Arguments
Trenberth on Tracking Earth’s energy: A key to climate variability and change
Posted on 12 July 2011 by Kevin Trenberth
Energy and Climate
Climate change is very much involved with energy, most commonly in the form of heat but other forms of energy are also important. Radiation comes in from the sun (solar radiation at short wavelengths), and every body radiates according to its temperature (proportional to the fourth power of absolute temperature), so that on Earth we, and the surface and atmosphere radiate at infrared wavelengths.
Weather and climate on Earth are determined by the amount and distribution of incoming radiation from the sun. For an equilibrium climate, global mean outgoing longwave radiation (OLR) necessarily balances the incoming absorbed solar radiation (ASR), but with redistributions of energy within the climate system to enable this to happen on a global basis. Incoming radiant energy may be scattered and reflected by clouds and aerosols (dust and pollution) or absorbed in the atmosphere. The transmitted radiation is then either absorbed or reflected at the Earth’s surface. Radiant solar (shortwave) energy is transformed into sensible heat (related to temperature), latent energy (involving different water states), potential energy (involving gravity and altitude) and kinetic energy (involving motion) before being emitted as longwave infrared radiant energy. Energy may be stored, transported in various forms, and converted among the different types, giving rise to a rich variety of weather or turbulent phenomena in the atmosphere and ocean. Moreover the energy balance can be upset in various ways, changing the climate and associated weather.
Hence the incoming radiation may warm up the ground or any object it hits, or it may just go into drying up surface water. After it rains and the sun comes out, the puddles largely dry up before the temperature goes up. If energy is absorbed it raises the temperature. The surface of the body then radiates but also loses heat by transfer through cooler winds or by evaporative cooling. Some energy gets converted into motion as warm air rises and cold air sinks, and this creates winds and thus kinetic energy, which gets dissipated by friction. Over oceans the winds drive ocean currents.
The differential between incoming and outgoing radiation: the net radiation is generally balanced by moving air of different temperature and moisture content around. Air temperature affects density as warmer air expands and thus it takes up more room, displacing cooler air, thereby changing the air in a column whose weight determines the surface pressure. Consequently, this sets up pressure differences that in turn cause winds, which tend to blow in such a way as to try to offset the temperature differences. The Earth’s rotation modifies this simple picture. A result is that southerlies are warm in the northern hemisphere and northerlies are cold. And so we get weather with clouds and rain in all of its wondrous complexity.
The changing seasons illustrate what happens as the sun apparently moves across the equator into the other hemisphere. In summer some excess heat goes into the ocean, which warms up reaching peak values about the equinox, and in winter the land cools off but heat comes out of the oceans and this is carried onto land, and so oceans moderate the seasonal climate variations. Much of the exchange involves water evaporating and precipitating out, and thus the hydrological cycle.
The same can happen from year to year: heat can accumulate in the ocean and then later be released, leading to warmer spells and cooler spells. This commonly happens in the tropical Pacific and gives rise to the El Niño phenomenon. El Niño is the warm phase in the tropical Pacific while La Niña is the cool phase. During and following an El Niño there is a mini global warming as heat comes out of the ocean, while during La Niña, heat tends to get stored in the ocean. The El Niño cycle is irregular but has a preferred time scale of 3 to 7 years.
Ocean heat storage can last longer: for decades or centuries and inevitably involves ocean currents and the much deeper ocean. In the North Atlantic, cold waters sink and move equatorward at depth while the Gulf Stream at the surface takes warmer waters polewards, creating an overturning circulation that can also involve density changes in the ocean associated with both temperature and salt (the thermohaline circulation). Salty water is denser. Nonetheless, much of the ocean overturning circulation is wind driven. The overturning may involve the ocean down to several kilometers and can take many centuries to complete a cycle.
As well as the ocean taking up heat, heat can be lost by forming ice, as glaciers, ice caps, or major ice sheets (Greenland and Antarctica) on land, or as sea ice. Extra heat can melt this ice and may contribute to sea level rise if land ice melts. Surface land can also absorb a small amount of heat but not much and not to great depths as it relies on conduction to move heat through the land unless water is flowing. Land energy variations occur mostly in the form of water or its absence, as heat goes to evaporate surface water. Highest temperatures and heat waves typically occur in droughts or deserts.
The atmosphere can not hold much heat and is dependent for its temperature on links to the underlying surface through conduction and thermals, convection, and radiation, as well as the wind in moving it around.
The global energy budget
In the past, we (Kiehl and Trenberth 1997) provided estimates of the global mean flow of energy through the climate system and presented a best-estimate of the energy budget based on various measurements and models, by taking advantage of the fact that energy is conserved. We also performed a number of radiative computations to examine the spectral features of the incoming and outgoing radiation and determined the role of clouds and various greenhouse gases in the overall radiative energy flows. At the top-of-atmosphere (TOA) values relied heavily on observations from the Earth Radiation Budget Experiment (ERBE) from 1985 to 1989, when the TOA values were approximately in balance.
Values are given in terms of Watts per square meter. The incoming radiation is about 342 W m-2. But there are about 5.1x1014 square meters for the surface area and so the total incoming energy is about 174 PetaWatts (=1015 watts, and so 174 with 15 zeros after it or 174 million billion). About 30% is reflected back to space and so about 122 PW flows through the climate system. For comparison, the biggest electric power plants are of order 1000 MegaWatts, and so the natural flow of energy is 122 million of these power plants. If we add up all of the electric energy generated and add in the other energy used by humans through burning etc, it comes to about 1/9000th of the natural energy flow. Hence the direct effects of human space heating and energy use are small compared with the sun, although they can become important very locally in cities where they contribute to the urban heat island effect.
New observations from space have enabled improved analyses of the energy flows. Trenberth et al. (2009) have updated the earlier global energy flow diagram (Fig. 1) based on measurements from March 2000 to November 2005, which include a number of improvements. We deduced the TOA energy imbalance to be 0.9 W m-2, where the error bars are ±0.5 W m-2 based on a number of estimates from both observations and models.
