Guest Post By Steve Fitzpatrick
Introduction
Projections of climate warming from global circulation models (GCM’s) are based on high sensitivity for the Earth’s climate to radiative forcing from well mixed greenhouse gases (WMGG’s). This high sensitivity depends mainly on three assumptions:
1. Slow heat accumulation in the world’s oceans delays the appearance of the full effect of greenhouse forcing by many (eg. >20) years.
2. Aerosols (mostly from combustion of carbon based fuels) increase the Earth’s total albedo, and have partially hidden the ‘true’ warming effect of WMGG increases. Presumably, aerosols will not increase in the future in proportion to increases in WMGG’s, so the net increase in radiative forcing will be larger for future emissions than for past emissions.
3. Radiative forcing from WMGG’s is amplified by strong positive feedbacks due to increases in atmospheric water vapor and high cirrus clouds; in the GCM’s, these positive feedbacks approximately double the expected sensitivity to radiative forcing.
However, there is doubt about each of the above three assumptions.
1. Heat accumulation in the top 700 meters of ocean, as measured by 3000+ Argo floats, stopped between 2003 and 2008 (1, 2, 3), very shortly after average global surface temperature changed from rising, as it did through most of the 1990’s, to roughly flat after ~2001. This indicates that a) ocean heat content does not lag many years behind the surface temperature, b) global average temperature and heat accumulation in the top 700 meters of ocean are closely tied, and c) the Hansen et al (4) projection in 2005 of substantial future warming ‘already in the pipeline’ is not supported by recent ocean and surface temperature measurements. While there is no doubt a very slow accumulation of heat in the deep ocean below 700 meters, this represents only a small fraction of the accumulation expected for the top 700 meters, and should have little or no immediate (century or less) effect on surface temperatures. The heat content in the top 700 meters of ocean and global average surface temperature appear closely linked. Short ocean heat lags are consistent with relatively low climate sensitivity, and preclude very high sensitivity.
2. Aerosol effects remain (according to the IPCC) the most poorly defined of the man-made climate forcings. There is no solid evidence of aerosol driven increases in Earth’s albedo, and whatever the effect of aerosols on albedo, there is no evidence that the effects are likely to change significantly in the future. Considering the large uncertainties in aerosol effects, it is not even clear if the net effect, including black carbon, which reduces rather than increases albedo, is significantly different from zero.
3. Amplification of radiative forcing by clouds and atmospheric humidity remain poorly defined. Climate models do not explicitly include the behavior of clouds, which are orders of magnitude smaller than the scale of the models, but instead handle clouds using ‘parameters’ that are adjusted to approximate the expected behavior of clouds. Adjustable parameters can of course also be tuned to make a model to predict whatever warming is expected or desired. Measured tropospheric warming in the tropics (the infamous ‘hot spot’) caused by increases in atmospheric water content, falls far short of the warming in this part of the atmosphere projected by most GCM’s. This casts doubt on the amplification assumed by the CGM’s due to increased water vapor.
Many people, including this author, do not believe the large temperature increases (up to 5+ C for doubling of CO2) projected by GCM’s are credible. A new paper by Lindzen and Choi (described at WUWT on August 23, 2009) reports that the total outgoing radiation (visible plus infrared) above the tropical ocean increases when the ocean surface warms, which suggests the climate feedback (at least in these tropical ocean areas) is negative, rather than positive as the CGM’s all assume.
In spite of the many problems and doubts with GCM’s:
1) It is reasonable to expect that positive forcing, from whatever source, will increase the average temperature of the Earth’s surface.
2) Basic physics shows that increasing infrared absorbing gases in the atmosphere like CO2, methane, N2O, ozone, and chloro-fluorocarbons, inhibits the escape of infrared radiation to space, and so does provide a positive forcing.
3) There has in fact been significant global warming since the start of the industrial revolution (beginning a little before 1800), concurrent with significant increases in WMGG emissions from human activities.
There really should be an increase in average surface temperature due to forcing from increases in infrared absorbing gases. This is not to say that there are no other plausible explanations for some or even most of the increases in global temperatures over the past 100+ years. For example, Lean (5) concluded that there may have been an increase of about 2 watts per square meter in average solar intensity (arriving at the top of the Earth’s atmosphere) between the little ice age and the late 20th century, which could account for a significant fraction of the observed warming. But regardless of other possible contributions, it is impossible to refute that greenhouse gases should lead to increased global average temperatures. What matters is not that the earth will warm from increases WMGG’s, but how much it will warm and over what period. The uncertainties and dubious assumptions in the GCM’s make them not terribly helpful in making reasonable projections of potential warming, if you assume the worst case that WMGG’s are the principle cause for warming.
