing that deniers (recently) admit the climate is changing but claim it has "always changed". Of course, the climate has changed in the past, but it has not "always changed" in the sense that there have been long periods of relative stability/very slow change in the recent and distant past. But the really telling thing about this argument is the implicit acceptance of the paleoclimate research that identified dramatic climate change events going back as far as hundreds of millions of years. Of course, these are bona fide research results which should be accepted in the absence of convincing evidence to the contrary. But these same deniers will scoff at paleoclimate reconstructions going back only a few thousand years and showing that the recent onset of global warming is highly unusual, unexpected and unexplainable in the absence of AGW theory.
So I put the question to Newsel: Is paleoclimatology a legitimate science or not? If not, quit claiming that the climate "has always changed" because there is no evidence for that outside of paleoclimatology. If it is legitimate, then you must accept the work of Mann, Marcott and many others who have proven that the recent GW event does not look like a natural event and can only be explained by human GHG emissions.
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michael sweet at 01:43 AM on 12 May 20152015 SkS Weekly Digest #19
It might be interesting to open a thread where people can post old quotes from deniers claiming that the climate is not changing. They used to argue that climate was not changing. Now they claim that:
"The reality is that the climate changes and that no one on either side of the debate argues otherwise."
It might not be necessary to have an OP, just a place where people can put links to old quotes. I recall that Lindzen testified to congress in 1989 that the climate would stay the same. WUWT claimed the climate was not changing until a few years ago. Singer still claims that change is natural and the climate is not changing at the same time.
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KR at 01:37 AM on 12 May 2015Climate's changed before
skeptic1223 - As numerous posters have pointed out, there is really no evidence supporting a risk of sudden glaciation right now. The ice age cycles have in the past been driven by Milankovitch forcings, orbital changes, episodes like the Younger Dryas cooling event were as far as we can tell due to conditions (giant ice dams releasing) that simply don't exist today, and were regional, not global.
Our emissions have essentially removed any chance of a glaciation for the next Milankovitch cycle - we're just not at risk of an ice age. On the other hand, the warming we've already committed to points toward mass extinctions (as climate change exceeds the speed of species movement to keep up with their environments), considerable impacts on agriculture, disease, weather, and many many other impacts.
You've presented no evidence whatsoever supporting your hypothesis, and therefore your suggestion that we need another 100-200ppm of CO2 is just absurd. There's no risk of sudden cooling, and multiplying the impacts of warming seems just foolish.
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hank at 01:36 AM on 12 May 20152015 SkS Weekly Digest #19
Kolbert, not "Kobert"
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hank at 01:36 AM on 12 May 20152015 SkS Weekly Digest #19
Typo:
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PhilippeChantreau at 01:23 AM on 12 May 20152015 SkS Weekly Digest #19
Newsel,
What scientific sources argue that the projected levels will lead to a "runaway temperature increase"? I'm sure that scientific litterature treating of such an idea would have defined too, so I won't ask you what you mean by that.
Which predictions from scientific sources has not materialized within the time frame you seem to be considering (i.e. to present day)? Sources for these predictions are necessary.
When was it proposed and who has seriously advocated the redistribution of developed nations wealth under "UN guidance"? What exactly would that consist of?
I'm not asking here for blog posts or newspaper editorials but substantive sources.
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rkrolph at 01:06 AM on 12 May 2015Climate's changed before
Advocating increasing C02 to prevent a future ice age sounds like someone saying "Let's burn our house down today to prevent the possibility of flooding due to rising sea levels next year."
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bozzza at 00:50 AM on 12 May 2015Antarctica is gaining ice
"climate change advocate" = a non-denier of climate change
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DSL at 00:22 AM on 12 May 20152015 SkS Weekly Digest #19
Talk is cheap, Newsel. How about supporting your claims with evidence?
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Newsel at 00:17 AM on 12 May 20152015 SkS Weekly Digest #19
To the “message” in the cartoon and other similar comment: They are factually incorrect but now that the discussion has changed from AGW to CC or GW allows for this disinformation.
The reality is that the climate changes and that no one on either side of the debate argues otherwise.
What is challenged is that the climate changes due anthropogenic (AGW) causes rather than natural variability. Given that the runaway temperature increases ascribed to increasing levels of CO2 within the IPCC models (since 1995) has not materialized and the multitudes of dire predictions (also since 1995) have not materialized has to give one cause to wonder why?
It is clear that the science is not settled and to waste precious resources and to advocate the redistribution of developed nations wealth under the guidance of the UN while trying to pretend to be able to control Mother Nature makes zero sense. It is at best a futile exercise and worst case a politically driven fraud.
