Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings

All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

Recent Comments

Prev  2508  2509  2510  2511  2512  2513  2514  2515  2516  2517  2518  2519  2520  2521  2522  2523  Next

Comments 125751 to 125800:

  1. Hockey sticks, 'unprecedented warming' and past climate change
    In addition to the papers Chris cites in #17 and #34, there is Mann et al.s most recent (Sept 2008) PNAS paper on the proxy reconstructions over the past 2000 years: www.pnas.org/cgi/doi/10.1073/pnas.0805721105, which brings together the work on S hemisphere as well as N. And concludes that the MWP was a variable phenomenum and was at a lower temperature than current. This was indicated as likely by the National Academy of Sciences review in 2006, as well as by the IPPC AR4. NAS reckoned more data was needed, which the paper provides. McKitrick et al. still try to show otherwise (of course) but Mann rebuts their criticism in PNAS 2009.
  2. Predicting future sea level rise
    At first glance, I must say that I don't like fig 3a in the paper, your fig 2, because they dont follow the development up to 2009. (It seems to have been last revised in October). The last years, we have had a trend closer to 2.5 cm/decade, the longer term trend still being ca 3.4 cm/decade. Furthermore, I feel a bit unsure about the modeling in the light of observations from the last 10 years. We may in fact have an accelerating ice cap melting going on with little surface temperature changes.
  3. Predicting future sea level rise
    Riccardo@26 Quite correct. The open question for research is why there is no correspondence between the local and global trend. This is peculiar, since the obvious causes(in particular sinking/rising land) are all carefully measured, and do not explain the difference. A related issue which is important for the long term implications for Holland is the recently re-discovered effect of 'self-gravitaion'. This is not yet included in the KNMI 2006 scenario's, but will be in the 2013 version. Self-gravitation refers to the effect that large ice-sheets on land attract the sea through the force of gravity, leading to a substantial local increase of the sea-level. The surprising implication is that a complete melting of the Greenland ice-sheet would hardly lead to any sea-level increase on the shores of Greenland. The gravitational effect of the Greenland ice sheets is still very noticable in Holland. Model calculations from different researchers are not in agreement yet, but as a rough indication it would probably diminuish the impact on sea levels at the Dutch shore by a factor three. So instead of a rise by 6-7 meters after a complete melt of the Greenland ice-sheet, the increase of the sea level at the Dutch shores would only be 2 meters. On page 15 of the popular publication of the Delft Technical University 'Delft Outlook' 2009-02 (url below) you can find a bit more context about this, in an article primarily about the new GOCE sattelite. http://tinyurl.com/yht6tdj
  4. Hockey sticks, 'unprecedented warming' and past climate change
    "Here you are linking sensitivity and temperature. It's correct, they are by DT=lambda*DF. So the issue is wether the forcing is logarithmic or not. If it is, whenever CO2 concentration happens to double, you'll get 3 °C." I don't see the situation that way. While we can be pretty sure that the forcing is approximately logarithmic at the current levels of CO2, our 3 °C estimate for sensitivity is the estimated mean of an unknown pdf with quite big variance. Furthermore, there is a very long adaptation time, so it can't be safely estimated even 20 years after forcings have changed. Several 'proofs' of low sensitivity are based on such short time observations. The basic, zero-feedback forcing of ca 1.0 °C/doubling of CO2 is usually derived under the assumption of independence from other GHGs - as far as I can see. If we use Chris Colose's http://chriscolose.wordpress.com/2009/10/08/re-visiting-cff/ presentation, we have dT0 = k * ln(2) * lambda_Planck. lambda_Planck is the reciprocal of the partial derivative of Stefan-Boltzmann wrt temperature, with approx numerical value of 0.27, an often used approximation of k is 5.35, and it all multiplies to approximately 1. Different degees of overlap with H2O could influence the sensitivity.
  5. Was there a Medieval Warm Period?
    Given normal climate cycles, how valid is it to compare an estimted (proxie) global average for a three hundred year period to a recent ten year period. There must have been a good number of 10 year periods during the 300 years that varied well outside the average.
  6. Predicting future sea level rise
    neilperth @27: I don't know if we're getting anywhere; you aren't saying very much and you repeat a high proportion of what you have said. Regarding your last question, my answer is "Not necessarily -- it depends on future forcings." Read this: http://www.skepticalscience.com/High-CO2-in-the-past-Part-2.html
  7. Predicting future sea level rise
    Steve @23..... Hey we are getting somewhere in our discussion! So you agree that sea level and temperature changed over time in the absence of anthropogenic forcing and that they will continue to change while humans are here and after humans are extinct. Do you also agree that it is likely that the cyclical ice-ages which have occurred on earth over the last 600 million years will continue to occur in the future ?