Figure 1. The global annual mean Earth’s energy budget for 2000 to 2005 (W m–2). The broad arrows indicate the schematic flow of energy in proportion to their importance. From Trenberth et al (2009).
The net energy incoming at the surface is 161 W m-2, and this is offset by radiation (63), evaporative cooling (80), and direct heating of the atmosphere through thermals (17). Consequently, evaporative cooling and the resulting water cycle play a major role in the energy balance at the surface, and for this reason, storms are directly affected by climate change. The biggest loss at the surface is from long-wave radiation but this is offset by an almost as big downward radiation from greenhouse gases and clouds in the atmosphere to give the net of 63 units.
Updates included in this figure are revised absorption in the atmosphere by water vapor and aerosols. The direct transfer of heat has values of 17, 27 and 12 W m-2 for the globe, land and ocean, and even with uncertainties of 10%, the errors are only order 2 W m-2. There is widespread agreement that the global mean surface upward longwave (LW) radiation is about 396 W m-2, which is dependent on the skin temperature and surface emissivity.
Global precipitation should equal global evaporation for a long-term average, and estimates are likely more reliable of the former. However, there is considerable uncertainty in precipitation over both the oceans and land. The latter is mainly due to wind effects, undercatch and spatial coverage, while the former is due to shortcomings in remote sensing. The downward and net LW radiation were computed as a residual and compared to various estimates which tend to be higher but all involve assumptions and models. The correct depiction of low clouds is a continuing challenge for models and is likely to be a source of model bias in downward LW flux. For example, there are sources of error in how clouds overlap in the vertical and there is no unique way to treat the effects of overlap on the downward flux.
The new observations from space have enabled improved analyses of the energy flows, their variations throughout the annual cycle, for land versus ocean, as a function of location, and also over a number of years. There is an annual mean transport of energy by the atmosphere from ocean to land regions of 2.2±0.1 PW primarily in the northern winter when the transport exceeds 5 PW. It is now possible to provide an observationally based estimate of the mean and annual cycle of ocean energy, mainly in the form of ocean heat content.
Note that the sum of all the values at the TOA and at the surface in the figure leaves an imbalance of 0.9 W m-2, which is causing global warming. As carbon dioxide and other greenhouse gases increase in the atmosphere, there is initially no change in the incoming radiation, but more energy is trapped and some is radiated back down to the surface. This decreases OLR and leads to warming. At the surface the warming raises temperatures and thus increases the surface radiation, but there is still a net amount of energy that partly goes into heating the ocean and melting ice, and some of it goes into increasing evaporation and thus rainfall. To achieve an energy balance, the vertical structure of the atmosphere changes, and the radiation to space ultimately comes from higher regions that were originally colder. In that sense, the figure is misleading because it does not show the vertical structure of the atmosphere or how it is changing.
There is often confusion about how the greenhouse effect works. Greenhouse gases are those with more than two atoms, and water vapor is most important (H2O). But water has a short lifetime in the atmosphere of 9 days on average before it is rained out. Carbon dioxide (CO2), on the other hand, has a long lifetime, over a century, and therefore plays the most important role in climate change while water vapor provides a positive feedback or amplifying effect: the warmer it gets, the more water vapor the atmosphere can hold by about 4% per degree Fahrenheit. Most of the atmosphere is nitrogen (N2) and oxygen (O2) and does not play a role in the greenhouse effect. Oxygen does play an important role through ozone (O3) though, especially in the stratosphere where an ozone layer forms from effects of ultraviolet light. Ozone is not well mixed throughout the atmosphere as it has a short lifetime in parts of the stratosphere, and in the lower atmosphere its life is measured in months as it plays a role in oxidation.
The air is otherwise well mixed up to about 80 km altitude and heavier gases like carbon dioxide do not settle out owing to all the turbulent motions, convection, and so on. Also the other long lived greenhouse gases are well mixed and connect to the non-greenhouse gases with regard to temperature. Air near the surface has a temperature not much less than the surface on average, and therefore it radiates back down with almost as much energy as came up from below. But because the air gets thinner with height, its temperature falls off, and air is a lot colder at 10 km altitude where ‘planes typically fly. This air therefore radiates less both up and down, and the net loss to space is determined by the vertical temperature structure of the atmosphere and the distribution of greenhouse gases.
Changes in energy balance over the past decade
With the new measurements from space, variability in the net radiative incoming energy at the top-of-atmosphere (TOA) can now be measured very accurately. Thus a key objective is to track the flow of anomalies in energy input or output through the climate system over time in order to address the question as to how variability in energy fluxes is linked to climate variability. The main energy reservoir is the ocean (Fig. 2 below), and the exchange of energy between the atmosphere and ocean is ubiquitous, so that heat once sequestered can resurface at a later time to affect weather and climate on a global scale. Thus a change in the energy balance has consequences, sooner or later, for the climate. Moreover, we have observing systems in place that nominally can measure the major storage and flux terms, but due to errors and uncertainty, it remains a challenge to track anomalies with confidence.
Figure 2. Energy content changes in different components of the Earth system for two periods (1961–2003 and 1993–2003). Blue bars are for 1961 to 2003; burgundy bars are for 1993 to 2003. Positive energy content change means an increase in stored energy (i.e., heat content in oceans, latent heat from reduced ice or sea ice volumes, heat content in the continents excluding latent heat from permafrost changes, and latent and sensible heat and potential and kinetic energy in the atmosphere). All error estimates are 90% confidence intervals. No estimate of confidence is available for the continental heat gain. Some of the results have been scaled from published results for the two respective periods. From (IPCC 2007, Fig. TS.15 and Fig. 5.4).
A climate event, such as the drop in surface temperatures over North America in 2008, is often stated to be due to natural variability, as if this fully accounts for what has happened. Aside from weather events that primarily arise from instabilities in the atmosphere, natural climate variability has a cause. Its origins may be external to the climate system: a change in the sun, a volcanic eruption, or Earth’s orbital changes that ring in the major glacial to interglacial swings. Or its origins may be internal to the climate system and arise from interactions among the atmosphere, oceans, cryosphere and land surface, which depend on the very different thermal inertia of these components.
