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apiratelooksat50 at 03:06 AM on 9 February 2012Still Going Down the Up Escalator
Personally, I don't see what all the fuss is about. There are obviously periods of cooling trends (depending on the date range chosen), but overall the trend is rising (since the start date chosen). Skeptic or believer, it's as plain as the nose on your face. -
Tom Curtis at 02:57 AM on 9 February 2012Medieval Warm Period was warmer
jzk 54, a comparison between a single decade and several centuries is far from ideal. There is, however, some justification for it in this instance. In particular, very solid evidence suggests that this will be the coolest decade of the next several centuries. (How many depends on just how soon we break the fossil fuel habit.) That being the case, we know that the average global temperature over the next few centuries will be higher than that for the current decade, and hence higher also than the average over the several centuries of the MWP. In other words, the comparison does strongly suggest that the current warming will result in greater overall warmth in this century than at anytime in the MWP. Of course, it is not appropriate to look at a decade to century comparison and conclude that this decade is warmer than any decade in the MWP. However, a large number of studies have been done which suggest exactly that. It is more likely than not, on current evidence that this decade, and even the 1990s was warmer than any decade in the MWP. However, the evidence for that is not so strong that it can be stated categorically. -
dana1981 at 02:52 AM on 9 February 2012Volcanic Influence on the Little Ice Age
Yes, the Maunder Minimum would have effectively amplified the volcano and feedback-caused cooling, if this theory is correct. However, the notion that we're just 'recovering' from the LIA is faulty, because we're currently warming much faster than the MWP warming or LIA cooling, and volcanoes and solar activity have had little influence over that warming, especially over the past ~50 years, as we showed here. -
jzk at 02:48 AM on 9 February 2012Medieval Warm Period was warmer
Rob, Let me put this another way. I could take Mann's data from the MWP and produce that global chart based on 950 to 1250. Then I could produce another chart with the same data, but only 980-990. Then, I could put them next to each other. One would be all red, and the other would be all white. Could I make the claim "The MWP was warmer than the MWP?" How is that a helpful comparison? Again, none of what I say contradicts the premise that the MWP was cooler than today, just the way that the charts are used to illustrate that position. -
MangoChutney at 02:46 AM on 9 February 2012Volcanic Influence on the Little Ice Age
@muoncounter #11 If volcanic eruptions were the start of the LIA, as has been suggested, wouldn't the Maunder Minimum, which occurred midway through the LIA, just have exasperated the cold period started by erupting volcanoes? -
Dikran Marsupial at 02:34 AM on 9 February 2012Global Warming: Trend and Variation
Tom & CBDunkerson - great minds think alike! ;o) As I said, sea level observations are not my forte, but even I knew that station data are not a reliable indicator of global sea level when taken in isolation and that there were good reasons for this. I also knew that Google Scholar is a handy way of investigating whether an argument has some merit to it before I use it. -
CBDunkerson at 02:29 AM on 9 February 2012Global Warming: Trend and Variation
Disclaimer: Tom Curtis and I are not, in fact, sharing the same brain. Any similarities between our postings, choice of papers to cite, and/or wording (e.g. 'random conspiracy blog' / 'random internet guy') are purely coincidental. -
Tom Curtis at 02:11 AM on 9 February 2012Global Warming: Trend and Variation
Dikran Marsupial, Captain Ross's benchmark at Port Arthur was examined by Pugh et al, 2002. Based on that, they conclude that sea level at Port Arthur has risen 0.13 meters in the interval, or 0.8 mm per year. Fred Staples want to ignore the peer reviewed literature because some random internet guy says he should. As I understand it, here at SkS "some random internet guy" is not considered an authority. That being the case, it is up to Staples to both present the information from Pugh et al (without cherry picking), and to show why Pugh et al's conclusion is wrong. As it stands, Staples has not bothered to do that, and does not even bother reporting accurately the random internet guy who is his source. Specifically, as quoted by John Daly,""My principal object in visiting Port Arthur was to afford a comparison of our standard barometer with that which had been employed for several years by Mr. Lempriere, the Deputy Assistant Commissary General, in accordance with my instructions, and also to establish a permanent mark at the zero point, or general mean level of the sea as determined by the tidal observations which Mr. Lempriere had conducted with perseverance and exactness for some time: by which means any secular variation in the relative level of the land and sea, which is known to occur on some coasts, might at any future period be detected, and its amount determined. The point chosen for this purpose was the perpendicular cliff of the small islet off Point Puer, which, being near to the tide register, rendered the operation more simple and exact; the Governor, whom I had accompanied on an official visit to the settlement, gave directions to afford Mr. Lempriere every assistance of labourers he required, to have the mark cut deeply in the rock in the exact spot which his tidal observations indicated as the mean level of the ocean."