Moderator Response:[TD] Welcome to Skeptical Science. Among the commenting rules here is the requirement to comment on the appropriate posts, to keep the discussion organized. You have listed several topics, so please read the posts rebutting these myths, and then if you desire comment on those posts:
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Jim Hunt at 00:15 AM on 12 May 2015Antarctica is gaining ice
bozzza@385 - As the self same "Arctic Nerd" mentioned by Glenn above I'm afraid that I don't understand your question in this context. Is there any chance that you can rephrase it? What precisely is "a climate change advocate" in your terminology?
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skeptic1223 at 22:36 PM on 11 May 2015Climate's changed before
@469, it doesn't directly, however it states that the reason for the glaciation were atmospheric and oceanic conditions plus a tilt in the Earth's axis, it doesn't say anything about a sudden drop in CO2 and we know that 3 million years ago CO2 concentrations were the same as today's, so.
"Scientists believe that the most recent period with a 400 ppm level of carbon dioxide in the atmosphere was the Pliocene, between five million and three million years ago, according to the Scripps Institution of Oceanography, which keeps track of the Keeling Curve."
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MA Rodger at 21:58 PM on 11 May 2015Climate's changed before
skeptic1223@467.
You write "So, according to the article the ice ages started at levels of CO2 close to today's..."
Where exactly does the article make this assertion?
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CBDunkerson at 21:38 PM on 11 May 2015Monthly global carbon dioxide tops 400ppm for first time
I'm glad this article specified that we are talking about 400 ppm as the monthly average. Too many media reports have just said 'first time ever'... which might cause confusion amongst those who remember readings hitting 400 ppm a couple years ago... as a daily total.
No doubt in another year or so we'll hit 400 ppm as the annual average.
As to the fossil fuel vs renewables and 'economics' debates. The victory of renewables is inevitable at this point. Today even the nominal price is cheaper than fossil fuels for more than 50% of the people on the planet, and if the difference in health, environmental, national security, and/or direct subsidy costs is factored in then fossil fuels aren't even close to competitive. All they've got going for them at this point is inertia... the existing infrastructure and vested interests will continue to prop up the facade of a fossil fuel future for a few more years. However, for anyone paying attention it is already clear that they are on the way out. It's really just a question of how many more years (decades are off the table) before they peak. I doubt we'll be able to stay under 2C, but 3C is now a real possibility.
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skeptic1223 at 20:55 PM on 11 May 2015Climate's changed before
@465, 1-200ppm from now, that number is just an example, when the ice ages started CO2 concentration was similar to today's, before that the climate was relatively stable, so some level of CO2 above today's should make matters safe
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skeptic1223 at 20:41 PM on 11 May 2015Climate's changed before
@466, thanks, this is a nice article, and a great support for my thesis. So, according to the article the ice ages started at levels of CO2 close to today's due mainly to atmospheric and oceanic conditions. Let me quote
"These preconditions—moisture plus an Arctic nucleus for cooling—would have made the climate system highly susceptible to ice sheet growth. Even modest changes in the global environment would have been sufficient to tip the scales and lead to the onset of major Northern Hemisphere glaciation.
Just such a change occurred between 3.1 and 2.5 million years ago, as Earth’s axis fluctuated so that the planet’s tilt toward the sun was less than today’s angle of 23.45 degrees."
So, what's stopping the same thing happening today, I mean not due to an axis tilt but for example due to a major volcanic eruption or decline in solar activity, the other conditions seem to be the same.
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MA Rodger at 19:46 PM on 11 May 2015Climate's changed before
skeptic1223@458.
Within your mercurial argumentation & hypotheising you write:-
@456, 454 - so, why did the ice ages epoch start in the first place then, CO2 concentrations before it started were above current levels. It is of course possible that the CO2 got sucked somewhere first, but do we know of such an event.
A bit of light reading for you. While the conclusions from such studies as presented within the linked document remain incomplete, knowledge of what is under examination may stop painfully simplistic assertons about CO2 levels and the causes of glaciation.
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bozzza at 19:39 PM on 11 May 2015Climate's changed before
@462, do you mean 1-200 ppm from now or from then? Why shouldn't we go up 300 ppm from now to be really safe? (Are you sure you are prepared to be questioned about this ad hoc policy?)
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skeptic1223 at 17:30 PM on 11 May 2015Climate's changed before
@461, I agree :)
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skeptic1223 at 17:28 PM on 11 May 2015Climate's changed before
@460, 457, for GISP2 I meant the green line, but I agree I was wrong, it's not smoothing, it's worse, it's polynomial fit
the Vostock data was an example that quick CO2 decline is possible, I wasn't trying to relate it to the temperature
I don't have the actual data about past temperatures, so I can't quote numbers, that's why in 440 I said that I have to rely on people who do have it and I will quote them again
"Over the last 400,000 years the Earth's climate has been unstable, with very significant temperature changes, going from a warm climate to an ice age in as rapidly as a few decades."