Climate Sensitivity
If we knew the true climate sensitivity of the Earth (expressed as degrees increase per watt/square meter forcing) and we knew the true radiative forcing due to WMGG’s, then we could directly calculate the expected temperature rise for any assumed increases in WMGG’s. Fortunately, the radiative forcing effects for WMGG’s are pretty accurately known, and these can be used in evaluating climate sensitivity. An approximate value for climate sensitivity in the absence of any feedbacks, positive or negative, can be estimated from the change in blackbody emission temperature that is required to balance a 1 watt per square meter increase in heat input, using the Stefan-Boltzman Law. Assuming solar intensity is 1366 watts/M^2, and assuming the Earth’s average albedo is ~0.3, the net solar intensity is ~239 watts/M^2, requiring a blackbody temperature of 254.802 K to balance incoming heat. With 1 watt/M^2 more input, the required blackbody emission temperature increases to 255.069, so the expected climate sensitivity is (255.069 – 254.802) = 0.267 degree increase for one watt per square meter of added heat.
But solar intensity and the blackbody emission temperature of the earth both change with latitude, yielding higher emission temperature and much greater heat loss near the equator than near the poles. The infrared heat loss to space goes as the fourth power of the emission temperature, so the net climate sensitivity will depend on the T^4 weighted contributions from all areas of the Earth. Feedbacks within the climate system, both positive and negative, including different amounts and types of clouds, water vapor, changes in albedo, and potentially many others, add much uncertainty.
Measuring Earth’s Sensitivity
The only way to accurately determine the Earth’s climate sensitivity is with data.
Bill Illis produced an outstanding guest post on WUWT November 25, 2008, where he presented the results of a simple curve-fit model of the Earth’s average surface temperature based on only three parameters: 1) the Atlantic multi-decadal oscillation index (AMO), 2) values of the Nino 3.4 ENSO index, and 3) the log of the ratio of atmospheric CO2 concentration to the starting CO2 concentration. Bill showed that the best estimate linear fit of these parameters to the global mean temperature data could account for a large majority of the observed temperature variation from 1871 to 2008. He also showed that the AMO index and the Nino 3.4 index contributed little to the overall increase in temperature during that period, but did account for much of the variation around the overall temperature trend. The overall trend correlated well with the log of the CO2 ratio. In other words, the AMO and Nino3.4 indexes could hind cast much of the observed variation around the overall trend, and that overall trend could be accurately hind cast by the log of the CO2 ratio.
There are a few implicit assumptions in Bill’s model. First, the model assumes that all historical warming can be attributed to radiative forcing. This is a worst case scenario, since other potential causes for warming are not even considered (long term solar effects, long term natural climate variability, etc.). The climate sensitivity calculated by the model would be lowered if other causes account for some of the measured warming.
Second, the model assumes the global average temperature changes linearly with radiative forcing. While this is almost certainly not correct for Earth’s climate, it is probably not a bad approximation over a relatively small range of temperatures and total forcings. That is, a change of a few watts per square meter is small compared to the average solar flux reaching the Earth, and a change of a few degrees in average temperature is small compared to Earth’s average emissive (blackbody) temperature. So while the response of the average temperature to radiative forcing is not linear, a linear representation should not be a bad approximation over relatively small changes in forcing and temperature.
Third, the model assumes that the combined WMGG forcings can be accurately represented by a constant multiplied by the log of the ratio of CO2 to starting CO2. While this may be a reasonable approximation for some gases, like N2O and methane (at least until ~1995), it is not a good approximation for others, like chloro-fluorocarbons, which did not begin contributing significantly to radiative forcing until after 1950, and which are present in the atmosphere at such low concentration that they absorb linearly (rather than logarithmically) with concentration. In addition, chloro-fluorocarbon concentrations will decrease in the future rather than increase, since most long lived CFC’s are no longer produced (due to the Montreal Protocol), and what is already in the atmosphere is slowly degrading.
To make Bill’s model more physically accurate, I made the following changes:
1. Each of the major WMGG’s is separated and treated individually: CO2, N2O, methane, chloro-fluorocarbons, and tropospheric ozone.
