Guest Post by Ira Glickstein
Some of the net Global Warming since 1880 is undoubtedly due to human actions, but how much?
[Update 10 April. My PowerPoint Show that includes the following graphic is available for download here: https://sites.google.com/site/iraclass/my-forms/2014%20Global%20Warming%20Civil%20Discourse.ppsx?attredirects=0&d=1 ]
The height of the bars on the graphic indicates the relative magnitude of Natural Processes and Cycles (in BLUE) versus Human-Caused Warming (in RED). The scale on the left is in °C with corresponding °F on the right.
Going from left to right:
The first BLUE bar represents the Atmospheric “Greenhouse” Effect, responsible for about 59°F (33°C) warming. This is the Natural Process that makes life as we know it possible on Earth. The mean temperature on the surface of the Earth is about 59°F (33°C) warmer due to Atmospheric absorption of long-wave radiation by water vapor (H2O), carbon dioxide (CO2), and other so-called “Greenhouse” gases, and the subsequent “back-radiation” of some of this heat energy towards the Earth surface. (See my WUWT Visualizing series [Physical Analogy, Atmospheric Windows, Emission Spectra, and Molecules/Photons
The second bar represents the major Natural “Ice Age” Cycles that have occurred about every 100,000 years according to the ice core records from the past 400,000 years. The climate is always changing, with up and down temperature jigs and jags at all time scales. The major Ice Age Cycles change temperatures over a range of about 13°F (7°C ).
The third bar represents the Human-Caused Warming that my wife and I experienced when we retired from full-time employment and moved from Upstate New York to Central Florida. The average temperature in Florida is about 20°F (11°C ) warmer than that in New York. I miss cross-country skiing a bit, but, overall, we are happy here and we enjoy water aerobics. While not exactly “Global” Warming, this warming was certainly caused by our Human-Caused decision to move and, of course, we enjoy the resulting moderately higher temperatures :^).
The fourth and fifth bars represent the YEARLY 43°F (24°C ) temperature range (July mean minus January mean), and the DAILY 19°F (11°C ) temperature range we experience here in Central Florida. Please notice that these ranges are much larger than the Ice Age Cycles, and they recur on a daily or yearly basis.
The sixth bar represents the mean Global Warming since 1880 based on the official NASA GISS accounting. It is 1.4°F (0.8°C). According to the IPCC, the majority of this Global Warming is due to human activities (mainly unprecedented burning of fossil fuels and land use that has reduced the albedo of the Earth). I have interpreted “majority” to mean about 70% and have therefore allocated 1°F (0.6°C) to Human-Causation and the remaining 0.4°F (0.2°C) to Natural Cycles.
The seventh bar represents my personal opinion as to the actual Global Warming since 1880, discounting the “adjustments” made by the official Climate “Team” that I believe have inflated the temperature record. We know that the US thermometer record is so unreliable that it has had to be “adjusted” several times by the official US Climate “Team” at GISS, see The Past is Not What it Used to Be, and Skeptic Strategy.
The above GISS email from Makiko Sato to James Hansen details seven adjustments to the US thermometer record, made from 1999 to 2007. According to GISS, the very warm year 1998 was originally thought to be 0.541°C (0.97°F) COOLER than 1934, which, in a warming world, would be, let us say Inconvenient. It took multiple “adjustments” to bring them to a dead heat. Further adjustments to the thermometer records subsequent to the 2007 Sato email have brought 1998 up to a significant lead over 1934 :^).
When this email came to light due to a Freedom of Information request, it was explained away by Warmists as follows:
1) The adjustments correct for differing Times of OBServation (TOBS). OK, that could be true, but why did it take so many analyses to come to the correct result? It seems one or two would be sufficient. Also, the 1998 data has been warmed more by the TOBS adjustments than the 1934 data has been cooled. Are we to believe that TOBS was less standardized in 1998 than it was in 1934?
2) The US is only 2% of the Globe. Therefore, any adjustment to US data would have only a minor effect of Global data. True enough, but, if US data is so unreliable that it has had to be adjusted so much, are we to believe that world data is any better? Does anyone really think that years-old data from Asia, Africa, South America is more reliable than US data? That ocean data based on some seaman dropping a bucket overboard, hauling it back, and sticking a thermometer into it, is any better than US thermometer data?
