# Arctic Ice Returning? **URL:** \ **Category:** Great Debates\ **Created:** [February 26, 2008, 5:11pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239 "2008-02-26T17:11:55Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 11:48am UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/21 "2008-02-27T11:48:23Z")
From a philisophical perspective, my problem is this: If the Artic had had a very warm January, it seems likely that it would have been cited as evidence of catastrophic man-made global warming. So if a cold January is dismissed as a fluctuation, it seems like there is a bit of a double standard at work. Not only that, but if a cold January is cited as evidence of catastrophic “climate change,” one wonders what would NOT be considered such evidence. Perhaps an average January. The trouble is that somewhat extreme weather is always happening somewhere on the globe. So whether catastrophic global warming theory is true or false, there will always be some evidence to support it. And that raises a falsifiability problem. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [February 27, 2008, 1:05pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/22 "2008-02-27T13:05:28Z")
[QUOTE=Slypork] **jshore** , since you are the AGW expert here\*, can you please tell us if there is any validity to [the info on this site?](http://www.dailytech.com/Temperature+Monitors+Report+Worldwide+Global+Cooling/article10866.htm) Should we be talking about Anthropogenic Climate Change instead of Anthropogenic Global Warming so if temperatures dramatically drop we can look at a manmade cause? [/QUOTE] As others have already pointed out, the blog where the Daily Tech got their data has already disassociated itself with their interpretation of the data as wiping out nearly all the warming over the last 100 years…and there are good reasons that they did. First of all, that claim is not even true numerically. While it may be true that the global average temperature has dropped from January 2007 to January 2007 by an amount that is almost equal to the total quoted warming in the last 100 years (of about 0.7 C or so), the former refers to temperatures averaged over one month where the latter refers to temperatures averaged over a year (and, then in fact, further averaged over a few years). So, in particular, the anomaly value in January 2007 was higher than the anomaly over the entire year. Thus, we see that from the Daily Tech’s own figure that the anomaly value for January 2008 is still positive (using a 1951–1980 baseline), i.e., the January 2008 temperature was higher than the average over the period 1951-1980, which itself was already higher than 100 years ago. Second of all, there are always going to be fluctuations in temperature over shorter timescales. To give an analogy, when it got above 60deg in Rochester a few weeks ago, did that wipe out nearly the entire drop in temperature associated with the season that we here call “winter”? As for their argument attributing this correlation to reduced solar activity, the old’ “correlation is not causation” argument comes into play. (Worse yet, they haven’t even tried to show how good the correlation looks in time…and it may not look good at all.) If solar activity were a dominant factor and the climate could respond this quickly to such changes, then there ought to be a stronger climate signal due to the known fluctuations in solar activity associated with the 11-year solar cycle. As it is, studies suggest that any such signal seems to be pretty small. A more likely explanation for the change is the dramatic shift in the last year from El Nino conditions to La Nina conditions. In fact, you can see in the data a drop that looks quite analogous in 1998/1999 when we had a similar shift from El Nino to La Nina. ---
**Author:** ![RTFirefly](https://avatars.discourse-cdn.com/v4/letter/r/c77e96/32.png) [@RTFirefly](https://boards.straightdope.com/u/RTFirefly)\ **Post date:** [February 27, 2008, 2:20pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/23 "2008-02-27T14:20:30Z")
[QUOTE=brazil84] From a philisophical perspective, my problem is this: If the Artic had had a very warm January, it seems likely that it would have been cited as evidence of catastrophic man-made global warming. So if a cold January is dismissed as a fluctuation, it seems like there is a bit of a double standard at work. [/quote] No. The ‘double standard’ you refer to is that of making a distinction between illustrating an argument with an example, and providing an example without an associated argument. An argument without an example, like a cat without a grin, stands on its own. But the example helps the argument _connect_. But an example without an argument, like a grin without a cat, doesn’t stand on its own - outside of Wonderland, anyway. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [February 27, 2008, 4:50pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/24 "2008-02-27T16:50:11Z")