2. Concentrations of each of the above gases are converted to net forcings, using the IPCC’s radiation equations for CO2, methane, N2O, and CFC’s (6), and an estimated radiative contribution from ozone inceases.
3. The change in solar intensity with the solar cycle is included as a separate forcing, assuming that measured intensity variations for the last three solar cycles (about 1 watt per square meter variation over a base of 1365 watts per square meter) are representative of earlier solar cycles, and assuming that sunspot number can be used to estimate how solar intensity varied in the past.
4. The grand total forcing (including the solar cycle contribution), a 2-year trailing average of the AMO index, and the Nino 3.4 index are correlated against the Hadley Crut3V global average temperature data.
This yields a curve fit model which can be used to estimate future warming by setting the Nino 3.4 and AMO indexes to zero (close to their historical averages) and estimating future changes in atmospheric concentrations for each of the infrared absorbing gases.
To find the best estimate of lag in the climate (mainly from ocean heat accumulation), the model constants were calculated for different trailing averages of the total radiative forcing. The best fit to the data (highest R^2) was for a two year trailing average of the total radiative forcing, which gave a net climate sensitivity of 0.270 (+/-0.021) C per watt/M^2 (+/-2 sigma). All longer trailing average periods yielded somewhat lower R^2 values and produced somewhat higher estimates of climate sensitivity. A 5-year trailing average yields a sensitivity of 0.277 (+/- 0.021) C per watt/M^2, a 10 year trailing average yields a sensitivity of 0.289 (+/- 0.022) C per watt/M^2, and a 20 year trailing average yields a sensitivity of 0.318 (+/- 0.025) C per watt/M^2, ~18% higher than a two year trailing average. As discussed above, very long lags (eg. 10-20+ years) appear inconsistent with recent trends in ocean heat content and average surface temperatures.
Oscillation in the radiative forcing curve (the green curve in Figure 1) is due to solar intensity variation over the sunspot cycle. The assumed total variation in solar intensity at the top of the atmosphere is 1 watt per square meter (approximately the average variation measured over the last three solar cycles) for a change in sunspot number of 140. Assuming a minimum solar intensity of 1365 watts per square meter and Earth’s albedo at 30%, the average solar intensity over the entire Earth surface at zero sunspots is (1365/4) * 0.7 = 238.875 watts per square meter, while at a sunspot number of 140, the average intensity increases to 239.05 watts per square meter, or an increase of 0.175 watt per square meter. The expected change in radiative forcing (a “sunspot constant”) is therefore 0.175/140 = 0.00125 watt per square meter per sunspot. When different values for this constant are tried in the model, the best fit to the data (maximum R^2) is for ~0.0012 watt/M^2 per sunspot, close to the above calculated value of 0.00125 watt/M^2 per sunspot.
Regional Sensitivities
Amplification of sensitivity is the ratio of the actual climate sensitivity to the sensitivity expected for a blackbody emitter. The sensitivity from the model is 0.270 C per watt/M^2, while the expected blackbody sensitivity is 0.267 C per watt/M^2, so the amplification is 1.011. An amplification very close to 1 suggests that all the negative and positive feed-backs within the climate system are roughly balanced, and that the average surface temperature of the Earth increases or decreases approximately as would a blackbody emitter subjected to small variations around the average solar intensity of ~239 watts/M^2 (that is, as a blackbody would vary in temperature around ~255 K). This does not preclude a range of sensitivities within the climate system that average out to ~0.270 C per watt/M^2; sensitivity may vary based on season, latitude, local geography, albedo/land use, weather patterns, and other factors. The temperature increase due to WMGG’s may have, and indeed, should have, significant regional and temporal differences, so the importance of warming driven by WMGG’s should also have significant regional and temporal differences.
Credibility of Model Projections
Some may argue that any curve fit model based on historical data is likely to fail in making accurate predictions, since the conditions that applied during the hind cast period may be significantly different from those in the future. But if the curve fit model includes all important variables, then it ought to make reasonable predictions, at least until/unless important new variables are encountered in the future. Examples of important new climate variables are a major volcanic eruption or a significant change in ocean circulation. The probability of encountering important new variables increases with the length of the forecast, of course. So while a curve-fit climate model’s predictions will have considerable uncertainty far in the future (eg 100 years or more), forecasts of shorter periods are likely to be more accurate.