As can be seen, Ross had not reason to believe Port Arthur was particularly stable, and such a belief did not enter into his reasons for placing the benchmark there. As an aside, I suspect his reporting of Einstein is no more accurate than his reporting of Captain Ross. An google search of his quotation shows that Fred Staples is the only person on the internet who quotes it. -
CBDunkerson at 02:03 AM on 9 February 2012Global Warming: Trend and Variation
Or, rather than reading the ramblings of conspiracy theorists on some random blog, we could look at what the peer reviewed scientific literature says about the Capt Ross sea marker in Tasmania; "Observations of sea level at Port Arthur, Tasmania, southeastern Australia, based on a two-year record made in 1841–1842, a three-year record made in 1999–2002, and intermediate observations made in 1875–1905, 1888 and 1972, indicate an average rate of sea level rise, relative to the land, of 0.8 ± 0.2 mm/year over the period 1841 to 2002. When combined with estimates of land uplift, this yields an estimate of average sea level rise due to an increase in the volume of the oceans of 1.0 ± 0.3 mm/year, over the same period." The amount of sea level rise varies across the globe due to effects of gravity, fluid dynamics, land uplift, and other factors. However, given that the volume of water in the oceans is increasing (due to both ice melt and thermal expansion) the long term trend is upwards... everywhere. Including this site in Tasmania. -
Composer99 at 01:53 AM on 9 February 2012Global Warming: Trend and Variation
Fred: Sorry, that's still cherry-picking. Anecdotes from television shows, quotes from famous scientists, and measurements from a single site do not refute the aggregate of tidal gauge and satellite data showing mean global sea level rise is occuring. After all, those are all, by your own standard, observations, and each singly would be enough, by your own standard, to refute a claim that global sea level is not increasing. -
Dikran Marsupial at 01:45 AM on 9 February 2012Global Warming: Trend and Variation
BTW Fred, have you performed a Google scholar search to see if you can find out whether Australia [provides] An Unstable Platform for Tide-Gauge Measurements of Changing Sea Levels or not? If it doesn't provide a stable platform, perhaps that explains why the Tasman sea tide-guages may not give a reliable indicator of global sea levels. -
Dikran Marsupial at 01:36 AM on 9 February 2012Global Warming: Trend and Variation
Fred Staples Einstein was perfectly correct. However the the observation of sea level at one location does not refute the hypothesis that sea levels are rising or that AGW is occuring. To see why, you need to look into both the observations and the physics in more detail. Firstly not every location is a good place to cite a tide guage, because there are other factors that affect the measurements, such as glacial rebound, silting, tectonic movements etc. Also sea level does not rise uniformly around the globe (water is a viscous liquid, the distances involved are large and evaporation is not the same everywhere), so you need to take an average over multiple tide guages, preferably ones located in geologically stable locations. Which is what the scientists actually do. Was Captain Ross a geologist? Did Captain Ross have the scientific understanding of sea level that we have now? No. He was right about taking the measurements, they are indeed interesting and useful, but that doesn't mean you can ignore the wider context. If it was O.K. to pick a single data record and base your argument solely on that, why shouldn't I pick temperatures at some high Arctic station to show that global temperatures were rising very sharply? Simply because it would be a cherry pick, and would be neglecting the broader picture. What is sauce for the goose is sauce for the gander. What you are doing is equally unreasonable. The difference is that I know it is a cherry pick and wouldn't use it as the basis for a serious argument. -
Fred Staples at 01:23 AM on 9 February 2012Global Warming: Trend and Variation