    Response: These are fundamental and well established issues. Every climate scientist will agree that:

    1. Temperature has changed naturally in the past (before humans).
    2. As sea level is directly affected by sea level (as established in Vermeer 2009) then sea level has changed naturally in the past

    Do not fall into the logical fallacy that past natural climate change means humans can't influence climate now. On the contrary, past climate change shows us that climate is sensitive to radiative forcing - to energy imbalance. As we are currently imposing an energy imbalance through an enhanced greenhouse effect, past climate change is actually evidence for our climate's sensitivity to CO2.

    Is it likely that cyclical ice ages will occur in the future? In the short term (geologically speaking), the peer reviewed science says no. The radiative forcing from CO2 far outstrips the radiative forcing from orbital changes that initiate cyclical ice-ages. I touch on this tangentially on We're heading into a new Little Ice Age although that page is talking more about the forcing from falling solar levels, not orbital forcing. However, orbital forcing is even less than solar forcing so the argument stands (one of these days I'll do a post specifically focusing on Milankovitch cycles).
  8. It hasn't warmed since 1998
    Tim228, i guess you refer to fig.1. The paper from which it is taken is an observational study, they measured the actual heat content of the oceans. Consequently the latent heat of evaporation of sea water as well as all the other energy related effects are automatically included.
  9. It hasn't warmed since 1998
    I haven't seen reference to the effect of heat of vaporization on the temperature of the oceans. Has this been done and, if so, what were the findings. It seems that since the Heat of Vaporization for water is 3.76 times greater than Heat of Fusion I would expect to see this factored in if melting the ice formations is.
  10. Predicting future sea level rise
    FrankT, i did not doubt that no increase in the rate sea level rise is discernible in the Dutch coastal stations data. I said that it cannot be seen in any case due to noise and that the similarity of the Dutch trend with the global trend is an indication on what to expect. This is an important point because, as i'm sure you know, the local response might be different from the global average; it looks like it is not the case in The Netherland.
  11. It's cooling
    tulkki, regarding lag: Appetizer 1: It’s the sun, but skip down to the section "Ocean Thermal Inertia." Note that there is a ten-year lag from solar increase. Not 50 years. Appetizer 2: It’s the ocean. Main Course: How we know global warming is still happening
  12. Predicting future sea level rise
    As evidenced by our near total inaction on global warming to date; mankind does not do preparatory adaptation well. Added to our psychological short comings is that we really do not know what the seal level rise will be, ignoring changes in dynamic factors or only considering limited factors means that the estimate is likely too low. Ignoring changes to the carbon cycle, it is likely that temperatures will increase 2 or 3 degrees. Paleontological evidence suggests a 6 meter rise over time, but what time? As more evidence is analyzed that time lime seems to be shortening. For example how long have we been looking at a new Sydney Airport? About 40 years. And how far have we gone? Nada. Is there any chance that Sydney Airport will be fully functional past mid century? Don't look at the average elevation look at the low points. Add to average mean sea level: high tide, storm surge waves and wave ramping. Some articles you may find interesting Responding to Changes in Sea Level, Engineering Implications. National Academy Press 1987. (Based on lower slr estimates considers levees a practical solution for airports) http://www.smh.com.au/environment/threats-looming-fast-for-vital-facilities-20091113-iepx.html (I know a newspaper not peer reviewed) The Adaption Myth; Robert Repetto http://environment.research.yale.edu/documents/downloads/v-z/WorkingPaper13.pdf http://www.climatesciencewatch.org/index.php/csw/details/markey-adaptation-hearing/ http://www.swissre.com/resources/387fd3804f928069929e92b3151d9332-ECA_Shaping_Climate_Resilent_Development.pdf (A bit in there spread through the paper) http://www.newscientist.com/article/mg20126965.200-prepare-for-a-climatechanged-world-say-engineers.html (Not so much on SLR) Increasing flood risk and wetland losses due to global sea-level rise: regional and global analyses (1999) And don't forget James Hansen's 5m by 2107 Bradley Opdyke from ANU has some rather pessimistic views on how quickly various parts of the WAIS could collapse
  13. Predicting future sea level rise
    Riccardo@20 Sea level rise is certainly taken serious in Holland. My point was that so far there is no indication locally that there is any increase in the rising of sea levels due to CO2. The Royal Dutch Meteorological Institute (KNMI) published a brochure in 2009 with an update on their 2006 scenario's. On page 20 (blue frame) it is stated (in Dutch): "In the past century the sea level has risen by appr. 20 cm. and there has been no clear local acceleration in the past decennia. On a global level there are indications for an acceleration in the rise of sea levels". http://www.knmi.nl/klimaatscenarios/documents/brochure09.pdf
  14. It's cooling
    Hello, this is my first comment on this page. My question: Wouldn't it be possible that the heat contet of oceans rise even after radiative forcing has stopped changing? I would assume that the "response time" of oceans to global warming is much longer than that of the atmosphere because of the drastic differences in their heat capacities.
