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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 107001 to 107050:

  1. Explaining Arctic sea ice loss
    RSVP "I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result." What waters would be cooling? The waters from the Pacific do flow into the Arctic and they can be very warm from an el Nino a year or so earlier. And the strength of an el Nino is related to CO2 heating the atmosphere and the oceans at large. The more warm water there is, and the higher its temperature, the more melting of sea ice from below.
  2. Explaining Arctic sea ice loss
    RSVP: "I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result." Read post 22 again. If you have no understanding of the most basic science concerning what you are talking about you do not make a good impression. Warm ocean waters coming from both the Atlantic and the Pacific are part of the problem with melting Arctic ice. The warm ocean is the primary concern with Greenland. If you do not know what the issues are you cannot make informed comments about those issues. The meridional overturning circulation in the North Atlantic moves enormous amounts of energy and changes in it cause concern for the future. By contrast, references to waste heat just remind us that you do not understand energy transfer either.
  3. Do the IPCC use alarmist language?
    barry writes: Checking with the grammar police - 'panel' is singular, so shouldn't the title be "Does the IPCC use alarmist language?" "Panel" is a group noun or collective noun, and different English-speaking countries have different usage. In the US, collective nouns are generally treated as singular, whereas in the UK they're often treated as plural.
  4. New temperature reconstruction vindicates ...
    protestant writes: Your post maybde had an intention of also vindicating the original hockey stick shape and that the current temperature trend would be unprecedented. The original study doesnt support that. I'm not sure what you mean by "vindicating the original hockey stick shape". My post compares this new reconstruction (Ljungqvist 2010) to several others (see Fig. 2 and Fig. 3). The current decadal mean temperature (2000-2009) is in fact higher than any decade in the reconstruction. This is true whether you use the instrumental record "as is", or whether you just take the 2000s-1990s difference and add it to the end of the reconstruction (the method you specifically recommend in your previous comment). protestant continues: If you want to be credible also in the eyes of us sceptics', next time, when someone publishes a new proxy-reconstrucion, please cite the graphs used in the papers ant not making your own with your own undocumented un-peer-rewieved methodologies. I cited and linked to the Ljungqvist paper in the first two sentences of the post, and provided links to all other data sources. There is no peer-reviewed paper that shows the comparison I was making in this post (comparing Ljungqvist 2010 to previous reconstructions by Loehle, Mann, and Moberg). If there were a paper with figures showing that comparison, I would have used it. protestant writes: And if you add temperature data to Loehle, you get basically same results as Ljundgqvist. She shapes on both are remarkably similar. [...] It does NOT vindicate Mann, except with the apples-to-oranges comparison you just did and which was justifiedly strongly critisized on my last posts. The shapes of the original studies simply DO NOT agree. There is no way to "add temperature data to Loehle" other than the kinds of methods I used in Fig. 2 or Fig. 3 -- recentering it to match some other temperature record during some overlap period. The raw data in Loehle 2008 are just centered on their own mean. More to the point, Loehle 2008 is supposed to be a global reconstruction. Ljungqvist 2010 is a mid- to high-latitude Northern Hemisphere reconstruction. If you want to claim that "the shapes match" then that is a sign of problems with Loehle because a global reconstruction should not show a larger MWP-LIA amplitude than a mid- to high-latitude Northern Hemisphere reconstruction. In contrast, the Mann and Moberg reconstructions shown in Fig 3 are both Northern Hemisphere only. Thus, comparing them to Ljungqvist is much less of an "apples to oranges" comparison than the comparison of Loehle to Ljungqvist.
  5. Do the IPCC use alarmist language?
    Roger Wipage said "I know enough to know that I have neither the prerequisite background nor the tools to predict the probabilistic distribution of anything more than simple statistical examples." and then goes on to tell us that the IPCC cannot calculate probabilistic distributions. Why do these deniers always tell us about stuff they admit they do not understand? Alan Marshall: Many of the IPCC final conclusions were LOWERED by the government reviews before the report was approved. Remember that the Bush administration, Saudi Arabia and Australia all had to accept the conclusions. The lawers from countries who cause the most warming changed many of the risk levels.
