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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.

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Comments 111151 to 111200:

  1. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    Daved, The paper can be viewed here. Their models do not consider CO2 but instead consider SSTs and atmospheric and ocean circulation patterns. Those models do a good job of representing modern TC actvitity so there is reasonable confidence in their Pliocence "forecast".
  2. Berényi Péter at 22:31 PM on 3 September 2010
    Urban Heat Islands: serious problem or holiday destination for skeptics?
    I have selected 270 GHCN stations worldwide with a reasonably uniform distribution over land in such a way, that all of them had almost complete coverage of the years between 1990 and 2000. Then I have computed base 2 log population density difference of that decade for each station along with temperature trend at that location. The stations are divided into three classes according to population density around them in 1990: dense: more than 15/km2 medium: between 0.8/km2 and 15/km2 sparse: below 0.8/km2 (but at least 0.01/km2) As you can see the scatter plot is not very different for these categories. Therefore, if there is a dependence of UHI on local population density, it extends well below 1/km2 indeed with no breakdown of the relation in sight. But the most important finding is that there is a (not very strong) correlation between these two parameters, so a regression line can be computed. Average temperature trend for these stations was about 0.32°C/decade between 1990 and 2000. But part of this increase is due to the 0.2 increase in base 2 logarithmic population density during this timespan, so we have to consider the regression line at zero. It is about 0.15°C/decade there. So more than 50% of the trend is due to increase in local population density around GHCN stations (most of the rest is probably NH soot pollution over snow and ice). This effect is also known as UHI (Urban Heat Island), although as we have seen it has not much to do with urbanization as such, it's just the local effect of increasing population density, even in very sparsely populated areas. I think this is the proper way to look for an UHI effect in land surface temperature records. That is, one should analyze the connection between changes in local population density around measurement points and surface temperature trend at the same location. I am afraid it is not done (yet) by those, who are responsible for maintaining these datasets, although by now many thousand billion dollar political and business decisions are dependent on their correctness (or its lack thereof). Also, I can see the problems with the GPWv3 dataset. Perhaps satellite shots of night light distribution is a better proxy for UHI than population density trends averaged over administrative districts.
  3. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    Miekol, #2, More like "more than 500 years" for dyke building in Holland, rather than 100. Jared Diamond has a good section on Holland in his book Collapse, which I am re-reading. The dykes go hand-in-hand with a co-operative ethic. Each "polder" (dyked area) pumps water into the neighbouring polder until it reaches the sea. Each polder depends on the one nearer the sea. Ironically, the Dutch had the world's first capitalist economy and stock-exchange. Also, the world's first speculative bubble (in tulip bulbs). We may have a lot to learn from the Sutch experience!
  4. Climate change: Water vapor makes for a wet argument
    davidwwalters, no CO2 doesn't 'hold onto' heat energy at all. Think of each CO2 molecule as a tiny spinning mirror which is transparent to visible light, but reflective to infrared. A photon of sunlight hits the CO2 molecule and goes right through... down to the surface where it heats up a rock or something. The rock then emits a photon of infrared radiation upwards towards space. With no greenhouse gases in the atmosphere that heat would just go up and escape. WITH CO2 and other GHGs it goes up, hits a CO2 molecule, and bounces off in a random direction. Maybe it continues going upwards (to escape or bounce off another GHG molecule) or maybe it goes back down and 're-heats' the surface. The greenhouse effect does not work by 'trapping heat' within molecules of greenhouse gases. It works by slowing down the rate at which heat escapes the atmosphere into space. That heat winds up in molecules of other gases, liquids, and solids rather than just traveling up and out to space.
  5. The surprising result when you compare bad weather stations to good stations
    @Dappledwater: just replace "blood pressure" with "EKG". Definitely, if the cardiac graphs recorded by people of dubious competence were very similar to the ones recorded by the experts, it would be a surprising result that would suggest further investigation is needed before declaring the patient as "healthy" or "sick". For EKGs we do have guidelines, it's not too difficult to record them incorrectly if you don't know what you're doing, equipment may be out of date, it gets replaced, etc etc. Just like with USHCN stations. This should help understand the relevance of the analogy. @michael sweet: for the n-th time, we are not talking about "warming trends" in general. We are talking about the warming trends that appear for both well-sited and poorly-sited USHCN stations. This is the topic of the blog but for some reason people keep trying to talk about something else (in your case, the content of the AR4 SPM of all things). Please try to stay on-topic.
