Calculating the greenhouse effect

Filed under: — gavin @ 21 January 2006

In another forum (on a planet far, far away), the following quote recently came up:

….the combined effect of these greenhouse gases is to warm Earth’s atmosphere by about 33 ºC, from a chilly -18 ºC in their absence to a pleasant +15 ºC in their presence. 95% (31.35 ºC) of this warming is produced by water vapour, which is far and away the most important greenhouse gas. The other trace gases contribute 5% (1.65 ºC) of the greenhouse warming, amongst which carbon dioxide corresponds to 3.65% (1.19 ºC). The human-caused contribution corresponds to about 3% of the total carbon dioxide in the present atmosphere, the great majority of which is derived from natural sources. Therefore, the probable effect of human-injected carbon dioxide is a miniscule 0.12% of the greenhouse warming, that is a temperature rise of 0.036 ºC. Put another way, 99.88% of the greenhouse effect has nothing to do with carbon dioxide emissions from human activity8.

We’ve discussed the magnitude of the greenhouse effect before, but it might be helpful to step through this ‘back-of-the-agenda’ calculation and see what the numbers really give. (Deltoid has also had a go at some of these mis-statements).

The quote comes from a lecture by an Australian climate ‘contrarian’ and frequent contributor to the southern hemisphere op-ed pages. Where did he get this from? One might assume that reference ‘8’ was a scientific text, but one would assume wrong. It was in fact our old friend at Fox News, who may in turn have picked up his (junk)science from here. It is not clear whether this is the original source, but it’s close enough.

So, starting at the top:

• “33 ºC” is the difference between the mean surface air temperature of the planet and the blackbody radiating temperature (i.e. the temperature a blackbody would need to radiate at to be in equilibrium with the incoming solar radiation given an albedo of about 0.3). So far so good. While that is one way to assess the strength of the basic greenhouse effect, another one is measure the amount of long wave radiation from the surface that is absorbed in the atmosphere (by greenhouse gases (incl. water vapour), clouds, aerosols, etc.). That is currently about 150 W/m2 and would be zero with no greenhouse effect at all.
• “95% of this warming is caused by water vapour”. This is sourced to a couple of chaps who may have worked for Accu-Weather, but a) is misquoted – their ’90-95%’ is for both water vapour and clouds, and b) just wrong and c) irrelevant anyway.
Dealing with b) first, if you remove all water vapour and clouds you still absorb about 34% of the long wave radiation, and conversely, if you only have water vapour and clouds you absorb 85% (calculations here). Thus the effect of water vapour and clouds is between 66 and 85% – the range being due to the spectral overlaps with the other absorbers. These calculations were done with the GISS GCM radiation code, which matches line-by-line codes to about 10% – but the numbers are very similar to Ramanathan and Coakley (1978), and so probably aren’t too far off what you would get with any decent radiation code. I’ll get to ‘c)’ below….
• “The other trace gases contribute 5% … amongst which carbon dioxide corresponds to 3.65%”. That is just 100 minus 95% of course, but really it should be 15 to 34% – of which CO2 on its own is between 9 and 26% (op cit). If you were to naively estimate the total temperature contribution of the CO2 it would be between 3 and 9 ºC – but see below.
• “The human-caused contribution corresponds to about 3% of the total carbon dioxide in the present atmosphere,”. This one is blatantly false and is erroneously credited to the US Dept. of Energy in the original source (their Table 1)! The ‘3%’ number actually comes from comparing the human emissions with the gross emissions from natural sources while neglecting to consider the large natural sink. Because of the rapid cycling between the biosphere, the atmosphere and the upper ocean, that is an irrelevant comparison – kind of like comparing the interest on your bank account and your salary and expecting to be able to say something about your savings without thinking about your spending. The correct statement is that CO2 is around 30% higher than it was in the pre-industrial period, and all of that rise is due to human emissions (fossil fuel use and deforestation principally).
• “Therefore, the probable effect of human-injected carbon dioxide is a miniscule 0.12% of the greenhouse warming”. That’s just 0.03*0.0365 of course – but even that is calculated wrong (it should be 0.11% by my calculator). But from our numbers, it would be between 3 and 8%.
• “a temperature rise of 0.036 ºC”. More like 1-2.6 ºC actually, but although this gives numbers that are in the ballpark of the IPCC estimates (0.6 to 1.7 ºC warming for an increase of 30% in CO2 at equilibirum) this is not a sensible way to calculate climate sensitivty.

Why do I claim this is an irrelevant and not very sensible calculation? Firstly, it assumes linearity – all of the gases contributing according to their effects today when it is obvious that overlaps and saturation effects are large and important, and more importantly, it ignores feedbacks. The calculation above gives the impression that what you are calculating is the change of temperature that would result if you remove all the CO2. But since water vapour concentration is a feedback not a forcing, it can’t be assumed to remain constant as the planet cools. Water vapour does in fact change (roughly keeping relative humidity, as opposed to specific humidity, constant) and this has been shown in the real world as a function of volcanic cooling (Soden et al, 2002) and for longer term trends (Soden et al, 2005, discussed here), and is well reproduced in climate models.

What then is an appropriate calculation? Well, it’s simply the estimate of climate sensitivity for the present climate – how much would you expect the planet to warm if you doubled CO2? We’ve discussed this numerous times before, and in my opinion the best answer so far comes from looking at the difference between the last glacial period and the modern era – this gives a number around 3 +/- 1 ºC at doubling.

For the 30% rise in CO2 there has been so far, that would imply that would represent around 3% of the natural greenhouse effect – a good order of magnitude bigger than that suggested above. Of course, this is at equilibrium and not applicable to a transient change. If one takes into account the human-induced changes in the other GHGs (CH4, N2O, CFCs), you’d get something like double that. Given that even a 5 or 6 ºC cooling was associated with the huge ice sheets 20,000 years ago, and that 33 ºC cooling would reduce our planet to a near-snowball-like state, a potential increase of 5 to 6% of the natural greenhouse effect is not to be sniffed at… nor dismissed as irrelevent with highly misleading arithmetic.

One could make the point that my calculations are ‘just another web page’ no more and no less authoritative than the links above. In some sense that is correct (though I’d argue my sourcing is a little better!). But you will never find a peer-reviewed rebuttal of such a bizarre line of reasoning as we are dealing with here – basically because such a line of reasoning is highly unlikely to make it past peer-review itself. There are innumerable ‘proper’ references to estimates of the climate sensitivity though, and one should indeed hesitate to accept calculations like this example over the mass of peer reviewed studies.