El Niño
As an example of natural variability, the biggest El Niño in the modern record by many measures occurred in 1997-98. Successful warnings were issued a few months in advance regarding the unusual and disruptive weather across North America and around the world, and were possible in part because the energy that sustains El Niño was tracked in the ocean by a new moored buoy observing system in the Tropical Pacific. Typically prior to an El Niño, in La Niña conditions, the cold sea waters in the central and eastern tropical Pacific create high atmospheric pressure and clear skies, with plentiful sunshine heating the ocean waters. The ocean currents redistribute the ocean heat which builds up in the tropical western Pacific Warm Pool until an El Niño provides relief. The spread of warm waters across the Pacific in collaboration with changing winds in turn promotes evaporative cooling of the ocean, moistening the atmosphere and fueling tropical storms and convection over and around the anomalously warm waters. The changed atmospheric heating alters the jet streams and storm tracks, and influences weather patterns for the duration of the event.
The central tropical Pacific SSTs are used to indicate the state of El Niño, as in Fig. 3 presented below. In 2007-08 a strong La Niña event, that spilled over to the 2008-09 northern winter, had direct repercussions for cooler weather across North America and elsewhere. But by June 2009, the situation had reversed as the next El Niño emerged and grew to be a moderate event, with temperatures in the top 150 m of the ocean above normal by as much as 5°C across the equatorial Pacific in December 2009. Multiple storms barreled into Southern California in January 2010, consistent with expectations from the El Niño. The El Niño continued until May 2010, but abruptly reversed to become a strong La Niña by July 2010.
Figure 3. Recently updated net radiation (RT=ASR-OLR) from the TOA http://ceres.larc.nasa.gov/products.php?product=EBAF. Also shown is the Niño 3.4 SST index (green) (left axis); values substantially above the zero line indicate El Niño conditions while La Niña conditions correspond to the low values. The decadal low pass filter is a 13 term filter making it similar to a 12-month running mean. Units are Wm-2 for energy and deg C for SST.
We can often recognize these changes once they have occurred and they permit some level of climate forecast skill. But a major challenge is to be able to track the energy associated with such variations more thoroughly: where did the heat for the 2009-10 El Niño actually come from? Where did the heat suddenly disappear to during the La Niña? Past experience suggests that global surface temperature rises at the end of and lagging El Niño, as heat comes out of the Pacific Ocean mainly in the form of moisture that is evaporated and which subsequently rains out, releasing the latent energy.
The values and patterns of SSTs in the northern summer of 2010 undoubtedly influenced the extremes of weather, from excessive rains and flooding in China, India and Pakistan, the active hurricane season in the Atlantic, and record breaking rains in Colombia. Later the high SSTs north of Australia contributed to the Queensland flooding. The La Niña signature has also been present across the United States in the spring of 2011 with the pattern of drought in Texas and record high rains further to the north, with flooding along the Mississippi and deadly tornado outbreaks.
Anthropogenic climate change
The human influence on climate, arising mostly from the changing composition of the atmosphere, also affects energy flows. Increasing concentrations of carbon dioxide and other greenhouse gases have led to a post-2000 imbalance at the TOA of 0.9±0.5 W m-2 (Trenberth et al. 2009) (Fig. 1), that produces “global warming”, or more correctly, an energy imbalance. Tracking how much extra energy has gone back to space and where this energy has accumulated is possible, with reasonable closure for 1993 to 2003; see Fig. 2. Over the past 50 years, the oceans have absorbed about 90% of the total heat added to the climate system while the rest goes to melting sea and land ice, and warming the land surface and atmosphere. Because carbon dioxide concentrations have further increased since 2003 the amount of heat subsequently being accumulated should be even greater.
While the planetary imbalance at TOA is too small to measure directly from satellite, instruments are far more stable than they are absolutely accurate. Tracking relative changes in Earth’s energy by measuring solar radiation in and infrared radiation out to space, and thus changes in the net radiation, seems to be at hand. This includes tracking the slight decrease in solar insolation from 2000 until 2009 with the ebbing 11-year sunspot cycle; enough to offset 10 to 15% of the estimated net human induced warming.
In 2008 for the tropical Pacific during La Niña conditions, extra TOA energy absorption was observed as expected; see Fig. 3. The Niño 3.4 SST index is also plotted on this figure and the slightly delayed response of the OLR to cooler conditions in the record and especially in 2008 is clear. However, the decrease in OLR with cooler conditions is accompanied by an increase in ASR as clouds decrease in amount, leaving a pronounced net heating (>1.5 W m-2) of the planet in the cooler conditions. And so this raises the question as to whether a coherent perspective that accounts for both TOA and ocean variability can be constructed from the available observations. But ocean temperature measurements from 2004 to 2008 suggested a substantial slowing of the increase in global ocean heat content, precisely during the time when satellite estimates depict an increase in the planetary imbalance.
Since 1992, sea level observations from satellite altimeters at millimeter accuracy reveal a global increase of ~3.2 mm yr-1 as a fairly linear trend, although with two main blips corresponding to an enhanced rate of rise during the 1997-98 El Niño and a brief slowdown in the 2007-08 La Niña. Since 2003, the detailed gravity measurements from Gravity Recovery and Climate Experiment (GRACE) of the change in glacial land ice and water show an increase in mass of the ocean. This so-called eustatic component of sea level rise may have compensated for the decrease in the thermosteric (heat related expansion) component. However, for a given amount of heat, 1 mm of sea level rise can be achieved much more efficiently – by a factor of 40 to 70 typically – by melting land ice rather than expanding the ocean. So although some heat has gone into the record breaking loss of Arctic sea ice, and some has undoubtedly contributed to unprecedented melting of Greenland and Antarctica, these anomalies are unable to account for much of the measured TOA energy (Fig. 4). This gives rise to the concept of “missing energy” (Trenberth and Fasullo 2010).
