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BC at 08:49 AM on 5 May 2012Ocean Heat Content And The Importance Of The Deep Ocean
DSL. Thanks for the links. I'll do some browsing, which may take me a while. I've read much of the first link in your blog on the 2 May post, and the rest look good too. What I'm interested in reconciling for myself are these two facts 1. the large ocean flows can move heat quite effectively on decadal timeframes, as explained in this post 2. CO2 doesn't get mixed quickly in the oceans, despite these flows, and CO2 absorption only happens at century and thousands of years timescales - "mixing of shallow and deep oceanic waters takes place over hundreds to thousands of years" - SKS post 2 May,-"Two centuries of Climate Science". So the oceans don't absorb as much as was expected in the past; hence the atmospheric build up that is occurring -
JimF at 06:21 AM on 5 May 2012Why Are We Sure We're Right? #2
Not being a scientist, my discussions with friends and skeptics here in the US tend to be less clinical and much more philosophical, I think. But I do like to ask them one question: "What would it take to change your mind from being a skeptic to a believer?" Is there a scientific organization, a temperature, a climatic series of events, or anything that will make them consider the reality of AGW? I never get an answer, which leads me to believe that nothing short of a tag on CO2 molecules which says "from car exhaust" will ever change their minds. I tell them that if trusted scientific organizations such as NAS or AGU become skeptics, I will change my mind. Or if my candytufts bloom on Mother's Day like they used to rather than 2 weeks earlier like they have for the past number of years, I will change my mind. But I can't even get them to even consider the question. Which tells me they are VERY sure that they are right. Or even unwilling to consider the alternative. -
DSL at 05:38 AM on 5 May 20122012 SkS Weekly Digest #17
Yah, it's important to remember that Heartland knows quite well that the logic is flawed. They're not actually stupid. They know that even though most people will reject the logic, they'll also carry forward the unconscious association. And now, of course, the internet is blasting that association all over the place, inadvertently serving to further Heartland's interests. Heartland should be characterized as anti-democratic because their stated goal is to increase doubt. The hoaxers will undoubtedly agree that the logic is spot on but that Heartland shouldn't have exposed themselves to the liberal media (this is the WUWT response). -
Composer99 at 05:15 AM on 5 May 20122012 SkS Weekly Digest #17
I'm surprised Monckton didn't make the list of speakers. As for the billboards, the empty, flawed logic behind them is easily exposed and disposed of with the following argument: Heartland Billboard Argument P - The Unabomber (and other undesireable characters) claimed it is important to combat climate change C - Therefore, people who claim it is important to combat climate change are like the Unabomber Analagous Argument P - Hitler owned and loved dogs C - Therefore, people who own and love dogs are like Hitler I'd say the billboard campaign makes it very obvious that the Heartland Institute is indeed engaged in scientific denialism rather than any honest skepticism. If they had a strong case to make using scientific evidence, they'd never have had to resort to such a foolish endeavour to begin with. -
Islander at 04:01 AM on 5 May 2012CO2 lags temperature
If the Milankovitch forcing triggers the beginning (and end) of interglacial periods with the release of CO2 and other greenhouse gasses providing the positive (and negative) amplification, then I think that it is very important to understand why the heating at the beginning of the Holocene ended short of the previous maximum temperature of the previous four interglacial periods. The benign temperature stability of the Holocene is a major factor in the development of civilization which arguably might not have happened at a higher (or lower) temperature. I haven't seen an argument as to why the heating ended prematurely. Can you direct me to relevant research? -
vrooomie at 03:47 AM on 5 May 20122012 SkS Weekly Digest #17