240 Responses to “Calculating the greenhouse effect”

1. 51
Tom Rees says:

Ferdinand is right – in GCMs, at least, there is considerable overlap betweent he effects of solar and GHG forcing – at least down here on the surface. Regarding the Dust Bowl, according to Schubert et al, 2004, it was caused by anomalous Pacific SSTs. However, there is no consensus, as far as I know, that this anomaly was caused specifically by solar warming. Certainly, I’m not aware of any study showing this. It may simply have been natural variability – such multidecadal droughts have happened in the past.

2. 52
Pat Neuman says:

47.

Coby,

The meaning of “climate” which is used by NOAA’s NWS Climate Prediction Center is much shorter-term than the meaning of “climate” used in discussions on global or regional climate change.
NOAA/ National Weather Service
National Centers for Environmental Prediction
Climate Prediction Center
http://www.cpc.ncep.noaa.gov/

Coby, also…

Regarding your reply: “That’s why I thought it was incorrect to infer anything about a climate change, much less what forced it, from a regional drought that was less than a decade.”,

I believe that the early 1930s drought and heat wave was extreme in more ways than an absence of rain. The humidity was extremely low across very large regions (Great Plains, Midwest …). There have been other “droughts” in the Midwest which occurred after the dust bowl years. BTW, I didn’t use that term in my reply to Ferdinand in #43, you added the term drought in your comments which followed. Droughts that occurred in the Midwest after the dust bowl years until current (1976-77, 1987-88) have been much less severe than the dust bowl dry period, without the prolonged extremely low humidity in the early 1930s. I’ve made comparisons in Mississippi River monthly flows at Minneapolis for the early 1930s vs other dry periods… the flow on the Mississippi River (used for Minneapolis-St.Paul water supply) was much lower in the early 1930s than other low water years that occurred later in the 20th century. The dust bowl years was a very unusual period of extreme dryness and no clouds. It seems likely to me that the humid warm years, which followed the early 1930s heat and cloudless period, were heavily influenced by prolonged El Nino, ENSO which too place mid-1930s to 1940s, and may have been triggered by the extreme dry hot and clear dust bowl years (which may have been occurring over the ocean, leading to the subsequent El Ninos during the decade that followed the dust bowl years of the early 1930s).

In my input to public comment on draft U.S. Strategic Plan (18 Jan 2003), http://groups.yahoo.com/group/ClimateArchive/message/2696

My comments on the draft CSSP Strategic Plan in 2003 included:

“Please, add: Temperature data by itself is inadequate in monitoring changes in climate. Changes in enthalpy (temperature, humidity, phase change – latent heat exchanges) are very important. It can be misleading to look only at temperature measurements without considering changes in humidity (dewpoints). Near surface humidity is very important in determining the rate of snowmelt, and ice thaw due to the latent heat exchange from the condensation of water vapor on cold surfaces.” … “All dewpoint and relative humidity data from historical records should be made available in digital format for modeling and analysis.”

I haven’t seen any action taken on the above, which I considered as very important in Jan 2003 (and still do).

Coby, also…

After rereading what you wrote: “I did reread the thread, and I think I still agree with Ferdinand about not being able to seperate solar forcing vs GHG forcing based on regional responses”.

I still disagree with you (and Ferdinand), based on my discussion (above) and based on statements made by Drew Shindell – March 1999, in: Solar Variability, Ozone, and Climate, at:
http://www.giss.nasa.gov/research/briefs/shindell_03/

3. 53
Pat Neuman says:

In comment #48 by JohnnyBGoode it says: “You still have not made a case for the above claim”.

The claim I made in my comment #43 to Ferdinand was that: “It isn’t that difficult, and certainly not impossible, to see the difference between global warming triggered by GHG emissions and global warming initiated by a solar radiation surge.”

It not clear to me what kind of a case Mr. JohnnyBGoode is looking for. I think I have made a case, above. From my experience in hydrologic modeling and prediction, many river gaging sites show a quick surge in flows and levels from local runoff, followed by a more gradual but larger increase in flows and river levels from the larger portion of the river basin further upstream. It takes a sharp eye and focused attention to notice these types of characteristics in physical systems. Also, like increasing river flows, if the rate of rise during the beginning periods of a flood event (or warming climate trend) is much quicker than was earlier expected, it may not be just the timing that’s off. It’s more likely that the volume (or warming maximums) are being underestimated. For example, “David Field, another Scripps researcher who has been working with several Mexican and US colleagues, has found evidence that global warming is beginning to penetrate the ocean today. Dr. Field, now at the Monterey Bay Aquarium Research Institute, and his co-researchers described that warming earlier this month in Science.” http://www.csmonitor.com/2006/0126/p16s01-stss.htm

4. 54
Douglas Hoyt says:

All the climate models omit a strong negative feedback that only applies to greenhouse warming. Briefly put, a narrowband greenhouse effect will not warm a moist planet because the photons will be shuttled to cover the entire IR spectrum and hence energy will be lost to space through the IR windows. A detailed explanation is given below.

The absorption coefficient for liquid water as a function of wavelength is given at http://www.lsbu.ac.uk/water/vibrat.html (see the figure near the end). Thermal infrared in the Earth’s atmosphere is around 10 to 20 microns where the absorption coefficient (A) is about 1000 cm-1. For the transmission in liquid water (T), we have

T = exp(-A*L)

where L is the depth of penetration. For the case where 1/e or 27% of the incident photons remain unabsorbed and with A=1000 cm-1, then L= 1/1000 cm = 0.01 mm. 98% of the incident photons will be absorbed within 3 times this distance. So one can see from the figure, than practically no infrared photons penetrate beyond 0.03 mm. A more precise estimate of A is 5000 cm-1 at 15 microns where carbon dioxide is emitting radiation, so 0.006 mm is a more accurate number for the depth of penetration of 98% of the photons arising from carbon dioxide forcing. Since the liquid water is such an effective absorber, it is a very effective emitter as well. The water will not heat up, it will just redirect the energy back up to the atmosphere much like a mirror, but not exactly a mirror, and this is an important point.

For A = 5000 cm-1 at 15 microns, the implied water emissivity is 0.9998 implying that of the incident radiation only 0.02% of it will ultimately be absorbed in the water. The emitted radiation will closely follow a blackbody emission curve whereas the incident flux from carbon dioxide is confined to a band centered at 15 microns. The implication of this is that much of the radiation emitted will escape directly to space through the IR windows, so it could be viewed as a negative feedback. Alternatively, this mechanism implies that climate will be less sensitive to greenhouse gas warming than it would be to an equal solar radiation forcing. In addition, there are many moist areas over land, so this negative feedback or reduction in climate sensitivity may also be operable over portions of the continents.

