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Climate Hustle

The human fingerprint in the seasons

Posted on 3 December 2010 by John Cook

In 1896, Svante Arrhenius mentioned that greenhouse warming should cause winters to warm faster than summers (Arrhenius 1896), citing an earlier prediction by John Tyndall (Tyndall 1865). During summer, a region receives more sunlight and warms. During winter, the region receives less sunlight and cools by radiating heat to space. Greenhouse gases stop some of this heat from escaping to space so an increased greenhouse effect slows down the winter cooling. Consequently, if greenhouse gases are causing global warming, we expect to see winters warming faster than summer.

A pair of studies (Braganza et al 2003, Braganza et al 2004) recognise that within the temperature record are a number of climate indices that can tell us more about what's causing temperature change than mere global temperature. The difference in trend between summer and winter, between land and ocean warming, between the equator and the poles - these all hold vital clues into what has caused climate change since the instrumental record began in the 1800s.

They found that winters have been warming faster than summers. What's interesting is how the seasons have changed over time. In the early 20th century, they find the warming is a combination of man-made and natural forcing (eg - from the sun) as well as some internal variability (eg - ocean cycles). In the latter 20th century, man-made forcing accounts for nearly all the observed temperature changes (Braganza et al 2004).

To check this out for myself, I tried plotting the winter vs summer trend using the CRUTemp Northern Hemisphere land temperature record. Robert Way kindly helped out by working out the winter and summer temperature anomalies and plotting them  (here's the Excel file for the curious climate tragic).

 

Figure 1: Yearly temperature anomaly for Northern Hemisphere winter (light blue) and summer (light red) plus five year moving average for winter (thick blue) and summer (thick red). Data comes from CRUTemp, base period is 1961 to 1990.

Not only does the faster warming winter provide evidence for greenhouse warming (on top of many other lines of evidence for man-made global warming), it also provides evidence that the sun isn't the cause of recent global warming. If global warming was driven by the sun, we should see summer warming faster than winter. This is just one of the "solar fingerprints" that we would expect to see from solar warming, that we don't see. Interestingly, many of the solar fingerprints are quite different to the patterns expected from greenhouse warming

For example, greenhouse warming predicts nights should warm faster than days while solar warming is the other way around. Observations are consistent with greenhouse warming. Similarly, if global warming was driven by the sun, we should see the stratosphere warming as well as the troposphere. Greenhouse warming, on the other hand, warms the troposphere but cools the stratosphere. Again, observations match greenhouse warming.

Solar warming should result in the tropics warming faster than the poles. What we observe instead is the poles warming around 3 times faster than the equator. All these pieces of evidence paint a consistent picture - greenhouse gases, not the sun, are driving global warming.

UPDATE 10 Dec 2010: In the original posting of this blog post, I mistakenly posted a graph of global temperature, not northern hemisphere temperature (which is a bit annoying - back when I was preparing this post, Robert and I looked at both NH and global trends then I mistakenly used the wrong Excel file when exporting the final graph). I've updated the post with the NH temps.

UPDATE 11 Dec 2010: Many thanks to muoncounter who went to the trouble to compare Northern Hemisphere winter vs summer temperatures in the satellite record - a handy way to independently confirm the surface measurements (here's the Excel file):

 

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Comments 101 to 150 out of 177:

  1. #47 muoncounter
    My first point is that in the tropic band the majority of heat absorbed from the sun is absorbed in the ocean because the ocean comprises the majority of the earth's surface in that band. And CO2 energy absorbtion doesn't have the same effect over the ocean that it does over land because the ocean re-radiates almost nil energy via radiation. Solar radiation that goes in the water stays in the water unless released through evaporation and convection. You can see this by following the tracks of hurricanes using sea surface temperature.

    So my second point is that solar radiation that is absorbed by the ocean in the tropics can be transported northward without regard to CO2 effects.

    As far as see ice formation under the ice, I say this because I have seen it. I watch too much TV. NOVA had a penguin with a camera go under the ice. You could see the ice crystals accumulating under the antarctic ice shelf. The little fish the penguins eat live amongst the ice crystals. The commentator also made a comment to this effect.
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  2. Would we expect this once in twenty year event twice in 6 years if GHG where causing an increase in winter temperatures. So far December 2010 is running below normal temperatures.

    http://climate.umn.edu/doc/journal/superior030603.htm

    http://wattsupwiththat.com/2009/03/07/lake-superior-is-freezing-over/

    Now Lake Superior is a good proxy for GHG warming because it is not connected with any ocean currents, thermo-haline systems, underwater volcanism and such like. It is a fresh water lake that is very deep and has a very small out flow. It is not near any large population centers and is relatively unpolluted. Winter shipping is nil.