  15. Models are unreliable
    Thanks Tom I will a
  16. Models are unreliable
    Allrooney, see also Tamino's demonstration that only the fine-tuning of predictions requires "fancy computer models."
  17. Models are unreliable
    Allyrooney, saying that "modeling is the main evidence cited by the IPCC" is like saying "epidemiological models are the main evidence for the germ theory of disease." The true root and bulk of the evidence is basic physics, with details added in the form of progressively more advanced physics. But the media and public have gotten the misimpression that (a) scientists are merely guessing that human-produced greenhouse gasses are responsible for the portion of warming that scientists' models can't otherwise predict; and (b) there might be no unusual temperature rise needing to be explained, because the temperature hockey stick graph might be wrong. You will save yourself a lot of time and frustration if you read a quick overview of the wide range of evidence from cce's The Global Warming Debate. (Be patient, his server is slow, and sometimes gets completely bogged down; try again later). Then get a quick history from Spencer Weart's The Discovery of Global Warming; his summary Introduction is nicely short, but the rest of his site is quite rich. If you want to continue reading background material after that foundation, look at the Start Here section on RealClimate, which has links to materials categorized by level of technical background required. But if instead you then want to pursue pointed questions, this SkepticalScience site is a great place to turn next. Note there are two types of posts here: the concise Skeptic Arguments linked at the top left of the page (click "View All Arguments"), and the longer "Posts."
  18. Predicting future sea level rise
    neilperth @20 -- your points are not substantial, then. 1. Yup, sea level and temperature changed over time in the absence of anthropogenic forcing. 2. Yup, they will continue to change while humans are here and after humans are extinct. In the meantime, however, it's worth pointing out that temperatures and sea levels will rise (probably accelerating for the latter) into the foreseeable future because of anthropogenic CO2 (and human choices will influence the rate of that rise). All else being equal, if anthropogenic influences on climate were removed, these rises into the foreseeable future would not occur.
  19. Predicting future sea level rise
    The only long term record i know of in the Netherland is Amsterdam (untill 1932 when it was separated from the sea). It shows a very slow increase of about 1.5 cm/century up to the second half of '800. Then, using also other coastal tide gauges, it started rising at about 17 cm/century up to today. It is quite similar to the world average during the same period. This points to a sea level rise along the Dutch coast similar to the world average, even if the noisier local record still cannot detect it. Indeed, as far as i know the Dutch have taken really seriously the threat posed to their country by sea level rise.
  20. Models are unreliable
    I'm a medical doctor with no climatology experience beyond a recent lay interest. I've got some grounding in research and am doing an MD (a UK higher medical research degree) and a Cochrane review of a medical topic. I'm trying to bring these transferable skills to bear in helping me make my own mind up about anthropogenic global warming. I was concerned to hear our Prime Minister (no less) publicly dismiss those who question the scientific orthodoxy as "flat-earthers". My reading of this whole article (and sources referenced in the few balanced websites I can find - apart from this one, climatechangefacts.com and sourcewatch.org are good) is that the modeling can be criticised enough to plant 'reasonable doubt' regarding future projections. I think that this is a strong argument against AGW; correspondingly it requires a strong refutation. I don't think this article and thread has achieved this. Regarding global temperature data, the very simple point I'd like to make is that Hansen (2006), whose results you cite as the main defence of model prediction, themselves state that "a 17-year period is too brief for precise assessment of model predictions [because of inherent uncertainty within the model]". They continue, "close agreement of observed temperature changes with simulations [for scenario B] is accidental given the large unforced variability in the real world". I think this is appropriate scientific caution and does not necessarily disprove the model - yet this sense of balance is missing from your headline response to skeptics: "[climate models] have successfully predicted future climate change". I also note that the point at which scenarios A and B divide (ie discriminate between predictions) has not yet occurred, or is occurring now. Overall I would say the Hansen data is not irrefutable evidence that models work. Incidentally Hansen 2006 also suggest that the volcanic eruption estimated for the 1990s, (which you single out for special mention) was 'sprinkled' there - my reading of the paper is that the authors simply dispersed three eruptions across a 50-year period. Certainly any suggestion that the eruption was a spectacular success of the general climate model would seem to be misleading. I'm not sure that was your intention. This is very important because as I understand it modeling is the main evidence cited by the IPCC, which in turn is driving the current political process. If they are inaccurate (as, intuitively, they may well be if they do not include unknown forcing) then predictions are scientifically meaningless. As I say, the fit of the Hansen model is described, at best, as tentative by the authors themselves. I don't believe it's constructive to label critical questioning and rational scepticism as "denial", being "full of junk" or "spouting rubbish" as one blogger has done in this thread. I would also caution against automatically rejecting any article that is not peer reviewed. Peer review is also flawed; it is often not double-blind and therefore can be biased, and because peer-reviewed journals are extremely competitive, articles in them may tend to be those based on well-funded research; funding often following political agendas (and then there is the separate problem of publication bias). The source is simply something that must be weighed along with everything else. al
  21. Predicting future sea level rise
    "Meanwhile, we cannot detect climate change on the Dutch coast" is the heading (in Dutch) of a summary of a presentation given in March 2009 by one of Holland's main government advisors on sea-level (Douwe Dillingh), who works for Deltares (www.deltares.nl), the main Dutch research institute for everything related to water technologies. The graph on the link below shows an essential linear trend of appr. 15cm / century increase of sea-level from 1900 to today. The text asserts that this linear trend started earlier, and can be dated to at least 1800. In Dillingh's opinion the 30cm/century measured by sattelites is no reason to conclude that there is an increase in sea-level rise, since the measurement methods are too different (sattelite vs. tidal gauge locally). Bottomline: on the Dutch coast the sea level does rise, but exactly as it has been doing for the past 200 years. No sign yet of any increase due to CO2 based global warming. Of course, this is a local situation, and one can think up all sort of hypothesis why this is just a local peculiarity, if it is. The link is: http://www.waterforum.net/index.asp?url=/template_a1.asp&que=paginanr=6609 The website 'waterforum' is a news site for Dutch professionals involved in water management.