The above mechanism works because the initially absorbed infrared energy cannot be transferred to the ocean depths by conduction (too slow), by convection (too small an absorption layer compared to the size of convective cells), or by radiation (too opaque). It must escape by the fastest way possible meaning upwards radiation away from the water.

Consequently, the only way to explain the ocean heating in depth is for the solar radiation to change and decreasing clouds, as measured by ISCCP, indicate increasing solar radiation is occurring right where the ocean heating is reported to be occurring. The Willis paper does not even mention the ISCCP data that has a similar geographic distribution to the water warming. Simply put, where clouds decrease in amount, the water warms. It has nothing to do with carbon dioxide. A handy plot of the ISCCP results can be found as Figure 3 at http://www.worldclimatereport.com/index.php/2006/01/11/jumping-to-conclusions-frogs-global-warming-and-nature/ where clouds are shown to decrease for 1987-2000. In the Willis paper, Figure 4b, covering 1992-2003, is the one that should be compared to Figure 3. Although the dates do not exactly overlap, the spatial patterns are very similar. There is a need to plot both variables over the exact same time interval, but it is unlikely it would change the major conclusions presented here. Clouds have large natural variations going up and down entirely independent of any greenhouse effect. The climate models do not predict these variations and apparently Willis and others are unaware of these variations.

[Response: The idea that ocean warming can only occur by SW radiation is erroneous. While SW does penetrate further into the interior, fluxes at the surface (which include sensible and latent heat as well downwelling long-wave) affect the mixed layer equally. The mixing of the upper ocean (to produce the ‘mixed’ layer) is dominated by the wind (with some buoyancy related effects) and serves to mix surface fluxes of both heat and freshwater over the mixed layer in it’s entirety. Clouds both influence and react to sea surface temperatures and correlations between SST and clouds would be expected. The fact remains that the oceans have been warming at a rate of at least 0.6 W/m2 over the last ten years, demonstrating clearly that the planet is out of energy equilibrium – as the climate models suggest. -gavin]

5. 55
Pat Neuman says:

In #51, Tom Rees wrote: …

Posts which I already made earlier this morning in reply to Coby and JohnnyBGoode were counter to the comments which Tom Rees made in #51, thus there is no need for me to reply that I can see now.

6. 56

Re sunspots — aren’t sunspots COOLER than the rest of the Sun’s surface, since the magnetic field strength is greater in a sunspot and the “molecular” (ion) motions accordingly less random? Please correct me if I’m wrong.

[Response:Yes. However,that is balanced by the surrounding faculae which are more bright than the sunspots are dark. See some of Judith Lean’s papers for details. – gavin]

7. 57
Douglas Hoyt says:

Gavin,

One hardly knows where to begin replying to your confused comments in #54. The heating of the ocean will be dominated by solar radiation and lead to the creation of a mixed layer. The mixed layer does not cause the heating.

Much of the reported ocean warming occurs in areas where there is little or no wind. How could downwelling infrared radiation heat the ocean in such circumstances? In your world view, it could not.

Your worst mistake is to assume a slow moving mixed layer is a better transport of heat than infrared radiation. The 15 micron radiation is absorbed in a layer much thinner than a human hair. It will escape from that layer by the most efficient means possible, meaning predominantly radiation upwards back to space.

You really need to think the problem through and it is clear that you haven’t.

[Response: The confusion is all yours. Solar radiation on it’s own is stabilising and would not lead to mixing at all. Even in the climatological average, LW heating is dominant over SW. If such large values of downwelling LW were all being absorbed and re-radiated at the skin layer, the skin SST would be tens of degrees warmer than the mixed layer value. As it is, the differences are around 0.5 deg C at max. The physics of that skin layer can only be explained with significant mixing down into bulk ocean. I suggest you read some of the relevant papers (wick et al, for instance). Your claim that warming occurs in regions with no wind (and presumably no mixed layer?) is completely unfounded. The southern oceans for instance (Gille et al, 2002)? Plenty of wind there! – gavin]

8. 58
JohnnyBGoode says:

#53

Not only have you been unable to support your claim, but now you claim to be an authority of some sort and jump to a different subject about rivers. Your claim that it isn’t difficult to differentiate between solar driven and GHG driven warming shows a lack of understanding of the complexities of this subject.

The Shindell paper points to early 20th century warming being driven by solar forcing and it does make the case that the last 3 decades of warming agree with models of GHG driven warming. This is based on models of forcings and their correlation with observed global temperature trends. What the Shindell paper does not do is show the dust bowl of the 1930’s or Twin Cities dewpoints are in any way related to or a sign of specific causes of climate change. Such regional changes do not even provide an accurate picture of global climate and definitely do not point to a specific driver of global climate change.

Perhaps Gavin could explain this from his science based perspective before people read your comments and wrongly assume that regional weather and/or regional climate is actually an accurate indicator of the drivers behind global climate change.

9. 59
Pat Neuman says:

In #58 JohnnyBGoode wrote: “What the Shindell paper does not do is show the dust bowl of the 1930’s” …

JohnnyBGoode,

There were no human satellites to even estimate the amount of clear skies and solar radiation over the ocean in the early 1930s. I know from personal observations of lake ice that a clear sky with no snowcover on area lakes can weaken the ice a great deal, even during periods when the air temperature is below freezing. Such was the case in Minnesota and Wisconsin during a recent winter. Lots of snowmobiles, pickups and SUVs went through the ice that year who were not aware of the penetration of solar radiation through clear ice can do to the ice.

10. 60
Douglas Hoyt says:

This will be my last post on this subject.

11. 61
Coby says:

Hi Pat,

It does not bother me to disagree on the main points we were discussing. I did want to note the following:

Climate – The average of weather over at least a 30-year period. Note that the climate taken over different periods of time (30 years, 1000 years) may be different. The old saying is climate is what we expect and weather is what we get.

This is from here, a part of the NOAA site you referenced above. You undoubtably have good reason to have come away with the impression they use a shorter term working definition, but at least officially 30 years seems to be the time frame.

12. 62
Lynn Vincentnathan says:

More household science, a bit closer to topic. Water vapor really doesn’t stay in the air very long, expecially in cold times; we have to keep refilling our humidifier. Fried fish smell, however, will last for days, long after the steamy effect has ceased (this goes beyond CO2, but that’s as close as I could come, just using bodily senses to estimate effects).

Another argument (gun-lovers will love), “Guns don’t kill people; people kill people.” Water vapor does not heat the earth (by itself), but the heating that increases the WV heats the earth, & gets WV to help out. The warming causes more retention of water vapor. As we know from my above experiences, that water vapor is constantly vanishing (not into thin air, but back into the solid & liquid environment, I suppose), being replaced by more vapor. I think they refer to it as the hydrological cycle. This is quite natural, & we wouldn’t expect any net increased warming from that.