Cherry Picking? As Einstein said, “10000 observations may support a theory, it only takes one to refute it”. Science works like that. After all, the millions of stars seem set in their courses. Navigators use them every day. The earth is clearly at the centre of the universe and every thing revolves around us. Would you let a few wandering planets, and some indistinct moons, refute so well established a theory? Captain Ross marked that sea level because it was the most stable land he knew with the least tidal rise and fall. He thought future generations would be interested. Now you have a theory that human CO2 emissions will cause dangerous sea level rises. If you wish to retain that theory, you are required to explain why it has not happened in the Tasman Sea. While you are about it, you can explain the Comment from the President of the Maldives Federation on the Today programme a year or so ago. He was complaining that his entire country would be inundated if CO2 emissions continued to rise. John Humphreys asked how much the sea levels had risen so far he replied, “about a centimetre”. -
muoncounter at 00:25 AM on 9 February 2012Volcanic Influence on the Little Ice Age
Mango#9: No and no. It's still not established that the LIA was caused by volcanic eruption - especially if no one can point to which volcano erupted at what time. Nor can we suddenly leave out the Maunder minimum entirely. As for 'we could cancel the LIA,' what do you mean? The very existence of the LIA, whatever its causes, shows there is not just one long warming. Even if that were so, why would the modern warming be at a more rapid pace? -
CBDunkerson at 00:16 AM on 9 February 2012Volcanic Influence on the Little Ice Age
owl905, I don't know if we are having some sort of semantic breakdown or if you really believe things to be exactly the opposite of my understanding. The Miller 2012 paper absolutely does suggest that volcanic eruptions caused cooling, which in turn was amplified by climate feedbacks, which resulted in the centuries of cooler temperatures generally known as the LIA. I mean, the bloody title of the paper is, "Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks". If you disagree with the above then you are going to need to explain what you think the Miller paper is about. If you don't have some radically different understanding of the paper then you must somehow be reading my original post to mean something other than what I said above. At which point I'd suggest that, as a general principal, it would be wise to consider all possible meanings of words and phrases you read and then not assume that interpretations which conflict with reality were the ones intended. -
jzk at 23:49 PM on 8 February 2012Medieval Warm Period was warmer
Rob, I refer only to the two chart chosen by Skeptical Science to contrast todays warming with the MWP. The Mann chart shows a several hundred year period that includes, according to his data, both years of warming and years of cooling. The Skeptical Science chart shows only a decade at a warming peak. It is it any wonder one shows "red" and the other not? It may very well be that the MWP was cooler than today, or not. Let the science show us that. -
MangoChutney at 23:23 PM on 8 February 2012Volcanic Influence on the Little Ice Age
If the LIA was caused by erupting volcanoes and we could cancel out the LIA, is possible that the current warming is just one long continuation of the Medieval Warming Period, Roman Warming Period, all the way back to ..... ? -
Tristan at 22:48 PM on 8 February 2012Still Going Down the Up Escalator
Interesting! BTW DM, is your identity 'outed', or was it something you never bothered to hide?Response:[DB] As a general note, when an individual uses a "nom de plume" rather than their actual name, that decision is to be respected. Period. This is irregardless of whether or not other indiviuals behave less respectfully and then "out" that individual. I'm sure that you'd agree that sharing of personal, privileged data without the express consent of the source of that information is wrong.
Please treat it no differently than the acquisition of stolen (intellectual) property.
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Dikran Marsupial at 21:54 PM on 8 February 2012Still Going Down the Up Escalator
In case anyone is interested, I tried recomputing the credible interval on the regression taking into account the stated uncertainties in the estimates of GMST provided by BEST (I didn't use the last two values due to the lack of coverage of the stations used). Here again is the Bayesian regression analysis using the estimates themselves:
Here is the Bayesian regression analysis taking into account the uncertainty in the BEST estimates.