  22. Predicting future sea level rise
    Steve L, Pico. My points in relation to sea level changes and, by inference temperature changes, were that : 1- These change markedly over time due to natural causes. 2. Over time sea levels and temperature will rise and fall whether man-kind is on this planet or not. So I ask : do you consider statement 1 true or false? do you consider statement 2 true or false?
  23. Predicting future sea level rise
    neilperth: By your logic, given that people sometimes die in car accidents even when everyone is being responsible, it is therefore perfectly OK for drivers to get blind drunk and career around ignoring the speed limit. People will inevitable die either way right, so why be careful?
  24. Predicting future sea level rise
    neilperth @17 -- what's your point? People can die of natural causes, species can go extinct from natural causes, terrible living conditions can result from natural causes.... Therefore? neilperth @6 -- when did humanity make the biggest strides? Was it during the big swings in global climate and sea level or was it during the period of relative stability?
  25. Predicting future sea level rise
    It is a fact that sea levels can rise and fall over 100 metres due to NATURAL causes. This has happened in the past and no doubt will happen again in the future. If the sea level rises say only 5 metres over the next 1000 years, obviously this will cause problems for low-lying areas of the world. But the world was never designed to be optimal for human habitation. If you buy a house near the coast, you should be aware that over time there is the possibility that it will be flooded by the sea. If you buy a house in a city located on top of a Benioff Zone ( eg Seattle, Vanouver ), you should be aware that it may be destroyed by an earthquake. Of course people living in say Bangladesh have little option but to live in low-lying coasstal areas. But over time sea levels will rise and fall whether man-kind is on this planet or not.
  26. Predicting future sea level rise
    jliungman, i think it's a success of this site if people like you come asking questions, read the papers and solve by themselves.
  27. Predicting future sea level rise
    Sorry, now that I actually read the paper I see that the authors do address my point: "In addition, highly nonlinear responses of ice flow may become increasingly important during the 21st century. These are likely to make our linear approach an underestimate."¨ As a non-physisist, I feel just a little bit proud for having seen that coming... ;-) John
  28. Predicting future sea level rise
    Thank you for your reply, Riccardo. However, the original posting also stated: "This calving process is accelerated by warming but the dynamic processes are not strongly understood." We attempt a theoretical model including glacial dynamics (and a lot of other parameters) but we find that those dynamics are hard to predict. So we try the "semi-empirical" approach instead, making the assumption that "highly non-linear events such as the collapse of an ice sheet" don´t happen. Then have we really solved the problem of collapsing ice sheets? NB. I´m not claiming that anyone is wrong, just trying to get my spontaneous objections resolved.
  29. Predicting future sea level rise
    jliungman, actually the model is not linear. Whatever it is, extrapolation is always a tricky business and you need solid physical basis to be confident with it. If, for example, you push it too far to a situation in which there is no more ice anywhere the extrapolation will for sure be unjustified. But if you consider that the contribution to sea level rise is mostly due to only two processes (sea water warming and ice sheet melting, both in the end driven by GHG forcing) we might be confident enough that no dramatic changes will show up in a century. The model has also been tested tested against a simulation along a time span of 1000 years (fig.2 in the paper).
  30. Predicting future sea level rise
    Hello, and thanks for an interesting post! In the original post you state: "There are limitations to this approach. The temperature record over the past 120 years doesn't include large, highly non-linear events such as the collapse of an ice sheet." Isn´t the problem even more serious? If we view sea level as some kind of funtion of temperature, derived by looking at the evicence of the very narrow range of temperatures we have observed since 1880, how can we make any claims about a different range of temperatures? I´m not a scientist, but it seems to me that with so many variables involved, linearity would be the last thing to expect. The method seems interesting, but needs to be calibrated using more information about other temperatures and sea levels historically. And I don´t know if this information exists? Or am I mistaken? Thanks, John
  31. Predicting future sea level rise
    re #6 neilperth, your statement simply doesn't accord with the evidence:
    How can you blame man for sea levels rising when about 99% of that rise since the last ice age occurred before man built the pyramids, much less SUVs? A rise in sea level over the last century should not be surprising; it's been rising for the last 20,000 years.