So we have to look at what is causing increased water vapor in the atmosphere. Who’s pulling the trigger on the gun? Must be the warming. But if it were only warming from the WV effect, then I’d be able to cook without a heat source — just let the steam effect feedback into heating up my pot.

So now we’re back to either it’s CO2 (& other forcing GHGs), the sun, or Godzilla who’s heating up the planet.

13. 63
Pat Neuman says:

Lynn,

I think I made it pretty obvious (in #31) that the heating up of the planet in recent decades is due to CO2 accumulation in the atmosphere from fossil fuel burning, not the sun. I think Godzilla should be ruled out too.

Regarding a #58 by JohnnynotBGoode,

One should note that annual temperatures in Oregon were warmest of record at climate stations in 1934. Thus, dust bowl heat in 1934 extended from the Great Lakes to the west coast, and perhaps out to sea, – a very large “region”.

http://pg.photos.yahoo.com/ph/patneuman2000/my_photos

14. 64
Lynn Vincentnathan says:

Pat (#63), yes, the scientists tell us there has not been any overall increase in solar output, so for now it cannot be blamed for the earth’s warming.

However, I have to thank the denialists for drawing our attention to the sun as possible source of heating. I suppose solar output could increase in the future and add to our warming woes. Which means we should redouble our efforts to reduce our GHGs (even more than we might need to for AGW) to be on the safe side, just in case the sun starts contributing more heat. Afterall, we can’t do much to turn down solar radiation.

I’m sure denialists would agree with that – the sun can be a very dangerous thing, be prepared, do what we can do…

15. 65
EdTed says:

Lynn, I think you’ve been found out – surely a contrarian stooge.

16. 66
Pat Neuman says:

Coby,

I hope you will forgive the mistake I made in one of my earlier post where I called you Colby instead of Coby. I’m originally from near Green Bay, Wisconsin.

In #61 you wrote … “Climate – The average of weather over at least a 30-year period”…

In a post to Pittsburgh IndyMedia Center titled “Winter not coming” I show a plot of annual temperatures at Minneapolis from 1960 to 2005, and a discussion of a change (increase) in the 30 year average or “normal” annual temperature at Minneapolis as the calendar went to the next decade in year 2000. The increase went from an annual temperature of 44.7 F to about 45.3 F, reflecting the average for the latest 30 year period increasing about 0.6 F. Do you want to comment on that?

However, the main purpose of my Jan 19 post to Pittsburgh IndyMedia Center was to show that annual temperatures at Minneapolis have been above “normal” since 1997. In looking at the right side of the plot at the link below, it really looks strange to me. I’ve notice the same pattern at other stations in the Upper Midwest and Great Plains, showing that what used to be fluctuation about the 10 year trend line is recently showing all at or above it. It also appears that the variance about the mean in recent decades has been decreasing, but I doubt that will continue beyond the next El Nino year (ouch).

http://pittsburgh.indymedia.org/news/2006/01/22241.php

17. 67
Coby says:

No problem about the name, Pat, I’ve been called Corby, Toby, Colby, Cody, Cory and even Doby not to mention the numerous phonetically correct mispellings! (Ok, “Doby” was by a 3-yr old, it was very cute :-) But it takes more than that to get under my skin.

Your indymedia post does raise an interesting point about redefining normal. I have thought about that often listening to weather reports about “N degrees above/below normal today”. I imagine that it is standard practice at all weather bureaus to update the benchmark averages in the face of long term trends. It should perhpas be local news when such an adjustment is made. Surely there is a risk that these long term changes are then forgotten when normality is just redefined, then again we have to put the stick in the sand somewhere!

What should continue to alert people are the record breaking events. It is a tempting mistake to think that given a steady climate, we should expect to see on average a steady rate of extremes recorded. But actually, every time a new extreme hot or cold is recorded this should reduce the probability of that record being broken again in any given year. Eventually, a record high or low would be extremely rare.

I don’t know if there have been any studies of the rate of occurence of extremes but this would be an interesting and possibly informative exercise. It would not be surprising though if there is too much uncertainty in individual measurements to draw any conclusions.

18. 68
Timothy says:

Coby – “I imagine that it is standard practice at all weather bureaus to update the benchmark averages in the face of long term trends.”

Indeed it is. See for example http://www.metoffice.gov.uk/climate/uk/averages/index.html where they state as such, and also have 1961-1990 and 1971-2000 averages to compare [no difference maps though!].

As to your final point, I believe that there was an earlier RealClimate post which touched on the subject of extremes in timeseries data.

Yes – found it! http://www.realclimate.org/index.php?p=175#more-175

19. 69
JohnnyBGoode says:

#59 #63 Pat Neuman

You jump from topic to topic but never address the points. This isn’t a contest to see who can submit the most comments to RealClimate.

We all realize that you can’t back up the claim that it isn’t difficult to see the difference between warming from solar and GHGs. You can’t because it’s simply not true. If it wasn’t difficult you could easily provide scientific references instead of jumping from Oregon weather to no satellites in the 1930’s to SUV’s breaking through the ice in the upper Midwest.

This topic is complex enough without you making such such unfounded and unsupportable claims.

20. 70

This is for Mr. Mann…..The Fox News “Science Reporter” has been exposed for taking \$95,000 from big tobacco, while writing attacks on second hand smokings effects. I believe he was used in the attacks on Mr. Mann. Was he getting checks from big oil too? Here’s the link:

21. 71
Pat Neuman says:

re #69

Johnny,

It is not difficult for me to see the difference between climate warming from solar and GHGs, as I explained in post #31 and subsequent posts today (all in reply to posts by others – not “a contest to see who can submit the most comments to RealClimate” as you said). It’s like many other things which people do and become good at… after awhile a person develops a knack for what to look for to get the right answer, like putting a 500 piece puzzle together (which I’m no good at because I don’t do 500 puzzles). On the other hand, because I’ve done a lot of looking at what happens in hydrology, my track record on flood predictions has been very good (some have said “almost uncanny”).

22. 72
Terje Petersen says:

I was hoping that somebody could tell me the answer to this question:-

If humans had all dropped dead from a disease 300 years ago then what would be the current climate trend according to the best climate models? Would things be cooling down or warming up or staying static?

23. 73
Coby says:

Re 71

You can see some model hindcasts of the 20th century here: http://www.grida.no/climate/ipcc_tar/wg1/figspm-4.htm – both with and without anthropogenic forcings.

They seem to agree that things would have cooled very slightly.