So, unless we believe that the world temperature record is more reliable than the US record, it is likely the world record has also been similarly “adjusted”. Therefore, I have discounted the GISS estimate of Global Warming by about 30%, so actual warming is about 1.0°F (0.6°C). As for allocation of this actual warming to Human- vs Natural-Causes, I believe the IPCC has over-estimated Climate Sensitivity by a factor of two or three, so I have allocated the majority of the warming 0.8°F (0.5°C) to Natural Cycles, and the remaining 0.2°F (0.1°C) to Human-Causation.
I’d appreciate comments on my estimates and conclusions. advTHANKSance
Ira
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This is going to be tricky but here goes ….. you are confusing a temperature measurement with a temperature change. You need to remember that the Fahrenheit scale has an offset of 32 degrees F. The above conversions are correct.
Without the greenhouse effect earth’s average temperature would be -18 deg C (or 0 deg F). The actual average temperature is 15 deg C (or 59 deg F). The greenhouse effect is, therefore, responsible for 33 deg C (or 59 deg F)
“1) The adjustments correct for differing Times of OBServation (TOBS). OK, that could be true, but why did it take so many analyses to come to the correct result? It seems one or two would be sufficient. Also, the 1998 data has been warmed more by the TOBS adjustments than the 1934 data has been cooled. Are we to believe that TOBS was less standardized in 1998 than it was in 1934?”
The changes in TOBS are all validated.
A climate skeptic did the validation.. all the way back in John Daly’s day.
Its been rechecked many times.
[Steven Mosher, thanks for the information. I said correction for TOBS “could be true”, but which one of the SEVEN analyses (from 1999 through 2007) reported by Makiko Sato in her 2007 email to James Hansen is “true”? Please look at the second graphic in my posting above which reproduces the Sato email accounting. The “adjustments” are all different and they differ by tenths of a degree! And, if one of the Sato analyses is correct, why is the data for 1934 and 1998 that I obtained from the GISS website last month different from all of her numbers? For example, 1998 is now listed as 1.328 and the last value for 1998 in the Sato email is 1.226, a difference of 0.102. If TOBS correction methodology is “validated”, why does it seem to change EIGHT times for the same raw data?
Also, please address why 1998 data has warmed up more than 1934 data has cooled down. I think that 1998 Times of OBServation would have been standardized to current values and therefore require less “adjustment”. Inquiring minds want to know! Ira]
Finally, you can avoid the TOBS adjustment entirely by doing one simple thing.
Station A: location (x,y); Thermometer (model X). Time of observation ( 7pm)
When station A CHANGES its location or its instrument or its method of observing you simple do
what every skeptic demanded: you call it a different station. Why? because it IS a different station. When you change the location, you no longer have the same station. When you change the instrument its a new station. And when you change the TOB its a new station.
Methods like GISS and CRU however MUST do adjustments. Why? because they need long records. So they adjust for station moves, and instrument changes and TOBS changes.
Berkeley used the method recommended by skeptics. Take the record and slice it when the station changes. A station that moves from sea level to 1000meters high.. its a new station. Instrument changes from LIG to MMTS.. new station. Change in TOB.. new station.
Here is what you will find. This empirically driven approach to “adjustments” just cutting the data because the station is different, yeilds roughly the same answer as theoretical adjustments.
As a non scientist layman, I agree strongly with what the text says. However, I could not make heads or tails of the graphs. They look like sunday morning paper comics section.
So after a couple of moments I just stopped trying.
Sorry.
nutso fasst says:
April 7, 2014 at 8:09 am
“How much of the 1880-2012 average temperature rise is in Tmin and how much is in Tmax?”
————–
I figure bout 98% of the 1880-2012 average temperature rise is in the Tmin column.
Averages are like boats, ….. they rise regardless of which “end” of the “temperature” tide is rising. Either the “low” end or the “high” end, …. makes no difference unless the “high” end is falling at the same time.
And if the “high” end is rising at the same time ….. then you get a 2X rise in average temperature. Tmin % increase + Tmax % increase.
Michel says:
April 7, 2014 at 5:07 am
“what accumulated in the atmosphere (a 400-280=120 ppm rise that corresponds to 960 billion m. tons of CO2), ”
————————–
By my calculations a 120 ppm rise would correspond to 600 billion metric tons of CO2.