    The description of the 2003 freeze over is a situation in which GHG would be expected to play a very big role in preventing a freeze over. Almost no wind and high pressure which means clear sky. Radiation is the dominant force here. Both freeze overs where documented in March.

    In fact if you look at Marquette Michigan's temperature graph from 2008 on you will see normal to below normal temperatures dominating during the deep winter months when the jet stream prevents warmer air from the south intruding.
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  3. TOP
    I think you are invoking a few weather events. So I am countering with weather events from your source:
    Here is 2010 data - started El Nino, ended La Nina.

    Note that there are record highs set. That the temps are in the normal to high band, and not in the low band. Note that no new record lows were set.
    http://www.crh.noaa.gov/images/mqt/KMQT2010plot.png

    We could do this all day long, and not learn a thing about climate change.
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  4. #104: "Lake Superior is a good proxy for GHG warming"

    Indeed it is. See the Canada thread, where our own correspondent from the UP (aka The Yooper) confirms that the Great Lakes are anomalously warm.

    Please do not quote 'weather reports' from WUWT after they were caught in this fraud.
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  5. Re: TOP (104)

    Sorry, TOP, you just tripped my nonsense-meter with your whole comment:
    "So far December 2010 is running below normal temperatures. "
    Since the remainder of the comment entirely deals with Marquette and Lake Superior, let's see what 2010 looks like:



    Hmm, above normal Winter @ Spring temps, with the remainder of the year largely within the seasonal noise/variation. Including December.
    "In fact if you look at Marquette Michigan's temperature graph from 2008 on you will see normal to below normal temperatures dominating during the deep winter months when the jet stream prevents warmer air from the south intruding. "
    OK, let's finish this exercise, starting with 2009:



    and 2008



    Seems to me pretty much more of the same: weather falling largely within historical norms.

    "Both freeze overs where documented in March. "
    Depends on what your definition of freeze-overs of Lake Superior is? Is it 90%+? Then I'd agree with you. By local definitions? Not since around 1980 has Lake Superior frozen over.

    But what do I know, I only live in Marquette. Oh, did I forget to mention that? Then I probably forgot to mention this: Lake Superior reaches record temperature
    by mdr on Aug. 20th, 2010
    .

    Indeed, I've commented on local warming elsewhere on this site, including here.

    Note: You can monitor water temps of Lake Superior here.

    Oh, and Lake Superior shipping usually only shuts down for winter maintenance on the Soo Locks (in January, for about 2 months, I believe). Otherwise, a year-round event with modern icebreakers. Back in the 40s and 50s, ice limited operations to an 8-month shipping season.

    The Yooper
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  6. Hmm. Given that muoncounter concurs that Lake Superior is a good proxy for GHG (that is two votes in favor!) - take a look at the TOPs link:
    http://climate.umn.edu/doc/journal/superior030603.htm
    But look at temperature year 2006-2008 - you can actually SEE the warmer winters this post is all about.

    Very cool (and OK - really scary!)
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  7. TOP, Lake Superior has warmed quite a bit over the past century, and ice cover is now about half what it was a century ago.

    A century of temperature variability in Lake Superior

    There has been a lot of work done on global lake ice records, e.g. by Magnuson et al. I know a bunch of the people involved; if I get a chance I'll try to write up a summary some time.
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  8. Hi Ned... Just so you know, that link you posted requires a log in.
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  9. #108: My concurrence and $3.00 might get you a cup of coffee, although I make no guarantees. You did note that I concurred because I knew the Big Lake is anomalously warm.

    If you like spaghetti charts, look here.
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  10. 111 muoncounter,

    From looking through the graphs it seems that El Nino effect has somthing to do with the warmth of the Big Lake. Check out 1998 and you can see a comprable temp.
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  11. Just wondering. Why should this be? "Similarly, if global warming was driven by the sun, we should see the stratosphere warming as well as the troposphere."

