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The greenhouse effect is real: here's why

Posted on 14 June 2011 by John Cook

Reposted from The Conversation. This is the second article in a two-week series Clearing up the Climate Debate: read the opening statement here: Climate change is real: an open letter from the scientific community.

CLEARING UP THE CLIMATE DEBATE: Bureau of Meteorology scientist Karl Braganza explains why we know the climate is changing, and what’s causing it.

In public discussions of climate change, the full range and weight of evidence underpinning the current science can be difficult to find.

A good example of this is the role of observations of the climate system over the past one hundred years or more.

In the current public discourse, the focus has been mostly on changes in global mean temperature.

The greenhouse effect is fundamental science

It would be easy to form the opinion that everything we know about climate change is based upon the observed rise in global temperatures and observed increase in carbon dioxide emissions since the industrial revolution.

In other words, one could have the mistaken impression that the entirety of climate science is based upon a single correlation study.

In reality, the correlation between global mean temperature and carbon dioxide over the 20th century forms an important, but very small part of the evidence for a human role in climate change.

Our assessment of the future risk from the continued build up of greenhouse gases in the atmosphere is even less informed by 20th century changes in global mean temperature.

For example, our understanding of the greenhouse effect – the link between greenhouse gas concentrations and global surface air temperature – is based primarily on our fundamental understanding of mathematics, physics, astronomy and chemistry.

Much of this science is textbook material that is at least a century old and does not rely on the recent climate record.

For example, it is a scientific fact that Venus, the planet most similar to Earth in our solar system, experiences surface temperatures of nearly 500 degrees Celsius due to its atmosphere being heavily laden with greenhouse gases.

Back on Earth, that fundamental understanding of the physics of radiation, combined with our understanding of climate change from the geological record, clearly demonstrates that increasing greenhouse gas concentrations will inevitably drive global warming.

Dusting for climate fingerprints

The observations we have taken since the start of 20th century have confirmed our fundamental understanding of the climate system.

While the climate system is very complex, observations have shown that our formulation of the physics of the atmosphere and oceans is largely correct, and ever improving.

Most importantly, the observations have confirmed that human activities, in particular a 40% increase in atmospheric carbon dioxide concentrations since the late 19th century, have had a discernible and significant impact on the climate system already.

In the field known as detection and attribution of climate change, scientists use indicators known as fingerprints of climate change.

These fingerprints show the entire climate system has changed in ways that are consistent with increasing greenhouse gases and an enhanced greenhouse effect. They also show that recent, long term changes are inconsistent with a range of natural causes.

Is it getting hot in here?

A warming world is obviously the most profound piece of evidence.

Here in Australia, the decade ending in 2010 has easily been the warmest since record keeping began, and continues a trend of each decade being warmer than the previous, that extends back 70 years.

Globally, significant warming and other changes have been observed across a range of different indicators and through a number of different recording instruments, and a consistent picture has now emerged.

Scientists have observed increases in continental temperatures and increases in the temperature of the lower atmosphere.

In the oceans, we have seen increases in sea-surface temperatures as well as increases in deep-ocean heat content. That increased heat has expanded the volume of the oceans and has been recorded as a rise in sea-level.

Scientists have also observed decreases in sea-ice, a general retreat of glaciers and decreases in snow cover. Changes in atmospheric pressure and rainfall have also occurred in patterns that we would expect due to increased greenhouse gases.

There is also emerging evidence that some, though not all, types of extreme weather have become more frequent around the planet. These changes are again consistent with our expectations for increasing atmospheric carbon dioxide.

Patterns of temperature change that are uniquely associated with the enhanced greenhouse effect, and which have been observed in the real world include:

  • greater warming in polar regions than tropical regions
  • greater warming over the continents than the oceans
  • greater warming of night time temperatures than daytime temperatures
  • greater warming in winter compared with summer
  • a pattern of cooling in the high atmosphere (stratosphere) with simultaneous warming in the lower atmosphere (tropopause).

How do we know it’s us?

By way of brief explanation, if the warming over the 20th century were due to some deep ocean process, we would not expect to see continents warming more rapidly than the oceans, or the oceans warming from the top down.

For increases in solar radiation, we would expect to see warming of the stratosphere rather than the observed cooling trend.

Similarly, greater global warming at night and during winter is more typical of increased greenhouse gases, rather than an increase in solar radiation.

There is a range of other observations that show the enhanced greenhouse effect is real.

The additional carbon dioxide in the atmosphere has been identified through its isotopic signature as being fossil fuel in origin.

The increased carbon dioxide absorbed by the oceans is being recorded as a measured decrease in ocean alkalinity.

Satellite measurements of outgoing long-wave radiation from the planet reveal increased absorption of energy in the spectral bands corresponding to carbon dioxide, exactly as expected from fundamental physics.