  6. Do the IPCC use alarmist language?
    There are other threads here to discuss particular weather events, but SME's comment caught my eye: While events such as the Pakistan flooding are complex and cannot be simplistically categorised, a major point is that this disaster was NOT driven by an especially extreme weather event. The overall rainfall is reported to have been in the 20 year flood to 30 year flood range. Really? How about a reality check from the World Meteorological Organization? We don't have to guess at these things, there are people on the planet who know what they're talking about. For more circular discussion on the topic of weather extremes and their relationship to climate change, I'll tout this thread: NASA-GISS: July 2010-- What global warming looks like
  7. Do the IPCC use alarmist language?
    Roger A. Wehage wrote : "JMurphy @22: I believe that one should not use the severity or lack thereof in individual events as arguments for or against global warming or climate change. The same goes for floods and heat waves. Their frequency and severity certainly appear to be increasing. At the same time their impacts on the human population are becoming more severe because of artificial changes we've made to the environment and because of increased population density." All true enough but the problem is that the so-called skeptics try to pretend that things are not really that bad because such things have happened a few times in the past, while failing to realise that such things are happening more regularly now and are affecting more and more people, now and in the future. It's similar to suggesting that people, animals and plants, etc. will be able to cope by migrating, as they have done in the past when necessary - forgetting about those big populations, behind their political and national boundaries, who won't be so keen on helping others to mitigate global warming in their backyards.
  8. Do the IPCC use alarmist language?
    Key term in Chris' post: ...The 1936 North American heat wave... Here on SkS the topic is planetary-scale, secular change.
  9. New temperature reconstruction vindicates ...
    @protestant: I guess my original post was too "hot" and got deleted. I agree with the terms of use on this blog, and so will not complain about it. I'll simply repeat that you totally miss the point by accusing me of cherry-picking. The goal was *precisely* to show that short terms - including the one from 1998 - are not statistically significant when trying to analyze trends. "And if you add temperature data to Loehle, you get basically same results as Ljundgqvist." Uh, no, you don't. See Tamino's convincing argument to the contrary. "Seconly, the warming happened until 1998 until it halted to the "high" level." ...except it didn't. You know, unless you're cherry-picking, i.e. using an unusually warm year as a starting point. "What if the halt lasts also next 10 year, will you be then using 20yr avg to prove "warmest 20 years in the recorded history!"?" The "halt" has already stopped, as temperatures are once again appearing to go up. Of course, we'll have to wait a couple of years to make sure there's a clear trend, but so far there's *no* statistically-valid reason to claim the warming has stopped.
  10. Do the IPCC use alarmist language?
    Checking with the grammar police - 'panel' is singular, so shouldn't the title be "Does the IPCC use alarmist language?"
  11. Explaining Arctic sea ice loss
    ach, from* the surroundings
  12. Explaining Arctic sea ice loss
    Regarding, "I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result. " Does the ice melting in a glass of water cause the water to get cooler? No, it only prevents it from getting warmer. It does not stop the glass from absorbing energy from its surroundings; it just stops the temperature of the glass from rising until the latent energy required to melt the ice is matched by the energy absorbed by the surroundings.