[QUOTE=The Flying Dutchman] Tell us something we don’t know [/quote] Well, okay, yes it is obvious that the ice will get thicker in the winter. This was still worth saying given that the National Post piece was pretty sloppy with exactly what they were describing. > [@](#): > > Again, everyone knows the ice grows in winter. Since you’re critiquing The National Post article, I think yiou may have misread their statement on the ice recovery. They weren’t saying the ice is thicker since the summer. They are saying the ice is thinker than the same time last year. Big difference. And, unfortunately, you misread **my** statement. In this part I was now no longer talking about the absolute amount of ice but about the anomaly, which means that the season variation has been factored out. > [@](#): > > Well the annual mean has been below the baseline mean for almost 10 years and steadily decreasing. The past year has seen the most dramatic decrease and an **even more dramatic** recovery in ice coverage to an annual high point over that of 2007 and even with 2006. That means its been a pretty damn cold winter up there. Sure we aren’t back to the base line yet, but that would require, given the smallest area of ice in history to start with last summer, a winter so cold we haven’t seen it in our lifetime. My point is that such a partial recovery is not unexpected…and in fact as the RealClimate piece that I linked to showed, there was at least a significant fraction of scientists at the AGU meeting who seemed to expect a recovery such as this. [Actually, there was a significant fraction who even expected a recovery on a year-upon-year basis rather than a partial year basis…which is all the data we have at this point since this summer’s record low extent.] For one thing, I am pretty sure that the models predict more decrease in ice extent in the summer (relative to what it was before global warming) than decrease in ice extent in the winter (relative to what it was before global warming)…which means that the anomaly itself will tend to get more negative in the summer and less negative in the winter. For another thing, global warming does not repeal the fact that there are significant fluctuations in the system. Just as the global temperature does not monotonically increase each year but also has quite a bit of noise, so too this will be true of the sea ice ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 27, 2008, 4:59pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/25 "2008-02-27T16:59:55Z")
The thing is (and correct me if I’m wrong here) that a year or even a couple of years (or in this case a season) of cooler temperatures in a region or even globally (though I’ve seen no indication of that) doesn’t disprove the theory of AGW/GW. It’s not like the temperature is always going to go up everywhere on the earth…or even that the average temperature is always going to go up. There will be all sorts of variations if I understand the theory correctly…even VERY cold local conditions. That’s why a lot of the folks I’ve talked to who work at Sandia prefer Global Climate Change to Global Warming…it better represents what is going on they say. An anomalous data point (as referenced in the OP) is simply that…ONE data point. If we see a trend in the next decade or so then THAT may be something to think about. Maybe there is some other factor at work that wasn’t previously understood. Obviously the CO2 IS rising…and that is going to cause SOME effect. But right now this evidence doesn’t mean anything…it certainly doesn’t disprove or even dent the theory of climate change happening. In fact, quite the opposite…as from what I can tell it is EXPECTED that there will be a great deal of local variance as the climate shifts about due to the extra CO2 in the atmosphere. -XT ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 5:11pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/26 "2008-02-27T17:11:14Z")
[QUOTE=RTFirefly] No. The ‘double standard’ you refer to is that of making a distinction between illustrating an argument with an example, and providing an example without an associated argument. An argument without an example, like a cat without a grin, stands on its own. But the example helps the argument _connect_. But an example without an argument, like a grin without a cat, doesn’t stand on its own - outside of Wonderland, anyway. [/QUOTE] I’m not sure I see your point . . . are you saying that if a pro-AGW individual cites a few melting glaciers, or a hot year, that he or she is merely providing an example to illustrate an argumnt? On the other hand, if a skeptic cites a few instances of colder weather, are you saying that he or she has no underlying argument that’s being illustrated? ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [February 27, 2008, 5:35pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/27 "2008-02-27T17:35:28Z")