It is important to remember that the enhanced greenhouse effect is not the only factor acting on the climate system.

In the short term, the influence of greenhouse gases can be obscured by other competing forces.

These include other anthropogenic factors such as increased industrial aerosols and ozone depletion, as well as natural changes in solar radiation and volcanic aerosols, and the cycle of El Niño and La Niña events.

By choosing a range of indicators, by averaging over decades rather than years, and by looking at the pattern of change through the entire climate system, scientists are able to clearly discern the fingerprint of human-induced change.

Case closed

The climate of Earth is now a closely monitored thing; from instruments in space, in the deep ocean, in the atmosphere and across the surface of both land and sea.

It’s now practically certain that increasing greenhouse gases have already warmed the climate system.

That continued rapid increases in greenhouse gases will cause rapid future warming is irrefutable.

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Comments 1 to 50:

  1. The more evidence gathered, the more virulent and vicious the deniers, backed into a corner, fight.
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  2. Oh dear, John. (Your website is indeed a WorldCenter — thank you). You just hit the spot of it all (How do we know it’s us?) — but there is still a (much) more simple »summing of the proof» (still me though, with a minimum of ingredients, not nearly as sophisticated as yours, however nevertheless in purpose to kill ALL opposition against AGW so we can start DO the cure) that MAY convince even the most »stoned» of any skeptic or denier, just watch this — especially this one in light from the article’s text ”That continued rapid increases in greenhouse gases will cause rapid future warming is irrefutable”: With EXACTLY the same PREDICTIVE POWER as the (dotted) periods shown as, illustrated by already familiar established sources (compiled here for a collected illustration) in, — the measured NASA temperature curve we refer to as the only prevailing proof of Global Warming (GW): industrial fossil carbon emissions during the 20th century (questioned by skeptics and deniers) + natural sea variations (not exactly known due to great and diverse difficulties on global averages) — the pronounced temperature raising intervals in 1910-1940 and 1972-2005*, the latter named »The Great Pacific Climate Shift», see Page 1 bottom of will be followed by a third steep raise about 2038-2070 — unless some radical change will come (about right NOW), nothing said about additional effects. No theory. Just an equivalent. The measured NASA-temperature global warming curve (the bare proof of GW) may have ANY (at least) two EQUAL components (as in 3 = 2+1, just pick any). But only components corresponding to known phenomena will satisfy an equivalent definition (EQUAL to the measure — no need for a theory any longer). ”Case closed” would just be the term. — The Sun does not cooperate with the Industrial Fossil-Carbon emissivity, at least not as I have experienced, and neither does the Sun drill holes in the ground in general to look for gasoline to fire up on the surface to get the bananas home. The only known fit, hence, IS the 20th century industry + natural sea variations. (Otherwise you have to kill me). — Fossil fuel to feed the human natural evolution of technology (market, world-trade) was a mistake. Yes. But also: We cannot stop human evolution (technology, the energy-curve feeding the hard facts of scientific improvement); — Nature (she made humans though, and must not deceive us now when we need her the most) MIGHT have a solution for us other than gasoline to get it home. Might. That is, obviously, our next problem to solve (and it seems nuclear power is NOT the practical alternative, although it is technically already in action). (I mean, the several spread out fine-detailed already established AGW-proofs in themselves are perfectly OK — but in lack of a collecting general [more simple to the eye] illustration, the details have a tendency of diverging on the blow of argument). wkg/Gwinnevere
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  3. Two of the 'fingerprints' listed as "uniquely associated" with greenhouse warming are things this site hasn't identified as such previously; * greater warming in polar regions than tropical regions * greater warming over the continents than the oceans Do we know the scientific basis for these? Arctic amplification would obviously take place with any sort of global warming. Thus, I'd expect to see greater warming at the poles UNLESS the particular cause of warming was itself concentrated in the tropics... perhaps an orbital shift where more sunlight was hitting the mid-latitudes at the same time that total irradiance was increasing? Or is this really "uniquely" tied to enhanced greenhouse warming in some way? The greater warming over land bit seems intended to counter a suggestion that warming is being caused by heat escaping the oceans (as explained in subsequent paragraphs). It certainly disproves that assertion (as does the simple fact that the oceans are ALSO warming), but are there no other factors which could warm land faster than ocean? Indeed, what is it about greenhouse warming which causes land to warm faster?
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  4. "Case closed" (which I've come to understand is true) and "practically certain" (from the final section above) sound like contradictory statements to a denier. (I work with deniers; hear their easy dismissal of the scientific evidence, and anger when supporting evidence is offered.) I read the concluding section to mean: using numerous practical objective measures, the case for AGW is closed. Deniers I know would read into these final words: scientists are not yet certain (case closed: AGW isn’t real!). As I’ve read in comments on various AGW-accepting blogs (and observed in a few AGW-denying blogs), deniers will do everything they can to twist the language we use to psychological maintain their 'moral' and 'virtuous' position.
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  5. All at once - not as a comment. In addition, many "simplifications" in one place, as many do not want to comment ... Two examples: For increases in solar radiation, we would expect to see warming of the stratosphere rather than the observed cooling trend. Significant warming - at least quaternary - have never been caused by changes in the TSI. For example, Milankovic cycles is a change of place and time to provide solar radiation energy. Natural warming is always an increase of greenhouse gases in the atmosphere. The additional carbon dioxide in the atmosphere has been identified through its isotopic signature as being fossil fuel in origin. Former natural warming have the same "isotopic signature" as the present - see here.