To demonstrate this, the model constants were calculated using temperature, WMGG forcings, AMO, and Nino3.4 data for 1871 to 1971, but then applied to all the 1871 to 2008 data (Figure 4). The model’s calculated temperatures represent a ‘forecast’ from 1972 through 2008, or 36 years. Since the model constants came only from pre-1972 data, the model has no ‘knowledge’ of the temperature history after 1971, and the 1972 to 2008 forecast is a legitimate test of the model’s performance. The model’s 1972 to 2008 forecast performance is reasonably good, with very similar deviations between the model and the historical temperature record in the hind cast and forecast periods.
The model fit to the temperature data in the forecast period is no worse than in the hind cast period. The climate sensitivity calculated using only 1871 to 1971 data is similar to that calculated using the entire data set: 0.255 C per watt/M^2 versus 0.270 C per watt/M^2. A model forecast starting in 2009 will not be perfect, but the 1972 to 2008 forecast performance suggests that it should be reasonably close to correct over the next 36+ years.
Emissions Scenarios
The model projections in Figure 1 (2009 to 2060) are based on the following assumptions:
a) The year on year increase in CO2 concentration in the atmosphere rises to 2.6 PPM per year by 2015 (or about 25% higher than recent rates of increase), and then remains at 2.6 PPM per year through 2060. Atmospheric concentration reaches ~518 PPM by 2060.
b) N2O concentration increases in proportion to the increase in CO2.
c) CFC’s decrease by 0.25% per year. The actual rate of decline ought to be faster than this, but large increases in releases of short-lived refrigerants like R-134a and non-regulated fluorinated compounds may offset a large portion of the decline in regulated CFC’s.
d) The concentration of methane, which has been constant for the last ~7 years at ~1,800 parts per billion, increases by 10 PPB per year, reaching ~2,370 PPB by 2060.
e) Tropospheric ozone (which forms in part from volatile organic compounds, VOC’s) increases in proportion to increases in atmospheric CO2.
The above represent pretty much a “business as usual” scenario, with fossil fuel consumption in 2060 more than 70% higher than in 2008, and with no new controls placed on other WMGG’s. The projected temperature increase from 2008 to 2060 is 0.6834 C, or 0.131 C per decade. This assumes of course that WMGG’s are responsible for all (or nearly all) the warming since 1871; if a significant amount of the warming since 1871 had other causes, then future warming driven by WMGG’s will be less.
Separation of the different contributions to radiative forcing allows projections of future average temperatures under different scenarios for reductions in the growth of fossil fuel usage, with separate efforts to control emissions of methane, N2O, and VOC’s (leading to tropospheric ozone).
One such scenario can be called the “Efficient Controls” scenario. The year on year increase in CO2 in the atmosphere rises to 2.6 PPM by 2014, and then declines starting in 2015 by 0.5% per year (that is, 2.6 PPM increase in 2014, 2.587 PPM increase in 2015, 2.574 PPM increase in 2016, etc.), methane concentrations are maintained at current levels via controls installed on known sources, CFC concentration falls by 0.5% per year due to new restrictions on currently non-regulated compounds, and N2O and tropospheric ozone increases are proportional to the (somewhat lower) CO2 increases. These are far from small changes, but probably could be achieved without great economic cost by shifting most electric power production to nuclear (or non-fossil alternatives where economically viable), and simultaneously taxing CO2 emissions worldwide at an initially low but gradually increasing rate to promote worldwide improvements in energy efficiency. Under these conditions, the predicted temperature anomaly in 2060 is 0.91 degree (versus 0.34 degree in 2008), or a rise of 0.109 degree per decade. Atmospheric CO2 would reach ~507 PPM by 2060, and CO2 emissions in 2060 would be about 50% above 2008 emissions. By comparison, the “business as usual” case produces a projected increase of 0.131 C per decade through 2060, and atmospheric CO2 reaches ~519 PPM by 2060. So at (relatively) low cost, warming through 2060 could be reduced by a little over 0.11 C compared to business as usual.