[QUOTE=brazil84] I’m not sure I see your point . . . are you saying that if a pro-AGW individual cites a few melting glaciers, or a hot year, that he or she is merely providing an example to illustrate an argumnt? On the other hand, if a skeptic cites a few instances of colder weather, are you saying that he or she has no underlying argument that’s being illustrated? [/QUOTE] _Anybody_ who cites only a hot year or a few instances of colder weather has no underlying argument, no matter what they’re trying to show. Climate change is a long term process, and the temperature for any given year is nothing more than a single data point. You can’t draw any conclusions from one data point, and you can’t use one data point to prove anything. You can do two things with a single data point: illustrate the continuation of a trend, or show that the point is outside the expected range and point out that the expected trend doesn’t account for that data. If you want to do the second, you’d better understand the hypotheses and models you’re trying to disprove. Your conflation of “a few melting glaciers” with a “hot year” is misleading as well. A hot summer is one season, but a melting glacier (over a reasonable time frame) is a climatologically significant phenomenon. Because of the summer-winter cycles, most glaciers are constantly losing and gaining mass. Every summer, some of the glacier melts, and every winter the glacier accumulates more mass. Changes in glacier are quantified using an annual balance that takes into account both summer and winter processes. A “melting glacier” is one that has been losing water consistently over a multi-year period. The majority of glaciers on earth fit into this category over the last 50 years, and the rate of water loss has increased significantly over the last 10-15 years. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 5:42pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/28 "2008-02-27T17:42:31Z")
[QUOTE=Enginerd] _Anybody_ who cites only a hot year or a few instances of colder weather has no underlying argument, no matter what they’re trying to show. [/quote] Here’s a quote from realclimate: > [@](#): > > Here are the recent Svalbard monthly surface temperature measurements, the long-term (1961-1990) means (“ybar”) and standard deviations (“sd”), and associated anomalies i.e., departure from average (“delta”) for Dec 2005 through April 2006 (all in degrees C): > > ``` > Month Value ybar sd Delta > Dec 05 -3.8 -13.3 4.4 +9.5 > Jan 06 -2.7 -15.3 4.7 +12.6 > Feb 06 -9.8 -16.3 3.7 +6.5 > Mar 06 -13.1 -15.8 3.7 +2.7 > Apr 06 0.0 -12.4 2.7 +12.4 > > ``` > > The numbers are fairly remarkable. April’06 was warmer than any previously recorded May, and January '06 was warmer than any previously recorded April. The previously warmest April was -7.0C (1996) -4.3C (2004). There is currently an absence of sea ice off much of the coast of Svalbard, which is also unprecedented for so early in the year. > > The April mean temperature is almost 5 standard deviations above the mean, a “5 sigma event” in statistical parlance. Under the assumption of stationary ‘normal’ statistics, such an event is considered astronomically improbable (\< 1 in 106), and, like the summer heat wave in Europe in 2003 (which was a 5 sigma event in Switzerland, 3 sigma over Europe as a whole), deserves special attention. As we have nonetheless remarked before on RC, particular events, even seasonally-persistent anomalies as unusual as these, do not “prove” anthropogenic warming. But in a statistical sense, large outliers like this make it more probable that the underlying distributions are shifting and give us a glimpse into the types of anomalies we might expect to become more common in the decades ahead. Do you agree or disagree? And by the way, I wish you’d been around back in the 1990s when a college professor of mine cited a couple hot summers as evidence of man-made global warming. > [@](#): > > Your conflation of “a few melting glaciers” with a “hot year” is misleading as well. A hot summer is one season, but a melting glacier (over a reasonable time frame) is a climatologically significant phenomenon. I wasn’t necessarily thinking of any particular time frame. But anyway, to avoid confusion, please just assume I was talking about more limited events. Thank you. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 27, 2008, 5:48pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/29 "2008-02-27T17:48:01Z")
[QUOTE=brazil84] Do you agree or disagree? [/QUOTE] Agree or disagree with what exactly? Your cited quote is showing a single data point to illustrate a TREND. As opposed to the single data point in the OP which illustrates…a single data point. -XT ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 5:51pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/30 "2008-02-27T17:51:21Z")
[QUOTE=xtisme] Agree or disagree with what exactly? [/quote] Mainly I was asking about the last 2 sentences. But I would also be curious to know if **Enginerd** thinks there is an “underlying argument.” ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [February 27, 2008, 5:58pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/31 "2008-02-27T17:58:43Z")