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  6. CBDunkerson @4, non of the "fingerprints" are uniquely associated with a green house warming. What is uniquely associated with the greenhouse warming is the pattern of all the "fingerprints". Thus greater warming over land is a feature of any warming sourced through the atmosphere, whether greenhouse, solar, change in aerosol load or change in cloud cover, but it does rule out the surface warming as being a product of release of heat from the ocean. Greater warming at the poles is trickier. There is a subtle direct effect from greenhouse warming that warms the poles faster than the tropics. This is a consequence of the different balance between insolation and surface radiation at different latitudes: Clearly in increase in insolation will result in a greater increase in net radiation in the tropics than at the poles, because it increases the larger component of the energy budget. But likewise, a decrease in the rate at which surface radiation escapes to space will warm the poles more because that also increases the larger component of the energy budget at the poles (and the smaller at the tropics). This effect is not as strong as the different rate of warming for land and sea. Consequently, in the Northern Hemisphere, which gets progressively more land at higher latitudes until the Arctic circle is reached, this effect is reinforced. In the Southern Hemisphere, in contrast, there is progressively less land at higher latitudes until the Antarctic circle is reached, which counteracts this effect. If we reach an equilibrium temperature, temperature increases over land and sea will equalize, resulting in a stronger warming gradient in the Southern Hemisphere and a weaker gradient in the Northern Hemisphere. Finally, in the Northern Hemisphere the effect is significantly reinforced by Polar Amplification, ie, the increased summer melt of sea ice. This is a consequence of any warming, but will be slightly stronger for greenhouse warming because of the initially greater relative warming at the poles. Note that in Antarctica, the existence of a large ice covered continent surrounded by ocean prevents polar amplification, one of three features of Antarctica which make it highly unusual in terms of response to warming.
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  7. CBDunckerson You're right that those two examples are not "greenhouse only" occurrences, and in fact polar amplification appears to be robust to not only a wide variety of forcings but a wide variety of toy modeling experiments (e.g. no high latitude ice cover, turning off evaporation feedbacks in the tropics, etc). I don't agree with Tom Curtis (#7) on this one, but I don't think amplification in the Arctic is as well understood as many people think.
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  8. I agree with Tom Curtis, in order to be credible CBDunkerson would need to account for all fingerprints, cherry picking a few to discredit something does not increase any ones knowledge. As it stands the enhanced green house effect is robust, to dislodge it you need something that could account for existing need fingerprints and more.
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  9. Chris, I agree. As Tom mentioned, the polar amplification is largely one-sided; large warming in the Arctic, virtually no change in the Antarctic. I do not necessarily agree that the difference is due the loss of sea ice as the Arctic warming occurs before the sea ice begins to retreat. It could amplify the warming, but the initial warming should occur at both poles. I maintain that warming of the North Atlantic had much more effect on the sea ice and temperatures.
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  10. Remember that Arrhenius in 1896 predicted the fingerprints of AGW (he did not predict stratospheric cooling, the stratosphere had not been discovered yet). The fingerprints have been known for over 110 years and have been extensively tested and confirmed. This also counters the "skeptic" argument that AGW cannot be experimentally falsified. No other method of warming includes all the fingerprints.
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  11. Chris Colose @8, would you care to expand on your disagreement. I'm always looking for a chance to learn more.
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  12. Paul D, I think you misunderstand CBD. I don't think he was attempting to discredit the main theme; I think he was merely asking honest questions on points that were not clear. Tom and Chris C, Thanks, I was thinking along those lines, but your answers are more clear, or at least the combination of them is, than I probably would have produced. I think if you increase the insulation qualities of the atmosphere, you end up with a more even distribution of energy, but, yeah, albedo changes through snow and ice loss also play a part, and those changes can have multiple causes. Related to the article itself, I'm thinking the greenhouse effect is more directly an effect related to energy, and temperature is really just a proxy for energy content. Different substances have different heat capacities, and winds, evaporation/precipitation, convection, phase changes (ice vs. water), are all affected by changes in energy content that may be less easy to measure than changes in temperature. Temperature is a pretty good proxy, but it isn't the only change taking place as a result of the increase in GHGs.
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  13. On the asymmetry of polar amplification under enhanced greenhouse scenarios. The delayed Antarctic response to enhanced greenhouse warming was predicted from models of various complexity from up to 30 years ago as described in a 2007 review by Manabe and Stouffer. Can't find an online version of the paper, but I summarized some of the points from that review in a post here some time ago.
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  14. Arkadiusz, I'm not sure what your point is. Yes, carbon released through geologic processes will have a similar isotopic signature as long-sequestered carbon released through the burning of fossil fuels. Rocks weather more when they are exposed to weather than when they are buried under ice. Weathering of rocks draws down the level of CO2, and this tends to have a slow (very slow) balancing effect on carbon released from whatever sources. I think you are implying something, but what that is, is not clear.
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  15. Oh, I just had a thought, probably not an original one, but... I've been puzzling over how we might detect when feedbacks such as permafrost melt (rot) or clathrate releases might overtake the rate of anthropogenic GHG emissions. I was thinking we'd have to wait until after a real effort was made to reduce our emissions and see how much the increase in GHG content reduced. The rate is accelerating; so, I'd first be looking for a reduction in the rate of increase rather than a leveling off. But, if you closely monitored the isotopic signature, you might be able to detect when these feedbacks started to play a significant role a bit sooner. Anyone got any references in this area?
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    [DB] If you go here, you can select your station (this one is centered on Svalbard, for example) and the GHG parameter of interest.  HTH