As I suspected, the 90% credible interval is a little wider, but the difference is barely detectable, which suggests Brigg's criticism of the handling of uncertainty is not much of a cause for concern.
The expected trend for the BEST estimates is 0.0257 (95% credible interval 0.0048 to 0.0464) and when the uncertainties in the estimates are accounted for it becomes 0.0255 (95% credible interval 0.0026 0.0486). Note that the credible interval does not include zero or negative values whether the uncertainty is accounted for or not.
Technical note: The Bayesian regression is performed by sampling from the posterior distribution of regression parameters (including the variance of the noise process). To incorporate the uncertainty in the estimates, I just sampled from the distribution of the responses assuming that the BEST estimate is the mean and the stated uncertainty is the standard deviation (RATS, reading the documentation it is the 95% confidence interval, so it is actually twice the standard deviation, so my analysis overstates the uncertainty by a factor of two - and it still doesn't make much difference!).
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Rob Painting at 19:51 PM on 8 February 2012Medieval Warm Period was warmer
And as if to complicate the situation once again - Last Millennium Climate and Its Variability in CCSM4 - Landrum (2011) suggest something else again. -
Ari Jokimäki at 19:47 PM on 8 February 2012New research from last week 5/2012
One difference with Younger Dryas seems to be that Younger Dryas event might not have occurred globally at the same time (Antarctica seemed to be warming when Northern Hemisphere cooled). -
Doug Mackie at 18:57 PM on 8 February 2012Major Study of Ocean Acidification Helps Scientists Evaluate Effects of Atmospheric Carbon Dioxide on Marine Life
Not quite William. Buffering describes the process by which additions of acid and/or base cause minimal pH changes to a solution (compared to if the acid and/or base had been added to an unbuffered solution).* When oceanographers refer to alkalinity** they mean the acid neutralising capacity of the water with respect to pure carbonic acid (H2CO3). That is, you use H2CO3 as your base unit. It is sort of like currency trading and referencing everything to the $US. Seawater is not usually thought of as a multi-buffered system. Yes, there are other things that function as buffers but they present at low levels and generally poorer buffers; buffering is thus dominated by the carbonate system.*** As for measuring alkalinity, it doesn't really matter what you measure: As we detailed in our OA series (see the button, left side, main page) the CO2 system can be fully described (i.e. calculated) from any two of pH, total alkalinity (AT), pCO2, and total dissolved carbon dioxide (CT). Researchers thus can freely convert between any of those parameters. It comes down to the particular apparatus used. For example, AT and CT are easily measured with good precision and good accuracy but require discrete samples – as opposed to continuous measurement like using a pH electrode. (See the OA series for more on this). *The mechanism by which this is achieved is really cool and we'd be dead without our carbonate buffered blood. The details are senior high school chemistry and if there is sufficient interest I will write up a post about it and try simplifying. **There are several shades of 'alkalinity', including 'total alkalinity'. In the interest of brevity, I am going to concatenate them all here but in later posts I will be more precise. ***Details of this are enchantingly subtle and complex. Read the OA series and come back with questions. -
owl905 at 18:18 PM on 8 February 2012Volcanic Influence on the Little Ice Age
@KR-No idea what your response is about - dropped years is years without rings = missing rings (Mann even uses the term p.3). Your statement about tree-line is straight off both RealClimate and the Mann paper. Dana introduced the Mann paper, so it is part of this thread. And no, it's not "quite frankly unrelated". Both papers focus on different aspects of the forcing effect and timing of volcanic events. Miller's case is boosted if Mann's suggestion of a stronger forcing effect is true. As for the "language you seemed concerned about", no again. It's Mann that's putting up the warning flags not too leap too far too fast with the suggestion. Part of Mann's requirement is to find other tree-types in the same region as controls. -
Bernard J. at 18:13 PM on 8 February 2012Hiding the Incline in Sea Level
...that it would have... -
GillianB at 17:16 PM on 8 February 2012Global Sea Level Rise: Pothole To Speed Bump?