    Looking into this, the major cause of warming in the stratosphere is when something gets up there that can absorb solar radiation (like particles from a volcanic eruption). Under normal conditions, Ozone levels are what cause most of the stratospheric warming (absorption of UV energy). What part of the solar spectrum would be absorbed in the stratopshere to cause it to warm?
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  12. #112: "it seems the El Nino effect has something to do with... "

    Hi Norman,

    Or maybe its a longer term thing:

    Lake Superior summer (July–September) surface water temperatures have increased approximately 2.5C over the interval 1979–2006, equivalent to a rate of (11 ± 6) 10-2C /yr, significantly in excess of regional atmospheric warming. This discrepancy is caused by declining winter ice cover, which is causing the onset of the positively stratified season to occur earlier at a rate of roughly a half day per year.

    Remember this little ditty from a few years back?
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  13. Re: Norman (113)

    Barton Paul Levenson, an atmospheric physicist, covers that pretty well here.

    The Yooper
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  14. Re: muoncounter (114)

    Actually, the warming of Lake Superior is in fact caused by waste heat slowly rising from the warmer deeps to the colder surface from The Wreck of the Edmund Fitzgerald. Recent revelations from Wikileaks have finally unveiled the truth: that the Fitzgerald sank on its maiden voyage to sea test a prototype thorium reactor. Unfortunately, what should have been a three-hour cruise to the Soo and back was interrupted by a violent storm initiated by the galactic cosmic rays attracted to the emissions from the thorium reactor.

    The captain said 'let's put this one to bed' before the waves turned the minutes to hours.

    Officially, there's no consensus as to the cause of the sinking.

    Replicators from the NTSB have so far been unsuccessful in determining the actual cause.

    Feelin' Lucky to be a Yooper
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  15. Daniel, that comment made my day. Thanks.
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  16. #117: Yooper,
    Your theory regarding the WotEF is clearly junk science as it is not falsifiable.

    Evidence is mounting, on the other hand, for competing theories:
    a. The WotEF was caused by a catastrophic accidental load shift (CALS) in its cargo of hockey sticks intended for a WhiteFish Bay area youth hockey league.
    b. The WotEF was caused by a catastrophic release of methane from the previously uncharted clathrate deposits of Gitchigoomie.

    You will note as well, that according to the noted Canadian climatologist G. Lightfoot, "the snows of November came early". Clearly there has been no warming since 1975.

    Personally, I blame it on El Nino.
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  17. 115 Daniel Bailey,

    I have read some things by Barton Paul Levenson. Here is something from NASA on this line of thought.

    Cause of Stratospheric Cooling.

    Quote from this page: "The stratosphere gets warmer during solar maxima because the ozone layer absorbs ultraviolet light; more ultraviolet light during solar maxima means warmer temperatures. Ozone depletion explains the biggest part of the cooling of the stratosphere over recent decades, but it can’t account for all of it. Increased concentrations of carbon dioxide in the troposphere and stratosphere together contribute to cooling in the stratosphere." The claim is that ozone depletion explains the biggest part of the cooling.

    In post 55 by HumanityRules I checked up on the article he linked to and it explains that a very active Sun cycle will destroy some ozone so an active Sun can cool the stratosphere by damaging the ozone layer.
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  18. I think some of the lines of thought are oversimplified in this thread.

    "Solar warming should result in the tropics warming faster than the poles. What we observe instead is the poles warming around 3 times faster than the equator."

    Why form this conclusion. This would be a true statement if the air did not move heat around. The reason the Poles do not get as cold as the Darkside of Moon is because warmer air moves to the colder areas and moderates the temperature. With heat being a moveable quantity on Earth, it is too simplistic to assume the Equator would warm faster. Here is another possible explanation. If the Sun was hotter and adding more heat to the Equator, what could happen, the added heat goes into water evaporation. This process keeps the measured temperature from rising much even though the area has more total heat energy (an assumption this is a thought experiment). Now this warm moist air rises, cools and rains. The condensation returns the evaporation heat back to the upper troposphere, the rising air is in the form of a Hadley Cell and moves until it starts to sink where it is dry and warms via adiabatic heating. Through this process a heated equator can move the excess heat to the poles warming them more than it is warmed.

    Chinook winds.