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skeptic1223 at 17:19 PM on 11 May 2015Climate's changed before
@459, not geoengineering, just an increase of CO2 by another 1-200ppm to be on the safe side. The effects of geoengineering as a broad term are not well known while I hope you would agree the effects of CO2 increase are pretty well known
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bozzza at 12:13 PM on 11 May 2015Monthly global carbon dioxide tops 400ppm for first time
@3, these are the problems that arise when governments pick winners aka intervening in the market place: the so called invisible hand of free-market theory can't operate efficiently... so when the phenomena of diminishing returns raises its ugly head how does a pastiche of next-to-random activity logically respond?
Economies are meant to be robust so let us all heil more government intervention to save our skin from the madness of Jevons Paradox!!
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jenna at 11:12 AM on 11 May 2015Monthly global carbon dioxide tops 400ppm for first time
Part of the problem with just hoping fossil fuels will gow away is this; Every new coal fired plant or gas fired plant being built today is going to be around for decades. Govermnents and power utilities don't spend that kind of cash to shut them down after 5 years or so.
We need viable renewables sources now, and the sooner the better. I;'m not just talking about endless solar farms, etc. It's not working in Germany or China (never mind India). Those 3 countries (and others) continue to build coal and gas infrastructure.
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bozzza at 10:01 AM on 11 May 2015Climate's changed before
@ 447, the counter to this is that California isn't a global indicator no matter what those guys handing out cds on the boulevarde say !
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Tom Curtis at 10:00 AM on 11 May 2015Climate's changed before
skeptic123 @457, if you only presented GISP2 as an example of an unsmoothed record, you deliberately presented an irrelevant example in that Marcot et al is not a smooth of the GISP2 record.
Presenting the Vostock graph as an example of rapid declines in CO2 level is even worse for your case given that declines in CO2 level are less rapid than are declines in temperature in the Vostock record. (Ie, my points are even stronger as applied to CO2.)
A 2-3 C drop on global temperature over a century or two would indeed be no fun at all. However, the likelihood of such an event with 280 ppmv of atmospheric CO2 is very low. We know this because only three events in the holocene come close to such a situation. The largest of these, the 8.2 kiloyear event was the result of a sudden spike in sea level resulting from the release of damned melt water durring the melting of the laurentide ice sheet. That cause is not applicable for stable preindustrial conditions or indeed at anytime except following the end of a glacial. The 5.9 kiloyear event and the 4.2 kiloyear event where much smaller and preceded the rise of CO2 concentrations to 280 ppmv. The most recent similar event was the Little Ice Age, with global temperatures declining by just 0.2 to 0.4 C.
With respect to the LIA, if that is the sort of unexpected climate variability we have to worry about, you need to make the difficulty argument that a low risk of a 0.3 C decline in global temperature is more threatening than a very high probability of a 3-5 C rise in global temperature. You also need the face the fact that these events seem to have a period of about 1500 +/- 500 years, and with the most recent event starting less than 500 years ago, the next event cannot be expected for at least another 500 years.
In short, it is absolute folly to not intervene to prevent an almost certain, large and very rapid event starting now because of the low risk of a small, relatively slow event that may occur 500-2000 years from now. Yet that folly is the basis of your argument.
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bozzza at 09:57 AM on 11 May 2015Climate's changed before
@445, So you are promoting geo-engineering of the planet?
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skeptic1223 at 08:56 AM on 11 May 2015Climate's changed before
@456, 452 - I claim that we can not predict volcanic eruptions, not the effects of them
@456, 453 - ok, so where do the statements from IPCC and GRIDA about rapid glaciations in a matter of few decades come from?
@456, 454 - so, why did the ice ages epoch start in the first place then, CO2 concentrations before it started were above current levels. It is of course possible that the CO2 got sucked somewhere first, but do we know of such an event
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skeptic1223 at 08:49 AM on 11 May 2015Climate's changed before
@455, my mistake about GISP2, it was more an example of smoothing
as for the Vostock data, it was given as example of CO2 levels, since CO2 is fairly evenly distributed, it should still be valid even if it is regional
about the rapid changes, a 2-3 degrees drop for a century even if it reverses itself would still have some quite bad effects
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Tom Curtis at 08:13 AM on 11 May 2015Climate's changed before
skeptic123 @452 - In fact climate models predict more abrupt temperature changes as a result of volcanic activity than actually occur. Your claim, therefore, is the exact reverse of the truth.
@453 As I have just shown, changes from interglacial to glacial are relatively gradual, with the most rapid representing a mean rate of temperature change at Vostock of less than 0.01 C per decade, ie, a tenth of the rate of the current trend (which the AGW deniers insist on calling a pause). Transitions from glacial to interglacial are typically much more rapid, and projected temperature increases over the coming century being much more rapid again, with the equivalent temperature increase to that between interglacial and glacial within 200 years on the outside (with BAU).
