Clive Best

I have been reading several new books about climate science, “climategate” and the IPCC. The first is The Climate Files  by Fred Pearce who is a widely respected science journalist with New Scientist and the Guardian. The next is a new book “Climate - the counter consensus” by Robert Carter who is an Australian professor and long standing so-called “skeptic”. I also read the Hockey Stick Illusion by AK Montford and re-read John Houghton’s excellent briefing on Global warming. What is beginning to emerge in my mind is:

A group of privileged scientists who helped initiate and sustain the IPCC process, then consequently benefited from it through the ensuing flood of research funding and would then appear then to have excluded other scientists with different viewpoints. On the other hand a growing group of critics have been  attacking them sometimes justifiably and sometimes totally unjustifiably. This unfortunately caused a siege mentality of secrecy and elitism to develop among  these climate scientists, who blocked openness in the science, with attempts even to suppress publication of alternative interpretations. The CRU (Climate Research Unit) has had one of the crucial roles in measuring whether there has in fact as predicted been any warming over the last 100 years or so. It is essential that these measurements are trustworthy and completely transparent, as otherwise this debate stops being scientific.  The raw data and algorithms used to derive global temperatures should open to all to replicate because that is the way science works. Otherwise climate science will allways remain a bit like kitchen sink  alchemy because  there are a huge number of variable parameters, and there are still many “unknown unknowns”. Climate Models are huge computer programs modelling complex differential equations, with some built in assumptions, and endless knobs to twiddle.  In the end it can  only be measurements and experiments that control the science behind these models.

The basic physics of the greenhouse effect is well established and pretty much accepted by everyone. Surprisingly though, its direct  effects are really not that bad, despite all the hype of impending disaster, rising sea levels and melting glaciers. Mankind burning of fossil fuels has caused a 30% increase in CO2 concentration in the atmosphere since 1750. Absorption of infrared radiation from the earth’s surface in narrow wavelength bands by CO2 and re-emitted by CO2  results in trapping some extra heat within the earth /atmosphere system. Adding more CO2 to the atmosphere has a progressively smaller and smaller (logarithmic) effect because the absorption in these bands was already saturated at pre-industrial levels.  So if no action is taken and man were to continue burning fossil fuels to peak at a doubling of CO2 levels in the atmosphere by the end of this century, then  global temperatures could rise by about 1 degree. Far larger natural variations than this have occured over the last 100,000 years. The transition from an Ice age to a warmer interglacial period causes a rise of about 9 degrees globally. This anthropogenic rise of about 1 degree by 2100 is what the basic physics of a doubling of CO2 in the atmosphere predicts.

All the scientific controversy is actually  about  feedback effects which have been predicted. This is the crux of the argument and in reality  no-one currently really knows what will happen. These are the examples feedbacks given:

1. If ice caps recede from the poles then more solar energy will be absorbed due to a reduced  albedo leading to enhanced warming.
2. Warmer oceans lead to more evaporation and more water vapour in the atmosphere. Water vapour is the main greenhouse gas by far on Earth contributing at least 5 times as much as CO2.
3. More water vapour however leads to increased cloud cover which on average cools the Earth. Models show that an increase in cloud cover of just 3% would be enough to offset all the enhanced greenhouse effect caused by a doubling of CO2. Some estimate also that more rain will reduce water vapour from the atmosphere and thereby reduce the greenhouse effect.
4. Ocean circulation. The oceans have an enormous heat capacity and transport energy across the world through currents like the north atlantic drift which warns Europe. Any changes in these currents would have large changes regionally but probably not globally.

The IPCC estimate a net positive feedback effect giving their prediction of a much higher higher 2-5 degree rise in global temperatures. Despite all the money flowing into research and all the conferences these figures haven’t really changed much over the last 20 years. The science itself also hasn’t changed that much - it is just a question of how it is interpreted. If Milkowski turns out to be right then nothing will happen because he argues the greenhouse effect is already maximised. That is why direct experimental measurements are so important.

The climate change debate has now become far more about politics than about science. If you are green, possibly left wing, favor state intervention to  rampant capitalism, oppose globalisation and unfettered growth,  then climate change is real, very dangerous and the West is to blame. If on the other hand you are maybe right wing and believe in low taxes, free enterprise, growth, individual rights and oppose state interference, then climate change is myth and hype to bring discredit to enterprise capitalism etc. etc.