    "As moist winds from the Pacific (also called Chinooks) are forced to rise over the mountains, the moisture in the air is condensed and falls out as precipitation, while the air cools at the moist adiabatic rate of 5°C/1000 m (3.5°F/1000 ft). The dried air then descends on the leeward side of the mountains, warming at the dry adiabatic rate of 10°C/1000m (5.5°F/1000 ft).[4]"
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  19. Most the posts seem to feel that the TSI is the only important item to look at when determining if the Sun is a climate forcing agent. What about Sunspot number?

    You can see in the graphs that Sunspot numbers have increased in our century. Very cold periods were noted during times of low sunspot number.

    Graph of Sunspot number.

    In the graph below, Sunspot number Vs Global SST, is this correlation even if one does not know the cause?.
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  20. corrct link for Sunspot number vs Global SST.
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    Response: Norman, you'll notice the graphs at your link are very old. The reason for this is because the latest data indicates solar activity and climate have been moving in opposite directions in recent decades. For instance, that graph uses a 1991 graph of solar cycle length compared to temperature. Since that paper (now nearly 2 decades old) came out, one of its authors have updated their data and found solar cycle length and temperature diverge when the recent global warming of the last few decades began:


    The top figure compares temperature to solar cycles. The bottom figure plots the difference between temperature and solar cycle length, showing a strong divergence in the mid 1970s (Lassen 1999).

    Similarly, solar activity as calculated from sunspot numbers and direct satellite measurements have found sun and climate have been moving in opposite directions in recent decades:

    Global Temperature vs Solar Activity (Total Solar Irradiance)

    You have to wonder about a webpage that uses 2 decade old data when more recent data by the same author refutes their argument. Are they aware of the updated data and intentionally excluded it? Or merely ignorant?
  21. Re: Norman (121, 122)

    From your terracycles website you refer to:
    "The Aether Physics Model reveals the physics for generating new matter. Just as the Casimir effect generates new electron-sized photons from Aether, a similar process (mistakenly called fusion) generates new proton-sized photons from Aether. The proton-sized photons convert to protons within the nucleus of atoms, thus transmuting the elements and adding mass to the Earth (and Sun, Mars, Moon, etc). The transmutation of atoms further causes a continual change in the Earth's chemistry."
    Um, Norman, you may want to exert a little more discretion in your source selection.
    If you want to be taken seriously, anyway.

    Just sayin'

    The Yooper
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  22. Norman @120, the rate at which heat flows in a given medium depends on the temperature gradient. Consequently, while increased temperature in the tropics will result in greater heat flow to the poles, it will only do so while the temeperature difference between tropics and poles is greater than in the original condition. Consequently, it cannot result in the temperature gradient being less, ie, the poles warmer relative to the tropics.

    Further, the same effect applies in reverse. Increased warming at the poles relative to the tropics will reduce heat flow from the tropics to the poles. That means a given increase of temperature at the poles relative to the tropics requires an even larger prefferential heating of the poles to sustain it. Therefore the large relative increase of temperature at the poles compared to the tropics can only come from a forcing with a distinctive bias towards heating the poles - ie, a Green House Gas.
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  23. #39 Tom Curtis wrote:

    "Fourth, water vapour is largely confined to the troposphere, so the water vapour feedback will not result in stratospheric cooling."

    This must be wrong? Isn't it so that the stratosphere is cooling because less radiation escapes the optically "thicker" troposphere in the presence of increased GHGs? So it also cools with more water vapour, just in other wavelengths. Or am I missing something?
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  24. babelsguy @125, I refer you to Patrick 027's comment @99, and my responce @102.



    As shown at Science of Doom, the concentration of water vapour is between 3 and 5 ppm in the stratosphere, while that of CO2 is, of course, around 380 ppm. If the water vapour was as heavily concentrated in the stratosphere as is CO2, then it also would contribute to stratospheric cooling. But because it is so thin, it contributes little to the energy balance of the stratosphere, and so has little effect on either heating or cooling.
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  25. #124 Tom Curtis,

    " the rate at which heat flows in a given medium depends on the temperature gradient. Consequently, while increased temperature in the tropics will result in greater heat flow to the poles"

    This is true with thermodynamics but atmopshere will alter the normal flow. Instance. A Low pressure system is moving across the US. In Omaha the temperature (depending on the strength of the low) will rise maybe 10 F above normal temps as the low draws up warm air from the Gulf. After the low passes the area it will pull down cold air from the north and drop temps below normal. The temp gradient effect you described does not stop the warm air from flowing into an area at a very rapid rate. The temp gradient (normal temp in Omaha vs New Orleans) has no determination of the rate of heat transfer, the strength of the Low pressure is the primary cause of the heat flow.