Thanks for this. I didn't realise that sea levels would vary with El Nino and La Nina. It makes sense. -
Rob Painting at 16:31 PM on 8 February 2012NASA scientists expect more rapid global warming in the very near future (part 2)
Muon - here's a couple of papers: Response of global upper ocean temperature to changing solar irradiance - White 1997. Who state: "For penetration depths of 80-160 m(etres) observed in this study, back radiation anomalies come into balance with solar insolation anomalies over equilibration timescales of approximately 1.5-3 years, yielding model phase lags of 40°-75° that are similar to those observed"
And:
Temperature responses to spectral solar variability on decadal time scales - Cahalan (2010). Whom write:
"We find surface atmospheric response ∼1 K, about twice as large as the mixed layer response. The surface air response lags the TSI variation by ∼1 month, while the ocean mixed layer response lags the surface air response by ∼2 years for both in‐phase and out‐of‐phase SSI (spectral solar irradiance) forcings."
No doubt there's a great deal more literature on this, but that's the extent of my search. No real surprise here, scientists from NASA are right about the ocean thermal lag, and people on the internet are wrong.
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chirhophoros at 16:18 PM on 8 February 2012New research from last week 5/2012
A very well assembled compilation - it's great being able to have a look at the papers minus a pay wall. Wrt Lundqvist et al, Does anyone have any idea to what extent the 19 -20 century warming shift resembles or differs from the apparently abrupt termination of the Younger Dryas? CC -
Rob Painting at 15:35 PM on 8 February 2012NASA scientists expect more rapid global warming in the very near future (part 2)
Don 9000 & Pirate - I've received a reply From Dr Hansen, he does not consider that the omission of "implies" changes the meaning of that passage. And as Pirate points out, Dr Hansen is revising the paper anyway. -
Volcanic Influence on the Little Ice Age
owl905 - Mann's paper is about accounting for 'dropped years' from minimal/no growth at marginal tree environs. The trees chosen for tree-ring paleo data are deliberately in marginal regions so that they more clearly show the effects of temperature, rather than fertilizer, local bear populations, insect infestations, etc. In other words, the Mann paper is about improving the time accuracy of tree-ring data. The Miller et al paper discussed in this thread, on the other hand, is about considering an ocean circulation tipping point caused by a series of strong volcanic eruptions, leading to the LIA period lasting hundreds of years. That's a different question entirely, and quite frankly (aside from year-resolution of tree-ring data) unrelated. Identifying the volcano(s) would be very interesting, although they did not show much data for that other than the near-equatorial location due to both hemispheres being affected. The Mann paper is quite interesting - and the language you seem concerned about (your "...warning flag" comment) is entirely reasonable for an initial effort that should be followed up with additional work. -
muoncounter at 13:59 PM on 8 February 2012Volcanic Influence on the Little Ice Age
Here is a large eruption database, from a comment by David Benson on the RC thread. There's only one VEI 6 volcano (Krakatoa class) in the 13th century. -
barry at 13:57 PM on 8 February 2012Global Sea Level Rise: Pothole To Speed Bump?