Dikran@5: It may be that, to *us*, but to many who are 'on-the-fence' about the so-called "controversy" (and, in my position as an earth scientist, I see it {snip}, even from colleagues) it may {snip} slow down) efforts to make this critical science issue as effective as they must be, if we're to get any real handle on slowing down the depradation of our planet. I've been to this horse race before, in the automotive industry, and shibbolths and outright lies persist. They *especially* perdsist if not foguth, hard and forcefully, with facts, data, and clear rationale. As scienctists and activists, we have but a few tools at our disposal, and one is {snip}, when they make foolish moves, like HI has done, and undoubtedly will continue to do. As a practicing scientist (trained classicallly, raised in the classical 'rational and dispassionate' scientific bent) to be confrontational towards efforts like HI, Koch Industries, you name it, is a bit crosswise to that training. However, when battling fire...sometimes, as Wag Dodge found out in Montana, in 1949, you *must* use fire to fight it. It can be done non-ad hominem style, but {snip} be done with the full force of factual analysis. So, like BoulderBob in another thread, I'm {snip}Moderator Response: TC: All caps snipped, for compliance with the comments policy. Given the extent of all caps in this post, it would have been much easier to just delete the post. Please read and comply with the comments policy in future posts to avoid that possibility. Thank you. -
pbjamm at 03:15 AM on 5 May 20122012 SkS Weekly Digest #17
Here is the list of speakers: http://climateconference.heartland.org/speakers/ I don't think any comment can be made that would do more damage to the credibility of the Conference than that list does. -
Kevin C at 02:28 AM on 5 May 2012HadSST3: A detailed look
Thanks. While we're at it, I've spotted another detail I forgot to describe to the text. I added an offset of -0.03C to the red line in Figure 3 to highlight the similarity between the change in the adjustments and the change in the final data series. This offset comes from the net change in the mean over the baseline period. Some of the residual differences are presumably also attributable to the new methods, however I don't think that the remaining differences can be isolated using just the published data. -
Bob Tisdale at 02:14 AM on 5 May 2012HadSST3: A detailed look
Kevin C: Kennedy et al (2011) was a two-part paper. You've only provided a link to part 2 at the end of your opening. The first part is here: http://www.metoffice.gov.uk/hadobs/hadsst3/part_1_figinline.pdf -
KR at 02:12 AM on 5 May 20122012 SkS Weekly Digest #17
pbjamm - I would agree; it's the Argument Clinic. This is one of the purest examples of the Argument by Association fallacy I have ever seen. Heartland is shooting itself in the foot with this - I cannot imagine what they thought this would accomplish. I guess this just demonstrates that the 'skeptic' side, the ones arguing that there is no problem, have no factually based arguments left... -
Kevin C at 02:11 AM on 5 May 2012HadSST3: A detailed look
Original introduction:The Hadley centre of the UK Meteorological office has for a number of years maintained a dataset of sea surface temperatures (SSTs), HadSST2, which has formed the basis for estimating global surface temperatures. The HadSST2 dataset was used in the widely quoted HadCRUT3 temperature record, as well as forming the basis for an interpolated record, HadISST, which is used along with ERSST in NASA's GISTEMP record. The source data is the International Comprehensive Ocean Atmosphere Data Set (ICOADS), which includes historical records from many sources.
Updated introduction:The Hadley centre of the UK Meteorological office has for a number of years maintained a dataset of sea surface temperatures (SSTs), HadSST2, which has formed a basis for estimating global surface temperatures. The HadSST2 dataset was used in the widely quoted HadCRUT3 temperature record, as well as providing the in-situ sea surface temperature component of HadISST since 2007. HadISST is used along with Reynold's OISST in NASA's GISTEMP record. The source data are versions of the International Comprehensive Ocean Atmosphere Data Set (ICOADS), which includes historical records from many sources.