Figure 4. The disposition of energy entering the climate system is estimated. The observed changes (lower panel; Trenberth and Fasullo 2010) show the 12-month running means of global mean surface temperature anomalies relative to 1901-2000 from NOAA (red (thin) and decadal (thick)) in °C (scale lower left), carbon dioxide concentrations (green) in ppmv from NOAA (scale right), and global sea level adjusted for isostatic rebound from AVISO (blue, along with linear trend of 3.2 mm/yr) relative to 1993, scale at left in millimeters). From 1992 to 2003 the decadal ocean heat content changes (blue) along with the contributions from melting glaciers, ice caps, Greenland, Antarctica and Arctic sea ice plus small contributions from land and atmosphere warming (red) suggest a total warming for the planet of 0.6±0.2 W m-2 (95% error bars). After 2000, preliminary observations from TOA (black) referenced to the 2000 values, as used in Trenberth and Fasullo (2010), show an increasing discrepancy (gold) relative to the total warming observed (red). The quiet sun changes in total solar irradiance reduce the net heating slightly but a large energy component is missing (gold). Adapted from Trenberth and Fasullo (2010). The monthly global surface temperature data are from NCDC, NOAA: http://www.ncdc.noaa.gov/oa/climate/research/anomalies/index.html ; the global mean sea level data are from AVISO satellite altimetry data: http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/ ; and the Carbon dioxide at Mauna Loa data are from NOAA http://www.esrl.noaa.gov/gmd/ccgg/trends/.
To emphasize the discrepancy, Fig. 5 presents an alternative version of Fig. 2 for 1992 to 2003, as a contrast to 2004 to 2008. The accounting for all terms and the net imbalance is compatible with physical expectations and climate model results, with the net imbalance about 0.7 W m-2 at TOA for 1992 to 2003. However, for the 2004 to 2008 period, the decrease in solar radiation associated with the sunspot cycle and the quiet sun in 2008 contributed somewhat, but the Ocean Heat Content (OHC) change is a lot less than in the previous period and a residual imbalance term: the missing energy, is required.
Figure 5. The energy entering the climate system is estimated for the various components: warming of the atmosphere and land, ocean heat content increase, melting of glaciers and ice caps (land ice), melting of the major ice sheets (Greenland and Antarctica), and changes in the sun. For 1993 to 2003 these are summed to give the total which is equivalent to about 0.7 W m-2. For 2004-2008, TOA measurements are used to provide an increment to the total based on comparisons with 2000-2003, and the quiet sun has contributed, but the sum is achieved only if a spurious residual is included. Units are 1020 Joules/year.
Further inroads into this problem will no doubt become possible as datasets are brought up to date and refined. In the meantime, we have explored the extent to which this kind of behavior occurs in the latest version of the NCAR climate model. In work yet to be published (it is submitted), we have found that energy can easily be “buried” in the deep ocean for over a decade. Further preliminary exploration of where the heat is going suggests that it is associated with the negative phase of the Pacific Decadal Oscillation and/or La Niña events.
Clearly, tracking energy and how and where it is stored, and then manifested as high SSTs which in turn affect subsequent climate is an important thing to do.
[DB] "Your own bolehole plot proves my point"
Quite the opposite, actually.
Sorry, not in the business of disproving something that doesn't exist. And the only business I'm in is the propounding of the scientific method and climate science.
Straw man, to the point of incoherence.
As Lincoln said, calling a dog's tail a leg doesn't make it a leg. You can say anything you want; doesn't make it true.
You mean, other than the global borehole plot I supplied earlier which shows you wrong?
Been there, done that.
Straw man, no one said it was. AGW stands the test of time due to the consiliance of multiple, independent lines of converging evidence. All of which you'd have to overturn in order to have your hypothesis endure. As such, it fails quite miserably.
And we're back to this: the onus being on you to produce any peer-reviewed, published evidence to support your hypothesis.
We're still waiting.
The links to Trenberth's papers in this post by Trenberth are broken, because all his files were moved to a new spot at UCAR. Will somebody please update the links?
[DB] All links are now updated; thanks!
Old Sage (from an inappropriate thread), you are ignoring what KR pointed out: The numbers in that energy budget are based on actual measurements by hundreds of scientists, refined over many years. You can read about their methods by following the links to the original peer-reviewed papers. That budget does not violate any laws of physics. Really, it does not. It's not even hard to understand. But first you must actually try to understand it. It is clear from all of your comments on Skeptical Science so far that you are not really reading, let alone really trying to understand, anything. You would fail an Introductory Climatology class simply by refusing to read and try to understand.
TD - high time the calibration of spectrographs was investigated if measured.
I cannot get my head round 3 kgs of CO2 absorbing and emitting 350 watts of energy surrounded by 3000 times as many other molecules - do they all agree not to bump into them. I also cannot get my head round the alleged 2.9 w/m2 surplus from GG's. That's equivalent to raising earth's atmosphere 10 degrees p.a. - I think we would notice that!
The 2.9 Wm-2 surplus doesn't heat the atmosphere; it heats the entire planet. My back-of-envelope calculation (literally !) suggests that should result in an annual temperature rise of 0.0082K
Phil - Actually, a 2.9 W/m2 top of atmosphere forcing should directly raise temperatures by about 0.877 C, not including feedbacks.
Calculation: start with the Stefan-Boltzmann relationship of
or Power = emissivity * SB constant * Area * Temperature4
The Stefan-Boltzmann constant is 5.670373*10-8 Wm-2K-4, surface temperature in Kelvin averages 15 C + 273.15 = 288.15 K, and for area we can assume one square meter.
Starting effective Earth emissivity = Power / (SB constant * T4) = 240 W/m2 /(SB * 1 * 288.154) = 0.6139
With 2.9 W/m2 missing, effective emissivity = 237.1 W/m2 /(SB * 1 * 288.154) = 0.60652
To radiate 240 watts with a lower effective emissivity, and remove the energy imbalance, a higher temperature is required. T = (240 W/m2 / (SB * 0.60652)) -4 = 289.03 K = 15.877 C. That's a direct, pre-feedback temperature difference of 0.877 C.
[DB] updated image link per request.