To wit:
The average mass of the atmosphere is about 5 quadrillion (5,000,000,000,000,000) metric tons.
The current atmospheric CO2 is 400 ppm ….. or 0.04% of the atmosphere
And 0.04% of 5 quadrillion metric tons is 2 trillion (2,000,000,000,000) metric tons
And 2 trillion metric tons per 400 ppm CO2 … equals … 5 billion metric tons per 1 ppm CO2.
Therefore, 120 ppm times 5 billion metric tons equals 600 billion metric tons.
=======================
“Without emission by artificially burning fossil fuels and making cement there is no great possibility that the CO2 concentration would have changed in such a significant manner.
This is why I consider this as non-controversial.”
——————–
Well now, in the grand scheme of things, ….. the artificially burning fossil fuels and making cement, ……. beer, wine, soda pop, … and the baking of breads …. hardly puts a ripple in the natural emissions of CO2 into the atmosphere.
A warming ocean as a whole emits CO2 ….. and a bi-yearly warming of the ocean surface emits CO2 whereas a bi-yearly cooling of the ocean surface absorbs CO2.
Green growing biomass and raindrops strip CO2 from the atmosphere and the rotting and decaying of biomass emits CO2 into the atmosphere.
Damp and increasing surface temperatures greatly enhances the rotting and decaying of biomass whereas dry and/or cooling to freezing surface temperatures greatly retards and/or inhibits the rotting and decaying of biomass.
The bi-yearly cycling of the Keeling Curve Graph’s CO2 ppm measurement is ample proof/evidence of the above.
To all who had trouble understanding my first graphic:
When I presented that graphic this morning to our local “Civil Discourse” Club in our Central Florida retirement community, it was animated such that the leftmost bar and associated images appeared first and I described it. Then, the second bar and images appeared, and I explained that, and so on. Everyone in the mostly non-technical audience seemed to understand. Perhaps it would help if you placed a piece of paper over the graphic and moved it to the right to expose each bar in turn.
Again, I am sorry for the confusion and I hope the text description was sufficient to get my basic point, namely that even the anthropogenic Global Warming claimed by the IPCC is a small fraction of the warming and cooling we experience every day, year, and whenever we travel.
Ira
A busy chart can be useful when a person is giving a live talk. You keep the one chart on the media display and move from topic to topic. It keeps the entire argument within the visual range of the student. However, this fails when it appears in a paper or any sequential media. It is better to have each point displayed in a simple graphic right before discussing it.
“How much of the 1880-2012 average temperature rise is in Tmin and how much is in Tmax?”
————–
I figure bout 98% of the 1880-2012 average temperature rise is in the Tmin column.
—
If anything close to 98% of temperature rise is in the Tmin column, then why should we be concerned with global warming? Most people would welcome warmer minimum temperatures as long as max temperatures don’t rise. It would be net beneficial. Can anyone verify the 98% estimate?
Green growing biomass and raindrops strip CO2 from the atmosphere and the rotting and decaying of biomass emits CO2 into the atmosphere. — Samuel C Cogar
—
That comment prompts a question. If rotting, decaying, or burning biomass emits greenhouse gasses, do cows really make much difference? The biomass is going to decay over time anyway, so it seems to me that a cow’s digestive system only speeds up the process. But does it really make any difference in the amount of GHG emitted into the atmosphere in the long run? If so, please explain how.
[Louis, GREAT point! From the point of view of Atmospheric CO2, it seems to me that only long-term sequestered fossil fuels make a significant difference. Fossil fuels contain carbon that was absorbed from the Atmosphere eons ago when the trees and plants and animals were growing and when they got buried and turned into coal, gas, and oil. Thus, CO2 from fossil fuels we dig up or pump out of the ground is, in effect, “additional” carbon added to the Atmosphere. On the other hand, as you point out, when a tree or plant grows it absorbs CO2 (aka “Plant Food”) from the Atmosphere. That CO2 is released back into the Atmosphere in a relatively short time if the tree or plant dies and rots away, or if it gets eaten by an animal that breaths it out or that dies and rots away. So, net GHG in the Atmosphere is pretty much unaffected by the short-term growth and digestive carbon cycle of plants and animals. On the other hand, our burning of unprecedented quantities of fossil fuels that would otherwise have remained undisturbed underground does increase Atmospheric GHG. Ira]
Great post. AGW certainties are an endless amazement to any ISO 17025 accredited laboratory.