  6. Climate change: Water vapor makes for a wet argument
    -I'm no scientist, but I want one who is to explain how the phase change of water affects water vapor's role as a green house gas relative to CO2. My understanding is that when water vapor condenses as water droplets in clouds, it releases its latent heat energy at that point. So, water constantly is gaining and loosing heat energy, and CO2 just holds on to the heat energy?
  7. How we know an ice age isn't just around the corner
    GC #27, using the UAH temperature data we can calculate five year average global anomalies; 1990-1994: -0.04 1995-1999: 0.14 2000-2004: 0.18 2005-2009: 0.23 All other data sets show GREATER warming. So no, this is not a matter of 'which data you look at'. ALL data sets show warming and your claim of cooling the past ten years (the hottest decade on record in all data sets) is simply false. The years 2007-9 were relatively cool... but then 2010 thus far is at +0.55 C anomaly in the UAH data... which is higher than the 0.52 C record they have for 1998.
  8. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    Would someone like to write Basic post on storm surges? I think they are likely to cause a good deal of damage to lowlying places in the years ahead.
  9. Sea level rise: the broader picture
    HumanityRules at 14:18 PM on 3 September, 2010 If ENSO is affecting MSL variations about the longer term trend then we need records longer than a couple of maximum ENSO "cycles" to begin to be able to determine any underlying acceleration trend that is not biased by this variability (to do with Nyquist criterion, sample rate theory, - hope this makes sense). Looking over the longer term, I was trying to create a chart showing annual trend of 17 year gradients throughout the tidal/altimeter record, which I hoped would answer (or allow more informed discussion on!) your point as well as the valid ones Ken made earlier on the 1930s/1940s rise rate. However I realized Church 2008 has already done something similar with 20 year trends: Whether we tack on the 3.3mm 17 year altimeter trend to this or not, we see that there is an accelerating trend throughout the overall record, relatively high acceleration in the early 20th century, and more recent acceleration in the late 20th century. These trends and possible causal factors are discussed in more detail in Woodworth 2009.
  10. How we know an ice age isn't just around the corner
    GC @ 29 - as Phil Scadden has pointed out, the PDO 30 yr cycle thing seems to be based on imagination, not the data:
  11. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    Hi ProfMandia , If scientists cant agree on the effects of raised CO2 and Temps on TC in our own time how can we be sure that the Federov, Brierley, & Emanuel models truly represent an era 2.5 to 5 million years ago ? . Even if their half right its still scary but the big wave surfers will be happy .
  12. How we know an ice age isn't just around the corner
    GC writes: Which data is wrong? The satellites or the ground stations? I don't pretend to know the answer but until someone can come up with a convincing explanation for the discrepancies, we should all try to keep our minds open. What discrepancies? The RSS satellite record and all the major land+ocean temperature records currently agree to within 0.01C/decade. UAH is just slightly lower. When there were discrepancies in the past, they turned out to be due to errors in the processing of the satellite data, not due to errors in the surface data. For example, there was the famous case where UAH was accidentally applying the satellite-drift correction factor backwards. Also, FYI, contrary to your claim, none of the temperature records shows "temperatures have drifted lower over the last decade." Land surface, sea surface, and lower troposphere temperatures have all increased since 2000. Since these are measured using completely different -- and independent -- technologies, the agreement among them is quite convincing.
  13. The surprising result when you compare bad weather stations to good stations
    Chriscasnaris @ 58 - how many dodgy sphygmomanometers have you run across in the course of your practice?. Using analogies can be useful , but not irrelevant ones - the temperature record deals with temperature anomalies not absolute temperatures, and I've yet to see anyone claim that the US temp stations have all recorded the same temperature, on any given day. And if you find the Menne paper puzzling, this must cause you total befuddlement: from 70 USHCN stations
  14. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    During the Pliocene, about 2.5 to 5 million years ago, CO2 levels were comparable to today's levels (near 400 ppm) and the climate was about 3 oC to 5 oC warmer than pre-IR. Geographically, the Earth was also very similar to today so the Pliocene offers a glimpse of what the world may look like by the year 2100. Federov, Brierley, & Emanuel (2010) modeled the expected TC activity in the early Pliocene world. This figure is a comparison of modern TC activity (a) and that of the Pliocene (b). This image is a sobering look at what may lie ahead in our world by 2100.