Actually, KR, Phil was talking about the change per year, not the total change. If the 2.9W/m2 is held steady, it would take a little over 100 years to cause a total change of 1 degree.
I'm guess that Phil just took a mean water depth and heat capacity to get his number. One catch is that the entire ocean depth is not evenly mixed. Thus, the heat tends to warm the upper layers faster, so a surface temperature response will see a greater increase than the 0.082K per year in the early years, and the deep ocean takes a while before it shows heating.
Phil could explain the assumptions behind his back-of-the-envelope calculation a in bit more detail.
Bob Loblaw - Ah, that would certainly explain the difference in numbers; my misunderstanding then.
That back-of-the-envelope calculation would require specifying the transient climate sensitivity, and/or the mass directly involved. Timing is everything, after all...
Old Sage - your inability to understand something does not make wrong. You have been pointed to the text book stuff. Why dont you actually start there? I should also point out that the spectroscopy tests of theory have been repeated numerous times and the Radiative Transfer Equations predict the results of experiments with exquisite accuracy. If your conception of physics is at odds with experimental observations, then its time to revise your conceptions of physics. Pick up a text book.
old sage @216
It isn't just CO2, its all the GH gases. And the other non-GH molecules in the atmosphere are bumping into them all the time. In fact the kinetic energy of those collisions is the source of the energy that the GH molecules are radiating.
All the IR radiation in the atmosphere originates from the GH molecules, the non-GH molecules, O2 and N2 particularly cannot radiate in the IR wavelengths required. The radiation from the GH molecules comes from the fact that the individual atoms in the molecule are joined by flexible bonds between the atoms. So the atoms in the molecule are always vibrating, jiggling around like balls on springs. Essentially kinetic energy is stored in the bonds between the atoms. Some of this energy can then be released as a photon of IR radiation, resulting in the GH molecule vibrating a little less. However, the continuous collisions between molecules can quickly 're-energize' the GH molecule so that it is able to radiate again.
When you think of the energy being radiated from the atmosphere as coming from the combined energy of all the molecules in the atmosphere it may not sound so strange. It is just that in order to be radiated it has to be channelled through the GH molecules to 'get out'.
Let me just give a little lesson in physics as I understand it - tell me if I'm wrong.
1) earth's surface radiates a spectrum because it is a solid and the energy levels are practically continuous because atoms are forced together. The spectrum varies with the temperature - oscillation of lattice - and character of surface (water, ice, grass, etc).
2) gas molecules are so far apart, their excitation levels require a statistically insignificant collision of several of them to 'stop' say three and leave a fourth spinning off with photon levels of energy. You could work the figures out but it would not necessarily be a carbon level, that would be even less likely (Gases do not radiate!)
3) Carbon dioxide absorbs electromagnetic energy just as does any interfering substance the amplitude falling off exponentially as heat is dissipated in the dielectric. (goes for beta, gamma, wireless - anything, not alpha of course, not e/m radiation)
4) Water droplets in a cloud approach the solid situation, spectrum wil depend on size and T. This means clouds can radiate, the energy comes from somewhere - condensation if growing, sunlight if on the lit side and the surrounding gases in all cases. They do not conjure up energy from nowhere.
If co2 does not stop radiation completely in a clear sky from escaping, it is having little effect, even if it does it accounts for what, 1 % of the spectrum. Clouds simply provide an additional staging post for energy conversion and re-conversion.
On the quantum front, I suspect solar radiance is worked out by multiplying the normal figure by cross-section. Well, much e/m energy strikes the earth at a glancing angle, I don't expect anyone has worked out the amount totally reflected at the various boundaries for various frquencies - experiments I know have been carried out looking at i/r. But that would be fairly marginal given the scale of error introduced by that solar balance diagram on top of this thread.
I calculate that earth surface emits 56 w/m2 and what doesn't get straight out goes into gas kinetic energy. Follow the kinetic I say, find out where it goes and discover the cooling effect of radiation from the ionosphere!
@ Old Sage Is this the angle your comming from link
Old Sage @223:
1) Solids, like all elements and molecules, absorb and emit radiation at discrete wavelengths corresponding with the discrete energy levels of electron shells, molecular bonds and rotational and vibrational patterns. In solids there are so many elements, so closely packed that the number of such discrete wavelengths is very large so that the radiation will often closely approximate to that of a black body. Nevertheless, the discrete wavelengths of radiation and absorption are there, and are no different in principle in behaviour than that of gases.
2) I have already shown this to be wrong by observational evidence here.
3) Like all substances, CO2 radiates at specific frequencies. The intensity with which it radiates at those frequencies is a function of temperature, based on the laws of black body radiation.
4) At least you got this correct, if nothing else. Unfortunately everything that follows is wrong.
You write:
This illustrates the absurdity of your position. To actually claim that if CO2 stops 99% or IR radiation, it will have no effect because it is not 100% (ie, completely) is not only wrong, it is nonsensical.
You further write:
You are again wrong. The mean solar irradiance is calculated as the Total Solar Irradiance divided by the ratio between the surface area the Earth, and of a disc with the radius of the Earth perpendicular to the Sun's rays (which ratio happens to be 4) - then multiplied by one minus the bond albedo of the Earth. The bond albedo is the reflectance averaged over all angles. Therefore, the standard formula actually incorporates the information you say is ignored, and which you say is not measured.
You write:
Again, you are simply wrong. Below are radiative fluxes at the surface as measured over Lake Ontario. The upwelling surface flux is given as a negative value (dashed line) because it is in the opposite direction to the net short wave radiation (red line, consisting of incoming sunlight minus reflected sunlight) and the back radiation (short dashed line). Note that the surface flux never drops below 200 W/m^2 (as measured), nearly four times your estimated maximum value. It would be much larger in tropical areas, which constitute 50% of the Earth's surface.
jmorpuss - very good reference that, that is where I am coming from because from a global viewpoint - and any radiating surface - it is the boundary conditions which determine the performance and earths boundary is a shimmering mass of charged particles. Various lens-like changes occur with height. (I should point out my research - a long time ago - was in thin film superconductors of the second kind where magnetic field breaks down into quantised vortices) I imagine such movements high up generating long wave radiation correlated with atmospheric energy levels (hopefully).