The CRU temperature data  show a rise in temperature of around 0.5 degrees C over the last 150 years, but it is not a clear linear rise and there have been cooling periods as well such as during the 1940s - 1960s, and the temperature has stopped rising for more than a decade since in 1998. This means that natural variations must also be present and an unambiguous human  effect is still not confirmed. Critics argue  that these data are also effected by a different human effect namely the large expansion of urban areas leading to local heating through urbanisation - concrete, tarmac and heat from cars and buildings. Many weather stations were naturally close to cities and therefore may need correcting for this effect. The IPCC claim  no correction is needed based on a paper by Jones et al studying chinese weather stations in different locations, whose results are now being questioned because these locations now turn out to be uncertain.  This paper claimed there was no such urban heating effect, however I know from personal experience that central Milan is always a couple of degrees hotter than where I live in the countryside. Surely the only way to arrive at the truth is to make available the raw station data, their locations and to allow others to carry out independent analysis.

The drive to a low carbon economy may be anyway a good thing for innovation and for the environment in advanced countries. However it will not help developing countries in Africa, where most transport still depends on 10-20 year old trucks, buses and cars  shipped there from Europe and Asia, which  emit choking black smoke.

A radical but rather elegant theory has been proposed by a Hungarian Physicist Ferenc Miskolczi (see refs) that the Earth maintains a maximised greenhouse effect  to allow the Earth to cool as efficiently as possible. This self-regulation arises  because  70% of the Earth’s surface is water allowing both cooling through evaporation (latent heat) but also warming  through H20 being a greenhouse gas. Unlike CO2 the concentration of H2O in the atmosphere is governed by thermodynamic processes. Local thermodynamic equilibrium in the atmosphere ensures equality between the absorbed IR energy by all greenhouse gases from the surface and the  IR  energy emitted back to the surface by those same gases. Water evaporation and convection drives the Earth’s weather systems. Water Vapour also dominates the greenhouse effect of the Earth but has two  subtle feedbacks. Firstly evaporation mainly from oceans is a very efficient way for the surface to loose heat through latent heat. However cloud formation then leads to a higher albedo and to night time heat retention so there is a play-off beween this and the greenhouse effect of H2O. Miskolczi and Zagoni argue that the total average greenhouse effect on Earth depends only on the input energy of the sun plus a small geothermal component. This simple conclusion is backed up by  detailed radiation transmission model calculations and data comparisons.

The total greenhouse effect remains exactly what is needed to maximise cooling of the Earth. Any man-made CO2 increases are simply offset by a small decrease in water vapour so as to maintain thermodynamic equilibrium. They claim that the data show there has been a small 1% decrease in global humidity to offset all CO2 increases caused by  human emissions. The following slides try to explain the energy balance arguements they make. The crucial proposal is that the water content of greenhouse concentrations (H2O + CO2 + CH4) are maintained to be such that half the IR energy radiated from the surface is emitted into space from the top of the atmosphere while another roughly 60 watts/m passes clean through the IR wavelength window. The physics motivation for this first proposal is the virial theorum which states that the kinetic energy (heat) of the atmosphere is half the (gravitational) potential energy. The effective radiative kinetic energy is associated with the IR radiation emitted from the atmosphere to space(Te**4). The effective potential energy is associated to the IR radiation emitted from the surface (Ts**4). The second proposal is that the amount of energy emitted back to the surface is equal to that absorbed by the atmosphere. This is based on an assumption of overall local thermodynamic equilibrium (Kirchoff law). With these two assumptions the normalised greenhouse factor is and will remain equal to  1/3. The Earth’s temperature remains fixed unless the input energy changes through volcanic or human induced aerosols,  or through changes in the Earth’s orbit. The temperature  is however independent of any anthropogenic CO2 increases.

Global Circulation models assume that  rises in CO2 concentration lead to an enhanced greenhouse effect with rising temperatures causing yet more evaporation of H2O leading to an enhanced warming . This is the positive feedback which leads IPCC to give scary predictions of 3-7 degrees rise in global temperatures in the next 50 years or so. The effect of CO2 increase on the greenhouse effect alone would lead to less than a 1 degree rise.

The Saturated Greenhouse theory says that exactly the opposite happens. The Earth has an infinite amount of greenhouse gas available to it in the form of water, but the average relative humidity today at the surface is 78% and just 37% at 9000 m. So why isn’t it 100% ? The reason Miskloczi argues is that energy balance between the surface and the atmosphere (Kirchoff: ED = AA ) plus a requirement that the kinetic energy of the atmosphere = 2* the potential gravitational energy (Virial theorum: EU = 2SU) causes a saturated greenhouse effect therefore limiting the Earth’s temperature to its current level. The normalised greenhouse effect = 1/3 and will always remain so and the Earth’s temperature remains constant unless the external energy parameters change (solar). Therefore to compensate for any  rises in CO2 levels the Earth will adjust the relative humidity to maintain the same thermal equilibrium.