  16. Tom, thanks for the information on the direct component of polar warming from greenhouse gas accumulation. The bit about 'fingerprints' only being unique to greenhouse warming in toto rather than each individually is also new to me. I've been trying to think of another forcing which would cause accelerated night-time warming. Increased cloudiness might work... more clouds during the day = increased albedo and thus cooling / more clouds at night = less heat escaping and thus warming. Also, do you know what the physical mechanism for atmospheric warming being greater over land than the oceans is? Is it just net heat flow? That is, the ocean water absorbing more heat from the air than it expels TO the air?
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  17. CBDunkerson @17, the ocean warms slower because it has a greater heat capacity than the land. Consequently it takes more heat for each degree centigrade increase in temperature. Of course, that has no influence on the equilibrium temperature, so once the TOA energy balance reaches equilibrium again, the ocean and land will have warmed equally. Increased cloud cover will indeed warm the nights more than the days, but will only provide an overall warming if clouds are a positive feedback. Of course, increased cloud cover will also tend to warm the stratosphere rather than cool it (although probably not very much). Reduced aerosols will warm the troposphere and cool the stratosphere, but will also increase the diurnal temperature range, and the temperatures of summer relative to winter. If clouds are a negative feedback, reducing clouds will show the same pattern.
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  18. Tom Curtis, My only point was that polar amplification is a rather common occurrence in climate change scenarios, regardless of whether we are talking about deep-time greenhouse climates, Milankovitch (orbital) timescale changes, or modern global warming, and has been simulated for a variety of forcings as well as "aquaplanet only" or other flavors of idealized experiments. Moreover, feedbacks associated with atmospheric dynamics and heat transport (and are not directly dependent on snow or ice) can contribute to polar amplification (e.g., Pierrehumbert 2002, Alexeev 2003; Alexeev et al. 2005; Cai, 2005). The other thing is that there are still recognized problems in simulating the pole-to-equator temperature gradient that proxy indicators report in some early greenhouse climates, so it is not clear to me that we have a convincing and full-proof quantitative theory linking the behavior of the pole-to-equator temperature gradient (and the meridional heat transport carried by the atmosphere and ocean) to the mean climate, so there's still work to be done here.
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  19. CB, FWIW, my presumption on the greater increase over land than water is that it is primarily related to the heat sink/energy transport attributes of land versus ocean. There are thermoclines, but oceans mix more rapidly than dirt; therefore, any energy delta at the surface is distributed over a greater volume over the ocean than over land. Not only does the energy get transported to depth, but also across meridians. I would expect this to have a sort of buffering effect, though thermal inertia might be a better concept to invoke semantically. On clouds, I agree, but, of course, some mechanism would have to drive the change in cloud behavior. Aerosols might do it since more of them would tend to lower the occurrence of supersaturated states. But then there are complications in the tradeoff between water vapor content versus droplet content, and whether they are high clouds or low clouds. For that matter, GCRs _might_ have an influence, but that would require evidence that has so far been lacking, or at least had big gaps, to the best of my knowledge. My two cents.
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  20. I'd like to point out another minor inconsistency in the fingerprints. The idea that winters and nights will warm more than summers and days, while true, should also apply to a lesser degree to any forcing, since many of the primary feedbacks are themselves greenhouse gases (mostly H2O). At the same time, part of the overall feedbacks for even an initial GHG forcing include changes in albedo, which would not bear the same signature. So while a pure GHG increase from CO2 now will involve a larger degree of difference, it could be difficult to tease out the difference between, say, a pure CO2 forcing versus a pure solar forcing. Both will have non-winter/daytime components and winter/nighttime components, to different degrees. I've tried to find someone knowledgeable about various climate model runs, to figure out exactly what the difference might be, but so far with no luck, so I can't quantify this in any way. All I can say for certain is that any warming will have both a GHG component and an albedo component as part of the positive feedbacks, and as such the difference between an initial GHG forcing and another forcing may not be as pronounced as one might initially expect, or would want (to be able to discriminate, observationally, between the two forcings).
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  21. I must say that I find this article to be a very disappointing addition to a site that headlines itself as Science based. Long on assertion and ambitious in conclusions which stem from very little solid scientific argument. Need to do better.
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  22. Patrick @22, Your weeping dismissal of the alleged absence of science are quite ironic given that your post contains no science whatsoever, never mind any attempt to substantiate your position. Indeed, you need to do much better on a science site.