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Kevin C at 01:54 AM on 5 May 2012HadSST3: A detailed look
Bob: You certainly know more about the background material than me. I'm new to SST data and have not studied the history, or the other datasets in any depth. I'll check the background and update the post accordingly. As to the rest of the post, it is almost entirely a review of the Kennedy paper, and so should be less dependent on my limited (and flawed) background reading. -
Bob Tisdale at 01:29 AM on 5 May 2012HadSST3: A detailed look
Kevin C writes in the first paragraph of the post, “The HadSST2 dataset was used in the widely quoted HadCRUT3 temperature record, as well as forming the basis for an interpolated record, HadISST, which is used along with ERSST in NASA's GISTEMP record.” Error 1: HADSST2 and HADSST3 are based on different ICOADS datasets. Error 2: HADISST was introduced the 2003 Rayner et al paper “Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century.” http://www.metoffice.gov.uk/hadobs/hadisst/HadISST_paper.pdf HADSST2 was introduced 2 years later in Rayner et al (2005) “Improved Analyses of Changes and Uncertainties in Sea Surface Temperature Measured In Situ since the Mid-Nineteenth Century: The HadSST2 Dataset”. http://www.metoffice.gov.uk/hadobs/hadsst2/rayner_etal_2005.pdf So your claim that HADSST2 formed “the basis for an interpolated record, HadISST” is obviously wrong. Error 3: GISS uses HADISST from January 1880 to November 1981 and NOAA’s Reynolds OI.v2 SST data from Dec 1981 to present, not the NOAA ERSST.v3b data. http://data.giss.nasa.gov/gistemp/sources_v3/gistemp.html Would you like me to read the rest of your post? -
Pete Dunkelberg at 01:25 AM on 5 May 2012Why Are We Sure We're Right? #2
Rob, Dana, Andy, sometimes ordinary language is better than philosophy 101. I hope you're sure that it is unwise to jump off tall buildings, unwise for kids to take up smoking, and unwise for earth's humans to greatly increase the amount of greenhouse gasses blanketing our one planet, and unwise to persist in acidifying the oceans. btw a prominent link to the OA not OK pdf would be nice. It might be added to the little rectangular image as the letters 'pdf'. -
pbjamm at 00:57 AM on 5 May 20122012 SkS Weekly Digest #17
Sadly there are people who believe this stuff. I have argued with them in the past. Through most of it I thought I had chosen the wrong door in the Argument Clinic. -
Pete Dunkelberg at 00:50 AM on 5 May 2012Why Are We Sure We're Right? #2
Lucas Verma @ 1 Mind your words. 3°C is not a rate, it is equilibrium sensitivity. Transient sensitivity is closer to the idea of a rate. -
BoulderBob at 00:45 AM on 5 May 2012Why Are We Sure We're Right? #2
Now, I'm angry: Heartland Billboard CampaignModerator Response: [Dikran Marsupial] Better just to raise ones eyebrows and shake ones head in sadness, at least for the blood-pressure! The weekly digest thread is probably more appropriate for further discussion. -
Daniel Bailey at 00:35 AM on 5 May 2012Richard Alley - We Can Afford Clean Energy
All participants please note: Realist is just another sock puppet of Delmar/Tealy and will be dealt with accordingly. In the meantime, DNFTT and please return to your normal conversational activities. Have a noice day (pun intended). -
DSL at 00:30 AM on 5 May 20122012 SkS Weekly Digest #17
Oh, am I going to have fun with this one across the internets. -
Dikran Marsupial at 00:21 AM on 5 May 20122012 SkS Weekly Digest #17
IMHO they have just scored an own goal. It is so obviously mere rhetoric that anyone with more than half a brain will see it immediately for what it is an will feel vaguely insulted that the HI should think something so lacking in subtlety would fool anybody. Of course it could be ironic humour, but somehow I doubt it. -
pbjamm at 00:12 AM on 5 May 20122012 SkS Weekly Digest #17
Hot sure where else to put this but it is so crazy that it has to be posted. Other readers of Climatecrocks will prob already have seen this. http://climateconference.heartland.org/our-billboards/ "Scientific, political, and public support for the theory of man-made global warming is collapsing. Most scientists and 60 percent of the general public (in the U.S.) do not believe man-made global warming is a problem. (Keep reading for proof of these statements.) The people who still believe in man-made global warming are mostly on the radical fringe of society. This is why the most prominent advocates of global warming aren’t scientists. They are murderers, tyrants, and madmen." We are through the looking glass... -
DSL at 23:55 PM on 4 May 2012Ocean Heat Content And The Importance Of The Deep Ocean
BC, note the "related SkS posts" links at the bottom of the article above. -
DSL at 23:46 PM on 4 May 2012Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965
BC, there are a range of forces working at different speeds and volumes. Go here for a look at the basics of upper ocean mixing. Go here for a very thorough and technical look at mixing in general wrt energy exchange. Go here for a general look at large-scale ocean currents. Here is a SkS article on the subject, and that is where anyone else who replies to BC--and BC--should post. -
Realist at 23:25 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