    In fact the sea level rise from melting of polar ice during the last glacial to (present) interglacial transition was preetty much complete by a few thousand years ago. The evidence indicates that there has been little change in eustatic sea level since Roman times 2000 years ago, and if anything sea levels dropped somewhat (a small number of centimeters) in the nearly 2000 years up to around the middle of the 19th century, after which they've started to rise, increasingly so during the last century and especially during the last several decades: Pirazzoli PA (2005) A review of possible eustatic, isostatic and tectonic contributions in eight late-Holocene relative sea-level histories from the Mediterranean area Quart. Sci. Rev. 24, 1989-2001 “Finally, several data from tectonic and non-tectonic areas are consistent with nearly stable global eustasy since 6000BP, thus challenging the assertion of significant additional melting of Antarctica after the complete melting of the former Northern Hemisphere ice caps “ Lambeck K (2005) Sea level in Roman time in the Central Mediterranean and implications for recent change Earth Planet. Sci. Lett. 224, 563-575 “Part of this change is the result of ongoing glacio-hydro isostatic adjustment of the crust subsequent to the last deglaciation. When corrected for this, using geologically constrained model predictions, the change in eustatic sea level since the Roman Period is -0.13 +/- 0.09 m. A comparison with tide-gauge records from nearby locations and with geologically constrained model predictions of the glacio-isostatic contributions establishes that the onset of modem sea-level rise occurred in recent time at similar to 100 +/- 53 years before present.” Church JA et al. (2008) Understanding global sea levels: past, present and future Sustainability Sci. 3, 9-22 “While sea levels have varied by over 120 m during glacial/interglacial cycles, there has been little net rise over the past several millennia until the 19th century and early 20th century, when geological and tide-gauge data indicate an increase in the rate of sea-level rise.” Milne GA (2009) Identifying the causes of sea-level change Nature Geosci. 2, 471-478 ”The observed fall in sea level following the end of major melting (~7,000 yr bp; Fig. 3b) is due to isostatic processes52. A growing number of high-resolution records (Fig. 3c) detect an acceleration in sea level around AD 1850–1900 (refs 43–45)” etc...
  32. Hockey sticks, 'unprecedented warming' and past climate change
    Re #26 HumanityRules, I was highlighting the fact that the evidence of a non-spatially homogeneous MWP, has been around for some time, and is not the recent proposal of Mann thst you suggested. I don’t disagree that there is limited S. hemisphere proxy temperature data. However, there’s rather a lot of data that supports the interpretation of a non-homogeneous MWP (temporally and spatially) either focussing on the N. hemisphere (see papers in my post above), or considering less quantitative paleoproxy data from the S. hemisphere and central latitudes. So, for example, data from Pacific corals indicate that the tropical Pacific was cool during the period of the high N. latitude MWP: Kim M. Cobb et al. (2003) El Niño/Southern Oscillation and tropical Pacific climate during the last millennium Nature 424, 271-276 And this data has recently been extended through the 20th century, to pin the paleoproxy data to the 20th century temperature record Nurhati IS et al. (2009) Late 20th century warming and freshening in the central tropical Pacific Geophys. Res. Lett. 36 Art # L21606 Temperature records from the mid-latitudes (Tibet) and S. hemisphere (Tropics; Andes) shows either an insignificant warming during the period of the high N. hemisphere MWP (tropics and Tibet) or a small warming that is non-synchronous with the N. hemisphere MWP (Andes; it lags by ~200 years) L.G. Thompson et al. (2006) Abrupt tropical climate change: past and present Proc. Natl. Acad. Sci. 103 10536–10543 Likewise analysis of S. hemisphere glacier advance (New Zealand) indicates that the N. hemisphere and S. hemisphere warming at the time of the MWP was temporally asynchronous: J. M. Schaefer et al. (2009) High-Frequency Holocene Glacier Fluctuations in New Zealand Differ from the Northern Signature Science 324, 622-625 Likewise, analysis of paleoproxy data from S. America has indicated non spatially coherent warming and little overall warming in the region compared to MWP in Europe R. Villalba, 1990 Climatic fluctuations in northern Patagonia during the last 1000 years as inferred from tree-ring records Quaternary Research 34 (1990), pp. 346–360 Recently reviewed: J.A. Boninsegna et al. (2009) Dendroclimatological reconstructions in South America: A review Palaeogeography, Palaeoclimatology, Palaeoecology 281, 210-228 and so on… Now one may quibble about the limited “quantitative“ paleoproxy data from the Southern hemisphere. However there is rather significant evidence that the Pacific was displaying La Nina like conditions during the period of the warm high latitude N. hemisphere MWP signature, and that Southern hemisphere and mid-latitude glaciers were not responding in a manner consistent with warming during the period of warming in the high Northern latitudes. This is quite different for the spatially-and temporally homogenous nature of 20th century warming. This evidence has been around for a long time…the recent data tends to reinforce this interpretation.