Steve, a 5 meter rise by 2100 is a worst case potential discussed in the paper. Uncertainties and negative feedbacks that mitigate against this potential are clearly discussed by Hansen and Sato. The graph is a simple model of an ice-sheet loss doubling regime derived from paleo-records, and is not meant to represent an actual scenario for the year-by-year rate of sea level rise acceleration (Hansen says this explicitly in the 2007 paper the graph is modelled from). As mentioned above, the more likely realization of such a potential would come with short periods of massive inundations rather than a smooth rate increase. Hansen is not saying that he believes the 5 meter rise by 2100 is the likeliest outcome, just that it is not implausible and shouldn't be discounted. His general theme in this and other papers is that the official projections, like those in the IPCC, are too conservative presenting upper bounds. And even though we should be wary of focussing on short-term data, as you have done, it's worth pointing out that global sea level rise (and Arctic sea-ice decline) have so far been underestimated by the IPCC. Hansen may have a point; and he is aware of the limits of and arguments against his thesis, and has called for more study to test it. Whether consciously or not, you have misrepresented his argument here. Here's the monograph underpinning the graph that's got your attention: Hansen (2007): Scientific reticence and sea level rise Read the whole thing for comprehension and context. It's not long. -
muoncounter at 13:53 PM on 8 February 2012Volcanic Influence on the Little Ice Age
It's troubling that neither the Miller (paper discussed here) nor Gao et al 2008 say which volcano was the likely source of these eruptions. Statements like Miller's "two of the most volcanically perturbed half centuries of the past millennium" are too vague even for geologists. Emile-Geay et al 2006 suggest that ... a tropical location is likely, given the worldwide presence of the ashes and simultaneous presence of its signal in ice cores from both poles. El Chicon is possible. However, Timmreck et al 2008 found that this eruption, wherever it was located, wasn't much of a cooler-offer: The large AD 1258 eruption had a stratospheric sulfate load approximately ten times greater than the 1991 Pinatubo eruption. Yet surface cooling was not substantially larger than for Pinatubo (∼0.4 K). Incredibly, Miller does not cite either of these papers, which are clearly relevant. Another relevant source is Environmental History resource page on the impacts of volcanoes on European climate history. Mention is made of severe climate change during the mid 6th century "dust veil event," but nothing about 1258. -
owl905 at 13:29 PM on 8 February 2012Volcanic Influence on the Little Ice Age
@CBDunerson - the paper's thesis in no way suggests the volcanic effects lingered for centuries. Nor does it in any suggest that the long-term effect was "self-sustaining". There is an event co-incidence of volcanic activity, aerosols, and a temperature drop in the Alantic northern border. The LIA was global, long-term, and uneven in its onset. And the recap notes that the timeframe is not only localized, but earlier than usual dates associated with onset. A problem with the paper is identifying the volcano. It isn't huge (the 1258 super-eruption is still unsolved). But if the source is actually close to the coast of Iceland, the grouping of proxies could limit bigger implications. @Dana - that Mann link is a subtle game-changer. He forwards a very tentative case for missing rings, ... the disclaimers Mann himself puts into the article is a warning flag. -
Norman at 13:14 PM on 8 February 2012Global Sea Level Rise: Pothole To Speed Bump?
Forgot to include a link to the Ari Jokimaki article found using the Search option. Ari Jokimaki article I used. -
Norman at 13:12 PM on 8 February 2012Global Sea Level Rise: Pothole To Speed Bump?
DB @ 40, I followed your instructions to use the Search function to look for more current information on deep sea heat content. Here is what I found. Ari Jokimaki: "From 1993 to 2008 the warming of the upper 700 m of the global ocean has been reported as equivalent to a heat flux of 0.64 (±0.11) W m–2 applied over the Earth’s surface area (Lyman et al. 2010). Here, we showed the heat uptake by AABW contributes about another 0.10 W m–2 to the global heat budget. Thus, including the global abyssal ocean and deep Southern Ocean in the global ocean heat uptake budget could increase the estimated upper ocean heat uptake over the last decade or so by roughly 16%." The "could" is important. Also in the same article by Ari: "The warming below 4000 m is found to contribute 0.027 (±0.009) W m–2. The Southern Ocean between 1000–4000 m contributes an additional 0.068 (±0.062) W m–2, for a total of 0.095 (±0.062) W m–1 to the global heat budget (Table 1)." Look at the range of error so the total could be as small as 0.033 or as large as 0.157. Of the 0.64 heat flux in the 0-700 meter section of the oceans the deep ocean may contribute as little as 5% or as much as 25% more. It seems the method of determining the deep ocean heat content is not so well established and remains in the very high error bar range of possibilities. More research will need to be done before any declarative statements can be made about total ocean heat content. The graph you posted in #4 showing the ocean heat content may approach this value or again it is just as possible it may be much less and closer to the total energy found in the first 2000 meters of ocean water (which has much smaller error bars). -