TC you repeat what I said in 1 but ignore the consequences. CO2 does not radiate as a black body, it merely scatters and absorbs - that is until you get it up to several thousand degrees, and I don't know how many, but it doesn't occur where you assert it does!
I have just looked back at the reference you made TC refuting a previous post of mine about co2 radiating - and quite rude it was too. (CO2 obviously re-radiates a proportion of the energy by which it gets excited but your back-radiation - which will increase with concentration of CO2 - simply means more comes back becasue the number of scattering centres is denser.) Sorry, CO2 in gaseous form cannot convert kinetic to photon energy except under the rare circumstances I suggest, it would just defy the most basic conservation of energy rules. Dense concentrations in solids have that capacity by a process you seem to understand.
old sage.
I think I am beginning to discern the bridge more clearly here. You say @223 that "I calculate that earth surface emits 56 w/m2 and what doesn't get straight out goes into gas kinetic energy." I would be interested to see how you calculate the 56 w/m2.
And with this, you also assert @227 that "CO2 in gaseous form cannot convert kinetic to photon energy except under the rare circumstances." You appear to be proposing that gases do not emit radiation. It would be useful to know where do you get this idea from.
old sage claims:
Just so I'm clear here, old sage, which of the two below are you suggesting:
I'm assuming, based on the clause after the dash, that you are claiming #2.
Even based on less-reliable "common sense" inference this claim is plainly false, to say nothing of empirical measurements of the outgoing E/M emission spectrum of the Earth by satellite, which are consistent with emissions of longwave IR at temperatures well below "several thousand degrees".
As an approximation I would describe the Earth's emission spectrum as a composite of of blackbody-like curves between 220-320 K, consistent with the evidence presented by Tom (and others) and inconsistent with the bizarre claim you are attempting to advance.
(Incidentally, it seems to me that, for the purposes of E/M emission into space, you have got the wrong boundary.)
old sage - You make several absurd claims:
I cannot emphasize enough how wrong those statements are. CO2 (and CH4, and ozone, and CFCs) absorb (not scatter) and emit over a broad IR spectra, with photon emission coming from electron orbital relaxation, and electron excitation being easily converted between orbital and vibrational modes, with a corresponding ability to interchange kinetic and electronic energy. Ionized plasmas are simply not required.
You might find it useful to read up on Kirchhoff's law of thermal radiation, which states that "for an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity is equal to the absorptivity", meaning that the emission spectra at radiative equilibrium is identical to the absorption spectra.
Your assertions regarding gaseous IR emission, to be blunt, are total nonsense contradicted by physics and observations. If as you state you have a background in thin film superconductors, you should know better. Until and unless you decide to discuss physics, rather than Just So Stories, your posts are not worth anyones time.
I've made the physics as clear as a pike staff. The reason a solid emits as a black body is because the coming together of nuclei in close proximity forces the outer electronic bands so close together that they form a continuum of energy levels. Co-operative movements due to thermal oscillation means that lattice waves involving many nuclei, phonons if you will, in collision have sufficient energy to cause photon energy level transitions in the electron bands. It all goes on at the boundary layer as i/r cannot penetrate a solid for more than a skin effect depth so i/r cannot emerge from anything other than the skin.
This is practically impossible with CO2 molecules. CO2 molecules at STP are in the ground state - where do they get the energy to radiate? Your claim that they do is purely and simply due to external stimulation. CO2 is simply an agent, a receptor if you like, for radiation generated elswhere it then will obviously participate in transitions as it seeks to return to its groundstate. You confuse scattering, which involves re-transmission of a proportion of incident energy with spontaneous emission - which again cannot happen. Get your text book out.
I could also explain to you how phonon waves at very low temperature cause electrons to attract each other in pairs over very large distances (compared with the atomic diameter) but if you don't understand the above, you certainly wont understand that!
MA Roger - I just assumed stefans law with T 300 radiating to a body at 0K.
old sage - What I have been discussing is thermal radiation, observed in all matter at a temperature greater than absolute zero - where kinetic energies cause dipole oscillations and accelerated charges, and result in photon emission.
A significant percentage of CO2 at standard temperature and pressure is indeed above ground state, and radiating, as can be shown with IR spectroscopy. And that energy could come from incoming IR at CO2 absorption wavelengths or perhaps from a heated wire - spontaneous thermal emission, not scattering. The emission spectra is dependent on gas temperature, not on any incoming IR.
Again, your physics claims regarding thermal emission from gases are simply nonsense, contradicted by hundreds of years of both theory and observations.
old sage:
What parts of CO2 absorbs longwave IR from the Earth surface (or from radiating molecules elsewhere in the atmosphere) and CO2 molecules receive thermal energy from collisions with other molecules in the atmosphere are you having trouble understanding? Certainly these seem to qualify as "external stimulation" allowing CO2 molecules the opportunity to "get the energy to radiate".
Seriously, absorption and emission of longwave IR by greenhouse gases is observed & measured (as per graphs & sources provided in comments responding to you). Insofar as there is any actual contradiction between your claim (as quoted in this comment) and what is observed, you are putting readers into the position of having to accept one of the following:
I put it to you that the choice is obvious (and unfavourable to you).
The distribution of energy levels in a gas is decribed by the Boltzmann distribution. For atmospheric temperatures, several vibrational states above the ground state are populated for CO2 and all other greenhouse gases. However, this would still not guarantee a greenhouse effect if our atmosphere were homogenous in terms of pressure and temperature, which it obviously is not.
Textbook knowledge in one field (e.g. solid state physics) does not mean one understands gas phase physics, or can directly apply one to the other. In this case, an understanding of both (infrared-) spectroscopy and radiative transfer are needed. As oldsage seems to display major misunderstandings of even some basics, I suggest to tone it down and start form the beginning. As he said: "Get your text book out." Will you do that too oldsage?