Temperatures, gas concentrations, sea level variations – in an earth sized sample – up to fraction of a degree, percentage, millimeter accuracy. Any of these measurands could be illustrated in a nice graph like that – perhaps next to solar radiation variations, which AGW proponents claim to be constant.
This is why I suspect the term oxymoron will wear out before the politicians have finished brushing AGW under carpet.
@Bruce Cobb –
Agreed – the effect may exist, but doesn’t with any certainty, and in any event is too small to be separable from the noise and normal variation in all other factors influencing climate. I believe the historical record alone is sufficient to demonstrate beyond question the nugatory effect of CO2 on climate.
I second Samuel Cogar’s calculations of the mass of CO2 in the atmosphere, and the mass per ppm.
@Samuel Cogar & Chad Wozniak
Somehow someone has to have his calculation wrong.
Sorry to say that this is you by forgetting that air has an average molecular weight of 44 while air is at 29 (one fifth oxygen, 4 fifth nitrogen). The ppms are related to molecular parts not to weight.
Here is my calculation: https://db.tt/tNSjFy0D
And the spreadsheet can be downloaded: https://db.tt/JrQUytGd
Ira: I think your graphic is fine. It tells am interesting story. For publication elsewhere it could be simplified – for example, remove the last column. I would also expand the “Glacial” graph, and maybe plot CO2 on it. Still, your point: whatever little warming the IPCC (International Parade of Climate Clowns?) is projecting, is a drop in the bucket compared to what nature throws at us.
@Samuel Cogar
Biomass is growing and rotting (equivalent of slowly burning) all the time. The yearly variations of the CO2 concentration curve is an indicator of seasonal changes (and of inbalance of land surface between North and South hemisphere).
http://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/co2_data_mlo.png
But the continuous ramping at approx 2 ppm per year cannot be explained by biomass continuously growing and not decaying in the same quantities. If that would be true all carbon should have now, after millions of years, passed and stayed in the atmosphere.
I’m heretic on the climate sensitivity to CO2 emissions, in my opinion grossly overestimated by warmists and catastrophists.
But it is wrong to try to look away from fossil fuel burning since the beginnning of the industrial era and its impact on CO2 atmospheric concentration, or to deny that CO2 and H2O absorb energy in the long wave IR spectra. These facts should be non-controversial.
Sorry Ira, but I couldn’t get past the first bar (the graph, not the establishment). The Atmospheric Greenhouse Effect is not 33C – the value arrived at by Climate Science is based on a faulty assumption and a gross misapplication. To use your quote from Wiki: http://en.wikipedia.org/wiki/Greenhouse_effect
“If an ideal thermally conductive blackbody were the same distance from the Sun as the Earth is, it would have a temperature of about 5.3 °C.”
This is a faulty assumption. As it stands this point is correct (plus or minus a few degrees, depending on what the current average insolation is calculated to be), assuming the earth is absorbing the solar radiation as a blackbody and radiating as a blackbody. You will notice that I say radiating as a blackbody, not emitting as a blackbody – that is because if the surface of the Earth was emitting as a blackbody it would have a temperature of 0K on the nightside and a varying temperature on the dayside depending on the latitude and the solar time at the longitudes. If you then calculate the average surface temperature on what it is emitting, you will find that the average surface temperature is considerably less (~173 K based on my own dubious calculations). What Climate Science has done is adopted a principle from Astronomy for calculating the surface temperature of a body radiating like a blackbody. While this is perfectly valid for solar bodies which radiate approximately like a black body evenly across their surfaces, it is faulty when used to estimate the surface temperature of planetary bodies, which emit radiation at levels determined by the temperature of their surfaces. This is compensated for by assuming that we have an ‘ideally thermally conductive blackbody’ to overcome the impossibility of the equal distribution of temperatures across the surface of a body as large as the Earth.
Continuing the quote:
“However, since the Earth reflects about 30% of the incoming sunlight, this idealized planet’s effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C.The surface temperature of this hypothetical planet is 33 °C below Earth’s actual surface temperature of approximately 14 °C.The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.”