muoncounter at 12:52 PM on 8 February 2012New research from last week 5/2012
Global cloud height decreased between 2000 and 2010 I like this one a lot: ... a decrease in global effective cloud height over the decade from March 2000 to February 2010 Yet this was a decade of record high cosmic ray flux. More GCRs makes clouds decrease in height? Have to bury this paper under a flurry of obfuscation: In the same vein as The Escalator, down means up and up means down. -
pbjamm at 12:17 PM on 8 February 2012Examples of Monckton contradicting his scientific sources
Peter Hadfield's (aka potholer54)response to Monckton has been posted up on WUWT. Good dismantling of Monckton. Read the comments section only if you have a strong stomach. -
Rob Painting at 11:41 AM on 8 February 2012Medieval Warm Period was warmer
jzk - yes it would be neat if we had a whole bunch of global proxy data with sufficient resolution (detail), say at the annual (yearly) scale, but AFAIK there's not a great deal - and we know how worked up the fake-skeptics get about the tree-ring data. You just have to work with what you have. The real dagger to the heart of the MWP (to my mind) is the global circulations. Mann's reconstruction agrees very well with how we expect the circulations, and their teleconnections to operate. Not perfectly of course, but a warm MWP wouldn't agree at all. For instance ENSO (La Nina/El Nino) was weaker (lower amplitude) then, and the natural oscillation in ENSO was longer (around 80 years?). This is consistent with a cooler tropical Pacific than today. Additionally, the Amazon rainforest was wet - consistent with a more southward displacement of the ITCZ (inter tropical convergence zone) than exists today. Again suggesting a cooler global climate back in medieval times. -
scaddenp at 10:32 AM on 8 February 2012We're heading into an ice age
"The degree" varies wildly however. You can predict sunrise etc with very high degree of accuracy. You can also predict the changes in insolation due to the Milankovitch cycles which drive the ice cycle with a very high degree of accuracy, but climatic effect of that change also depends on other factors - especially level of GHGs. On the other hand, volcanoes are unpredictable with no known physical basis to a "cycle". A statistical recurrance period should never be confused with a prediction. Saying we are "long overdue" for an eruption smacks of pop-sci documentaries, and I would be interested if you have a science paper that says that. The basis for saying that there wont be an iceage soon is a/ Berger, A. and Loutre, M. F. (2002) which consider that orbital drivers, and b/ our GHG levels are getting to Pliocene levels - too high for an iceage. -
dana1981 at 10:26 AM on 8 February 2012Volcanic Influence on the Little Ice Age
Mann has a new paper out which discusses volcanic eruptions in the 13th Century too. RealClimate discussion here. -
dorlomin at 10:15 AM on 8 February 2012Volcanic Influence on the Little Ice Age
IIRC that region in Canada has been invoked as a likely key to triggering glacial periods, as snow lies on the Canadian archipelago and around Hudson Bay later during the summer as the summer sun weakens it reinforces the cooling trend allowing Hudson Bay to remain frozen all year round. This allows a very slow southward creep of summer snow which forms the begining of the glaciers. Norwegian Mountains and then the Scottish Highlands also play a role. That is that they are very close to the point where all summer snow can lie with a small amount of cooling. It is possible these volcanos did not cause the little ice age but their impact was enough to allow the build up of cold summers with snow all year round to drop the temperaturtes that was not able to clear fully before a slight drop in solar output refinforced the millenia long dropping solar energy in mid summer at high nothern latitudes. It is far from a done deal with this at the minute but it is a very interesting study and seems to just catch a point where the climate is valnrable to reinforcing changes. -
pingpong2727 at 08:05 AM on 8 February 2012We're heading into an ice age
OK this is stupid, we can predict things, but only to a degree. Apparently we are also long overdue for a super volcano eruption under yellow stone park, but it hasnt happened yet. The only thing that we have actually proved right from prediction, is that there is 365 days in a year, not counting leap years, So everyone can calm down, I dont think we will be in an ice age in any time soon. -
jzk at 07:29 AM on 8 February 2012Medieval Warm Period was warmer
Comparing 1999 - 2008 to 950 to 1250 is simply not a fair comparison. According to the Mann data, 1100 - 1250 was colder than average. (See his data set A for NH mean). How is that a relevant comparison? No such comparison occurs in Mann's paper. -
william at 07:01 AM on 8 February 2012Global Sea Level Rise: Pothole To Speed Bump?