A “Draconian Controls” scenario, with new controls on fluorinated compounds, methane and VOC’s, and with the rate of atmospheric CO2 increase declining by 2% each year, starting in 2015, shows the expected results of a very aggressive worldwide program to control CO2 emissions. The temperature anomaly in 2060 is projected at 0.8 C, for a rate of temperature rise through 2060 of 0.088 degree per decade, or ~0.11 C lower temperature in 2060 than for the “Efficient Controls” scenario. Under this scenario, the concentration of CO2 in the atmosphere would reach ~480 PPM by 2060, but would rise only ~25 PPM more between 2060 and 2100. Total CO2 emissions in 2060 would be ~15% above 2008 emissions, but would have to decline to the 2008 level by 2100. Whether the potentially large economic costs of draconian emissions reductions are justified by a ~0.11C temperature reduction in 2060 is a political question that should be carefully weighed.
Conclusions
The model shows that the climate sensitivity to radiative forcing is approximately 0.27 degree per watt/M^2, based on the assumption that radiative forcing from WMGG’s has caused all or nearly all the measured temperature increase since ~1871. This corresponds to response of ~1C for a doubling of CO2 (with other WMGG’s remaining constant). Much higher climate sensitivities (eg. 0.5 to >1.0 C per watt/M^2, or 1.85 C to >3.71 C for a doubling of CO2) appear to be inconsistent with the historical record of temperature and measured increases in WMGG’s.
Assuming no significant changes in the growth pattern of fossil fuels, and no additional controls on other WMGG’s, the average temperature in 2060 may reach ~0.68C higher than the 2008 average. Modest steps to control non-CO2 emissions and gradually reduce the rate of increase in the concentration of CO2 in the atmosphere could yield a reduction in WMGG driven warming between 2008 and 2060 of ~15% compared to no action. A rapid reduction in the rate of growth of atmospheric CO2 would be required to reduce WMGG driven warming between 2008 and 2060 by ~30% compared to no action.
Pamela Gray (13:50:16) :
“Where did you get your data from?”
Pretty clear that he pulled it out of……. um… the air.
Apparently Steve you are not the least bit scientifically literate so our discussion is done.
Pamela my data comes from NASA GISS, NOAA, Nature, Scientific American 3.0 where Kathy was actually there measurign methane levels; just look it up. Pick up the summer edition of 3.0, or go the Scientific American site. I forget her last name, but there are other researchers as well who show first hand heigtened methane emissions due to melting snow and ice releasing from plants in the soil. This is 100% fact not for debate.
Dear friends, please let us play nicely. Although Jacob may not agree with us, he has been responsive to requests for data, and has worked at supporting his arguments. If we hope to convince people, it is counterproductive to antagonize them.
There has been an uptick in Methane levels after it looked like they might actually stabilize. The highest Methane numbers seem to be in the high Arctic (where the highest annual variation in CO2 levels is also seen.)
It still looks like Methane is following a logarithmic trendline and will stablize soon. The oil and gas industry used to be the biggest contributors to the increase (not rice paddies) and now that Natural Gas (which is 98% Methane) has a higher value, they are plugging up the leaks and not burning it inefficiently/just releasing it to the atmosphere as they once did.
http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/brw/brw_ch4_ts_obs_00011.png
Jacob, citing Scientific American on a scientific blog is about a half step above citing the National Enquirer (a tabloid rag filled with aliens and Elvis sightings, for those non-Americans). You’d get a lot more traction if you took the time to look up the original report, which seems to be this one here. Then ignore all of the words and think about the numbers. Find a long-term series to compare them to. Then give us your thoughts about the numbers. Not what others have said. What you think the numbers mean.
Yes, methane did increase in the arctic last year, at least in Svalbard. It went up by a stunning 0.6% … EVERYBODY PANIC is how SciAm treats it. Me, I look at the longer term records. Atmospheric methane sources and sinks are poorly understood. After a decade of stability, world methane levels also rose after 2006 … by 0.6%.
Why? Well, we don’t know. All climate scientists should practice those words several times a day. We don’t know why methane went up by 0.6%, either in the Arctic or globally. Now, if you want to read some dark future into that, it is your right. Me … no thanks. We don’t have enough data or understanding to say much of anything about that.
Willis Eschenbach:
You are right, I should not have commented about Jacob’s data sources, even if he does not seem willing to critically evaluate those sources.
You are right too about Scientific American. 30 years ago it was actually a pretty good magazine that covered real science, and contained decent summary articles from a range of fields, but now it is just a dumbed-down mouthpiece for a particular political viewpoint. I haven’t purchased a copy in over 10 years. A little sad, when you consider that it has been around since well before 1900, but now is basically worthless.
Steve, thank you for your gentlemanly response. We can only sway public opinion if we treat it seriously.