  15. Climate change: Water vapor makes for a wet argument
    @Johnd You are not answering the fundamental question. The earth has been a system more or less in equilibrium for thousands of years . For thousands of years the amount of water evaporating has been roughly the same a the amount of water vapor condensing. The mechanisms of evaporation you describe have existed as long as the earth exists. The question is: What has caused the earth’s climate to deviate from this situation ? You cannot say “an increase in water vapor concentration in the atmosphere”, because then you have to explain why this concentration has increased in the first place. You cannot pull yourself up by your own hairs. The consequence can not be its own cause. The generally accepted answer to the question is: CO2. We have put an enormous amount of CO2 in the atmosphere, causing the levels of CO2 to increase by 35% compared to pre-industrial times. This caused a temperature rise, the temperature rise caused more water to evaporate, and more water vapour in the atmosphere in turn leads to even higher temperatures. If you have an alternative theory, I’d like to hear it.
  16. How we know an ice age isn't just around the corner
    GC writes: Global temperatures have drifted lower over the last decade and are likely to fall for at least another 10 years. No they have not. Here is the RSS satellite record: The pink line shows the trend through 2000. Note that from 2001 onward, most months have been above the pre-2001 trend line, with the notable exception of the 2008 La Nina.
  17. Climate change: Water vapor makes for a wet argument
    With regard to the JohnD/scaddenp conversation; be careful not to confuse rate with equilibrium. The speed at which any process occurs bears no relationship to how far it can go, and changes to the rate will not affect the "equilibrium" value. This sounds somewhat counter-intuitive, but that is a consequence of the fact that, in the real world, we rarely get a view of a complete system at equilibrium. Factors affecting the rate of water evaporation such as "global dimming", atmospheric "churn" (wind) and local heating of wet surfaces will not affect the total amount of water vapour the atmosphere can hold, but will affect (locally at least) the rate at which water evaporates. A high rate of evaporation is what is required for drying clothes.
  18. The surprising result when you compare bad weather stations to good stations
    Such close correspondence between two set of data has a somewhat surreal quality. To take the blood pressure example, you visit 100 doctors some of whom have good sphygmomanometers and some have dodgy ones. Let's say you visit the same doctors a year later - if your blood pressure has gone up, you'd obviously expect an upward trend in the overall picture. However, if every sphygmomanometer showed an almost identical rise in blood pressure of, say, 20 mm-Hg +/- 0.5 mm-Hg, you'd be wondering about the validity of the data set. The closeness of the correspondence at least as presented here seems out of keeping with the messy quality you find in real data which tends to meander and scatter. None of this disproves a rising temperature trend. However, there's something puzzling about the data.
  19. Arkadiusz Semczyszak at 18:49 PM on 3 September 2010
    Quantifying the human contribution to global warming
    ... from the point 3 of my comment, follows that the natural balance of flux - sink of CO2 - in the preindustrial era - natural balance can not be - not exist - unless the scale of n x thousand years.
  20. Quantifying the human contribution to global warming
    Dana, If by the range you mean 2-4.5°C then my understanding is that this range comes from the water vapour feedback. There seems good concensus that there would be around 1.5oC climate sensitivity directly from the properties of the CO2 molecule. The range comes from the extent to which water vapour plays a part. My question was really around whether water vapour has a linear response to the increase in CO2. I can accept that oscillations don't create heat but in terms of how we measure warming then I think an oscillation can 'retain heat' at least in terms of the measurements we make. If you catch an oscillation on the rise, and fail to measure the whole system (primarily the ocean) then it can lead to a trend in the measurements. Give it another 100 years (or a few decades of good ARGO data) and we'll probably have enough data to draw a line under this but neither you or me are happy with that answer. So I'm just looking for direction that the oscillations are recognised, measured and put to bed. One of the papers is this. You can infer from the results that ~2/3 of the recent warming is from the upstroke in a natural oscillation. The 50% estimate was in a private email from a climate scientist who says the work is due for publication. I'd be happy to send that mail to John Cook for him to confirm it, without naming the scientist, but I think that's probably pointless given we wouldn't be able to discuss the mechanisms involved. My point would be there are climate scientist out there who are looking at oscillations in the climate and think it is contributing to recent trends at least on the regional level. When the Basic version of polar amplification appears we can probably discuss this further.