  33. Predicting future sea level rise
    RSVP writes: But for the short run of 100 years, as oceans grow, would'nt that volume of extra water dampen global warming? (since the heat capacity of water is twice that of ice) Don't take this personally, but are you seriously suggesting that the change in the thermal mass of the ocean as a result of melting ice would have a significant effect on the rate of increase in global surface temperature? A few seconds with Google suggests that the mass of the oceans is 1.4 x 10^21 kg. (e.g., http://hypertextbook.com/facts/1998/AvijeetDut.shtml). The area of the ocean is 3.6 x 10^14 square meters. One cubic meter of water masses 1000 kg, so raising sea level by one meter adds 3.6 x 10^17 kg to the ocean. That presumably would increase the ocean's thermal mass by 0.0026%. Working that out took one or two easy Google searches, plus a small amount of very simple calculations. John, our host on this blog, tries to keep everything polite and I want to respect that. But I'd like to gently suggest that you, RSVP, could probably have figured out the answer to your question first, rather than throwing it out here as an objection that others then have to address. Okay, end of sermon.
  34. Predicting future sea level rise
    neilperth: The IPCC AR4 predictions of future sea level rise were specifically designed to be conservative, by simply omitting processes that are difficult to predict but are known to contribute to sea level rise. In other words, they are a lower bound on SLR, and sure enough, as we see from the first figure in this post, actual SLR is nicely tracking the very uppermost range of the IPCC predictions. The Vermeer et al paper being discussed here makes a convincing argument for sea level rise of 7.5 to 19.0 mm/year over the next century. This is much faster than most pre-modern changes in sea level, and in fact is of the same order of magnitude as some of the extreme spikes that occurred during deglaciation. That's disturbing, because unlike the situation 14,000 years ago, there are now over 600 million people living within less than 10 m of sea level. Not to mention lots of nice stuff like cities, airports, shipping terminals, and other valuable infrastructure. None of that existed during past episodes of sea level rise. In wealthy countries, we can afford to move people inland (a 1 m rise in sea level might only cost the US something like $400 billion, though other estimates would put the price tag higher). In poor countries, this will mean vastly more hardship. Of course, in the worst-case scenario, if people fail to take action on climate now, and we keep burning more and more oil and coal, at some point we'll lose at least a large fraction of both the Greenland ice sheet and the West Antarctic ice sheet. Let's just hope they don't break up as fast as the portions of the Pleistocene ice sheets that were responsible for meltwater pulse 1A, when sea levels rose at rates of 50 mm/year for three centuries. Anything even close to that would be an immense disaster.
  35. Predicting future sea level rise
    Referring to Figure 3. Even with a total Venus style greenhouse runaway scenario, on an expanded time scale, the curve would have to flatten out, as there is only a finite amount of ice in our polar caps. But for the short run of 100 years, as oceans grow, would'nt that volume of extra water dampen global warming? (since the heat capacity of water is twice that of ice)... in which case the curve would be a little flatter. Or does more ocean mean more water vapor and more global warming?
  36. Predicting future sea level rise
    to neilperth Obviously, you dont surf.
  37. Predicting future sea level rise
    The IPCC tells us that warmer temperatures lead to higher sea levels. Fortunately, there is only one ocean. And while sea levels vary with tides over the year, averages are probably fairly reliable. The IPCC does present a chart of sea levels and its trend is more obvious than the temperature trend. It shows a steady rise of about 200 millimeters in the last 120 years. That's about eight inches. Is eight inches over 120 years significant or alarming? Better yet, scientists have produced a long-term graph of sea level changes, about 20,000 years worth. The data behind this graph are widely known and accepted. NASA, for example, accepts this data and the government of Canada publishes a similar graph. Firstly the graph ranges over about 120 meters (not millimeters), about 400 feet. On the graph by comparison, a change of 200 millimeters (or the change in the last 120 years as per the IPCC) would be would be about the width of your eyelash. When the seas were 400 feet lower, people could walk from Russia to Alaska and from France to England. Global warmists are taking their micrometer, literally, to the last 120 years on this chart, and from that, extrapolating that we are all about to die. If sea levels go along with global temperatures, as the warmists frequently remind us, then this chart makes blatantly obvious that •Man has just about nothing to do with global temperatures, •Any temperature changes in the last 100 years are insignificant compared to longer term changes, •And current trends are most likely just the final flattening out of temperatures after rising from the last ice age. How can you blame man for sea levels rising when about 99% of that rise since the last ice age occurred before man built the pyramids, much less SUVs? A rise in sea level over the last century should not be surprising; it's been rising for the last 20,000 years. If anything, looking at this chart would convince me that long term temperatures are cyclic and that we are coming near the end of the warming part of the cycle. In fact, it looks like we are near the peak of that warming and could be about to enter the cooling-down part of the cycle. Over the last 20,000 years, man did pretty well. His population grew from fewer than 10 million to almost 7 billion. He had an agricultural revolution, an industrial revolution and an information revolution. He started cities. He started writing. He started recording his own history. He walked on the moon. Over that time, the sea level rose about 120 meters. If the current trend continues, it will rise two meters in the next 1000 years. If man thrived like he did when the seas rose 120 meters, why would the world end if they rise another two?