24. 74
Robert says:

re #64 – Lynn and Pat,

NASA reports show that the Sun is indeed “warmer” than in the past:

http://aom.giss.nasa.gov/srsun.html

It is very difficult to overlook this. A slight imbalance in Solar insolation could easily cause a +ve temperature gradient.

Compare that diagram to the “CO2 as cause of warming” theory.

To give you a visual perspective, the monitor you are reading this web-site on, is probably set to 1280×1024 which is a bit over 1 million pixels. CO2 is measured at around 330 parts per million, lets scale it up a bit to 400 ppm, since there are > 1m pixels.

If drawn side by side they would make a line less than a third of the way across one scan line of the display.

Scattered about the display you would be hard pressed to notice them.

Faced with this simple logic is it so difficult to see that people would hold contrary views, without needing to label them “denialists” ?

thanks
Robert

25. 75
Steve Bloom says:

Robert, it’s good to know we have nothing to worry about from bird flu since we are so very much larger (by a much bigger factor than your example) than those pesky little virii. Also, we don’t have to sweat the Iranians getting their hands on a few dozen kilos of highly enriched uranium, since after all such a comparatively tiny amount of material couldn’t make much of an explosion.

Speaking of proportions, you should perhaps have a look at the scale on the left side of the chart you linked. Also, note that the modern era of direct insolation measurements, roughly since 1950, is pretty flat even on that exaggerated scale, which is to say other forcings have been dominant.

26. 76
Mikel Marielarena says:

Going back to the very first post in this thread, my layman conclusions on the oft-cited calculations that were rebutted there would be as follows:

a) The anthropogenic contribution to the current amount of the trace gas CO2 in the atmosphere is not a mere 3% but rather around 30%.

b) H2O is another, much more abundant, greenhouse element in the atmosphere. But its relative contribution to the greenhouse effect is not as big as that of CO2, and its total contribution does not reach 95% but, at most, 85%.

c) In the current conditions a better calculation of the global temperature increase due to the anthropogenic portion of atmospheric CO2 could be estimated at around 0.99 °C (3% of 33°C), instead of 0.036 ºC.

d) There is still scientific discussion on the dimensions and even on the net sign of the other greenhouse elements feedback following the increased CO2 atmospheric concentration but the surface temperature records of the last 3 decades are not inconsistent with a net positive feedback that could be enhanced as the CO2 concentration continues to rise.

Would everyone agree on these conclusions?

[Response: Not b). Water vapour and clouds absorb more than CO2, just not as much as the quote claimed. -gavin]

27. 77
Timothy says:

Robert: “A slight imbalance in Solar insolation could easily cause a +ve temperature gradient.”

Indeed. The max change in solar imbalance implied by that graph is ~ 3 Wm^2. This is comparable to the radiative forcing for all GHG [CO2+CH4, etc] to date and is less than the ~4 Wm^2 figure for doubling of CO2 alone.

I don’t understand why you think the forcing from the sun would be more important than the larger forcing from GHG. The most important difference that I can see is that we can do something about the forcing from GHG, whereas we have not yet mastered control of the sun [although if we really wanted to we could try putting up some kind of parasol to reduce incident solar insolation].

It’s also worth bearing in mind that the figure you quote has no estimate of the error. There are other historical reconstructions of solar output and they don’t agree.

I find the contrast with the error estimates given with the much-maligned Mann et al (1999) temperature reconstruction for the past 1000 years [aka “Hockey Stick”] to be quite marked.

Where does all the sceptics scepticism go when they are faced with data that agrees with their pre-conceived notion that humans aren’t affecting the climate?

[Response: Note that the forcing from solar needs to be adjusted (for the albedo and geometry) to be comparable to the forcing from GHGs. So for an insolation change of 3 W/m2, the forcing is 3*0.7/4 = ~0.5 W/m2 – much smaller than GHGs (2.4 W/m2 and counting). – gavin]

28. 78
Eli Rabett says:

Just a rather short comment on absorption depth. Evidently the argument that Douglas Hoyt uses has been popularized recently, at least I have seen it a couple of times in the last few days, however, in detail it is wrong.

The calculation is based on Beer’s law, ln(I/Io) = -sigma N L or, if you prefer the decimal version log10(I/Io) = -A L, where A is the absorbance, and L the length (If you are interested in the first version you understand what N and sigma are, they are related to A fairly simply). The problem with, what I believe originated with Fred Singer, is that when the wavelength of the light exceeds 1/A, Beers law does not work anymore and the situation must be analyzed using Maxwell’s laws. That is the case Hoyt discusses. OTOH, the actual absorption depth even taking this into account, is pretty short, maybe 0.05-0.10 mm at most.

29. 79
Tom Brogle says:

GISS records show the slow cooling of the South pole since 1957. The extent of Antarctic ice in Dec 1914 is detailed in the book “South” by Ernest Shackleton(1919) recently republished (2000). The extent of antarctic ice today can be found at
https://www.fnmoc.navy.mil/products/SATELLITE/US058SCOM-IMGatp.SPOLE_IC_PS.gif
Data for Nansen I found with aGoogle search for “fridtjof nansen 1893″The extent of Arctic ice can be found at
https://www.fnmoc.navy.mil/products/SATELLITE/US058SCOM-IMGatp.NPOLE_IC_PS.gif
Nansen and Shackleton were not just sailors.There were many sailors sailing the polar regions (mainly south) every year hunting whales, no doubt there were many reports from same but they are not being investigated by climatologists.

30. 80
Hank Roberts says:

Eli Rabett — thank you for the detail, and possible source for the ideas in the absorbtion argument.

31. 81
Lynn Vincentnathan says:

RE the warming ocean. I interrupt the angels on pinhead counting to bring you this news from http://www.climateark.org/articles/reader.asp?linkid=51405

“Earth could warm up fast

Recent studies of some of nature’s environmental “records” show that global warming can penetrate deep into the ocean faster than scientists have realized. In fact, some such penetration may have already begun…

Geophysicists call the event the Paleocene/Eocene Thermal Maximum. Several degrees of global warming caused major changes in global ocean circulation patterns. This, in turn, brought warm water into normally frigid deep sea depths. It was accompanied by mass extinctions of bottom-dwelling marine life, according to the fossil record. This massive climate change happened in less than 5,000 years. However, Drs. Nunes and Norris point out that it may have happened even more quickly.