Losing Scientific American, the bible of my childhood in the 1950s, was a tragedy. As you say, at this point it is just a publicity-driven rag.
w.
http://eprints.soton.ac.uk/64607/
http://www.sciencedaily.com/releases/2008/12/081217203407.htm
“Dirk Wagner3 and Susanne Liebner3
(3) Research Unit Potsdam, Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
The Arctic plays a key role in the Earth’s climate system, because global warming is predicted to be most pronounced at high latitudes, and one third of the global carbon pool is stored in ecosystems of the northern latitudes. The degradation of permafrost and the associated intensified release of methane, a climate-relevant trace gas, represent potential environmental hazards. The microorganisms driving methane production and oxidation in Arctic permafrost soils have remained poorly investigated. Their population structure and reaction to environmental change is largely unknown, which means that also an important part of the process knowledge on methane fluxes in permafrost ecosystems is far from completely understood. This hampers prediction of the effects of climate warming on Arctic methane fluxes. Further research on the stability of the methane cycling communities is therefore highly important for understanding the effects of a warming Arctic on the global climate. This review first examines the methane cycle in permafrost soils and the involved microorganisms. It then describes some aspects of the potential impact of global warming on the methanogenic and methanotrophic communities.”
http://www.springerlink.com/content/xq5x2k8l4n686r26/
No doubt some things are poorly undertsood guys, but even infinitesminal rises in CH4 in conjunction with C02 greatly influences climate and can lead to more progressive warming. Since CH4, NO2, and CO2, are trace gases, we must be very cautious about what we consider to be a small % increase in light of the climate influences these gases exert. Nowhere in recent history have these levels been so high, and after the last ice age, these GHG’s led to drastic climate changes, and utlimately global warming.
http://blogs.nature.com/news/thegreatbeyond/2008/04/gloomy_emissions_data_shows_me.html
“Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections1, 2. Thaw lakes in North Siberia are known to emit methane3, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated3. Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 6–40 teragrams per year; refs 1, 2, 4–6) by between 10 and 63 per cent. We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,260–42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost." –http://www.nature.com/nature/journal/v443/n7107/full/nature05040.html
I have no problem acknowledging uncertainties, hence why more of these studies are performed, more observations of the Artic and Anatartic, etc… however, the linage between gases like methane and carbond dioxide are quite clear.
I will digress here with this final post for the night; I need my sleep as well, but Methane is 25 more times an efficient greenhouse gas than carbind dioxide per mole, so keep that in mind; as reported in environmental chemistry textboks, the journal nature, sciencedaily, and many other publications. A small increase in CH4 also leads to more C02 formation in the atmosphere, and the remaining CH4 leads to a greater forcing upon C02, which forces upon the water vapor and C02 provieds a postive feedback upon CH4 and H-O-H is a positive feedback upon C02. Yes, some microorganisms feed on CH4, which reduces the total emissions of this GHG, but NH4 is released along with CH4 from various bacteria and plant ineteractions; including at compost piles in addition to soil exposed in the Tundra and elsewhere in the globe. Also see NOAA paleoclimate data.
Jacob, you truly, truly need to learn to distinguish between observations and hypotheses. I can sympathize with you, as many climate “scientists” are incapable of doing it as well.
For example, you say:
We don’t know what effect small changes in trace gases have upon the climate. There is no evidence that they have led to “drastic changes” or “global warming” after the last ice age. Greenland ice cores show that since emerging from the last ice age, the earth has cooled. While we know that CO2 and the others are greenhouse gases and raise temperatures in theory, that’s just simple math, we don’t know what effect they have on the extremely complex climate system. Let me repeat my example from above:
Simple math and lab experiments and basic physics of IR absorption don’t help us here. Climate models are also of no help in this regard, as they can only do what their programmers program them to do.
The thing that model programmers love to overlook is that climate is a hugely complex, tera-watt scale, driven, multi-stable, chaotic, resonant constructal planetary heat engine. It consists of 5 separate subsystems (atmosphere, biosphere, cryosphere, lithosphere, and ocean). None of these subsystems is well understood. Each of these subsystems has its own known and unknown forcings, resonances, and responses. In addition, each subsystem interacts with the other subsystems in the form of positive and negative forcings and feedbacks, again both known and unknown. It is without a doubt the most complex system we have ever tried to model, and we’ve only been at it for a couple of decades. Our observational datasets are fragmentary, short, and subject to a host of problems. Even our satellite datasets, which at least have global coverage, are the subject of intense scientific dispute.