  38. An overview of Antarctic ice trends
    Is it possible to get data for land ice somewhere easy? I would like a longer periode to analyse on. For me 5 years isnt really enough to show a trend. Because if 5 years was enough for that, you could cherry pick and find data that actually shows that co2 has nothing to do with global warming. So a period of 40-50 years of data around land ice would be super, if anyone could help me with finding the right place to look.
  39. Predicting future sea level rise
    Those of you who have acces to Nature and are less inclined to the mathematical details of the anlysis should take a look at the published version of Kopp 2009 paper.
  40. Predicting future sea level rise
    HumanituRules, the thermal expansion coefficient of sea water actually increases with pressure; hence, heat going into the deep ocean has a larger effect on sea level. The fact that current model do not include warming in the deep ocean is one more contribution to the underestimation of sea level rise.
  41. Predicting future sea level rise
    I guess that temperature could be replaced with energy in this article. The important issue being that with warming globe sea level rise will depend on where that energy is flowing (into sea/land ice, land, atmosphere, shallow or deep water etc). In your post "Understanding Trenberth's travesty" you reported on recent work to suggest that some of the energy is following into the deep ocean. My understanding is that old theories ignored deep oceans as an unimportant energy sink, being relatively stable. Energy into here, due to the higher pressures, has little affect on sea level. I was wondering whether is work is intergrated into estimates of sea-level rise. On a broader point Trenberth seemed unable to balance both the energy bugget and observed sea-level rise based on what we presently know. Suggesting there may be room for an unknown in the energy budget equation. I was wondering what impact that has on the work you present here. Trenberth's paper
    Response: The issue of heat being sequestered into the deep ocean has no bearing on the semi-empirical method. I'm not sure to what degree it will affect the kinematic study but the general sense I get from both papers is that thermal expansion becomes less of a contributing factor as time goes on. The newly released paper on the last interglacial (Kopp 2009) backs this up, finding ice sheets are vulnerable to sustained warm temperatures.

    Pfeffer 2008 is freely available online (you can register on Science for a free account) so I leave this one as an exercise for the reader :-)
  42. Is Pacific Decadal Oscillation the Smoking Gun?
    farwalker, to be honest, i do not have the will to go through the 55 pages of that (unpublished?) paper. But just from the first few pages you may realize that the whole reasoning is based on a faulty assumption: recovery from the LIA. What does it mean recovery? Is there any predefined climate state that have to be restored? Does it happen without any forcing? This argument would make even the skeptics crazy, they who love the sun so much! Indeed, there has been an increasing sun activity from the Maunder minimum but it has stopped about 60 years ago. The temperature increase from the mid 19th century up the the mid 20th century is surely due in part to the sun; but from then on it can not be the sun. Another faulty claim is that global warming has stopped in the last decade. There are good reason to believe that it's not cooling; and there's no way to support this claim based on temperature data. (Also here).
  43. Hockey sticks, 'unprecedented warming' and past climate change
    SNRatio, this is where it all started in #14: "Apropos sensitivity: Who is quite sure that a 3 deg sensitivity at the doubling from 140 to 280 ppm necessarily implies a 3 deg sensitivity at the next doubling, to 560 ppm? I'm not :-)" Here you are linking sensitivity and temperature. It's correct, they are by DT=lambda*DF. So the issue is wether the forcing is logarithmic or not. If it is, whenever CO2 concentration happens to double, you'll get 3 °C. Now, maybe I misunderstood your question. Are you asking if climate sensitivity can be assumed constant? Then in #20 you mention absorption band overlap. In my mind sensitivy is defined by the relation above. Then overlap has nothing to do with climate sensitivity but, eventually, with the forcing. This is the rationale of my comment #29. CO2 forcing does not depends on overlap, it's already considered. Maybe I misunderstood again or maybe we call sensitivity two different things. In #30 you explicitly say that "100 year sensitivity may be only about half of equilibrium sensitivity". This sensitivity can not be used to compare different time span or different situations; for example, even keeping everything else constant the next 100 years you'll get a lower "sensitivity", given that the process of reaching equilibrium is not linear. So, you can use this different definition of sensitivity just for inter-model comparison ot to compare them with reality in the very same situation and time span.