  13. Do the IPCC use alarmist language?
    Let me point out the obvious, RSVP and Robert. We act in life and death situations every day with a pitifully tiny amount of information. We walk, run, drive, and ride, for example, with only guesswork and little hard data. We constantly use the well-it-worked-before logic, even though the conditions have changed. In short, we bet our lives--and the lives of others--on what are often totally unscientific leaps of cheap reasoning. A great many of us, in fact, bet our time, money, and happiness (and the time, money, and happiness of others) on the idea that there is a supernatural being that has ordered the universe in some detailed way, according to a book written some thousand or thousands of years ago or according to someone who clearly has a vested interest in having us believe such a thing. And yet that's ok. Then we have the IPCC, which has collected the research and input of thousands of scientists, carefully weighed the significance of the data, modeled it in several different ways, checked and re-checked and re-checked the results, and published the information complete with error bars, recognition of weaknesses, and a host of caveats. If the IPCC had simply collected the data and published it all together without providing any models, people would be beating down the doors demanding models--with all their weaknesses. Do we have to stick our hand in the fire to know that doing so will hurt? Not as adults, we don't. We could stick our hand closer and closer to the fire, but we never know that the feeling of heat will not plateau at a certain point. We have theories, and we use the proxy of a stick, noting that the stick is destroyed (as a stick, not as matter) and that the same will likely happen to us. Children have a hard time understanding proxies, and so they stick their hands in the fire, get burned, cry, and get angry (and then end up projecting that anger on the people who warned them not to do it).
  14. Explaining Arctic sea ice loss
    RSVP, Regarding, "If the problem were only due to CO2 the effects would be symetrical, and they are not. " I don't believe you'll find any claim that the variability of sea ice is only due to CO2. Weather patterns, changes in salinity, oscillations of current and upwelling flow, albedo feedbacks, etc. all interweave to produce the variability. Wind patterns are driven by differences in energy content, which is also effected by the radiative properties of the atmosphere (CO2 influenced). It's like a multi-body problem in Newtonian physics. If you move one body, the forces acting on the other bodies change; so, they move, which changes the forces acting on the original body, and so on. There is some evidence that the increase in sea ice around Antarctica is driven by some combination of increased snowfall (If you warm the ocean, it gives off more moisture. If it is still below freezing, that moisture will precipitate as snow, which changes the albedo of the surface water, etc.), lowered salinity, and increased outflow of the land ice.
  15. Do the IPCC use alarmist language?
    Roger A. Wehage, Your exemple about the rectangle is the typical calculation we do when we calculate error tree and Monte-Carlo methos can catch it very easily. By the way, you confuse risk management with quality control, which are quite different beast. When doing risk management, you put your brain in the paranoid mode. Your exemple from NASA are typical case of how exactely NOT doing risk management. For both Challenger and Columbia, the risk was identified but dismiss because it was annoying to adress it. Hum, looks like climate change debate for me. Also, NASA estimate for risks were too low. In the beguining of the program the estimate was 1/300 failure, while observe rate is more like 1/66. But administrators, put it at 1/10000 but it has to be that way.
  16. Do the IPCC use alarmist language?
    #30, #31 There are no risk-free alternatives.
  17. New temperature reconstruction vindicates ...
    #154: "I understand Ljungqvist's comment that you cite ("a very cautious interpretation of the level of warmth since AD 1990 compared to that of the peak warming during the Roman Warm Period and the Medieval Warm Period is strongly suggested") and have no problem with that." But your reconstructions DO have a problem with that. Your post maybde had an intention of also vindicating the original hockey stick shape and that the current temperature trend would be unprecedented. The original study doesnt support that. If you want to be credible also in the eyes of us sceptics', next time, when someone publishes a new proxy-reconstrucion, please cite the graphs used in the papers ant not making your own with your own undocumented un-peer-rewieved methodologies. "However, the key point of my post is to assess the degree to which Ljungqvist "vindicates" Loehle (2008) vs "vindicating" other reconstructions. Loehle's reconstruction is supposed to be a global reconstruction, yet it shows a greater amplitude for NH-centric episodes than actual NH reconstructions (Ljungqvist, Mann, Moberg). To me, that suggests that insofar as Ljungqvist 2010 "vindicates" anyone, it's a much better match to Mann or Moberg than Loehle." And if you add temperature data to Loehle, you get basically same results as Ljundgqvist. She shapes on both are remarkably similar. Some differences occur - like Loehle fails to show RWP and also shows LIA a bit colder. It does NOT vindicate Mann, except with the apples-to-oranges comparison you just did and which was justifiedly strongly critisized on my last posts. The shapes of the original studies simply DO NOT agree. #155: "I don't understand that strategy. Crests are, by definition, noise from