  21. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    Tell that to the Nigerians.
  22. Arkadiusz Semczyszak at 18:29 PM on 3 September 2010
    Quantifying the human contribution to global warming
    In that case, I also make a very short balance ... Of course, this has already been spoken, not once but worth it (to organize discussion) in a condensed recalled again (absolutely essential) and most real skeptical arguments: - Assessment - assessing the feedback resulting from the increase of CO2 made by different researchers are up to several hundred percent different from the above presented - They often get even a negative balance of feedback. Moreover, also the IPCC in its report (full version) draws attention to the considerable range for uncertainty in their estimation. - changes in the value of some RF far exceeds the size of RF CO2 during the analyzed period. For example, I recall: here: “... the total global cloud cover reached a maximum of about 69 percent in 1987 and a minimum of about 64 percent in 2000s ... ... a decrease of about 5 percent. This decrease roughly corresponds to a radiative net change of about 0.9 W/m2 ...” and albedo change - by (generally recognized in the scientific world), more recent reconstructions from ice cores with higher resolution (not to mention other than the "core" reconstructions) during the last millennium, the level of CO2 in the atmosphere has changed much more than that in Figure 1 (Max. 60 ppmv between circa 1150 to 1300 yr A.D.), often reaching 320 ppmv (remember this is based on ice cores), ... and as says F. Engelbeen: “A causes B and shows a good correlation. A causes C and shows a good corelation. Thus B causes C, because there is a good correlation between the two. But that correlation is completely spurious, as there is not the slightest physical connection between B and C.” (...) - The effect of the sun at the Earth's climate is not only the TSI, and the Sun is out in the absolute most of their superposition cycles and cycles associated with Sun.
  23. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    Easy, build dykes. The Dutch have been doing it for over 100 years.
  24. Climate change: Water vapor makes for a wet argument
    scaddenp at 13:44 PM, Phil, what I was trying to do is examine the link between two things. The known relationship between water vapour and atmospheric temperature, and the contentious issue of the apparent current lack of increased solar output whilst temperatures are supposedly still rising. Whether the output of shortwave radiation by the sun varies or not, it is not the only factor that determines the energy that is absorbed by the land and sea surfaces, which must occur before it can then be radiated off as longwave radiation. Variation in clouds is a significant controlling factor which is readily observed over short time frames with indications of longer term trends. With water vapour, although there is a known relationship between the saturation point and temperature, the evaporation process is driven by other factors that are not necessarily directly tied to temperature, those being the direct input of solar shortwave radiation and wind. Even though the oceans cover a larger area than land, I used the example of what occurs on land as it is well measured and understood, and something that I assume has been observed by most people, especially those with more than a passing interest in the processes that drive both the weather and the climate.
  25. Quantifying the human contribution to global warming
    dana1981 I like the article as it explains things very clearly, yet I have a comment similar to what HR brought up. Putting on my skeptic hat now, the precision of scalar 5.35 gets my attention when dF does not appear to depend on temperature itself. CO2 back radiation (if it is even real) is supposedly a function of temperature (in this case that of CO2) and that of changes incident solar radiation. Basing the change of radiative forcing on a ratio such as C over Co implies "all things being equal" (including the amount of incident solar radiation). However while the overall model assumes natural changes in solar irradiance, the formula assumes this to be constant, which is fine for a first order approximation, however, what then is the basis of the (+- .005 W/m2) precision based on? Put another way, while dF is theoretically not independent from changes in average global temperature nor incident solar irradiance, the formula reflects this assumption in its simplicity, while at the same time includes a factor with a precision out to two decimals places. How real is all this for the minor changes in temperature we are talking about?
  26. Hurricanes And Climate Change: Boy Is This Science Not Settled!
    The Basic versions that have appeared thus far are pretty good, I think, given the limitations of the format. Maybe someone can now post a Basic version of what cities can do to deal with sea level rise.