[snip]Moderator Response: [Dikran Marsupial] Please note that posting comments here at SkS is a privilege, not a right. This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum. Please take the time to review the policy and ensure future comments are in full compliance with it. Thanks for your understanding and compliance in this matter. N.B. Your earlier post (#65) was considered to be inflamatory/offensive by at least one poster (and I can understand the reasons). I didn't delete that post either. Perhaps your time might be better spent considering why your post elicited the response that it did, rather than causing unnecessary work for the moderators. This is my last word on the subject. Except to say that military budgets are now off-topic for this thread, any further posts that mention this will be deleted. -
muoncounter at 23:13 PM on 4 May 2012It cooled mid-century
"Any evidence that aerosol loading from tests and large enough and continuous enough to have a significant effect..." Not much. It takes a yield of at least 50 ktons to make a cloud tall enough to reach the stratosphere. Large yield testing didn't begin until 1952; mid-century cooling started several years prior to that (there's a lag problem). And the USGS shows that it is not dust as much as sulfate aerosol that causes detectable multi-year cooling. About the only significant climate-scale result from nuclear testing is the C14 spike. And that doesn't make a blip in the older cosmic ray records. -
BC at 23:10 PM on 4 May 2012Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965
Can someone explain how on the one hand the oceans' layers don't mix much at all. On the other hand there are the AMOC and La Nina and other ocean flows where the deeper layers come to the surface and vice versa? And these ocean flows have a huge impact on the worlds climate so they seem to be very significant. -
Realist at 22:46 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
[snip]Moderator Response: [Dikran Marsupial] It is the job of the moderators to draw the line where posts are considered to have contravened the comments policy, not yours. Making unnecessary work for the moderators by repeatedly posting moderation complaints is not doing you any favours. Please restart the discussion in more civil manner as I have asked both sides to do. If you feel a post is offensive, then please feel free to say so, but the best thing to do is not to respond in kind and instead prove your case using rational argument. -
CBDunkerson at 21:24 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
#69 "No my point is that some people will always argue the military budget is optional or too big, no matter how small." Umm... you do realize that no one here has made that argument right? I mean, people have pointed that out repeatedly now, but you seem to keep returning to this 'argument' that doesn't actually exist. -
pauls at 19:41 PM on 4 May 2012Lessons from Past Predictions: Hansen 1981
#7 dana1981 - Equilibrium climate sensitivity is usually measured in GCMs by incorporating a 'slab ocean' - i.e. an 'ocean' which is little more than a surface with a low heat capacity. This is done because fully equilibrating a GCM with a realistic model of the ocean can take several centuries to millennia due to thermal inertia, and that means a large computation expense. Point being, representation of oceans can't have much effect on ECS, as traditonally measured. -
John Cook at 19:05 PM on 4 May 2012Lessons from Past Predictions: Hansen 1981
"ancient projection"? 1981 wasn't that long ago, you whipper snapper! :-) -
Realist at 19:01 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
[snip]Moderator Response: [Dikran Marsupial] All concerned need to cool down. Please leave the moderation to the moderators. -
Realist at 17:17 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Phillippe [snip]. Libya, Afghanistan, Bali twin towers etc come to mind You can't wait for a war before forming a military. My reference to France and England was a reference to those saved by previous US budgets (and implied short memories). Scaddenp, you are one of the few who can disagree without resorting to personal insults and name calling which is too common on this site. I won't even bother answering #66. If you are not prepared to say it face to face you shouldnt say it online! No my point is that some people will always argue the military budget is optional or too big, no matter how small. Was probably happening in 1938 too.Moderator Response: [Dikran Marsupial] Inflamatory material snipped. Please can all parties get back to a more civil tone of discussion. -
Philippe Chantreau at 14:36 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Realist @ 65: that comment is underhanded and has nothing to do with the reality of the current geopolitical situation. If your allusion to France, England and Australia is in reference to WWII (which it inevitably is), then relating that to the current idea of "budget" is inappropriate. The circumstances back then (70 years ago) were so completely different as to make any discussion of "budget" misplaced and misleading. There was a world war against a madly destructive ideology. The situation was dire. It was not a matter of working out a budget but of devoting all available resources to the highest priority of the moment. Comparing that to anything happening nowadaysModerator Response: [Dikran Marsupial] Accusation of dishonesty snipped. Please accept my applogies, more was snipped than I had intended. -