The super El Nino effect in 1998 led to a rise in global temperatures. If it were the case that a temperature rise causes more water vapor through evaporation, causing yet more temperature rise, then one would expect temperatures to continue to rise after 1998, and result in a run-away effect. But the opposite happened, because temperatures fell as the greenhouse equilibrium mechanism restored the balance. The extra greenhouse gases rained out to restore the equilibrium. Miskolczi is arguing that exactly the same effect is happening now as has happened in the past with any sudden  perturbation in  CO2 levels. Energy balance of the Earth/Atmosphere  will cause water vapour content to increase or decrease in order to maintain an equilibrium situation with a saturated greenhouse effect g=1/3. In order to offset a potential  doubling of atmospheric CO2 levels caused by human activity the relative humidity would reduce by 3%. Miskolczi claims that existing data show that already a global reduction of 1% in relative humidity has occurred over the last 100 years. Data from NOAA Earth System Research Laboratory for the upper atmosphere  show that relative humidity has indeed been falling.

This theory depends on the two assumptions of local thermodynamic equilibrium (Kirchoff) and the applicability of the Virial theorem to the radiation fluxes from the surface and the top of the atmosphere. Mainstream IPCC scientists have all attacked this but direct measurements do really seem to support these assumptions. The pressure distribution of the atmosphere is a function of gravity and temperature P(h)=Po*exp(-mgh/kT). The effective black body radiation emitted by the atmosphere to space by greenhouse gases is a kind of measure of it’s “greenhouse” temperature and hence its kinetic energy, whereas the radiation emitted from the surface is related to the Po the pressure at height zero and hence the gravitational potential energy. I certainly will need to think harder about this one to be  convinced, but the theory is very attractive and if true would completely overturn mainstream climate change predictions.

References:

Ferenc M. Miskolczi, “Greenhouse Effect in Semi-Transparent Planetary Atmospheres“, Quarterly Journal of the Hungarian Meteorological Journal, Vol. 111, No. 1, January - March 2007.

Explanation by Miklos Zagoni

Model discusion

The saturated greenhouse effect

If our eyes were sensitive to the IR radiation in the main CO2 absorption bands then we would just see fog. The atmosphere is opaque to CO2 at well below pre-industrial levels with an absorption length of about 10 meters. This would be a very thick fog.  By adding more CO2 to the atmosphere man is just reducing a little that aborption length.

The CO2 greenhouse effect is caused by the reduction in IR radiation escaping into space from the higher atmosphere of the earth. As we add CO2 so the height where the fog disperses and radiation escapes increases.  The temperature is lower at these heights reducing the effective energy escaping by a small amount (Blackbody radiation proportional to T**4). The energy balance of solar input radiation to the Earth and heat loss to space by the Earth must remain in balance. Therefore the Earth warms slightly to emit a little more total IR radiation across the spectrum to compensate the small extra energy trapped by extra CO2. However the energy increase is only logarithmic because the absorption is already opaque.

All these effects based on accurate cross-sections have been included in a model of the atmosphere by the US navy. The model is called MODTRAN and has been validated by direct satellite measurements. It is very informative since one can simulate what effect CO2 has on energy output for different regions and by inference how the Earth’s temperature reacts. The atmosphere’s simulated are for different regions with different profiles of water vapour and clouds. Changing the water vapour factor actually has a much larger effect than changing the CO2 concentrations. Current concentrations of CO2 are 375 ppm.

One can also calculate the temperature rise caused by doubling current levels of CO2 from 375 ppm to 750 ppm. We do this by adjusting the Earth’s temperature as input to MODTRAN to give the same net radiated IR energy in watts/sqm as we had at 375 ppm. This is because we always need to balance the incoming solar energy against outgoing IR energy form the Earth at a given temperature and the solar energy doesn’t change. The temperature rise varies slightly from the Tropics to the Arctic and on whether we include clouds or not. However the temperature rise that results varies from about 0.7 to 0.8 degrees C. This is nothing like the predictions of the IPCC which talk of 2.5 to 7 degrees heating but more about that later.