Commenting on this in the Scripps announcement, Nunes said that the key finding is that “the Earth is a system that can change very rapidly.” The climate change involved a substantial rise in greenhouse gases such as carbon dioxide and methane. Although there was no human input, this is another example of the important role such gases play in climate change…

There does seem to have been a massive release of methane from the sea bed when warming thawed out frozen methane reservoirs there. This is a hazard in our own time. In the announcement of his group’s findings, Dr. Field said that “changes since the 1970s have been particularly unusual and show that ocean ecosystems in the northeastern Pacific have passed some threshold of natural variability.” “

32. 82
Coby says:

re #79

I’m all for getting data from as many places as possible. I am however, always surprised that the same people who (rightly) wonder about the certainty of the long-term sea surface temperature records because they are based on ship readings for the pre-satellite era will in the same breath point to 100 year old testimonials of polar ice extent.

Look, sometimes you have to take a step back and look at the whole picture. Are you really trying to say the world is not warming? Are you balancing modern satellite readings, 145 years of direct measurements, borehole analysis, well documented studies of sea ice over the last decades, ocean temperature studies etc, balancing all that against anecdotal accounts of sea ice in specific regions in specific years and concluding that the real trend is cooling?

Is that what you have learned that caused you to go from being convinced of AGW to being a sceptic?

33. 83
Lynn Vincentnathan says:

Robert (#74), I wouldn’t call people who speak of increased solar radiation causing warming as “denialists,” only those who do not think our human emitted GHGs can also cause warming. That is, they “deny” that our human emitted GHGs are causing or can cause warming, so the label would be accurate. And they would be “contrarian” in that they go against the bulk of science on this.

Now let’s hope that somehow the denialists & contrarians are right, the Galileos of our time, because the converse is really quite serious and dangerous. Maybe we’ll all wake up from a bad dream somehow.

Meanwhile, I’m doing what I can to reduce GHGs, just in case the bulk of scientist happen to be right. In fact, I think they might even be wrong in underestimating the dangers that may lurk ahead, as my previous post suggests scientists didn’t know just how rapidly the oceans can warm.

34. 84
Caio de Gaia says:

There are several issues here. First, it can not be a good thing changing considerably the atmospheric content of CO2 so we should do everything to cut emissions. Second, it’s clear now that temperatures are indeed rising. Third, GH models are the only thing that we do really understand, and they do reproduce some major aspects of Earth’s climate, although there are issues with things like cloud cover that I think are mostly empirically put in models (am I right?). Fourth, people here think that the only issue about the Sun is sunspot number and total energy output. In fact the issue is most likely galactic cosmic ray (GCR) flux, which depends on solar acivity (less GCR during solar maximum) and might have something to do with cloud cover. But solar activity (sunspot number) is not the whole story, the tilt of the sun’s magnetic neutral line affects also the GCR reaching the atmosphere during solar minimum. GCR flux seems to correlate well with the increase in temperature but it may be an accident, people are still trying to find a causal physical mechanism. So pelase do not dismiss the Sun based on sunspot numbers. Unfortunately we probably need another full solar cycle to understand how the Sun affects the climate. The problem is that a solar cycle is 22 years long.

By the way, these things about the warmest year on record and such always puzzle me. How do we average temperatures for the atmosphere globally? I understand that one can average heat content which depends on local temperature but also on the level of water vapor. How does the average temperature relate with the total heat content of the atmosphere?

35. 85
JohnnyBGoode says:

#71 Pat Neuman

Ok, thanks for the explanation. [rest of comment removed]

36. 86
JohnnyBGoode says:

#85 Gavin’s response

OK Gavin, could you please explain why Mr. Neuman can make such absurd claims without you ever stepping in?

Let’s be realistic sir, such comments do more to make this topic look foolish than any contrarian ever could, yet you remain silent. Why?

And wouldn’t a contrarian who claimed to be able to tell warming was by solar forcing be quickly corrected, if not completely censored? And yet Mr. Neuman’s unfounded opposite claim goes unchallenged?

I’m sure this comment will also be removed/censored, but at least as you delete it realize that such a biased treatment of comments is noticed by the public at large reading your blog.

[Response: My editing was a function of your tone, not your content. Feel free to crticise Pat or anyone else, but do it in constructive ways and leave the sarcasm at home. -gavin]

37. 87
Pat Neuman says:

Johnny,

I think I have supported my claims (in earlier comments and in #31. ref: … ” temperature plots for AK, the Upper Midwest and the U.S. Northwest at: http://pg.photos.yahoo.com/ph/patneuman2000/my_photos

Johnny, I have extensive experience in modeling and prediction of river flows and levels in the Upper Midwest (29 years and six months), and I have a master of science degree from the University of Wisconsin, Madison campus, in hydrology and water resources. I paid my own way through college, and I did not depend on government money until accepting a position in river forecasting in 1976.

In my understanding, accurate and timely prediction of river flows and levels is done not with physics and math alone, but also with developed understanding and judgment which is acquired by one’s self, and can not be passed on to others by seminars and training, particularly if those wishing to acquire similar operational expertise in hydrology have had little background or have little interest in hydrology. I think the same holds true for understanding climate change. A person must have a will to observe the details which can hide the relationships that are driving climate change. It is not any easier for me to explain how I am able to differentiate between solar driven and GHG driven warming, than it is for me to explain and teach another how I am able to make accurate operational flood predictions. Understanding and judgment need to be acquired by one’s self, in my view.

38. 88
PHEaston says:

To Pat Neuman and others with similar convictions.
I am a hydrogeologist (which includes surface water hydrology). I am experienced in 3D computer modelling (of groundwater flow) and am fully aware that ‘modelling’, while highly useful for understanding the world, can never represent a ‘proof’ – as it is so highly dependent on assumptions. I detest GW Bush and everything he stands for. I believe strongly in protecting the environment (One-car family, with a diesel rather than petrol/gasoline car, recycling most of our waste, etc, and detest SUVs in urban settings). What I request is that you (and others) do not fall into the trap of assuming that those who do not agree with you are either indifferent to environmental protection or in the pay of the ‘right wing oil producers’. My principal concern is that ‘science’ is not distorted by ‘opinion’ or political agenda. Whatever YOU may believe, there remain many who are unconvinced by the case for AGW. I do not have a closed mind which is why I read this site.

39. 89
Tim Jones says:

In post #74 it was noted that if 400ppm were viewed on a computer monitor with a million pixels it would be hard to detect on the screen. Please note that the number of molecules in a cubic centimeter of a gas under standard conditions is N = (60.62 ± .03) x 10 to the 22nd power. That is 606200 million million million molecules. There are a lot of molecules of CO2 in that cubic centimeter of air at the ~370 ppmv we have now. So much so that at even 280 ppmv it is observed that the atmosphere is already opaque to outgoing infrared radiation – at the wavelength CO2 absorbs it.

The CO2 molecule absorbs (and reradiates) infrared radiation at the 15 micron wavelength (700 cycles/cm frequency) bend absorption band most effectively. This band is saturated. Most of the infrared radiation from Earth at this wavelength is retained by the atmosphere and ultimately reradiated toward the ground. The question regarding CO2 then is how does an increase in CO2 add to the heat retained by the atmosphere?