short term phenomena. Connecting the dots from 1998's crest to 2009's crest is just as arbitrary as connecting the dots from 1993's trough to 2007's trough. The conclusion that 'there's no statistically significant warming 1998-2010' is to use two and only two data points. How is that not cherrypicking?" Since 1998-2010 ENSO has no significant trend (well it HAS a slightly POSITIVE one). Any other short-term trend will get biased by ENSO (La-Nina to El-Nino trendis 4 example). #156: A running decadal average (red below) would be better at extracting underlying trends with minimised ENSO influence, but as this clearly shows the underlying rising trend few deniers would recommend this methodology." Ok, first of all, you cant calculate running 10 year average to 2010. The graph must end on 2005 since you dont know the avg of 2011 yet (needed for calculating 2006 etc.) Seconly, the warming happened until 1998 until it halted to the "high" level. You are trying to debunk a 12 year trend with a 10year average which is almost as long as the whole trendline which was in question. That doesn't really address my argument, really. Even if 2000 decaedal averge is higher than 1990avg it does not mean the temperatures couldn have halted in the end of 90's. If they just stay on the same level they rose to, the decaedal avg will be simply higher. What if the halt lasts also next 10 year, will you be then using 20yr avg to prove "warmest 20 years in the recorded history!"?
  18. Do the IPCC use alarmist language?
    This is getting off-topic, but since comment #7 is still there... Roger Wehage says NASA spent billions of USD on reliability analysis for the shuttle and still couldn't get an answer that was in the ballpark. First of all, as for the claim of billions spent on risk assessment, [citation needed]. A billion dollars will buy you 4000 years of full-time work from senior engineers; that's a lot of Probabilistic Risk Assessment. But more to the point, he provides a link which destroys his own argument. Follow the link he gives in comment #7 to see that the median reliability of the STS, across numerous studies, ranges from about 1/80 to 1/130. Huh, pretty much exactly the observed reliability. So whence the claim that PRA is impossible, Roger? Yes that's right, the risk assessment by the experts was correct. Remember, in the case of Challenger, all the engineers said "don't launch" until they were overruled by management. Seems to me this whole story does nothing but support the notion that the experts are quite capable of risk analysis of even complex systems, and are to be ignored at your own peril.
  19. Berényi Péter at 23:49 PM on 14 October 2010
    Climate Cherry Pickers: Falling sea levels in 2010
    #107 kdkd at 12:02 PM on 11 October, 2010 there don't seem to be claims about accelerating sea level rise Of course there is one in this very thread. It is based on a post from the same author. "In point of fact, observed sea level rise is already above IPCC projections and strongly hints at acceleration" Or here is another one, this time from Peter Hogarth. "there is a significant weight of evidence of a recent acceleration in rate of sea level rise [...] The weight of peer-reviewed evidence for this acceleration in sea level rise is robust" The meme at this site must have been started by John Cook himself, with an even stronger claim. "So a broader view of the historical record reveals that sea level is not just rising. The rate of sea level rise has been increasing since the late 19th century" Here is a fairly recent one. "Sea-level rise is accelerating faster than the IPCC predicted" These claims are not supported by evidence, still, they keep popping up, undebunked. They are usually connected to alarming projections of even more acceleration in the future (yes, projections, whatever that's supposed to mean, never predictions), based on the alleged accelerating ice loss over Greenland. That acceleration is computed using eight years of GRACE data. Now that's cherry picking. But I can't see it'd meet much opposition here. As for the "scientific approach", University of Colorado at Boulder sea level data are next to useless. They lack error bars completely and the sampling interval is 9.9156 days (several samples missing). It is about one third of a synodic month, but not quite. The difference is 6230 sec (1 h 43' 50''). As the signal itself must contain strong components at multiples of lunar cycle frequency, it looks like an odd choice. The gradual phase shift makes up a full lunar cycle in about 11 years, so on timescales significantly shorter than that it can introduce false trends. This is why Steve Goddard's four month sea level trend does not make sense, not because it is "cherry picking" (it is not, it's just some recent data). It is actually a bit worse than that. He shows data with no inverted barometer correction. If correction is applied, there is no trend whatsoever. Of course in the long run barometric correction should not change the trend at all, because mass of atmosphere is given and there are limits to how uneven its distribution can get before strong winds restore uniformity. But this time span is not sufficiently long. Otherwise there is nothing wrong with the idea that the ocean itself can be used as a global thermometer to check ocean temperature and heat content measurements. This is what Trenberth is trying to do, with not much success so far. The main problems with this ocean thermometer idea is that as we have seen it is not reliable in the short term (neither its long term precision is good enough) and volumetric thermal expansion coefficient of seawater is highly dependent on both temperature and pressure while ocean mass also keeps changing.