With such poor data, such a complex system, and such rudimentary models, the idea that we can currently say “a 1% change in methane will lead to warming” is hubris of the highest order. We can’t predict next month’s weather, we don’t even know if the earth has a thermostat, and you seriously claim that after the last ice age “GHGs lead to drastic climate changes”? … sorry, but we’re not there yet. We can’t even say that the climate that we have seen in recent years is anything but natural variation. The world cooled fairly radically from about 1400 to 1650, and has been generally warming since then. In the last century alone, it warmed from 1910 to 1940, cooled to 1970, and warmed to 1998 … which of these are you claiming is human-caused, and why not the others?
There is nothing, I repeat nothing, in the observational record that can be shown statistically to be significantly different from earlier parts of the record. Most statewide high temperature records in the US were set in the 1930s … and at that time, people were making very similar statements to yours, that we were all going to fry. The recent warming is no different, either in length, steepness, or hype.
Finally, it is obvious that there are many things which we still don’t know. Contrary to IPCC claims and climate models, the world has not warmed in the last decade. Don’t know why. CO2 is still rising, but temperature is not. Don’t know why. We recently discovered that plankton make clouds to cool them down when they are too hot. How much does that affect the climate? We don’t know. We don’t understand why the sea level took a jump in 2004. We can’t explain a whole host of things about climate, and you want to tell us that methane is teh suxxor, and we should be “very cautious”?
Like I said above, you are free to worry about that change in methane if you wish. But trying to pass it off as science won’t work on this site. Our scientific understanding of climate is nowhere near that level, and likely won’t be for decades.
w.
PS – That’s just this web site. You can sell your particular brand of worry about trace gases at the Scientific American blog and find plenty of agreement. Here … we prefer facts, science, and people honest enough to say “we don’t know”. I laud you for your efforts here, but if you want to get traction, you need to present facts. Evidence. Observations. Then you need to draw supportable inferences and conclusions from those facts and data. Repeating someone else’s hysteria about arctic methane is meaningless.
Willis,
“PS – dear friends, remember significant digits. We can’t say the earth blackbody temperature is “254.802 K”, that’s a bridge too far.”
True of course. However I was forced to used too many digits in the calculation of blackbody temperature because I was trying to show the expected blackbody sensitivity value without using the inverse of the first derivative the Stefan-Boltzman equation with respect to temperature. To get a reasonably accurate sensitivity value without calculus, I had to compare the equilibrium temperatures at two closely spaced radiative energy levels (I used a 1 watt difference), do the calculation to a crazy number of digits, then subtract one from the other. Perhaps I should have just presented the correct sensitivity equation derived from Stefan-Boltzman, and not worried about losing some readers by using calculus.
Thanks for your many constructive comments on this thread.
Steve
Just noting that Methane levels are now well-below the IPCC’s A1B forecast and it seems likely that global levels will stay below 1900 ppb versus the peak in the A1B forecast of 2400 ppb.
So 20% less than the +3.0C forecast and trends that indicate Methane will only add a neglible amount further to global temperatures (barely measurable really) should give Jacob and Scientific American some comfort.
(But then, there will be another story soon how Methane has spiked another 2 ppb last year and there is a danger of a runaway Methane calthrate release like in the PETM).
>> Willis Eschenbach (01:37:58) :
The average surface albedo of the earth is about 0.85 <<
I think you mean emissivity, not albedo.
Jim
Willis,
It’s interesting that you are using an emissivity of 0.85. I’ve tried looking up this number and most consider that the Earth’s surface emissivity is closer to 0.95. From my (greatly simplified) calculations, I get numbers below 0.7. Emissivity is frequency dependent. The numbers used in climate are in the IR range. I think it makes more sense to use the total emissivity; however, I appear to be a minority of one. Where do you get your value for the surface emissivity?
Thanks,
Jim
The best estimate for Albedo is 0.298
The best estimate for Emissivity is 1.0 for ice and snow, 0.9907 for water, 0.98 for sand and desert and the overall Earth value ranges from 0.983 to 0.989
>> Bill Illis (11:45:03) :
The best estimate for Albedo is 0.298 <<
The error bars are around plus or minus 0.03 and may be (considerably) larger.