scaddenp at 13:13 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Realist, you seem to be missing the point - military budgets show that governments can raise the budgets to combat significant external threats. Climate change is surely one. If averting an asteroid strike required a similar expenditure without the ability to know who was going to take the main punch, do think we could raise the money? Or would the problem be so politically tough that we would take the "adaption" route and hope some other country would take the direct hit? -
Tom Curtis at 13:13 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Fantasist @65 holds cheap the Australian lives spent in support of their ally in Korea, Vietnam, Somalia, Iraq and Afganistan - conflicts in which Australia had (and in the case of Afghanistan, has) no national security interest. He thereby demonstrates not only that his world view is delusional, but that it is offensive as well. -
scaddenp at 13:09 PM on 4 May 2012It cooled mid-century
Hmm, I'm skeptical. Any evidence that aerosol loading from tests and large enough and continuous enough to have a significant effect on aerosol loading compared to industrial emissions? -
Realist at 12:56 PM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Andy I agree. Many countries would not be what they are today without what the US military budget has done for them. Poland, France, England, Australia, Libya to name a few. -
bill4344 at 12:26 PM on 4 May 2012Why Are We Sure We're Right? #2
Typo: Rob 3rd para 'dramaticly'.Moderator Response: [RH] Thanks. -
r.pauli at 11:58 AM on 4 May 2012It cooled mid-century
Between 1944 and 1980 there were more than 1800 nuclear explosions were conducted - many above ground - including the biggest H-bombs. This time period was a mini-nuclear winter. -
Andy Skuce at 11:56 AM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Realist @63 I wasn't actually advocating cutting the military budget, just pointing out that if we can afford spending sums like that protecting one country from possible threats from another, we could perhaps spend a smaller sum to protect everyone from probable harm resulting from everyone else's emissions. If we don't mitigate emissions, I expect that we'll have to increase military budgets to cope with the imbalances that climate change will provoke. The US military actually has a rather sane perspective on climate change, as Peter Sinclair's excellent video shows: US Military Forges Ahead with Climate Security. Deniers Still Looking for WMDs. -
Realist at 11:40 AM on 4 May 2012Richard Alley - We Can Afford Clean Energy
Andy #62 Why stop at cutting the military budget by half? You could also cut the budget of all police forces, justice systems and prisons by half to raise even more funds. -
supak at 10:22 AM on 4 May 2012Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965
@les They have all kinds of markets at Intrade. You can even predict when they'll find the Higgs Boson. But yes, the climate markets are the one market that's money in the bank if you play it right. And they encourage insider trading! @muoncounter This is the data they go by for the monthly and yearly temp anomalies. As I continue betting in the future, the chances of .55s paying off gets higher. -
Bob Loblaw at 09:53 AM on 4 May 2012Lessons from Past Predictions: Hansen 1981
Dan Olner (and dana1981): There is a really big difference between the 1981 and 1988 papers in terms of the type of models. The 1981 paper used a one-dimensional radiative-convective model, which resolves the vertical atmosphere and detailed radiation transfer very well, but has no "geography" - it simulates a global average condition, and the primary output is a single temperature profile. The 1988 paper used a 3-d general circulation model. Completely different beasts. It's not a matter of the 1988 work being a tweaking or adjustment of the 1981 model - it's a major change in the analysis. In 1981, a radiative-convective model (RCM) would have been well-developed, and the success in getting a sensitivity close to today's "best estimate" is [you choose] a) somewhat fortuitous, or b) an indication that even a 1-d model of this type can represent many of the important factors. You don't see much use of RCMs these days, when it comes to trying to narrow down sensitivity - they don't do the things that need to be examined. In 1988, GCMs were still undergoing significant development - as they are today, muchly due to greatly increased computing power. GCMs are hungry beasts, and eat CPU cycles like Chiclets. Everyone on the team likely wants some extra FPU time, and a faster computer will always let you do more stuff that was only a gleam in the eye last year. In 1981, Hansen et al wouldn't have had the horsepower to run a GCM (they did exist) over a time period like they did with the RCM. -
Andy Skuce at 07:46 AM on 4 May 2012Richard Alley - We Can Afford Clean Energy