  27. Arkadiusz Semczyszak at 17:23 PM on 3 September 2010
    Climate change: Water vapor makes for a wet argument
    Clouds also act as a buffer. High clouds such as the type cirrus - they are thin and have small albedo retain heat (long wave), in the tropics where high clouds are thicker, the albedo is higher - energy balance may be negative. At night, clouds not only retain but also to remove the energy - on its top surface - through the so-called: "thermal chimney". In high latitudes, "thermal chimney" is weaker than the effect of stopping energy through the clouds of radiation the Earth's surface - at night. In the tropics, such removal of energy - for example, are often very complex cumulonimbus (upward - until the tropopause and the stratosphere, even) can be even (so) larger than the energy of radiation stopped from the earth's surface. There should not be also consider the global energy balance cloud cover - although already a bit "already old" criticism on RealClimate, the tropics, can - through internal forcing of the Earth's climate system - significantly affect the size of the current warming. Not only as Mr Spencer says, but many researchers, in this and the IPCC (eg Solomon).
  28. Arctic sea ice... take 2
    Timothy Chase, My guess is that the author means thick ice takes a lot more heat to melt - simply because it is thick. In other words, we are talking about the heat needed to melt ice per square meter (surface), not per cubic meter (volume). As for salt and saltwater in the ice, there is almost no salt in sea ice once it is frozen.
  29. Sea level rise: the broader picture
    HR @72 - The satellite data for global sea level is inclusive of the period 2005- 2009 is it not?. Look at the graphic provided at @70 (from UCAR/NCAR) & the video from Kevin Trenberth. What acceleration are you referring to?, OHC has declined from 2005. Doesn't that go some way toward answering your question @72 & repeated again @74?. Unlike many skeptics, who are always dead keen to throw the baby out with the bath water, the missing heat concerns me. Many climate scientists, and I'm of a similar view, expect that there may be a few surprises the climate has in store - is this one of them?. Has some significant change occurred in the deep ocean that we're as yet unaware of?, and will (as Kevin Trenberth states) this come back to haunt us?. I hope not, but as far as I'm aware the "missing heat" has yet to be accounted for.
  30. Quantifying the human contribution to global warming
    #4, HR, keep in mind that on a fine enough granularity, everything is linear. The difference between a climate system at 300 degrees K, and 300.8 degrees K can be pretty well approximated by linear functions. In some places this isn't true, for instance at the freezing point of water -- there is a big discontinuity between a system that is at 0 degrees C and frozen, and one at 0 degrees C and thawed. That is why the arctic is such a big concern for climate scientists. Other aspects of the system may need to include non-linear effects, like the huge jump in CO2 in the past century or so. There are a large number of interacting factors that we are only beginning to understand. One can speculate, and one can extrapolate, and one can choose to believe whomever one wants to believe, but the reality is that we're running a gigantic uncontrolled experiment on the environment upon which we depend for our survival, and everything we understand about the science tells us that the situation isn't going to slow, stop, or reverse unless we change what we're doing. #6, Jim Meador, the water vapor feedback is included in the total climate sensitivity. It is a factor in the uncertainty in sensitivity that dana1981 cites.
  31. Quantifying the human contribution to global warming
    Well, the water vapor feedback in response to increasing CO2 should be contained within the climate sensitivity parameter.
  32. Sea level rise: the broader picture
    69 Peter Hogarth that's great Peter, I don't think I dispute what you write about the satellite record but I will hold you to a global, 18 year data set being a "relatively short record" when we clash over data sets in future posts. Please tell me why we don't see any acceleration in the satellite record.
  33. Sea level rise: the broader picture
    71 Ned Sorry I don't read what Jo Nova has to say. I'm prepared to accept your assessment of her as little more than a propagandist if you want.