The answer is that IR absorption can still occur at the edges of the 700 cycles/cm bend absorption band.
See: http://geosci.uchicago.edu/~archer/PS134/ps134_notes.ch3.pdf

The absorption of infrared radiation in the wings of the 700 cycles/cm bend band by a doubling of CO2 from 280 ppmv is thus calculated to go up proportionately to the log of the CO2 concentration. This gives us a small number of degrees centigrade elevation in atmospheric temperature – 2º to 5ºC for a doubling of CO2.

40. 90
Tom Brogle says:

There are many records of ice extent especially in the Antarctic from whalers (who went there every year} as well as explorers suuch as Shackleton, Nansen. Bruce, Filchner .Amundsen,etc.
For a description of the pack ice extent in 1914 read “South” by Shackleton (1919) republished in 2000.
For Nansen and the others I did Google searches. Pesent day ice extent can be found at https://www.fnmoc.navy.mil/products/SATELLITE/US058SCOM-IMGatp.NPOLE_IC_PS.gif
https://www.fnmoc.navy.mil/products/SATELLITE/US058SCOM-IMGatp.SPOLE_IC_PS.gif
Tre record of the South polar temp can be found at GISS
As a child my favourite light reading was polar exploration nowadays it is archeology. The archeology of Greenland indicates that Vikings were livestock and cereal farming in the 12th century about the 80th parallel.
You say that must have been a local effect but my historical knowledge of Europe Asia and South and Central America indicates otherwise.
In Australia if you compare temps listed in GISS as rural sites with those at populated sites you can easily infer that the Urban Heat Effect has not been accounted for.
For the UHI in Alaska see
http://www.geography.uc.edu/~kenhinke/uhi/

41. 91
Pat Neuman says:

PHEaston,

I think it’s good that you shared that information with the group (in #88). Outside from this group, my principal concern is the life of young people, especially those trying to make decisions on whether or not to have children. I don’t want to see people be hurt or feel guilty for having brought a loved one into this world and find out too late that the world is falling apart from global warming and diminishing energy.

On a lighter note, I would appreciate some feedback on the temperature plots which I’ve been adding to:
http://pg.photos.yahoo.com/ph/patneuman2000/my_photos

For example, I recently added a plot for Dickinson ND for February Mean Daily Air Temperature (1893-2005). February temperatures at all climate stations in the northern Great Plains and Upper Midwest show similar patterns, … a fairly sharp rise and fall during the 1930s-1950s period, a cold period in the 1960s and early 1970s, then increasing temperatures late 1970s to current.

As I said in earlier posts to RC, I believe that the dust bowl years of the late 1920s to early 1930s were influenced by a surge in solar activity, reflected by very high temperatures and low humidity over the Great Plains and Upper Midwest, and other regions. The warm years continued well beyond the early 1930s. Warm and humid conditions occurred from the mid 1930s to early 1950s, in the Great Plains and Upper Midwest, likely influenced by the moderate to strong El Nino conditions that occurred then, after the hot and dry years of the late 1920s and early 1930s. In “The Grapes of Wrath”, the hot and dry conditions of the early years of the dust bowl, and very wet conditions (CA) later during the 1930s were described.

It seems likely that the warm ENSO period from the mid 1930s through the 1940s was generated by strong solar activity with very hot and dry conditions in the Great Plains and Midwest in the late 20s to early 1930s.

As the El Nino warming effects lessened going into the 1950s the temperatures cooled in the northern Great Plains and Upper Midwest, and globally. El Ninos returned in mid-late 1970s, enhanced by increases in anthropogenic warming, making the 1980s and 1990s have strong warming.

What has many scientists concerned about record global warmth for 2005 is that it came without a strong El Nino. No one is saying much about what the next strong El Nino years may be like, but I wouldn’t be surprised to learn that many scientists are very concerned about that.

42. 92
Mikel Marinelarena says:

To be honest, the first time I read the quote that gave rise to this thread (indeed, from your ‘friend’ Mr. Milloy), I found it rather convincing. It was easy to google out the relative abundance of GH gases in the atmosphere and double-check his assertions.

However, having read Gavin’s rebuttal, I now find myself much more on his side. The percentage of anthropogenic CO2 in the current atmosphere that Milloy (et al) defends is quite visibly wrong. Still, I’d like to be able to assess how importantly this rebuttal affects the AGW debate. I presume that my personal conclusions on #76 would be acceptable for most anyone, whether contrarians/sceptics or mainstream climatologists. Only Gavin has made a correction to point b that does not seem to be very important in my view.

With that being the case, I continue thinking that a lot more research should be done, especially to rule out as much as possible the existence of alternative, non-anthropogenic explanations for the observed surface warming of the last 3 decades.

One of the few certainties that I now have is that, as we speak, money is already running out from my pocket (my country Spain has adhered to the Kyoto protocol). And more importantly, billions of dollars are running out from everybody’s pockets in order to reallocate resources away from market equilibrium points. As an economist, I can guarantee that this will have negative effects on the global economy (less growth, more unemployment). What if in the end the atmospheric concentration of trace gas CO2 is indeed of little importance?

Some of the questions that I think still demand a conclusive answer are:

1) Why did surface temperatures cool down from the ’40s through the ’70s, while CO2 and some other GH gases were rapidly growing in the atmosphere?
2) Why are surface temperature trends not in line with the lower tropospheric ones (as the AGW theory demands)?
3) Why are temperatures over Antarctica not warming fast, if at all?
4) What caused previous known global warming events, and particularly the one that began in the mid 19th century? Are we sure that the last decades’ warming is not primarily driven by the same force, whatever it is (and obviously not an anthropogenic GH gases build-up).

Of course, the idea is NOT to find plausible answers for the above questions (so that observed data do not disturb the AGW theory) but rather to integrate these facts into a theory that explains them better (or prove them wrong, as appropriate).

If I’m missing something important, I’d love to learn what it is.

43. 93
Pat Neuman says:

I gave my explanation to 1) and 4) posted by Mikel Marinelarena in #92. My answers are in #91 and #31. in this thread, and in reference to plotted monthly and annual average temperature data at U.S. climate stations from 1896 to current within the Midwest, Great Plains, Northwest and Alaska. Please see:
http://pg.photos.yahoo.com/ph/patneuman2000/my_photos

44. 94
Joel Shore says:

Re #92…There has been plenty of research going on to consider alternative explanations of the warming of the last 3 decades and research continues to be done. But, some people seem to want to research forever as a way of avoiding taking action. The scientific community (e.g., as expressed recently by the Academy of Sciences of 11 major countries, including the U.S.) has stated that the science is settled to the point where it is now time to take action. There are always those who won’t buy fire insurance until their house is actually ablaze but that does not make it wise policy.