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  23. 22 - paddy; leaving science to one side and concentrating on English comprehension, may I draw your attention to the top of the page "Reposted from The Conversation." This is not a SkS science article I'm not going to paraphrase your "need to do better" words as that would just be obvious and tacky.
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  24. Great discussion folks. I thought I had a pretty good grasp on greenhouse warming 'fingerprints'... but obviously there is alot more complexity to the issue than I thought. Thanks for the info.
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  25. Regarding my post @14, I mangled something in memory. I was thinking of radioactive decay, which would equalize the 14C in both fossil fuels and other sequestered carbon, but 13C is stable, and so would not be affected by long sequestration. However, apparently plants prefer 12C; so, that preference is what makes the difference between carbon bearing rocks and fossil fuels. So, it would indeed be surprising if the isotopic composition of the carbon in atmosphere were the same as today. However, I haven't see that yet.
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  26. "Former natural warming have the same "isotopic signature" as the present " I dont see how that can be concluded from the paper. This is part of investigation into carbon cycling with glacial cycle but it looked at 14C/12C ratios. 14C is handy for determining age of carbon. However, 14C ratios in modern atmosphere tell you nothing much except that we exploded nuclear devices in the atmosphere ruining any useful science. Instead, carbon cycle has to be investigated by 13C/12C ratios. Because fossil carbon is heavily depleted 13C, it shows excess CO2 in atmosphere is from fossil fuel not from ocean.
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  27. Scaddenp, I noted that as well, but decided I'd let Arkadiusz find truly relevant articles since I did not find a quick counter in Google scholar. But also, I still did not get it right at #25. If the source of the extra C in the past was methane from permafrost or clathrate, then the 13C / 12C ratio would be the same as fossil fuels. So, even if you showed that the increases that occurred in pre-history had the same isotope signature of the fossil fuel release currently, I'd think that would only be an indication of an organic source of the carbon instead of something like a flood basalt. In any event, I think Sphaerica has it. Everything is tied together and it would be difficult to ferret out the signature of the initial trigger. It might be safer to stick with a simpler narrative that we know we are releasing carbon with X isotopic ratio, and the ratio in the atmosphere (and ocean) has shifted to look more like X than it did. We know that CO2 inhibits the outbound flow of LW energy, and that there is no "saturation" level. Then add in that we have already seen all the indications of a warming world.
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  28. 27, Chris G, Yes, but with error bars. That is, I suspect someone out there may have the knowledge to quantify this properly... it's just that I don't, and can't find it. At the same time, I do think that putting together all of the expected differences, no matter how vague individually (poles, winters, radiation measurements, stratospheric cooling, etc.) might produce a final answer with very small error bars. Really, I think there's a whole scientific paper in there that needs to be written, to consolidate and properly quantify the evidence. Except I think that's only of interest to combating denial, and not really of interest to the scientists who don't feel the need to prove that... they've got better things to work on. [This came up in past months, on another thread, and there's a graph there in the post or in the comments that shows an increased diurnal effect coincident with expected AGW, so maybe the fuzziness isn't as great as imagined. But I can't seem to find it.] Again, I think it all comes down to proper quantification, rather than eyeballed, rule-of-thumb logical inference. [Last note... stratospheric cooling is, to me, sort of a show stopper. Nothing else causes stratospheric cooling, as far as I know, so right there, there's no real need for everything else, except that a wealth of evidence is always preferable in any case.]
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  29. Sphaerica @28 considering just the radiation, a reduction in aerosols will result in a cooling stratosphere and warming troposphere. That may (or may not) be countered (or reinforced) by chemical interactions between sulfates and ozone. I will point out three things with regard to your point @20: First, the H2O feedback effects which cause even solar warming to partially mimic the CO2 feedback are acting against the natural signatures of solar forcings, but reinforcing the natural signature of the greenhouse effect. Therefore the signature will be stronger for a greenhouse forcing than for a solar forcing. Second, the feedback effects will only significantly mimic the greenhouse signature overall if the H2O feedback is a strong feedback. If it is weak it will not swamp the opposite sign signatures from a solar forcing so that solar forcings mimic greenhouse forcings in both sign and (approximately) magnitude. Third, the H2O feedback will not mimic the stratospheric cooling because the H2O is not carried to the stratosphere because of the very low temperatures at the tropopause. The effect of these three points is that any honest analysis of the greenhouse signatures will place an honest skeptic in the position where they must either accept a GHG driven global warming because of the signatures, or accept it because they are committed to a strong feedback along with the cooling stratosphere.