  20. Anne van der Bom at 23:28 PM on 14 October 2010
    Do the IPCC use alarmist language?
    Roger A. Wehage, RSVP, in the words of my father, "Your guess is as good as mine." Then I'll take an educated guess over yours or RSVP's. I prefer to use the best available information instead of willfully keeping myself in the dark and pretending the world is just a big blob of unknowable uncertainties.
  21. Do the IPCC use alarmist language?
    Roger @22: Indeed, if the population of the planet was only 7 million, instead of billion, and was projected to rise to 9 million then the imperative to act on the projected change in climate would be less. There would be plenty of space and resources to deal with, at best, a 2C change in temperature. But our population is so great, our use of resources so profligate that to continue on the present path is reckless.
  22. Tai Chi Temperature Reconstructions
    Peter Hogarth, I have a question for your original post. The approach you describe for averaging the proxies seems in my view to be very close to the Composite-Plus-Scale (CPS) method. Especially as it is applied in Ljungqvist, 2010. What are your thoughts on this?
  23. Roger A. Wehage at 21:36 PM on 14 October 2010
    Do the IPCC use alarmist language?
    JMurphy @22: I believe that one should not use the severity or lack thereof in individual events as arguments for or against global warming or climate change. For example, about two hundred years ago the mid Mississippi valley had a powerful earthquake that changed the course of the river. Only a few people died then because only a few people lived in the area. If that same quake were to occur today, hundreds of thousands could die. The same goes for floods and heat waves. Their frequency and severity certainly appear to be increasing. At the same time their impacts on the human population are becoming more severe because of artificial changes we've made to the environment and because of increased population density. For example, heat waves are most severe in paved-over cities that consume hugh amounts of energy to run millions of air conditioners. The unlucky ones are the poor and elderly who cannot afford air conditioners. Many flood disasters are similar. Man has destroyed most of the world's hummus and forest cover and built giant levees to hold back the surging water, only to worsen the situation. Over many decades the U.S. has naively spent many billions of dollars through the Corps Of Engineers to mess with nature; now it is spending many more billions to fix their first mistakes.
  24. Roger A. Wehage at 20:53 PM on 14 October 2010
    Do the IPCC use alarmist language?
    RSVP, in the words of my father, "Your guess is as good as mine."
  25. Do the IPCC use alarmist language?
    Come off it, chriscanaris. You start off on natural disasters and then move on to some early heatwave records, posting some material from WIKIPEDIA but ignoring everything that followed on from the bits you liked - 10 to 15 times more information from the 1970s onwards with lots more records.
  26. Do the IPCC use alarmist language?
    It is redundant to say something is very possible. A thing can either be or not be,... it is either possible or impossible. If it is possible, you can then move on to consider its likelihood (i.e., probability). We know that global warming, for instance is 100% possible, however the probability is indeterminant as the sample space is one.
  27. Do the IPCC use alarmist language?
    chriscanaris yes, there has been heat waves, cold spells, floods, forest fire, etc., in the past. Then what? You're completely missing the meaning of probability, which is what James Wight is talking about. Your pedantic list of extreme events is useless as far as the probability of these events is concerned.