    I know of this effect directly and speculate that the same process can be taking place to transfer heat to the Arctic. Stronger Low pressure at the 60 degree lattitude would pump more warm air to the arctic and pull down more cold air, cooling the south and warming the north.
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  26. Norman, I believe that weather is just the structure placed on thermodynamic heat flows by the rotation of the Earth, the effects of convection (itself a thermodynamic process), and be geographical features. As such, the net effect of weather processes will be to move heat from hot to cold locations, at a rate approximately dependant on the temperature gradient between them. However, I am by no means expert enough to assert this as more than a hunch.

    What I am expert enough to assert is that you cannot have it both ways. If the rate at which heat is moved from tropics to poles is unaffected by the temperature differential between them, then because that rate is effectively constant, it will not act as a negative feedback on differential heating rates due to diferent mechanisms. So, either:

    1) My observation is correct, in which case your objection @120 is rebutted; or

    2) Heat flows are not effected by temperature differential at the poles; in which case those heat flows will not mask the difference in heating patterns of solar and greenhouse forcing; or

    3) Heat flows between tropics and poles become less as the temperature difference increases; in which case heat flows will constitute a positive feedback, and accentuate rather than masking the difference in heating patterns between solar and green house forcings.
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  27. #128 Tom Curtis,

    I don't think you included the other possiblilty. More energy into the system can create stronger flows between Tropics and Poles, warming the poles and cooling the tropics.

    What happened in Moscow in July was and example of a heat pump that would not move (High pressure). It pumped warm air to Moscow from the South but did also pull cooler air down from the North to cool Eastern Russia. Picture of this activity on this link...

    Russia July.

    More energy into the system (say from the Sun) maybe could intensify High and Low pressure systems so they act as more powerful pumps which can act to cool the Tropics and heat the poles at a higher rate than the norm.

    I could be wrong with my thinking, I will keep working on it, many years ago I did take a college level meteorology class, wish I still had the textbook.
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  28. #123 Daniel Bailey,

    Thank you for your research on Terracycles website. I will avoid this site if I continue to post on Skeptical Science.

    From information I had, it was not the TSI that effected the Earth's climate but Sunspot number (from the Maunder minimum). They were not measuring the TSI at that time. I was looking for information on sunspot number to correlate with Global temps and that sight had the graph I was looking for.
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  29. Re: Norman (130)

    It might be helpful to think of sunspot number as a surrogate marker for TSI. When lacking TSI data from modern measurements, sunspot number is a useful metric. But in this modern instrumental era, TSI is much more valuable. And as such, TSI shows at best a 5-10% attribution of the warming measured over the past 30 years.

    In the absence of CO2 forcing from anthropogenic fossil fuel emissions, such as in the paleo record, changes in TSI can act as a significant forcing (up or down) on global temperatures. As do Milankovich cycles.

    No observable mechanism other than the rise in CO2 explains also the rise in temperatures we've measured since 1980.

    So it's not the sun.

    It is what it is.

    The Yooper
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  30. Discussion of sunspots, TSI, etc. should probably go on the thread It's the Sun. I just posted a brief reply to Norman's comment over there.
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  31. Norman,

    Keep in mind that global climate is quite stable, even while local weather can be chaotic and unpredictable as shown by your Moscow example. What you are suggesting would require a global scale shift in pressure zones and circulation patterns; a catastrophic change compared to the effects predicted by the IPCC. At the very least, we would be able to detect if such a change was taking place.
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  32. #129: "What happened in Moscow in July was and example of a heat pump"

    I've posted this comment from How warm was this summer? in a number of places, but IMHO the content is so important I repeat it here:

    Weather in a given region occurs in such a complex and unstable environment, driven by such a multitude of factors, that no single weather event can be pinned solely on climate change. In that sense, it's correct to say that the Moscow heat wave was not caused by climate change.