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  30. 29, Tom Curtis, Yes. I agree with all of your points... but still, to me, the issue comes back to one of precise quantification. The logic is there, but (as we've seen is already the case with the simple task of measuring and computing what are obviously rising global temperatures) getting through the noise to an indisputable argument is tricky.
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  31. Speaking of CO2, the May Mauna Loa data is out: 394.16 [Source] No "bend" visible in the trend yet, so let's all hope that June won't continue the upward arc...
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  32. Daniel Bailey 31 Why exactly a concern for global warming when the change of global CO2 ppm is already bad enough? In other words, if 394 ppm is a detriment on its own right, what does correlating this to climate change bring to table?
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  33. RSVP@32 Having trouble parsing this question. "...if 394 ppm is a detriment on its own right..." Is it? I am pretty sure that the concern over CO2 concentrations has nothing to do with fear of suffocation and everything to do with climate change.
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  34. That's a good question, RSVP. May is usually the month where the seasonal peak is reached. Most years have 7 or 8 months of rise before the trees in the NH grow enough for their CO2 uptake to quell the rise and then start their seasonal drawdown of atmospheric concentrations of CO2. The fear is that enough environmental damage caused by the droughts in the Amazon, Australia, Texas & elsewhere could cause those areas to go from sinks to sources. One of the ways that could manifest itself is in the Mauna Loa monthly data. Instead of having years with 7 or 8 months of increases, we may start seeing years with 8 or 9 months of increases. I need not connect the dots for what that might imply (with the annual rates of increases themselves increasing).
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  35. @ pbjamm I believe RSVP was sincere in his question. 394 relative to 350 is bad. 394 relative to the historical interglacial max of 298.7 is bad. Obviously yet another monthly increase is bad. Hence his question. I had hoped that May would show a tapering of the increase.
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  36. ChrisG - "If the source of the extra C in the past was methane from permafrost or clathrate, then the 13C / 12C ratio would be the same as fossil fuels." No they are not. Clathrate methane appears to be predominately from microbial activity with d13 between -40 and -100, average ~60-65. FF is closer to plant with d13 around ~-30. This has been used as evidence against clathrates being big players in events like YD based on ice core methane. However, I am watching for more results from these studies, as well as ongoing work d13 in the PETM where clathrates are thought to be significant.
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  37. Just to add another wrinkle to the 12C/13C discussion. Not all plants preferentially absorb 12C. It depends on the photosynthesis mechanism they use. The simpler C3 photosynthesis pathway does produce reduced 13C. This appears to be an evolutionarily older mechanism. However the more efficient C4 pathway doesn't discriminate. C4 is believed to have developed relatively recently as an evolutionary adaptation to declining CO2 levels. The main plant species where this is a factor are the grains. Some of them are C3 and others C4. Most other types of plant families are C3. So an extra wrinkle in analyzing 12C/13C data is modern agriculture. We have substituted significant parts of the general biosphere with grain monocultures. So we have probably messed with the 12C/13C ratio for modern plant life compared to what it would be at the present time without the impact of human agriculture. Does this help us further in identifying a 12C/13C signature in atmospheric CO2? Possibly since fossil CO2 should be more 13C depleted than modern biogenic CO2. Can this be seen above the noise level? Dunno.
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  38. Scaddenp, Glenn, Hmm, I'd figurede that the bacteria producing methane were eating plant material and that would mean the same ratios throughout. I did not remember about the C3 versus C4 pathways. Interesting, thanks.
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  39. Daniel B (#34), That is a very interesting observation. Another round of thanks. Though, I'm not sure how to distinguish an introduction of positive feedbacks from an acceleration of FF use. Either would produce a greater number of months with increasing levels. The timing of the peaks or the shape of the curve might make do it, but that is likely a difficult signal to filter from the noise. I'll have to give it more thought.
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  40. Well, I think this isotope subthread is about worn out, but in case anyone else is still interested or comes back to it, bacteria impose their own preferences on the isotope ratio of methane, and that preference can vary under different conditions. There's a pay-wall, but the gist is in the abstract of Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane which says what scaddenp has said, with a bit more detail as to what conditions give rise to the wide ranges found.
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  41. case closed? From the results at randomly chosen weather stations it would appear that there is no warming caused by a green house effect: For the record and for those interested: (-Snip-)
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    [DB] If you've made a point before and it's also on-topic here, then provide a link to that point.  We're more than capable of following links.  The rest of your comment here is nothing more than pointlessly arguing cherry-pick fallacies (i.e., since cherries are red apples can not also be red). 