  28. The sun upside down
    Joe Blog you're right, it was poorly worded. What I wanted to say is that the effect of UV by itself is not new, as clearly stated before when I cited the two papers; though, it may be larger than previously thought. On the contrary, the anti-phase change in the VIS is new.
  29. Do the IPCC use alarmist language?
    Heatwaves go back well before the 1980s but this may be purely coincidental: ‘The record for the longest heat wave in the world is generally accepted to have been set in Marble Bar in Australia, where from October 31, 1923 to April 7, 1924 the temperature broke the 37.8 °C (100.0 °F) benchmark, setting the heat wave record at 160 days... The 1936 North American heat wave during the Dust Bowl, followed the one of the coldest winters on record—the 1936 North American cold wave. Massive Heat waves across North America were persistent in the 1930s, many mid-Atlantic/Ohio valley states recorded their highest temperatures during July 1934. The longest continuous string of 100 °F (38 °C) or higher temperatures was reached for 101 days in Yuma, Arizona during 1937 and the highest temperatures ever reached in Canada were recorded in two locations in Saskatchewan in July 1937.’
  30. Explaining Arctic sea ice loss
    adelady #34 "You're not distinguishing between sea ice and land ice." If you compare the geographies, the poles are almost perfectly inverted. As per links (below), the area contained within the northern 70 degree parallel is ocean, coinciding with the Antartic continent which is also roughly contained with the southern 70 degree parallel. In the one case the pole is at sea level (and encapsulated by land), and in the other, the region is mountainous, surrounded by water. I didnt see anything here about warmer waters causing ice in the north to melt. If anything the water would be cooling as a result. http://geology.com/world/arctic-ocean-map.shtml http://www.lib.utexas.edu/maps/islands_oceans_poles/antarctic_region_pol_2005.pdf
  31. Do the IPCC use alarmist language?
    SME wrote : "Lack of planning and foresight by authorities thus seems to be a major factor. A fine example of Murphy at work." It wasn't me, honest ! Anyway, looking at lists of natural disasters, it's curious how most of those involving heatwaves are since 1980. Or is it ?
  32. The sun upside down
    Riccardo specifically this line "But apart from the numbers, there's nothing new in Haig et al. 2010 for the UV range." Maybe i misinterpreted your summary, but it seemed to me you were implying that this articles findings didnt suggest maybe a larger dynamical effect through UV in the stratosphere, rather than a change in short wave forcing at the surface. No question more data is needed to verify these findings. But interesting stuff either way. Obviously more data is needed to draw firm conclusions
  33. The sun upside down
    Joe Blog could you please point me to the part of the post that disagree with this quote? I think I've said the same thing.
  34. Do the IPCC use alarmist language?
    The Pakistani floods had multiple causes such as: '...unprecedented monsoon rain... attributed to La Niña... Some of the discharge levels recorded are comparable to those seen during the floods of 1988, 1995, and 1997... An article in the New Scientist attributed the cause of the exceptional rainfall to "freezing" of the jet stream, a phenomenon that reportedly also caused unprecedented heat waves and wildfires in Russia as well as the 2007 United Kingdom floods.' Other factors: 'The Pakistani government was blamed for sluggish and disorganized response to the floods... President Asif Ali Zardari was also criticized for going ahead with visits to meet leaders in Britain and France at a time when his nation was facing catastrophe. In Sindh, the ruling Pakistan People's Party ministers were accused of using their influence to direct flood waters off their crops while risking densely populated areas. Pakistani ambassador for UN Abdullah Hussain Haroon called for an inquiry into allegations about rich landowners diverting water into unprotected villages to save their own crops.' Pakistan is no stranger to extreme weather events though these are the worst in its recorded history. The 1931 China floods are arguably the worst in world history with a death toll ranging from 1.3 – 4 million. Not an argument for complacency - mother nature is indeed an angry beast however we understand the recent tragedy.