    However, if one frames the question slightly differently: "Would an event like the Moscow heat wave have occurred if carbon dioxide levels had remained at pre-industrial levels," the answer, Hansen asserts, is clear: "Almost certainly not."

    The frequency of extreme warm anomalies increases disproportionately as global temperature rises. "Were global temperature not increasing, the chance of an extreme heat wave such as the one Moscow experienced, though not impossible, would be small," Hansen says.
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  33. #133 e

    I think there may be evidence of a change taking place at this time. Check out this article to see what you think.

    Possible evidence for e of global scale shift in pressure zones and circulation patterns.
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  34. #131 Daniel Bailey,

    "No observable mechanism other than the rise in CO2 explains also the rise in temperatures we've measured since 1980."

    Not totally correct. There is possible observations of Tropical clouds (the ones that would result in cooling due to albedo effect) decreasing at the same time the Globe has demonstrated warming. When I posted this possibility another guest demonstrated that the satellite data showing decrease in tropical cloud formation may not be valid. It does remain a possible explanation for at least some of the warming, other can be attributed to CO2. The question would be, If clouds are a factor then CO2 is only partially responsible for the observed warming trend.
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  35. Re: Norman (136)

    So you're saying it was cloudier before 1980...doesn't parse.

    I don't think you're standing back far enough & giving this enough thought. Because it seems to this observer you're grasping at straws.

    The Yooper
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  36. #136: "If clouds are a factor then CO2 is only partially responsible for the observed warming trend."

    I suppose we could also throw in a few dozen other unknown 'factors' if you like. But let's get back to the topic of this thread and the 'fingerprint' question. Cloud theories, electrical currents, little green men, don't produce the observed seasonal warming differentials.

    Further,
    In the latter 20th century, man-made forcing accounts for nearly all the observed temperature changes (Braganza et al 2004).

    If nearly all the temperature changes are accounted for, why dream up these other 'could be' and 'wannabe' ideas? If you want to be a skeptic, please be objectively skeptical -- look critically at all proposals, not just the one that involves CO2.
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  37. From my analysis of the temperature data, the only way that clouds could be a significant factor in the current trends is if they were covariate on CO2 concentration and also contributed a positive effect, as CO2 is currently masking any of the other major feedback effects (although solar variability is still contributing a small proportion to measured temperature anomaly).
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  38. #137 Daniel Bailey

    "So you're saying it was cloudier before 1980...doesn't parse."

    Not me saying it, the available data suggests it is a strong possibility. On this web site they warn the data may not be accurate but never-the-less, the chart shows low cloud cover decreasing (low clouds are thought to cause cooling overall).

    Cloud cover main page.

    Three different graphs show cloud cover has decreased since 1980.

    #138 muoncounter

    "I suppose we could also throw in a few dozen other unknown 'factors' if you like. But let's get back to the topic of this thread and the 'fingerprint' question. Cloud theories, electrical currents, little green men, don't produce the observed seasonal warming differentials"

    And why can't they? If the tropics are cloudier overall and the poles relatively less cloudy than before that would create the observed temperature difference between tropics and poles. It would appear. The statement that man-made forcing accounts for nearly all the observed temperature change is based upon an assumption for climate sensitivity, it is circular reasoning from what I have read. The current warming is attributed mostly to CO2 because they do not have another valid explanation for the warming so that is how the climate sensitivity was determined. I think a really good study of cloud cover is needed to ensure that this is not what is responsible for a majority of heating or cooling that has taken place in the last 100 years. So far none exists. The current satellite cloud cover study is not known to be accurate. At least answer one question. How can you be certain a considerable amount of the warming that took place was not from low cloud reduction? What is the basis of your answer to this question?

    #139 kdkd

    Have you played with the albedo calculator? A 1% change in albedo will change global temp by 1 F. Are you sure your analysis is sufficient to make your conclusion?
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  39. muoncounter,

    This claim "Solar warming should result in the tropics warming faster than the poles. What we observe instead is the poles warming around 3 times faster than the equator. All these pieces of evidence paint a consistent picture - greenhouse gases, not the sun, are driving global warming."

    Has a flaw in the reasoning. I linked to this article on a previous thread but a very important point should not be missed. I will post a quote and then a hyperlink to the article.