@454 Actually, the transition from glacial to interglacial typically occurs with CO2 concentrations 20-40 ppmv below preindustrial levels. No such transition has ever occurred with CO2 concentrations at modern values.
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Tom Curtis at 08:04 AM on 11 May 2015Climate's changed before
skeptic123 @428, last and most offensive first! The GISP2 ice core data represents a regional record only, not a global record. Are you seriously trying to suggest that global temperatures vary as rapidly as do regional temperatures (and regional temperatures with one of the most rapid rates of change of temperature found on the planet)? Further, are you seriously trying to suggest that the magnitude of temperature change from a regional record is also to be found in the global record? If so, you have largely disqualified yourself from the conversation on the basis of complete ignorance of basic relevant facts. If not, you have certainly disqualified yourself from the conversation on the basis of deliberately presenting evidence in a form you know to be misleading.
Taking the former, more generous interpretation, consider this graph of eight full holocene regional temperature proxies:
Individual proxies show rapid variation in temperature of considerable amplitude. Of those, GISP2 (light blue) shows the greatest variation, having the highest peak holocene temperature anomaly, and the lowest most recent temperature anomaly. Because peaks in various records rarely coincide, and some records are always out of phase with others (ie, have troughs where the others have peaks), the arithmetic mean of all 8 proxies shows both much less absolute temperature variation, and much lower rates of temperature change than do individual proxies. Consequently, presenting a single proxy (let alone the most variable proxy) as representative of either absolute magnitude of global temperature change or of rates of temperature change over the holocene is fundamentally misleading (whether from ignorance of the effects of regression to the mean, or intent to decieve).
(As an aside, the overall decrease in the mean temperature over the holocene is largely an artifact of a NH bias in the individual proxies (ie, there are more NH than SH proxies presented), a problem also with Marcott et al. An unbiased sample is likely to show much less, or possibly no decline over that period.)
The same basic problems afflict the Vostock proxy record (blue in the above graph). The absolute temperature magnitude shown in the Vostock record is approximately twice the absolute variation in the global record. Further, periods of rapid decline rarely coincide with other regional proxies so that periods of rapid decline in the Vostock record will coincide with much slower decline (or sometimes even increases) in a global record. Further, your quote from the caption of the Vostock graph that you show is misleading out of context, and not supported by the evidence in any event.
In particular, while rapid temperature changes can occur over only a few decades, the trend over successive decades will often greatly slow or reverse direction. The consequence is that multi-century temperaturetrends are typically very slow. This can be seen in a scatter plot of time intervals vs temperature change in the Vostock record:
While there are some very rapid short duration changes, they are seen to quickly reverse themselves. The result is that changes over a century or more are at rates of -1C per century or less. Typically much less. As the transition from inter-glacial to glacial in the Vostock record requires a temperature change of approximately -6C, that means transitions from interglacial to glacial cannot occure in less than 500 years or more. Indeed, based on a pixel count of the graph of the vostock record, the most rapid interglacial to glacial transition (taken as the interval between 0C and the bottom of the first trough below -4C, or to -6 C, which ever is shorter) takes 6250 years (approx 240 thousand years ago). The next most rapid, and most recent took thirteen thousand years.
Finally, the TAR quote references Alley 93, which analysed early icecore data from Greenland. The rapid transition it found was the Younger Dryas, which was primarilly a North Atlantic phenomenon, and which involved much slower transitions in temperature when averaged across a number of diverse locations. (In 1993, only Greenland proxies were available back so far in time.) It is, therefore, obsolete, having been disproved by more recent data.
(I've run out of time, and will return to the CO2 issue later.)
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skeptic1223 at 08:04 AM on 11 May 2015Climate's changed before
@442, well, ice ages started when CO2 levels were about today's, so it is entirely possible
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skeptic1223 at 07:39 AM on 11 May 2015Climate's changed before
@448, well, changes from glacials to interglacial are normally quite rapid (much more rapid than 20th century warming), so rapid warming is not something completely new for the climate system
Before the ice ages started (when CO2 dropped below today's levels) the climate was a lot more stable. I am not talking about extreme CO2 levels, just a 100, at most 200ppm more.
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skeptic1223 at 07:30 AM on 11 May 2015Climate's changed before
@449, I understand that climate models can not predict abrupt changes, that's why I am worried about abrupt climate changes that we can not predict, that's my whole point from the very start
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skeptic1223 at 07:23 AM on 11 May 2015Climate's changed before
@446, that's why I quoted IPCC and GRIDA that abrupt glaciations are possible, volcanic eruptions and solar activity were given just as examples of possible causes that we can not model reliably
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