If the Arctic ocean becomes ice free, we may see some real acceleration in sea level rise. A giant solar collector (the open Arctic ocean) beside a large block of ice (Greenland) may see a coupling of warm air rising from the collector to be sucked down by katababic cooling over the ice block. Basically a Foen Wind over a very large glacier. When a Foen wind hits ice, all the energy is concentrated right at the ice surface and is being imported from somewhere else, unlike solar radiation which can only supply so much energy per given area. -
CBDunkerson at 06:01 AM on 8 February 2012Volcanic Influence on the Little Ice Age
This theory that effects of the volcanic eruptions lingered for centuries after the events themselves seems like a new sort of 'tipping point' argument. That is, volcanic aerosols usually fall out of the atmosphere within a few years and have no significant long term effects... but this study is suggesting that a large enough set of volcanic events could introduce sudden sharp cooling which then becomes self-sustaining for hundreds of years. If that eventually proves out it would indicate that there are some major climate feedbacks that can be triggered on very short timescales... Arctic ice and ocean circulation for the study in question. There has long been concern about potential tipping points in these same areas with the gradual GHG warming we have been seeing, but this suggests it is possible that an otherwise temporary warming spike (e.g. El Nino) could result in a similar self-sustaining change. -
Michael Whittemore at 05:38 AM on 8 February 2012Public talk: Global Warming - The Full Picture
Tom Curtis @25 I have finial found the right information, it would seem they are still debating the actual compensation scheme but due to caps on the amount the carbon tax can increase by and the some what "predictable" Internationale price of carbon will be, they have concluded that "Tax cuts will increase over time with a second round of tax cuts in 2015-16 that will further raise the tax-free threshold to $19,400, matching the impact of the carbon price to 2020." (http://www.cleanenergyfuture.gov.au/clean-energy-future/securing-a-clean-energy-future/#content05) It looks like I was wrong, John Cook was right to explain that compensation will cover most of the costs. -
andylee at 05:19 AM on 8 February 2012Global Sea Level Rise: Pothole To Speed Bump?
Time is an enabler for change, for without it nothing can change. Time simply allows processes to take their course, not cause them. -
muoncounter at 05:18 AM on 8 February 2012NASA scientists expect more rapid global warming in the very near future (part 2)
RP#50: Maybe Scafetta and West 2005: The climate sensitivity to the 22-year cycle, Z8, is approximately 1.5 times stronger than the climate sensitivity to the 11-year cycle, Z7, and, on average, the 22-year climate response lags Hale solar cycles by approximately 2.2 ± 2 years. These effects are predicted by theoretical energy balance models. In fact, the actual climate response to cyclical forcing is stronger at lower frequencies because the damping effect of the ocean inertia is weaker at lower frequencies. They show a relatively poor quality graph (their Fig. 4) illustrating this lag. 2.2+/- 2 years seems like very high uncertainty; 18 months is well within that window. The 'damping effect' statement makes sense, but could be more clearly stated: ocean thermal inertia reduces climate response to short-term drivers. If the response to a 22 year cycle is much greater than the response to an 11 year cycle, such short period events like ENSO cannot be causes for climate change. The gradual buildup of GHGs, on the other hand, is a long period driver. -
Michael Whittemore at 04:35 AM on 8 February 2012Public talk: Global Warming - The Full Picture
Tom Curtis @25 Of course you say, I would like a link to that fact? -
Rob Painting at 04:34 AM on 8 February 2012NASA scientists expect more rapid global warming in the very near future (part 2)
Muon @ 48 - the peer-reviewed literature doesn't make it clear, but these are two separate issues. Firstly, the lag in surface air temperature response to a change in solar irradiance is about a month, but the ocean response is on the order of 18-24 months. Still trying to track down a paper that deals with this issue specifically. It's mentioned in a few papers, but only in passing.
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