  35. The sun upside down
    Thanks TOP for the link. Riccardo at 19:12 PM With the benefit of having read the article in question, id have to disagree with your summary of the conclusions of Dr Haigh. I believe in her own words, this better sums up the findings. "The SORCE observations are, however, consistent with a solaractivity-dependent change in the temperature gradient of the solar photosphere4, suggesting that the offsetting irradiance trends with wavelength seen in SIM should appear in each solar cycle. If this is the case, then it is necessary to reconsider the current understanding19 of the mechanisms whereby solar cycle variability influences climate: the impact on the stratosphere is much larger than previously thought and the radiative forcing of surface climate is out of phase with solar activity. At present there is no evidence to ascertain whether this behaviour has occurred before, but if this were the case during previous multi-decadal periods of low solar activity it would be necessary to revisit assessments of the solar influence on climate and to revise the methods whereby these are represented in global models." So basically this is suggesting that the sun may influence climate in the troposphere, through varying UV effects in the stratosphere.
  36. Anne van der Bom at 18:13 PM on 14 October 2010
    Do the IPCC use alarmist language?
    Roger A. Wehage "Because the space shuttle is a nightmare. A little O-ring failure here a little insulation impacting a tile there. A gas leak here a stuck valve there. I've a feeling Earth's climate is no different." Well said. A very good motivation why we should be careful not to change the composition of the atmosphere while we are in the dark about what the exact consequences are. Humanity at the controls of the climate feels about as safe as Homer Simpson at the controls of a nuclear power plant. ---------------------------------- Since you are an expert on models, that is the subject you concentrate on. That is a pitfall. The predictions are based on more than just models. Ice cores for example are another line of evidence that point in the same direction wrt climate sensitivity. Look at the full body of evidence.
  37. The sun upside down
    Joe Blog I fixed the Haigh 2005 link, thank you. UV impact, as we noticed before, is (almost) not questioned by anyone; some details may not be clear but scientists essentially agree that the effect is there. On the contrary, the GCR hypothesis is still missing a strong confirmation and it is anticipted that GCR have a small on our climate, if any.
  38. Do the IPCC use alarmist language?
    I must admit I have been frustrated by the conservatism of this projection, not so much now, but particularly when it appeared in earlier IPCC reports with a lower degree of certainty. “Most of the observed increase in global average temperatures since the mid-20th century is very likely (greater than 9 in 10) due to the observed increase in anthropogenic greenhouse gas concentrations.” With the mechanism for heat capture by greenhouse gases proven in the laboratory and confirmed by satellite measurements; with no other mechanism demonstrating sufficient forcing to account for the observed rise in temperature; with temperature and CO2 tightly coupled in paleo-climate data - what other explanation justifies the remaining 1 in 10 uncertainty? An alien secret weapon perhaps? I get annoyed that scientists are expected to prove that the warming is outside the bounds of “natural variation”, as if the latter were an independent phenomenon. It is clear that the natural variation in average temperature in both paleo and human history is predominantly driven by changes in CO2, even if initially triggered by smaller forcings such as variation in solar radiance. Yet the skeptics use the term as if it provides a valid alternate explanation. The rise in CO2 in the second half of the 20th century is obviously anthropogenic because we can make fairly accurate estimates of the oil, coal, peat and wood that has been burnt. When you have a proven relationship between cause and effect, and clear evidence for the cause, denying the effect is pure folly.