>> The best estimate for Emissivity is 1.0 for ice and snow, 0.9907 for water, 0.98 for sand and desert and the overall Earth value ranges from 0.983 to 0.989 <<
These are for IR frequencies. The emissivity for new fallen snow is not 1.0 in the visible light range. However, snow is essentially black in the IR range. I saw a US Navy report that says the surface emissivity of the ocean is 0.5. Unfortunately I don’t have a reference.
Jim
Jacob, why I pay no attention to what the IPCC and other “experts” have to say is condensed in this quote from 1989:
You can see how well that prediction turned out. Tell me the difference between that one and this one from 2009:
Thanks to Roger Pielke Jr., see his excellent site for real science.
w.
Jim Masterson (10:15:38), thanks for pointing out my error.
You are right, my bad, I was conflating 1- surface albedo and surface emissivity … can’t do dat’, huge mistake. Ignore alien orders, it was late, my brain was entirely out of gear.
My bible for many things climatic, including for the albedo and emissivity of common substances, is Geiger’s The Climate Near The Ground. He gives the following figures for IR emissivity at 9 to 12 microns:
Water 0.96
Fresh snow 0.99
Dry sand 0.95
Wet sand 0.96
Forest, deciduous 0.95
Forest, conifer 0.97
Leaves Corn, Beans 0.94
and so on down to things like:
Mouse fur 0.94
Glass 0.94
So yes, a reasonable global figure to use for the emissivity of IR (greenhouse) radiation would be around 0.95 – 0.96 or so. Which is why most people just ignore it.
w.
Jim Masterson (12:35:41) :
Bill Illis (11:45:03) :
“The best estimate for Albedo is 0.298”
“The error bars are around plus or minus 0.03 and may be (considerably) larger.”
Albedo is by no means a constant. Its variability should be worked into all climate models, since it is a major driver of climate. The IPCC had no idea how albedo worked, so they just ignored it.
[That last sentence may sound like a harsh statement, but I have had it confirmed independently by 3 scientists associated with or supportive of the IPCC. I can add that they clearly found it very convenient to ignore it.]
PALL¶E ET AL.: EARTHSHINE TRENDS 1999-2007
http://solar.njit.edu/preprints/palle1376.pdf
Abstract.
The overall reflectance of sunlight from Earth is a fundamental parameter for climate studies. Recently, measurements of earthshine were used to find large decadal variability in Earth’s re°ectance of sunlight. However, the results did not seem consistent with contemporaneous independent albedo measurements from the low Earth orbit satellite, CERES, which showed a weak, opposing trend. Now, more data for both are available, all sets have been either re-analyzed (earthshine) or re-calibrated (CERES), and present consistent results. Albedo data are also available from the recently released ISCCP FD product. Earthshine and FD analyses show contemporaneous and climatologically significant increases in the Earth’s reflectance from the out-
set of our earthshine measurements beginning in late 1998 roughly until mid-2000. After that and to-date, all three show a roughly constant terrestrial albedo, except for the FD data in the most recent years.
Using satellite cloud data and Earth reflectance models, we also show that the decadal scale changes in Earth’s reflectance measured by earthshine are reliable, and caused by changes in the properties of clouds rather than any spurious signal, such as changes in the Sun-Earth-Moon geometry.
Willis Eschenbach,
I think the confusion might not be between absorptivity and emissivity at the surface (due to Kirchoff’s law) but between albedo of the surface and the effective albedo of the earth system.
>> Mike Jonas (13:42:56) :
PALLE ET AL.: EARTHSHINE TRENDS 1999-2007 <<
It’s a great paper Mike. Thanks for the link. I’ve browsed it and will digest it later.
Jim
>> Willis Eschenbach (13:36:00) :
So yes, a reasonable global figure to use for the emissivity of IR (greenhouse) radiation would be around 0.95 – 0.96 or so. Which is why most people just ignore it. <<
I was hoping for 0.85, but I see I’m back to a minority of one. Thanks for the reference.
Jim
Willis, from the combination of observational record, proxy data, GCM’s, and correlational analysis, there can be no other major cause of the current warming trend. Now, if you have a suggestion that has not been considered, well, I am all ears, but your claims are inaccurate. I do appreciate you not engaing in name calling and lashing out as many posters do here often.
Also see here for history of climate science and how AGW was discovered and validated:
~snip~ “Denial…” “…denial…” “…denial…” Enough! ~dbstealey, mod.