[QUOTE=brazil84] Here’s a quote from realclimate: [quote snipped - Eng.] Do you agree or disagree? [/quote] I agree, and I have no idea why you’d post this. It illustrates the point I made perfectly - realclimate is using the small group of data points to show both the ideas I mentioned. They’re showing that the 5 sigma event fits AGW models that predict a rising global temperature (illustrating the continuation of a trend) and that it’s phenomenally unlikely that they would occur in the absence of a warming trend (illustrating problems with an alternative hypothesis). > [@](#): > > I wasn’t necessarily thinking of any particular time frame. But anyway, to avoid confusion, please just assume I was talking about more limited events. Thank you. You can’t discuss climate change without thinking of any particular time frame. I haven’t seen anybody cite single season summer glacial melt as evidence for AGW. If I make this assumption, your statement ceases to illustrate the point you were making - it’s clear that that’s not what you meant. I’m not going to assume anything for you. If you want to discuss various time-sensitive phenomena, you’re going to have to define the time scales you’re talking about. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 6:08pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/32 "2008-02-27T18:08:17Z")
[QUOTE=Enginerd] I agree, and I have no idea why you’d post this. It illustrates the point I made perfectly - realclimate is using the small group of data points to show both the ideas I mentioned. [/quote] But you said that "Anybody who cites only a hot year or a few instances of colder weather has no underlying argument, no matter what they’re trying to show. " Seems to me that’s basically what realclimate did. But to make things clearer, let’s reverse things. Suppose that somebody cited a few months of unusually cold weather and said “yes, this doesn’t PROVE that AGW is a hoax, but it fits in with and illustrates my ideas.” Would there be any problem with that? ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [February 27, 2008, 6:22pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/33 "2008-02-27T18:22:19Z")
[QUOTE=brazil84] But you said that "Anybody who cites **only** a hot year or a few instances of colder weather has no underlying argument, no matter what they’re trying to show. " [/quote] I bolded an important part of my quote for you. You can use a single data point _in context_ to illustrate or contradict a larger idea. That’s what realclimate did, by going into the standard deviations and expected values and probabilities. The article posted by the OP didn’t do it - they just threw out the point about a cold winter and arctic sea ice without any scientific analysis whatsoever. > [@](#): > > But to make things clearer, let’s reverse things. Suppose that somebody cited a few months of unusually cold weather and said “yes, this doesn’t PROVE that AGW is a hoax, but it fits in with and illustrates my ideas.” > > Would there be any problem with that? You’re making two different claims, I think. The first is with regards to the AGW hypothesis. If the data point that you’re citing fits into that model (and harsh winters certainly do fall into the range of expectations from many, if not most GCMs), there’s nothing to be said about that. The data point either does or doesn’t contradict those predictions. As far as the claim that it supports your ideas… do you have the statistical analysis to back up the statement? Do you even have a model or a firm hypothesis that you’re working from? If you do, then I think it’s a fine claim to make. It’s certainly possible to come up with differing mechanisms and models to explain the same phenomenon, especially when it’s something with as much uncertainty as climate change. Every new data point provides another way to test the robustness of a model. But you can’t do it in isolation. If you make that claim, you’ll then be expected to show how you explain other data sets as well. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 27, 2008, 6:24pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/34 "2008-02-27T18:24:35Z")
It would be equivalent to saying ‘These things that look like human foot prints next to these obviously dinosaur foot prints proves that the theory of Evolution is incorrect’. Unless you have a body of data AND a (testable) theory to go with it you are basically just pointing to anomalies and then saying this proves the theory is wrong. Show me an alternative theory to AGW and the data that backs it up (with the OP’s data being a single data point among many) and then we can talk. I’ve seen no such alternative theory with the corresponding data. ETA: Posted in response to brazil84’s previous post…didn’t see the other reply until after. IOW…never mind. Was said better by Enginerd. -XT ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 7:53pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/35 "2008-02-27T19:53:18Z")