  39. Do the IPCC use alarmist language?
    As a "truth seeker" (that's a person who is attacked and criticised by people at both extremes :-))I found that comment reasonably OK. I'd have minor quibbles but they are not enough to be worth raising. The addition at the end re Pakistan was unfortunate as it doesn't make the overall point at all well and the argument would have been better with the example excluded. While events such as the Pakistan flooding are complex and cannot be simplistically categorised, a major point is that this disaster was NOT driven by an especially extreme weather event. The overall rainfall is reported to have been in the 20 year flood to 30 year flood range. High - but within the range that people reasonably expect to have to deal with in a sensible manner. Damage would be expected, but not catastophe. In this case other factors appear to have been responsible for turning what should have been a modest disaster into a major one. The biggest apparent factor is a change in land use and irrigation practices in relatively recent times, so that drainage has been routed much more efficiently into areas requiring irrigation, and water which was previously wasted for this purpose is now channelled to where it is most wanted. Usually. Alas, as with many man-made optimisations, when the 25 year flood comes the drainage system does not drain as it did before and instead places the water where it is most unwanted, on this occasion, and fails to "waste" it by sending it to sea as it used to do. Lack of planning and foresight by authorities thus seems to be a major factor. A fine example of Murphy at work. SME
  40. Do the IPCC use alarmist language?
    Good to see this covered properly - thanks James. Understanding the nature of predictive science, which can only deal with probabilities, is key to appreciating the nature of the problems we face and the overwhelming likelihood that our actions are storing up great and disruptive problems for the future.
  41. Quantifying the human contribution to global warming
    John - the IPCC WG1 report. You have read this I hope. However, you comment is somewhat amnbiguous. A 50-100W/m2 FORCING would be deadly. More like 3.7 I think. Are you asking though about the amount of change in radiation from surface being absorbed by CO2 or the change in the amount of back radiation received by the surface from the amount of change in CO2 alone? You might want to look at Philipona 2004 or liberation.fr.
  42. Models are unreliable
    Continuing from here. "The algebra of probabilistic distributions is extremely complex ... Extrapolating complex environmental data described by complex statistical relationships into the future is indeed a difficult process" What you've described (in the linked comment) sounds like a fairly routine problem in particle physics. And yet we build devices that rely on the motion of electrons through semiconductors; we manage to collide protons and anti-protons with statistical certainty (and avoid hysterical claims that we'd be creating mini black-holes in the process). We can even make sense of the results and produce a very competent model of the sub-atomic world. Your argument suggests that if a problem is too complex, we can't put any faith in a model solution. The implication is that it's a waste of time and money to begin that process. Yet that is a challenge that has been met successfully in other disciplines. Some of the comments above suggest that it can work here as well.
  43. Medieval Warm Period was warmer
    Heidi, the trouble with simplified, nontechnical explanations is that they must leave out the very details required to make them fully articulate. We can distill and digest but it's a lossy form of compression. In the final analysis, to have understanding and more particularly fully justified confidence in perfect synchrony with the research, one has to dig into literature and end up on a parallel plane w/researchers themselves. Normally this is not a problem. I can give you a broad brush treatment of how a parachute works, I can point to the success of parachutes. You could walk away from such a conversation w/a reasonable degree of confidence in parachutes based on a lossy description. But such a treatment is not durable against concerted resistance. Compared to climate research, I don't have to worry about a bunch of parachute skeptics insisting that parachutes don't work because you and I do not have understanding of their aerodynamic principles up to NASA-Ames standards.
  44. Explaining Arctic sea ice loss
    Philippe Chantreau #22 "I don't know what you're trying to say there." Comparing the Artic with Antartica, I was saying that the Artic ice is mainly at sea level, and that Antartica ice is mostly mounted on land. Not sure if you ever noticed, but it gets colder as altitude increases, so without doing any reasearch, I made the not so unreasonable speculative comment that the Artic is more predisposed to what is actually being observed than Antartica for this reason. As for your question about my use of quotes around "water" and "land"... these refer to the substrate, whereas the surface is actually ice.
  45. Do the IPCC use alarmist language?
    #14: "The algebra of probabilistic distributions is extremely complex" Switching to Models are unreliable as per Mod request.
  46. Do the IPCC use alarmist language?
    Well I would have to agree with you on need to explore all parameter uncertainty, and I think (but dont know for sure) that they dont have computer power to explore full model. Annan has paper coming out on model ensemble determination. However, note the approach in climate sensitivity estimation.

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