    "Understanding Arctic temperature variability is essential
    for assessing possible future melting of the Greenland ice
    sheet, Arctic sea ice and Arctic permafrost. Temperature trend
    reversals in 1940 and 1970 separate two Arctic warming
    periods (1910–1940 and 1970–2008) by a significant 1940–
    1970 cooling period. Analyzing temperature records of the
    Arctic meteorological stations we find that (a) the Arctic
    amplification (ratio of the Arctic to global temperature trends)
    is not a constant but varies in time on a multi-decadal time
    scale, (b) the Arctic warming from 1910–1940 proceeded
    at a significantly faster rate than the current 1970–2008
    warming, and (c) the Arctic temperature changes are highly
    correlated with the Atlantic Multi-decadal Oscillation
    (AMO) suggesting the Atlantic Ocean thermohaline
    circulation is linked to the Arctic temperature variability on
    a multi-decadal time scale."

    Of significance "the Arctic warming from 1910–1940 proceeded
    at a significantly faster rate than the current 1970–2008
    warming."

    From what I have read, CO2 levels were much lower in 1910 as compared to today. Yet the Arctic had a higher amplification than current, this would be very strong evidence that the greater warming at the poles is not due to atmospheric carbon dioxide levels but some other unrelated phenomena.

    Here is a link to the article.

    Peer-reviewed and accepted.
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  40. Norman #141

    There are are a couple of mid-80s and/or early 90s environmental science text books on my bookshelves, and from memory, they showed that the output of climate models predicted precocious arctic warming under a CO2 forcing scenario, but either absent or not as strong where something other than greenhouse gasses were the driver of climate.

    Also, the solar hypothesis suggests that the early increases in temperature will be most measurable during day time, but that in fact we observe night time warming is most marked.
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  41. #142 kdkd

    "Also, the solar hypothesis suggests that the early increases in temperature will be most measurable during day time, but that in fact we observe night time warming is most marked."

    I do have a possilbe explanation for this one that does not require CO2 but can be explained by a more active sun. I will link to the page and pull out a factoid from it.

    Properties of moist air.

    Quote from this page: "Notice that water vapour, once generated, also requires more heat than dry air to raise its temperature further: 1.84 kJ/kg.C against about 1 kJ/kg.C for dry air."

    If the Earth received more energy (via less clouds and lower albedo) that energy would evaporate more water on land and sea (exception of desert climate). Warming this increased moist air takes more energy so the daytime does not warm as much relative to the night. Now what happens at night? This moist air is holding more energy than drier air and it cools off slower keeping the night warmer relative to less moist nights. Again I am not saying my point is valid or correct. Just challenging the three fingerprints of AGW, I don't think it is as clearly obvious as the Author makes it out to be.
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  42. Norman #143

    Well I've examined the relationship between CO2 and warming myself using the publicly available data (here), and my conclusion based on this data, and the theoretical evidence from physics, chemistry and to a lesser extent meterology, is that for the current situation not to be driven by CO2 would be a coincidence of fairly staggering proportions.
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  43. Re: Norman

    You have me torn, sir.

    On one hand, I dearly wish to aid you in strengthening your understanding of climate science.

    On the other hand, I believe your gaining an actual understanding is not something I can help you with. By no means am I implying, sir, that you are here under false pretense. But the overwhelming straw-grasping makes it difficult to even know where to begin to help you. Time and again others more knowledgable than I have picked you up, dusted you off and pointed you in the right direction.

    And to have you come back here and say, "Yes, but _________"
    (anything but what you were told).

    The more I have tried to help the less positive effect I seem to engender.

    So I will recuse myself and bid you adieu.

    And apologize for being the poor clay vessel I am.

    The Yooper
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  44. Norman @141,

    Regarding warming rates for polar amplification. You need to keep a couple of factors in mind regarding the the paper by Chylek et al. (2009) that you cited. They, understandably, have access to a few, widely separated stations, and they have consequently greatly underestimated the rate of warming north of 70 N after 1980, especially during the winter months.