[QUOTE=Enginerd] I bolded an important part of my quote for you. You can use a single data point _in context_ to illustrate or contradict a larger idea. That’s what realclimate did, by going into the standard deviations and expected values and probabilities. The article posted by the OP didn’t do it - they just threw out the point about a cold winter and arctic sea ice without any scientific analysis whatsoever. [/quote] Here’s an editorial from the Boston Globe: [http://www.boston.com/news/weather/articles/2005/08/30/katrinas\_real\_name/](http://www.boston.com/news/weather/articles/2005/08/30/katrinas_real_name/) Can we agree that it contains no scientific analsysis whatsoever? > [@](#): > > You’re making two different claims, I think. The first is with regards to the AGW hypothesis. If the data point that you’re citing fits into that model (and harsh winters certainly do fall into the range of expectations from many, if not most GCMs), there’s nothing to be said about that. The data point either does or doesn’t contradict those predictions. I’m not exactly sure what your point is but . . . would a mild winter fit in with the AGW hypothesis? A medium winter? Exactly what sort of weather DOESN’T fit in with the AGW hypothesis? ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [February 27, 2008, 8:30pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/36 "2008-02-27T20:30:00Z")
[QUOTE=brazil84] Here’s an editorial from the Boston Globe: [http://www.boston.com/news/weather/articles/2005/08/30/katrinas\_real\_name/](http://www.boston.com/news/weather/articles/2005/08/30/katrinas_real_name/) Can we agree that it contains no scientific analsysis whatsoever? [/quote] Yes. We probably also agree that it contains exaggerated threats and scare-mongering, and that it doesn’t advance the cause of science at all. > [@](#): > > I’m not exactly sure what your point is but . . . would a mild winter fit in with the AGW hypothesis? A medium winter? > > Exactly what sort of weather DOESN’T fit in with the AGW hypothesis? My point is to respond to your question. If you don’t know what the AGW hypothesis describes, maybe you shouldn’t be arguing that it’s incorrect. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 8:51pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/37 "2008-02-27T20:51:02Z")
[QUOTE=Enginerd] Yes. [/quote] Thank you. And I think it illustrates my point, so to speak. > [@](#): > > If you don’t know what the AGW hypothesis describes, maybe you shouldn’t be arguing that it’s incorrect. Maybe not. If the AGW hypothesis predicts that either (A) weather will trend warmer; or (B) weather will trend colder; or (C) weather will stay about the same in temperature, then I wouldn’t argue that it’s incorrect. I would simply argue that it’s non-scientific. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 27, 2008, 9:08pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/38 "2008-02-27T21:08:29Z")
[QUOTE=brazil84] Maybe not. If the AGW hypothesis predicts that either (A) weather will trend warmer; or (B) weather will trend colder; or (C) weather will stay about the same in temperature, then I wouldn’t argue that it’s incorrect. I would simply argue that it’s non-scientific. [/QUOTE] Well, if you put it like that then…sorry, there was too much straw blowing there. What were you saying? Do you understand the difference between average global temperature and average local temperature? Because it doesn’t seem so based on what you are saying in this thread. Unless you can show that the average GLOBAL temperature is down FOR THE YEAR then nothing shown here contradicts the GW hypothesis. From [Wiki](http://en.wikipedia.org/wiki/Global_warming) : > [@](#): > > Global warming is the increase in the average temperature of the Earth’s near-surface air and oceans in recent decades and its projected continuation. > > The global average air temperature near the Earth’s surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the hundred years ending in 2005.[1] The Intergovernmental Panel on Climate Change (IPCC) concludes “most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”[1] via the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.[2][3] These basic conclusions have been endorsed by at least thirty scientific societies and academies of science,[4] including all of the national academies of science of the major industrialized countries.[5][6][7] While individual scientists have voiced disagreement with some findings of the IPCC,[8] the overwhelming majority of scientists working on climate change agree with the IPCC’s main conclusions.[9][10] > > Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.[1] The range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.[1] > [@](#): > > Recent > > Global temperatures on both land and sea have increased by 0.75 °C (1.35 °F) relative to the period 1860–1900, according to the instrumental temperature record. This measured temperature increase is not significantly affected by the urban heat island effect.[49] Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade).[50] Temperatures in the lower troposphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with possibly regional fluctuations such as the Medieval Warm Period or the Little Ice Age. > > Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land.[51] The Northern Hemisphere has more land than the Southern Hemisphere, so it warms faster. The Northern Hemisphere also has extensive areas of seasonal snow and sea-ice cover subject to the ice-albedo feedback. More greenhouse gases are emitted in the Northern than Southern Hemisphere, but this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres. > > Based on estimates by NASA’s Goddard Institute for Space Studies, 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree.[52] Estimates prepared by the World Meteorological Organization and the Climatic Research Unit concluded that 2005 was the second warmest year, behind 1998.[53][54] Temperatures in 1998 were unusually warm because the strongest El Niño in the past century occurred during that year.[55] > > Anthropogenic emissions of other pollutants—notably sulfate aerosols—can exert a cooling effect by increasing the reflection of incoming sunlight. This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century,[56] though the cooling may also be due in part to natural variability. James Hansen and colleagues have proposed that the effects of the products of fossil fuel combustion—CO2 and aerosols—have largely offset one another, so that warming in recent decades has been driven mainly by non-CO2 greenhouse gases.[57] > > Paleoclimatologist William Ruddiman has argued that human influence on the global climate began around 8,000 years ago with the start of forest clearing to provide land for agriculture and 5,000 years ago with the start of Asian rice irrigation.[58] Ruddiman’s interpretation of the historical record, with respect to the methane data, has been disputed.[59] The trend is an increase in average global temperatures. That doesn’t mean that every year will necessarily increase…nor that local conditions everywhere will increase. There are all kinds of factors that influence the variation in global average temperature. One local data point is not going to disprove anything. A global trend for the next decade downward MAY disprove the GW part of the hypothesis…but until that happens the hypothesis remains the best model we currently have. Since it IS science (unlike your man of straw) it’s testable. If the hypothesis is wrong it will eventually be discarded in favor of a new hypothesis that refines the data and builds a new model. Thus far that hasn’t happened despite a decade of testing. That doesn’t mean it won’t prove false in the end…but the data point given by the OP proves nothing. -XT ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [February 27, 2008, 9:12pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/39 "2008-02-27T21:12:16Z")
[QUOTE=xtisme] Well, if you put it like that then…sorry, there was too much straw blowing there. What were you saying? [/quote] I’m not misrepresenting anybody’s opinion. > [@](#): > > Do you understand the difference between average global temperature and average local temperature? Because it doesn’t seem so based on what you are saying in this thread. Unless you can show that the average GLOBAL temperature is down FOR THE YEAR then nothing shown here contradicts the GW hypothesis. Two questions: If the average local temperature rises somewhere, does that support the AGW hypothesis? If the average global temperature decreases (for the year), does that undermine the AGW hypothesis? ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 27, 2008, 9:18pm UTC](https://boards.straightdope.com/t/arctic-ice-returning/439239/40 "2008-02-27T21:18:37Z")
[QUOTE=brazil84] I’m not misrepresenting anybody’s opinion. [/QUOTE] The statement I quoted from you was obviously a strawman…and having seen you in your 1000 years thread I know that YOU know it. [QUOTE=brazil84] If the average local temperature rises somewhere, does that support the AGW hypothesis? [/QUOTE] It neither proves nor disproves anything. It is simply an isolated data point. People who use a single local rise in temperature or some freak weather system (like, say, a hurricane) to ‘prove’ AGW/GW is right (without reference to all the other data) don’t know what they are talking about. Same with people attempting to ‘prove’ AGW/GW is wrong using local lows. There will always be local variations. [QUOTE=brazil84] If the average global temperature decreases (for the year), does that undermine the AGW hypothesis? [/QUOTE] No, of course not. Again, even globally there will be variations. Solar output for instance is a variable. It’s the trend that is important. You will get anomalies and variations. However if the trend is an increase (over time) and if it tracks with CO2 emissions rising then you have the basis of data pointing toward confirming the hypothesis. -XT [Previous page](https://boards.straightdope.com/t/arctic-ice-returning/439239.md?page=1) [Next page](https://boards.straightdope.com/t/arctic-ice-returning/439239.md?page=3)