  34. Sea level rise: the broader picture
    67 Dappledwater 1) As I say I recognise the point you were making. Large differences in ocean basins means estimates will be completely misleading unless we have data from all basins. This doesn't look good for the early tidal gauge data the Merrifield Figure 7 is enlightening. In fact there is a hint in Leuliette and Miller that Willis estimates of OHC in 2003 are biased by low spatial coverage of Argo in the southern oceans. Imagine what the pre-1950 bias toward the northern hemisphere is doing to tidal gauge measurements then. 2) Looking at the error margins all three estimates from Chang and Willis overlap. This is how Leuliette and Miller justify that 1.5 steric + mass balances is the same as 2.4±1.1 for the total SLR. It seems a fair thing to do. 3) I'm not disputing the general 3.4mm/year over the satellite period. I'd be more concerned with the comparison of this to the early tide gauge era based oo the reason contained in 1). I'm still curious why the 1992-2010 satellite data shows no acceleration over this longish record, we can see the fingerprint of AGW in climate change metrics, why not this one. It seems the story goes the rate was somewhere around 1.5mm/year for much of the 20C, this was measured as a consistent rate upto the end of the 1980's. In the 1990's the rate jumped to 3.4mm/year and if we take the satellite data as the best, the rate has continued like that for 2 decades. It seems difficult to understand how this fits with the real world. (Pleased somebody tell me why the satellite data isn't showing an acceleration when OHC and land ice melt are accelerating?)
  35. Quantifying the human contribution to global warming
    I found this posting to be very informative. I would be very curious to see how the feedback from water vapor affects this calculation. Is that something that can be estimated with any precision at this point?
  36. New presentation debunking Monckton's critique of IPCC predictions
    Superb analysis. According to the Climate Scoreboard we are headed toward +4 C by 2100.
  37. Quantifying the human contribution to global warming
    Yes, climate sensitivity is the key factor here, which is why I gave a range of possible values. I'll be working on the advanced climate sensitivity rebuttal in the near future. The temperature change is directly proportional to the radiative forcing (energy change), as you can see in the formulas above. But keep in mind, we're only looking at the temperature change in response to increasing CO2. If various feedbacks kick in, like a large methane release, that's a completely different forcing which this calculation doesn't account for. It's just that conveniently right now, the non-CO2 forcings happen to add up to roughly zero, so we can get away with focusing on CO2 for the time being. I would have a hard time believing that 50+% of the Arctic warming is natural, but I haven't seen the particular papers you're referring to. Rapid Arctic warming is a projected consequence of AGW, because the melting ice creates a positive feedback by decreasing local reflectivity. Oscillations like PDO don't contribute to long-term warming. They're just that - oscillations which alternate between positive and negative states, moving heat around from oceans to air, and vice-versa. They neither create nor retain heat, so they don't have the capacity to warm the planet as a whole. In the short term they can warm or cool the surface, but they also have the opposite effect on ocean temperatures. Whereas right now we're observing both surface and oceans warming.
  38. Climate change: Water vapor makes for a wet argument
    Johnd - but all your stuff about 1.4m for measurement etc is irrelevant. The process that increases water evaporation is increased SST. The process (on the whole) that increases SST is more radiation. The cause of more radiation is more GHG. You seem to postulating that in steady state (no FORCING in albedo, solar, aerosol or albedo), that is somehow a mechanism that could cause more water vapour to enter the atmosphere and that this process is not damped, and could create a temperature trend over a 30 year cycle? Have I got that right?
  39. How we know an ice age isn't just around the corner
    GC looked at Its the PDO? I am more interested in what you will think if temperatures trend up for next 10 years. Also, UAH and RSS dont measure ground temperature - they attempt to measure the lower troposphere (around 4000m from memory). However, they see the same 30-year TREND as GISS/HadCrut. Neither data set is wrong - just measuring something different.
  40. Climate change: Water vapor makes for a wet argument
    scaddenp at 11:33 AM, obviously the majority of evaporation occurs off the oceans, but the process is the same as what occurs on land, all the same factors are involved. The main reason I used the situation on land is because it is not only easier to measure, but all the relevant factors are well measured and understood because of it's relevance to agriculture. However the other reason was that I assumed most people could easily relate how the various forces come into the equation from what they have observed in their everyday lives, whether it is observing how quickly the ground dries out on a seemingly mild, but windy day as opposed to a hot still day, or perhaps drying the clothes on a line.
  41. Climate change: Water vapor makes for a wet argument
    Ooops, forgot the link ;-) http://scienceofdoom.com/2010/05/30/clouds-and-water-vapor-part-one/
  42. Climate change: Water vapor makes for a wet argument
    Clouds cause an approximate net effect o 18wm2 cooling... they prevent on average 48wm2 o solar radiation, and reflect 30wm2 LW. Clouds are an area of uncertainty.