Apologies to KR and Bob @219 @220, I should have explained in more detail, however Bob guessed my method correctly! it was really was intended as an "order of magnitude" calculation to suggest that old_sage's comments @216 were the result of a lack of sagacity on his part.
Since the conversation has moved on, I would add that there is, in fact no such thing as a ground state for a molecule, there are, of course, multiple. For a triatomic linear moeclue such as CO2 there are 2 degenerate rotational states, 4 vibrational ones (symmetric stretch, asymmetric stretch and double degenerate bend) as well as the electronic state. At STP CO2 molecules will be in many excited rotational states, several excited vibrational states - particularly the bend which is a lowest frequency, and almost exclusive in the ground electronic state. The black body radiation from Earth is absorbed and emitted by the CO2 bend since its frequency coincides with the radiation emitted by earth. This is in the Infra-red region of the EM spectrum and is what KR refers to as Thermal Radiation. old_sage's reference to excited electronic states is simply a strawman.
old sage @231.
Do you mean this Stephan's Law? So what is j* = 5.76040e-8 x 300^4? Of course it could be the answer is 56 wm^-2, but bless my quintessense, the abacus has run out of beads!!
And one question. Does it matter a ha'p'eth that the receptor is at 0ºK? Your calculation is the Earthly emissions, not net Earthly emissions. And I'm still very worried by the bridge!!!
old sage
You talk about "Co-operative movements due to thermal oscillation means that lattice waves involving many nuclei, phonons if you will, in collision have sufficient energy to cause photon energy level transitions in the electron bands"
In essence you are talking about Atomic spectrocopy. The absorption and emission of energy by an atom that involves transitions in that atoms internal energy levels.
This is not the basis of GH gas absorption/emission!
With GH gases we are dealing with Molecular Spectroscopy. The essential mechanism is as follows:
Think of a ball on a spring, bouncing around. If you wack that ball with a stick the ball may end up bouncing more fiercely. You have trtansferred energy to the ball/spring system that is now stored as kinetic/potential energy of the ball/spring system.
Molecular absorption/radiation is about changes in the kinetic and potential energy of vibration of atoms within a molecule, the energy being trasnported into and out of the molecule based on Maxwells Eqns, not changes to the internal energy levels within the atoms.
It is an inter-atomic phenomenon, not intra-atomic.
There seems to be a lot of misunderstanding here due to a little knowledge being a bad thing. My physics dna prompted me to say co2 molecules were in the ground state so I tried to check and could only confirm this indirectly. I did find the figures for H2O - and these probably copy across reasonably well. The extra dimensions to the translational degrees of freedom have critical temperatures of 5170,5400,2290 degs K.
Glen Tamblyn - all radiation is quantised these numbers tell you just how high the temperature has to be to jiggle your molecule enough to radiate. (Of course, by QM there will always be the rare event corresponding to a freak combination of collisions) Also, fwiw, the surface of a body is primarily formed of outer electrons, it is their transitions stimulated by the underlying lattice which generate BB radiation. I do know the magnitude of difference thank you for atomic - and molecular energy transitions.
Old sage - I havent seen much evidence that you have looked at any the text book physics so far, but I'd have to say "There seems to be a lot of misunderstanding here due to a little knowledge being a bad thing" made my day. The sticky details of the RTEs are done in this classic paper. Ramanthan and Coakley 1978 Perhaps you would like to fault it and provide an alternative theory that can reproduce the experimental results?
[TD] Will everyone please help get the conversations onto the right threads, since Old Sage is not cooperating but his/her comments and everyone's responses are too useful to delete?
There seems to me to be a bit of ageism creeping in here from young know-alls!
The minutiae of trying to model everything everywhere is an heroic task and good luck to those doing it. We could all be toast by the time it's finished.
There are two false premises upon which this GG quantum depends.
One is that the net energy from the sun all escapes within the envelope of the infra red. Is that reasonable? I do not believe that anyone holding their hand up to earth from a satellite would feel anything like the amount of heat radiating from it which these radiation models of i/r require. You would even notice this from a high snowy mountain pointing your hand at the valley.
Number two, the same really, is that all that kinetic energy absorbed by gases can only find its way out by direct radiation at i/r. A molecule highly excited can make a multistage transition say from rotational to vibrational as it relaxes giving rise to two or more lines but as its energy ultimately decays into thermal as a result of an inelastic collison the question is can this higher translational energy be handed back? It cannot in the absence of a background of i/r radiation because the gap is equivalent to several thousands of degrees. Can one then imagine an already excited molecule changing up a gear in an inelastic collision to a nearby level by the amount available from translational movement. The odds are stacked highly against this. Decay is available to a continuum of kinetic levels, recharging needs a precise collision into discrete levels with large, in kinetic terms, separation.
That means by reducing outgoing i/r as the only sink for energy generated - either by man or sun - you have to conclude there is another major activity going on taking up kinetic energy and radiating it.
That energy can only be found in the largely unexplored frequency ranges - and they might be spiky and intermittent (e.g. huge numbers of wireless energy radiators (^10-17 ergs) such as are found in the ionosphere.)
There is an analogy. Just as the underlying thermal oscillations prompt radiation from a solid's electron covering in BB radiation, the electrically charged ionosphere covers a pulsating, swirling and mobile atmosphere. This has to stimulate radiation and being at the top of the earth, it will escape unhindered. The earth's response to heating up has to be that robust a mechanism and not too sensitive to the gaseous constituents as it has supported life for millenia. That is not to deny the impact of man's activity, mankind is just an additional burden.
There is clear confusion, and not mine, between the emissions in gases - in which the spectral lines are far fewer than those observed in the absorption spectrum. But at bottom, the absolute determination to avoid any concept of heat transfer by conduction, convection and mass transfer within the atmospheric envelope to a cooler upper layer is fatal to the argument from my viewpoint. I don't dispute what Ramanthan and Coakley may have said, I simply don't wish to wade through it. It involves what is probably second, may be third or perhaps even fourth order argument involving the shuttling around of photons by CO2 before their final resting place as kinetic energy.