This is the gross misapplication. If the earth is reflecting 30% of the incoming sunlight then, by definition, it is no longer a blackbody and cannot be treated as a blackbody for either emitting or radiating. Looking at the Stefan-Boltzman equation, a commonly overlooked part is the emissivity coefficient, which is frequently taken as equal to 1 because the equation is usually applied to a blackbody. Since, with the application of a 30% reflectivity, the Earth is no longer a blackbody, this value is less than one. With a reflectivity of 30%, it can be readily assumed that the emissivity is 0.7, and when this value is plugged into the equation the resultant temperature rises to the value given in the first quoted statement. Juggling a few of the equations involved with Thermodynamics, you will quickly realize that the temperature of the surface being radiated upon is a product of the ratio of the absorptivity and emissivity properties of the surface.
You can confirm that the commonly used value, as calculated, is wrong by doing some calculations with the absorptivity and emissivity values from different materials rather than using the blackbody assumption – I got this idea when I visited NASA’s site and found that the side of the ISS exposed to the sun would rise above 100C while the dark side would fall below 0C. You will find that, contrary to the claims of AGW agitators, the temperature that the surface of the earth is dependent on the thermal and optical properties of the surface materials being subjected to solar radiation, not the Atmospheric Greenhouse Effect.
Steven Mosher says: April 7, 2014 at 11:27 am
I made the following comment as an addendum within Steven Mosher’s comment above, and I am concerned he might not see it up there. So, here it is again:
Steven Mosher, thanks for the information. I said correction for TOBS “could be true”, but which one of the SEVEN analyses (from 1999 through 2007) reported by Makiko Sato in her 2007 email to James Hansen is “true”? Please look at the second graphic in my posting above which reproduces the Sato email accounting.
The “adjustments” are all different and they differ by tenths of a degree! And, if one of the Sato analyses is correct, why is the data for 1934 and 1998 that I obtained from the GISS website last month different from all of her numbers?
For example, 1998 is now listed as 1.328 and the last value for 1998 in the Sato email is 1.226, a difference of 0.102. If TOBS correction methodology is “validated”, why does it seem to change EIGHT times for the same raw data?
Also, please address why 1998 data has warmed up more than 1934 data has cooled down. I think that 1998 Times of OBServation would have been standardized to current values and therefore require less “adjustment”. Inquiring minds want to know!
Ira
@michel –
Calculating by mass considers the molecular weight of CO2; therefore the calculations are correct.
You don’t measure salinity by the number of sodium and chloride ions, but by the weight of NaCl dissolved.
Had another thought, Ira, that I also wonder whether anyone has thought of analyzing before.
It is clear to me that the CO2 increase has clearly followed the growth in the world-wide human population. So the question I have is, has the increase also tracked with the change in land use from forest, untilled grasslands and brushland to tilled and annually utilized farmland to feed that growing population. Just the difference between tilled and untilled will change at least three things. Land that is covered year round with biomass will have different average annual albedo, different CO2 converting capacity and different water retention than land that is tilled and left uncovered with biomass for half the year because of weather. And land that is stripped of trees and either tilled or left barren will have even more dramatically differences in those effects, especially the annual capacity for extracting CO2 from the atmosphere. Not to mention that the land that used to be covered with grassland or forest that is now completely covered in building, parking lots and streets will have dramatically different albedo as well as change the turbidity of runoff into creeks, stream, and rivers. The land use changes will also have a cumulative affect.
Remember it is your analysis that has put things into perspective. We are talking about a long term variation that is .2 out of 43 for an annual variation, or .2 out of 59 for an eon variation. Has human repurposing of land affected 1 part in 200 of the tillable land on the planet? How about 1 part in 300? If either of these fractions seems plausible, then the entire change in “average” temperature might be solely attributed to human repurposing of available grass and forest lands, human destruction of forest for cheap fuel (think the entire island of Madagascar), human conversion of the Aral Sea (dark green) to the Aral salt desert (bright white), and human destruction of the Amazon. Is it possible that human repurposing of land has also been the sole cause of the change in CO2 because of the steady decline in the net CO2 sink this has caused?
Mike Tremblay says: April 7, 2014 at 5:06 pm
Mike Tremblay, thanks for your long detailed comment, but I need some help understanding it. I should start by noting that, as a System Engineer, rather than a physicist, I am often satisfied by approximate parameter values, so long as they are within some reasonable percentage of the “truth”.
So, if the Atmospheric “Greenhouse” Effect is not exactly 33 °C, I don’t really care, so long as it is, say, in the range 20 °C to 50 °C.