steve from virginia @45: "Alley's supposition is incorrect because it does not include the economic effect of a successful conversion on competitors." In many big European cities there was a job-intensive industry built around human waste disposal: emptying cess pits, hauling waste out of the city and selling it to farmers for fertilizer. Indeed, there was a lot of opposition to building proper sewage facilities from various vested interests, complacent government and even civil libertarians in the Victorian period. See my post on the Great Stink of London. "We cannot get a grip on our climate, fuel, food, water and other resource problems without acknowledging there will be large trade-offs and sacrifices. We cannot 'have it all'. " I tend to agree. The costs of mitigation are downplayed sometimes and the challenge we face in getting rid of carbon emissions is often made to sound too easy. However, if the world can afford spend 2.6% of its GDP on the military, as it does now, surely it could spend half of that sum instead on fighting climate change. The hardest part is the politics, not the economics or the engineering. -
scaddenp at 06:15 AM on 4 May 2012Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965
Just a further addition, the log relation of concentration to radiative forcing drops straight out of the RTE - see Ramanathan and Coakley 1978. The basic radiative properties of the gases is based on experimental data but going back a long time. I dont have them to hand, but try Weart's excellent Discovery of Global Warming for the historical work. The same equations also predict the spectral signature which can be compared to observed. Eg See Harries 2001. -
dana1981 at 04:09 AM on 4 May 2012Why Are We Sure We're Right? #2
Lucas @1 - surface temperature changes have been consistent with a 3°C equilibrium climate sensitivity. See here, for example. We'll have more on this issue next week as well. -
Dikran Marsupial at 03:13 AM on 4 May 2012There's no empirical evidence
@einhverfr further to what DSL wrote, the source code for several GCMs are in the public domain, so if the journal papers that explain the assumptions are not sufficient, you can always download the code and find out for yourself exactly how they work and test out the sensitivity of the projections to those assumptions by altering them and running some simulations. If you can show something interesting then there is nothing to stop you from submitting a journal paper questioning the assumptions. It is interesting to note there has been no attempt by the skeptics to make a GCM that explains the observed climate without CO2 (they seem to much prefer statistical models). I suspect that there is a good reason for this, which is essentially that it can't be done without making obviously unrealistic assumptions about the physics. -
Lucas Verma at 03:04 AM on 4 May 2012Why Are We Sure We're Right? #2
"the Earth's surface will warm on average approximately 3°C in response to doubled atmospheric CO2." Based on what we know, this seems a reasonable statement, CO2 should reduce emission to space and given observations, around a three degree rise in temperatures should be required to return emission to space to pre CO2 increase levels. But observations of surface temperature change indicate a rate that's about half of the 3 degree rate. We know we are right that CO2 should increase surface temperature, but we don't know how much. -
Tom Curtis at 03:04 AM on 4 May 2012Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965
Jeff18 @14, the constant change in temperature per doubling of CO2 is primarily a consequence of the fact that the radiative forcing of changed CO2 levels is constant per doubling. The direct radiative forcing is known from detailed studies using radiative transfer models, the results of which are directly compared with observations. To get an idea of the accuracy of the models, I suggest you read my post, "Warm Earth, Cold Atmosphere", particularly the sections, "No more hand waving" and " Settled science"; and also my comment 43. The actual temperature response depends on feedbacks, which are not as well known. Therefore they may vary from the equal temperature change per doubling of CO2, but because the change in forcing is constant, they will not vary much, and certainly not enough to make the response near linear. -
shoyemore at 02:57 AM on 4 May 2012New research from last week 17/2012
The Yiou et al paper on the Medieval Climate Anomaly appears to be saying that while temperature dropped in the Little Ice Age, there was not much change in weather apparent. We find that the transition from a Medieval Warm Period to a Little Ice Age in the North Atlantic does not imply changes in patterns or frequency of weather regimes, although the mean surface temperature change is significant. The MCA was 950 to 1250, the LIA 1350 to 1850 - if there was fairly uniform weather for that milennium, it seems to rule out the idea of balmy and mild weather around 1000 influencing historical events like the Norse expansion. Makes sense, since the alleged cold weather around 1600 did little to hinder English and French expansion to North America. Danish missionaries returned to Greenland in the 18th century. But maybe I am readng too much into it?
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