  42. MoreCarbon, you wrote the same exact post here Is there a reason you are posting the same thing on multiple threads?
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  43. Henry@Robert 1) in the case of the confidence interval: the question whether the warming is significant on a 1%, 2.5 % 5% or or 10% is irrelevant. We know warming ihas happened. The question is: is it natural or is it man made? 2) in this case here: you want to close a case without having seen any actual data?
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  44. You completely ignored my question. Why did you write the same exact post on two threads?
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  45. Robert Murphy, what is your point? Am I not allowed to make the same post at different discussions if it is on tpoic?
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    Moderator Response: [Dikran Marsupial] Please do not make duplicate posts. If you have made a post on one thread that you feel is relevant to another, then do feel free to post a message on that thread directing readers to the original post.
  46. 41, MoreCarbonOk, Followed your link. The logic there was as bizarre and incomplete as it was wrong. People need to base their own decision making capabilities on something with considerably more substance and less hand-waving than Henry's pool table (such as, among dozens of other fallacies, the completely unexplained and unsupported assertion of the a priori condition that greenhouse gas warming must operate by increasing minimum observed temperatures more than maximums). Henry should stick to playing games, because real science is beyond him. In the future, just as someone who is sharing this site with you, I'd ask that you limit the links you provide to substantive, reasonable and defensible science, rather than quite frankly weird, simplistic posts by Galilean-blog-science-wannabes.
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  47. MoreCarbonOK, Aside from the other faults of your argument, your first premiss is wrong; randomly selected stations show a similar rate of rise as those stations selected for the longevity of their records. At least, those are the results of the data so far. "Rather than pick stations with long records (as done by the prior groups) we picked stations randomly from the complete set. This approach eliminates station selection bias. Our results are shown in the Figure; we see a global warming trend that is very similar to that previously reported by the other groups" Richard Muller's Statement to Congress about Climate Change Pretty sure "prior groups" refers to Hansen, et al. You are being played. If the world is not warming, what is causing the change in the seasons? The physics of the GHE have been established for about 100 years; what makes you think you or Henry know more than everyone else? Global warming has already had its Galileo, his name was Arrhenius, or Tyndall, if you prefer.
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  48. Hello (no41) MoreCarbonOK; Yes. It is definitely man-made. The reason that any one of us — capable of performing basic calculations in mathematical physics (apart from reading the many convincing linked/argued documentations in Skeptical Science on the many details from many research groups) — can know why we certainly are on the right path in addressing Global Warming to Anthropogenic causes, is this one — please, MoreCarbonOK, and do tell your friends about it too: With a general human evolution of technology (illustrating image as below, details in AGW, the energy curve basic function as y=a[1–1/(1+[x/b]^n)], n=2, its derivative gives the effect [power] transient [ocean heat absorption, value 0,878 W/M² period 2000-2010, fairly in accord with other sources (Hansen group 2005), also in line with a more simple evaluation from Stefan-Boltzmann-radiation law, provided a correct interpretation], its integral gives the carbon-dioxide concentration [yielding a 98% match with measured values up to 2009, and further], both latter as long as t is added by fossil-carbon) Fossil-Carbon curve (black) from WIKIMEDIA COMMONS and RENEWABLE ENERGY — Critical Evaluation of the U.S. Renewable Energy Policy, 2009, respectively it is IMPOSSIBLE to omit an additional temperature component (t) from a general fossil-carbon combustion temperature (T) from an emitted (combusted) amount (m) of the fossil carbon into the local atmospheric mass locale (M), account taken upon a general emissivity or absorption coefficient (a), simply expressed as t/T=a(m/M) giving t = Ta(m/M) [Temperature and Energy are proportional — as in the familiar General Gas Law: pV=kT=E giving T=E/k]. With account taken for thermal resistance (R=t/P, P the irradiating power from the Sun: t catalyzes a thermal resistive increase from the already given irradiating Solar power) the expression enhances to yield for a double t := 2Ta(m/M) [Of course, as long as a T exists (for fossils roughly around 2000-2200 °C), also a t inevitably will follow. But with no T (or a very low negligible value of it), also no t will be added: zero AGW]. With the given industrial fossil-carbon curve and its adopted mass-scale to fit the general energy-curve (E), m/t can be calculated [adopted value from 2005 as (average yearly scale base) 10.17094 T12 