  43. Quantifying the human contribution to global warming
    I think the big one here is climate sensitivity, it's seems this is the most controversial (if you're willing to accept anything is controversial in climate science). As usual I've got heaps of questions You state "the temperature change is proportional to the change in the amount of energy reaching the Earth's surface". Is that linear/exponential? As we progress further and further away from a 'normal' level of CO2 do the feedbacks change so the relation becomes more complex/non linear? With regard to the expected surface temperature change by 2010 it strikes me that the sums demand not only do we have to have "heating in the pipeline" but we also need nearly all the warming we've measured so far to be from AGW, there is little room for natural variation to have contributed much. I have read several papers recently (and in fact hassled a couple of the authors with emails) that assign, at least on a regional basis, large proportions of the measured warming to natural variation. Particularly these were the northern polar region, which are contributing disproportionally to the global average. In this region these authors were assigning 50-60% of recent warming to natural variability. I wonder if we start assigning part of the 20th century warming to nature how much we have to scale back the future catastrophe? From memory the IPCC only consider the impact of solar intensity and volcanos when assigning most of the late 20C warming to AGW. Do they consider that multi-decade climate variation (oscilations/seesaw and the like) to contribute anything to the trend we have measured in global mean temperature?
  44. How we know an ice age isn't just around the corner
    gallopingcamel the suns out put 450mybp would have been around 97% o the present irradiance.... The location of the continents plays a large role in climate, the current configuration weighs the climate towards ice house.. there is a land mass over the southern pole, preventing transport of heat over the pole via the oceans, and the land masses around the northern pole greatly inhibit the transport of heat. As well as the location of the other continents playing a role in oceanic heat transport by the way they influence ocean currents. GHGs are important, but the continents set the stage.
  45. How we know an ice age isn't just around the corner
    scaddenp (#23), You got me. It is just a gut feeling although some people have suggested that there is an oscillation (PDO and other ocean effects) with a ~30 year period. If I am right and temperatures trend down for the next ten years, it would not surprise me to find rising temperatures after that.
  46. Climate change: Water vapor makes for a wet argument
    Agnostic, It is an interesting question, although, I'll make the assumption that you mean that the water vapor which condenses to form clouds is what reduces solar energy reaching the surface. In addition to the moderator response, you also have to keep in mind that during the day, clouds reduce inbound flow of energy, but they always reduce the outbound flow, night and day. A cloudy day is cooler than a clear day, but a cloudy night is warmer than a clear night. I don't know how they balance out offhand. If the negative, cooling feedback of clouds were enough to offset the initial forcing plus the positive feedback of water vapor, then I don't think it would be possible to have periods as warm as those which exist in the geologic record.
  47. How we know an ice age isn't just around the corner
    John Cook, (Response to my #22), There was an Ice Age in the late Ordovician (~450 million years before present). At that time the CO2 concentration was ~20 times what it is today. You say that the sun was cooler back then. I can concede that you are right about the sun's output being lower but that only raises more questions. If the sun's output was low, why was it so hot in the Cambrian period that preceded the Ordovician and in the Silurian that followed it?
  48. How we know an ice age isn't just around the corner
    John Cook, (Response to my #22), As Ronald Reagan would say, "There you go again". You keep quoting NASA/GISS and James Hansen. You need to check out some of the contrary data that can be found at UAH and RSS. Which data is wrong? The satellites or the ground stations? I don't pretend to know the answer but until someone can come up with a convincing explanation for the discrepancies, we should all try to keep our minds open.
  49. Quantifying the human contribution to global warming
    Thanks CBW. I had thought of that, but then again the smaller the forcing, the less of an energy imbalance, and the less of a role the ocean thermal inertia plays. I felt it was worthwhile to point out that even with unrealistically conservative assumptions, the majority of the warming is still anthropogenic.
  50. How we know an ice age isn't just around the corner
    Arkasiusz - that graph shows a bunch of very abrupt climate changes that happened moving from glacial to interglacial. While we would certainly like to understand them more (because yes, that rate of change would really seriously threaten civilization - how would farm in the face of such change), there isnt evidence for them happening during interglacial period - while its warm. It isnt in disagreement with fact that the transition to glaciation (if our atmosphere would still permit it), is something that takes place extremely slowly.

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