    Using ECMWF-interim data, Screen and Simmonds (2010) found warming of 1.9 C/decade in DJF for areas north of 70 N between 1989 and 2008, compared to 0.58 C/decade for the same area area and season (from 1980-2008) in Chylek et al. (2009). That is a huge difference. We are now clearly dealing with a very different beast than was the case back in the 1910-1940 window. Interestingly, the rate of warming during the winter determined by Chylek et al, for areas north of 70 N was 1.63 C between 1910-1940-- that value is very similar to the rate of warming obtained by Screen and Simmonds for the same season. One has to wonder why Chylek et al's analysis grossly underestimates the post 1980 warming-- did they perhaps use different stations for the two periods? Something does not add up.

    Also note that, according to Chylek, the rate of warming for the globe (from NASA GISTEMP data) between 1980 and 2008 was almost double (~0.20 C/decade) that observed between 1910 and 1940 (~0.10 C/decade), despite a slight decrease in insolation during after 1980. So Monckton should now be convinced that AGW is real (referring to his entertaining conversation with a Guardian reporter at Cancun)....but I digress.

    Be careful of confusing regional regimes and internal climate modes with drivers of global climate.

    That all said, I have no idea what your speaking to polar amplification of the Arctic has to do with the original post...
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  45. TOP,
    You hit my nonsense meter with this one, "...because the ocean re-radiates almost nil energy via radiation."

    Wrong. Please look up the definition of black body and Stefan-Boltzmann. Sea water is a reasonably good approximation of a black body; therefore it radiates energy quite well.
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  46. #146 Albatross,

    "That all said, I have no idea what your speaking to polar amplification of the Arctic has to do with the original post..."

    The conclusion of the original post "Solar warming should result in the tropics warming faster than the poles. What we observe instead is the poles warming around 3 times faster than the equator. All these pieces of evidence paint a consistent picture - greenhouse gases, not the sun, are driving global warming."

    The article on polar amplification suggests that warm poles relative to tropics does not appear related to either GHG or solar forcing. It is a unique phenomena based upon another climate factor.
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  47. Norman, as I said somewhere further up in this thread... it is true that various climate feedbacks would take place regardless of what the forcing was. However, it is not true that the feedbacks would be exactly the same.

    For instance, your claims about water vapor and polar albedo (aka Arctic amplification) feedbacks are demonstrably incorrect.

    When atmospheric CO2 levels increase they do so globally. The CO2 level goes up for the entire planet and thus the rate of infrared radiation escape goes down. Further, this is a year round phenomenon... the CO2 level only fluctuates slightly during the year, much less than the cumulative increase we have observed (indeed, the annual rate of increase is now about equal in magnitude to the annual fluctuation). As such it causes increased water vapor and increased surface warming worldwide and year round... obviously with large fluctuations for weather events.

    A solar forcing on the other hand would be geographically and seasonally localized. If it were exactly equal in total magnitude to a CO2 forcing most of that energy would be located in the tropics and during Summer. Thus, while Arctic amplification would still occur it would be much less pronounced because a much smaller proportion of the forcing is at work in the Arctic. Ditto water vapor. It would increase more in the tropics, but less for the rest of the world... resulting in an even more pronounced tropical warming signal over that of the Arctic. Likewise we wouldn't see the accelerated Winter warming that we have with CO2 because a solar forcing would be concentrated in the Summer months.

    Feedbacks can only respond to forcings when and where they occur. This is inescapable. Thus, you can't have a strong Winter feedback from a Summer forcing... nor a strong Arctic feedback from a tropical forcing.
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  48. Norman @148,

    Thanks for clarifying. I must still, however, agree the assessments made by CBDunkerson and others.

    I might take issue with the John Cook using the dichotomy of the tropics and poles-- maybe he meant to discriminate between the tropics and high latitudes. The northern mid-latitudes have also been warming more in the winter than in the summer.
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  49. #141: "Yet the Arctic had a higher amplification than current, this would be very strong evidence"

    That's not really strong evidence. Look here for a more thorough discussion of arctic amplification than in the Chylek paper you reference. We also said here that the early 20th century warming had a different cause than the current warming; why would expect the same responses?
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  50. Cris G wrote the following...
    "take to mean that you think there is a limit to how hot CO2 can get."

    based on my comment 79, which contained...

    "Given that water vapor has double the heat capacity of CO2, and abounds in excess of 100 times the anthropogenic contribution in CO2, this retained "energy" you are talking about represents at most 0.5% of the total ambient. I suppose that is energy, but it doesnt seem like much. "

    From this I can only "take to mean" you did not read what I wrote.
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