Also, the basic physical effects of the forcings due to greenhouse gases are to the point where it is not enough to simply propose an alternative explanation of the current warming. One also needs to provide an explanation of how the feedbacks in the climate system miraculously conspire to cancel out these effects. Some scientists like Richard Lindzen have been desperately trying to provide such explanations but they haven’t panned out.

In regards to your specific questions–

(1) GHGs are not the sole driver of climate change. In fact, it is only the latter half of this century that they have become the main driver. (In 1970, the levels of CO2 were still only ~40 ppm above the pre-industrial baseline; now they are ~100 ppm above.) Models run with the best estimates of all natural and anthropogenic forcings reproduce the cooling in the middle of the century (see http://www.grida.no/climate/ipcc_tar/wg1/figts-15.htm ), which I believe is due to a combination of factors both natural and anthropogenic (sulfate aerosol emissions).

(2) Your information on the lower troposphere temperature trends is out-of-date. See here- http://www.realclimate.org/index.php?p=170

(3) See here- http://www.realclimate.org/index.php?p=18

(4) See the graph in my answer to (1). The modeling can reproduce the temperature record from that period but it cannot reproduce the temperature record of the last 30 years without invoking anthropogenic effects. And, again, to actually fully explain the temperature changes of the last 30 years, you not only have to come up with an alternative mechanism to explain the warming, you also have to come up with some mechanism to prevent the GHGs from having their estimated effects on climate from basic physical principles (and more complicated modeling calculations employing the various feedbacks, etc.).

45. 95
Coby says:

Re #90
Tom,

I went to the GISS site and generated a global anamoly map. I generated a map setting Mean Period to Annual Jan-Dec for 2000-2005 compared to the default baseline. All the parameters I used can be seen here. I put a gif of the result here. There is no corelation between urbanization and high anamoly in Australia at all. 90% of the population in Australia lives in cities and virtually all are along the coast and widely spaced at that. There is no corelation for Canada either, a country with similarly large disparities in population density (80% of the population lives within 200km of the southern border). Both of these countries should be excellent illustrations of UHI bias if it existed. There is also no correlation in the US, or in Russia, or anywhere.

Why do you think UHI dominates the global temperature record? Or even just in Australia, which you specifically mentioned?

Also look at the Antarctic. Some parts of continental Antarctica are warming slightly, some parts are cooling slightly, the peninsula is clearly warming. Your contention that the antacrcic is cooling is clearly an oversimplification at best, more likely just flat wrong. Regardless, this is just one region perhaps dominated by regional mechanisms (currents in the Southern ocean and ozone depletion).

With regards to your reiteration of anecdotal testimonials of ice extent 100 years ago, I can only note that you did not respond at all to what I wrote in #82 so would just point to it again.

46. 96
Tom Brogle says:

I am not denying that warming is occurring I am simply saying
1) That it must been warmer than it is now in historical times.

[Response: It *must* have been? Why? – William]

2) There are indications that the Antarctic was as warm at the begining of the 20th century as it was at the end but that coolng must have occurred sometime in between.

[Response: I don’t know what you mean. Please clarify. There were no direct measurements then – William]

3) That the Urban Heat Effect has exagerated the Global temperature rise.

[Response: You want post 43]

4)That there is something the way that Sea temperature have been treated raise and the way the Hockey Stick denies history raises severe doubts in every one who investigates GW with an open mind.

[Response:] ?

Finally a lot of the arguments used in this web site are special pleading such as climatologists are better at statistics than a mining engineer and a economist who have studied statistical methods and I quote
“The reason has to do with the fact that the warmings take about 5000 years to be complete. The lag is only 800 years. All that the lag shows is that CO2 did not cause the first 800 years of warming, out of the 5000 year trend. The other 4200 years of warming could in fact have been caused by CO2”
There is no DIRECT proof that CO2 causes GW.
All attempts to find such a proof seem to have failed

[Response:There is a great deal of work on attribution; the most obvious place to read this is the IPCC TAR, chapter 12 – William]

47. 97
Coby says:

#92

With that being the case, I continue thinking that a lot more research should be done, especially to rule out as much as possible the existence of alternative, non-anthropogenic explanations for the observed surface warming of the last 3 decades.

This is an important area of research. My impression is that it is in no way being ignored and the process of elimination has been going on for decades, the primary cause that can’t be dismissed being CO2. The IPCC TAR has a section on detection and attribution of climate change here you might find interesting.

1) Why did surface temperatures cool down from the ’40s through the ’70s, while CO2 and some other GH gases were rapidly growing in the atmosphere?

I believe it is widely accepted that this was the result of a large rise in particulate pollution that was ameliorated by air quality controls.

2) Why are surface temperature trends not in line with the lower tropospheric ones (as the AGW theory demands)?

But they are. This discrepancy has been resolved and the models have been validated. See previous RC postings such as this.

3) Why are temperatures over Antarctica not warming fast, if at all?

See this RC post.

4) What caused previous known global warming events, and particularly the one that began in the mid 19th century? Are we sure that the last decades’ warming is not primarily driven by the same force, whatever it is (and obviously not an anthropogenic GH gases build-up).

Different past changes have had different causes. This is a similar question as your attribution one above. You might want to read some of the IPCC chapter on past climate changes, specifically 2.2 and 2.3 – http://www.grida.no/climate/ipcc_tar/wg1/048.htm

I don’t think it is correct to say a warming began in the mid 19th century.

48. 98
Tom Brogle says:

Re 94
Look at the individual sites not at the anomaly maps the sites marked rural with no population. These show lower temp rises and in some cases falling temps.

49. 99
Pat Neuman says:

re #95.

Coby,

I would like to see references and data used to explain the warming of the late 1920s – late 1940 and the cooling of the mid 1950s – early 1970s (other than the explanation I gave in #31 and #91).

50. 100

There is a lack of explanations of the greenhouse effect in near real times, present warm winter weather conditions are amazing all experts, and I have not read anything significant, like a proper analysis. I know that winter like air masses are keeping way up North, with no sign of them rushing down South in their usual winter routine. Was this scenario foreseen by any empirical GW model? Would like to know if it was. This is a very significant event, having an eager audience waiting for a plausible explanation.

I have seen this warm winter coming, I can explain it in terms of a Global conservation of heat, from a very warm summer and fall of 2005, but I leave the details of this greater heat to empirical modellers… Did you replicate this winters planetary waves and weak cold air masses in your models?

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