You make a point about the Earth not being a perfect “blackbody” because some 30% of incoming Solar radiation is reflected rather than absorbed. It seems to me that for an approximate solution, we could simply assume that the incoming Solar radiation is 30% less than it actually is, and then only count the long-wave outgoing radiation.
You also mention that the dark side of the Earth will be cooler than the sunlit side, which, of course is obviously true. But, since the Earth rotates every 24 hours, and since the surface has the ability to store heat, the dark side will never cool to 0 K, will it? So, how much will it cool in 12 hours?
These are the types of simplifying assumptions I, as a System Engineer, am used to making to get an approximate answer to check against the supposedly exact value the analysts provide. Once I’ve made these “back of the envelope” calculations (which used to actually be done on scrap paper in the early days, but are now done using spreadsheets :^) to obtain an estimate, I then wait for the analysts to come up with the supposed more precise result. If my estimate is reasonably close, I accept the more precise value from the analysts. If not, either I or they have made a serious mistake, most likely a misinterpretation of the situation.
In this case, based on calculations I have seen here at WUWT (by WIllis Eschenbach I believe) I believe the 33 °C value is close enough to the truth for my purposes, and I will accept it until I am convinced otherwise.
BOTTOM LINE: You have raised a number of valid points, but you have not provided an estimate of the APPROXIMATE warming effect of Atmospheric “Greenhouse” gases. At the end of your comment you say:
Do you really mean to claim that there is no warming effect on the Surface of the Earth from the downwelling radiation from H2O and CO2 gases in the Atmosphere? Or that there is no downwelling radiation from the Atmosphere to the Earth Surface?
If that is your claim, pleas read my WUWT series on “visualizing” the Atmospheric “Greenhouse” effect. If I have missed your point, please clarify. advTHANKSance
Ira
Ira – you’re wrong, and Hansen is correct. Circa 70% of the warming since the ’50’s IS due to humans. But not because of CO2. It’s due to the incessant adjustments of older temperatures down, down, down. Never up. And never any concrete explanation “why” for each mass adjustment, just because.
Great article.
[Barry Cullen, THANKS for your comment. Yes, a large portion of the GISS/IPCC REPORTED WARMING is due to human activities, namely questionable “adjustments” to the thermometer record by the humans working at GISS/IPCC :^). However, I do not believe the data “adjustments” are anywhere near the 70% you attribute to them. Possibly in the range of 30% though. Reminds me of a comment made by a friend many years ago: “Half of the current air pollution is due to auto exhaust and the other half is due the spouting of untruths by the radical environmentalists.” Ira]
“The mean temperature on the surface of the Earth is about 59°F (33°C) warmer due to Atmospheric absorption of long-wave radiation by water vapor (H2O), carbon dioxide (CO2), and other so-called “Greenhouse” gases, and the subsequent “back-radiation” of some of this heat energy towards the Earth surface.”
The oceans are a thermal reservoir that is heated at depth, which raise the mean surface temperature of a substantial proportion of the Earth’s surface regardless of atmospheric greenhouse effects.
DonV says: April 7, 2014 at 5:55 pm
Thanks, DonV for continuing our conversation. But, no it is NOT “… possible that human repurposing of land has also been the sole cause of the change in CO2 …” [my bold] The unprecedented burning of fossil fuels that have sequestered carbon for eons is, IMHO, the primary cause of the approximately 40% increase in Atmospheric CO2 we have experienced over the past century. Increased outgassing of CO2 from slightly warmer oceans and reduced uptake of CO2 to slightly warmer waters have also contributed, as have land use changes. However, unless someone provides a convincing analysis I find it hard to believe that land use on a mostly water-covered planet could have a larger effect on Atmospheric CO2 than burning of fossil fuels.
Ira
Louis says:
April 7, 2014 at 2:30 pm
Simple – Methane vs CO2 !
Everyone knows that methane is a stronger greenhouse gas than CO2.
Mike Tremblay says:
April 7, 2014 at 5:06 pm
A lot of people make this error. It is true that the blackbody emissivity and absorptivity are the same at a specific frequency (wavelength). However, since the solar absorptivity and the thermal emissivity are at different wavelengths, it makes sense that the Earth has a solar absorptivity of 70% (30% albedo) and a thermal emissivity of ~98% (close to one).