KG/°C, T for 10^+, with the reported yearly ca m=7 T12 KG fossil carbon to the measured total GW of ca t=+0.7°C], and (with a general Earth-based a=0.7, meaning ca 0.3 albedo) also M can be calculated [value 3.52138 T16 KG to be compared to the total atmospheric EarthM=5.3 T18 KG]. With simple figures [density at STP (Standard Temperature and Pressure) everywhere the same] M holds only at most h=60 meters above the solid Earth-surface to account for the measured t(AGW)-curve — which (hence) excludes any AGW-debate on higher lying atmospheric layers (type Christy’s arguments, but also Lindzen’s »climate sensitivity»): these may (and do) contribute, but have no significance in the AGW-basics. With a 50 pixel graphical square unit to draw from, and taking a more or less »simple» ocean (two-complex) period of type (cosx)+(cos3x) [coefficients must be added to get a scaling match to the other given curves] together with the basic t|E-smoothed fossil-carbon component, in all y = 6[1-1/(1+[x/10]^4)] + 0.222(0.9[(2cos (pi x/1.48)) + 0.5(cos (3pi[x-0.1]/1.48))]), or the corresponding now-year-based connection as t(NASA) = –0.4 + (1.765)[1–1/(1+[(YEAR–1815)/212.7]^4)] + 0.0653(0.9[(2cos pi (YEAR–1880)/31.48)+0.5(cos 3pi[YEAR–1880-0.1]/31.48)]) we have the dotted (5) from the already known and well recognized sources (as) in [The NASA-curve is reduced to 65% horizontally to match the time scale of Fossil-Carbon; The Fossil-Carbon vertical scale is then reduced to 33% to match (a closest possible approximation to) the (t|E)+(SeaPeriod) = NASA-curve vertical scale]. And as we clearly can see, the predictive power is unmistakable — however no account taken upon additive (radiative forcing) components (making the figure even worse); There is, obviously, only one known agent to account for the measured Global Warming: industry. Safely. Exactly. Precisely. While humanity is bound to the E-part of the t|E-function, it is necessarily not so to the t-part if, and only if, a solution is found in reducing the fossil energy source. (Meaning: we cannot stop human evolution, but possibly we can find another energy source than fossils to feed our [unstoppable] technological evolution, thereby removing a further t-increase). Christy and Lindzen give wrong arguments (causing public chaos) because they do not account for the (unnoticed but simple) math-base (t/T-form) making up (an unmistakable equivalent to) the measured NASA-curve: the industrial fossil-carbon driving the whole (land-marine max height=60 meter) measure. Radiative Forcing high above the Earth surface is explicitly not within the basic AGW-proof (the t/T-form giving a max h=60M), and therefore makes no contribution to the clarification of the AGW-quest itself. (Debates on the subject, not distinguishing the different aspects, make dead-end discussions). AGW is no natural variation. Hence, AGW cannot be explained by the general math referred to as Arrhenius’ expressions (often termed »radiative forcing» and associated with the higher atmospheric layers). To explain (mathematically) for AGW, hence, a strict isolated mathematical-physical complex must be found (»no Arrhenius math»), including all the seven (7) known ingredients to the observed (A)GW-complex [and too, it must include »Arrhenius curves» as a special case if given specific offsets — so is also the case, indeed]. That is what the simple t/T-connection does — with a seemingly fine alignment to already presented figures. wkg/Gwinnevere
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  49. Well you clever guys. If I were you I would still have a peek at my new and updated pool tables. No junk science there. No hypothesis. Actual results from actual measurements> Quite interesting results, too. I have split up the NH and the SH. Any ideas on the differences between NH and SH?
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    Moderator Response: [Dikran Marsupial] IIRC, it has already been pointed out to you that the difference in NH and SH trends is probably due to the unequal distribution of land mass between the two hemispheres. The problems with your pool have also been pointed out to you, repeatedly. Please do not repeat that discussion here, if you want to discuss your pool, please read the excellent series of posts by Glen Tamblyn (starting here), and if you still want to argue that your method is best, then first you need to explain why the methods used by the climatologists, who have looked into the issues in great detail, are defficient. That discussion should be posted on one of the articles in Glen's series, not here.
  50. HenryP (#49), From your site: if an increase in green house gases is to blame for the warming, it should be minimum temperatures (that occur during the night) that must show the increase (of modern warming). In that case, the observed trend should be that minimum temperatures should be rising faster than maxima and mean temperatures. That is what would prove a causal link. --- From this site: post-1970 results show monthly-minimum temperatures rising faster than monthly maximum temperatures. These results are entirely consistent with greater CO2 forcing later in the century than earlier. --- A Quick and Dirty Analysis of GHCN Surface Temperature Data (paragraph above Figure 3)
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