  44. Predicting future sea level rise
    Problem with this, and this goes to most PR/comms with the public from science (and is a big failure in engagement with the public by science) is that these numbers have zero immediacy with the public. I'm far from being a skeptic (I bled concern at heresysnowboarding.com/blog) but I look at 2050 and see anything from 20-60cm and I think, so what. What science needs to do is make it clear in terms of lost land (i.e. X%) or number of people displaced, amount of arable land lost etc etc. Putting up values of 4cm, 10cm etc doesn't mean much to fat, lazy, ignorant, unconcerned Western consumer...
  45. Predicting future sea level rise
    I just finished reading James Hansen's new book (Storms of my Granchildren) where he talks a lot about sea level rise and references a bunch of papers. Could you do a review and summary of Hansen's position vs. the other researchers in this area? Thanks.
  46. Is Pacific Decadal Oscillation the Smoking Gun?
    I think this is they correct place for this question, has anyone examined Akasofu's paper claiming that we are now in the cooling phase of the multi-decadal oscillation? http://people.iarc.uaf.edu/~sakasofu/pdf/two_natural_components_recent_climate_change.pdf Is there any merit to his arguments? It looks convincing but perhaps a little too neat.
  47. Climate's changed before
    Right; there are positive feedbacks, but they are not boundless. Water vapour can only be added into the atmosphere up to saturation point, counterbalanced by a tendency to rain more the more there is. Greenhouse gasses trapped under permafrost, ice, in the ocean and wherever else can only be released once, and there's only so much ice to melt to diminish Earth's reflectivity. One of the things that can counteract an excess of CO2 is excess growth/adaption of plants, and IIRC this is what eventually causes the atmosphere to bounce back and temperatures with it.
  48. Hockey sticks, 'unprecedented warming' and past climate change
    Batsvensson writes: "If CO2 can make the planet come out from an ice age isn't it also a plausible idea that CO2 can prevent the planet from entering an ice age as well? " As far as I understand it, there's a lot of disagreement as to the probable timing of the next glacial cycle in the absence of human intervention. Most people (but not all) now think that the current interglacial would have been longer than the Eemian (basically, cooling over the past millennia would have dipped towards the tipping point for initiation of a new glacial cycle, but probably not gotten cold enough). The next tipping point comes in ca. 50,000 years from now, when the Milankovich forcing almost certainly would be sufficient to start glaciation. Depending on how much CO2 we emit over the next 200 years, it's entirely possible that there will still be enough in the atmosphere to prevent the next glacial cycle from starting 50,000 years from now. That's a pretty astonishing thought, IMHO. See Clausen et al (2004), Did Humankind Prevent a Holocene Glaciation? Climatic Change, 69: 409-417. Not everyone agrees, however. I haven't discussed this with them, but my former colleagues Steve Vavrus and John Kutzbach have a paper out (coauthored with Bill Ruddiman) which allegedly confirms Ruddiman's hypothesis that we would already have started a glacial cycle if it weren't for the initiation of agriculture several millennia ago: Vavrus et al., 2008, "Climate model tests of the anthropogenic influence on greenhouse-induced climate change: the role of early human agriculture, industrialization, and vegetation feedbacks" Quaternary Science Reviews, 27: 1410-1425.
  49. Skeptical Science housekeeping: Twitter and double-posts
    pico writes: Lately I've been seeing 'skeptics' trotting out their lame argument that because there were vinyards in England during the Roman period, therefore global warming isn't happening. But you don't have that on your hottest skeptic arguments. Perhaps it is just too lame to add to your list, but it would be handy to be able to point them at a concise rebuttal. I like this rebuttal: Medieval warmth and English wine and a brief follow-up: English vinyards again To summarize: (1) Before 1200, there were at least 50 vinyards in England, all located south of a line running from Cambridgeshire to Gloucestershire. (2) During the 19th century, vinyards almost disappeared from the UK. In the 1800s, only 8 were reported. (3) In the 1950s, vinyards started reappearing, and they have increased in numbers rapidly over the past few decades. There are now over 400 in England, extending much further north than ever before (e.g., Yorkshire and Lancashire). English vinyards are probably not actually a good climate proxy, since they're affected by other factors like trade, the economy, consumption preferences, etc. But if one insists on using them as a proxy, they nicely agree with the consensus view: the North Atlantic experienced a mild Medieval Warm Period, a cool LIA, and a rapid warming post 1950, now to levels greater than the MWP (if you go by vinyards).
  50. Skeptical Science housekeeping: Twitter and double-posts
    Man, I send you a tweet last day thanking you for your efforts, let me thank you here again. Excellent Site

Prev  2508  2509  2510  2511  2512  2513  2514  2515  2516  2517  2518  2519  2520  2521  2522  2523  Next


The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us