[tD] Your "ageism" remark is inappropriate. And unless you are 100 years old, you are not older than all the people responding to you, let alone all the people who have written the peer-reviewed scientific papers being cited by your responders and the original post above.
Snippy, sarcastic answer: I can't imagine why that would be.
Actual answer: Age has essentially nothing to do with the objections raised against your claims.
The objections are:
old_sage @238
There seems to be a lot of misunderstanding here due to a little knowledge being a bad thing.
Thank you for concedeing that; the basics of Rotational and Vibrational absoption spectra can be learnt from any standard undergraduate text on Phyisical Chemistry. I learnt mine from P.W Atkins (aged 73). "Phyisical Chemistry" (OUP, 1st Edition, 1978) has an introduction to the subject in chapter 17, including the Boltzmann distribution mentioned by gws. He goes into more detail in Molecular Quantum Mechanics Part III (OUP, 1970), in Chpater 10.
For exhaustive detail on Rotational Spectroscopy (not strictly relevant to the GHE, but my "bible" during my Ph.D) see Microwave Spectroscopy by Townes and Schawlow (Dover Press, first published in 1955)
old_sage @238
Incidentally your biology is not too sharp either: there is no such thing as "physics DNA". What could you possibly have meant by that ?
Bit of a joke that - ageism - didn't go down well!
Anyway, I take it you folks all believe there is absolutely no radiation from earth other than i/r. Please allow me to beg to differ, and we will leave it at that. There are some solid physical reasons for believing alternative mechanisms not only can but must exist. There is obviously a lot of sense in studying the detailed influences of all the man made pollutants on radiative transfers in the atmosphere but I worry that it offers a distraction from a serious problem consuming the time of good men. An eye 2 cms from liquid helium at 1deg hardly increases the boil off - fail to keep a liquid oxygen cold trap several meters away down a room temperature tube topped up and the results soon get catastrophic. I would suggest more time be spent looking at kinetic transport and the cold trap. I might take another look at the nitty gritty but I doubt it.
Old Sage,
You have a lot of chutzpah for someone who has been demonstrated wrong several times. You need to break out your freshman physics textbook and review it again.
You keep making comments about the ionosphere. Everyone else knows that the ionosphere has no relationship to the surface temperature. This is a comment that is usually called "not even wrong" because it is so far off base. That is why no-one has responded to your points. The surface heat budget is allradiated from the top of the stratosphere in the IR spectrum. This is basic black body physics. If you do not understand why the ionosphere does not affect the surface either read your textbook or ask a question to clear up your misconception.
You will find that people are less cutting in their responses to you if you stop being so condescending to others. It is especially irritating since you are so often completely wrong and then you are demeaning to others who are in fact correct. For example, you frequently suggest others should read their textbook because you do not understand basic atmospheric physics. Tom can read his textbook all day and you will still be wrong. If you start asking questions about what you obviously do not understand you will come across much better. Your basic physics of the atmosphere is lower than a freshman physics student is expected to understand.
9 years to retirement here - I'm flattered to be young know-all. However, I still take the time to study what is actually being claimed before criticizing it, especially when out of my field. What I find irritating is your criticism of imaginary claims of climate science, and as far as I can see, a flat out refusal to actually look at what the science really says. Virtually nothing you say makes sense because this level of misunderstanding.
old sage:
Please provide direct quotes from other commenters explicitly making this claim. Otherwise it is a blatant misrepresentation of the responses directed to you.
What us "folks" have been doing is pointing out that physics theory, experiment, and empirical observation contradict your claims against the fact of longwave infrared absorption and emission properties of greenhouse gases in the atmosphere, a contradiction you have so far failed to effectively deal with.
Largely, it seems to me, by simply ignoring what people are actually saying in favour of resorting to unsubstantiated misrepresentations as the above.
C99 - look next but one comment above yours, it pretty well claims just that.
Also, for the benefit of others, whether something is true or not very often depends on other factors. The emission spectrum of CO2 for example - and my authorities are impeccable - will differ when it is in solution in a raindrop, as in a cloud.
Some of you I expect have invested a lot of time and energy in mapping radiation but meanwhile all the heat generated by man is getting dumped in the ice and waters courtesy of kinetic transfer. When I see formula one engineers changing their cooling arrangements depending on cloud cover I might believe it were otherwise but in the meantime, imv heat transfer by radiation is pretty feeble under atmospheric conditions compared with kinetic.
Fresher level physics(?), you're right there someone above - moving charged particles in a magnetic field generate e/m radiation.
old sage.
You have yet to explain how you obtained the 56 w/m^2 @223. It is a trivial calculation using Stephan's Law, which is the furmula you say @ 231
you used. You show yourself here as somebody who cannot even honestly perform simple arithmetical calculations but would rather talk nonsense about holding a hand out on a high mountain. Is a hand an appropriate measurement device? Especially given all the radiation whizzing about in all directions? But them you deny the existence of that radiation!
And, old sage, while you are about re-calculating the radiation from a body at 300K, perhaps you could also do another trivial back-of-the-fag-packet calculation. You are so wedded to conductivity as a means of energy distribution. So if the globe with a temperature 300K were surrounded by a solid with the same thermal conductivity as air (at STP), how large will the energy flux of conduction be? Consider this 'solid' atmosphere has constant properties with altitude. Call it 8km deep. Call it 1km deep if you like. Can you provide an honest answer here?
Well, I'm done directly responding to old sage; it's a waste of time.
But I should like to draw attention to old sage's blatant misrepresentation of michael sweet.
In comment #244, old sage suggests
When pressed for a direct, explicit quote, the best old sage can do is suggest that michael sweet, in comment #245, "pretty well claims just that". So, no direct quote explicitly stating what old sage asserts, just an insinuation. Further, old sage apparently can't be bothered looking upthread, before his comment #244, to support his claims.
However, the closest michael sweet comes to anything like old sage's claim is:
Nothing michael sweet writes in this paragraph can remotely be construed as claiming "there is absolutely no radiation from earth other than i/r", at least not by any observer reading what he actually wrote.