Similarly we can use MODTRAN also to estimate the total greenhouse effect of CO2 on planet Earth. i.e. how cold would it get if there were no CO2 at all in the Earth’s atmosphere ! The results are surprisingly little change in my opinion. The temperature would fall between 5 and 7.5 degrees C i.e. about the same change seen between the  Ice ages and inter-glacial warm periods. How can that be ? The main answer is that the most important greenhouse gas is water vapour and the temperature regulation of the Earth depends far more on small  changes in water vapour than on big changes in CO2.

Why does the IPCC predict much higher temperature changes than 1 degree for a doubling of CO2 ? This is because they are assuming  positive feedbacks exist which they include in their  climate models. So for example :

• A rise in temperature causes more evaporation from oceans leading to further warming by increasing concentrations of water vapour.  In fact MODTRAN demonstrates that increasing water vapour by just 10% leads to as much warming as doubling CO2 !  Of course the opposite is also true.
• A warming Earth leads to melting of the ice caps leading to a decreasing Albedo (solar energy reflection) leading to more absorbed energy leading to a warmer Earth surface.
• A rise in temperature of the ocean leads to a drop in  CO2 take up because less can be dissolved as temperature rises. However an opposite effect to this for increasing CO2 is that the biosphere will absorb more CO2 as plants and plankton grow faster. This feedback of the carbon cycle with temperature is called gamma (ppmv increase in CO2 per degree C) and is usually assumed to be a positive feedback. It can be adjusted to give big increases in temperature. If we define gamma to be the increase in CO2 (ppm.v) for each degree rise in temperature then plugging large values into climate models lead to much higher temperature rises.

I have been struggling to understand exactly how increasing CO2 levels leads to global warming using  basic physics, and the story is complex. The trapping of certain bands of infrared radiation emitted from the Earth by greenhouse gases is well known. The effective cross-section of CO2 of absorption for CO2 in its rotational bands is also well known (HITRAN). Using the current concentration of CO2 in the atmosphere it is also clear that essentially all the radiation emitted by the surface in these bands is already absorbed by CO2 at pre-industrial levels. In fact spectra from space show that the main CO2 bands are saturated in the lower atmosphere with minimal emission from the high atmosphere. The absorption of radiation follows a logarithmic law with distance assuming a uniform concentration of CO2 in air. All that happens if you double the concentration of CO2 in air is that the absorption length is halved. So more radiant energy is absorbed and reflected back to earth at  lower levels of the atmosphere than before. However the total energy balance would appear at first sight to be almost unchanged. In fact just such an experiment was performed by Herr. Koch and led Angstrom to  dismiss theories of man induced warming already back in the early 20th century (Realclimate: what Angstrom didn’t know).

There are 3 main CO2 bands of IR absorption at wavelengths 1388, 667, 2349 cm-1 (HITRAN) and these are already saturated at current levels of CO2 in the atmosphere. Infra Red measurements from space show that the atmosphere is  opaque at these wavelengths. However at high levels in the atmosphere this is not no longer true and this is the only argument for the enhanced greenhouse warming by CO2 warming which makes sense to me (see below).

Spectra of solar radiation and outgoing Infrared radiation. Note CO2 absorption bands ref: Barry & Chorley.

There is a very interesting paper here : http://brneurosci.org/co2.html which describes the basic physics. The absorption length for the existing concentration of CO2 is around 25 meters i.e. the distance to reduce the intensity by 1/e. All agree that  direct IR radiation in the main CO2 bands is absorbed well below 1 km above the earth. Increasing levels of CO2 merely cause the absorption length to move closer to the surface. Doubling the amount of CO2 does not double the amount of global warming. Any increase could be at most logarithmic, and  this is also generally agreed by all sides.

Lab experiments using tubes filled with CO2 to represent the atmosphere show that the IR transmission is essentially saturated and doubling the amount changes the transmission very slightly . So what is wrong and how are these arguments refuted by the majority of climate scientists? There are two main arguments  why global warming is important despite apparent saturation when man adds CO2 to the atmosphere (see  Realclimate ). The first of these is rather convincing.

1. IR scatters repeatably upward through layers of the atmosphere until at between 5-9 km  the air is so thin that the the atmosphere becomes transparent allowing CO2 emissions here to radiate out into space. At these levels there is little water vapour and CO2 dominates the energy loss. As CO2 concentrations increase so this level shifts to  higher levels in the atmosphere since a critical density must be reached for the radiation to escape.  These levels are colder (until we reach the troposphere) and IR loss is proportional to T**4 (Stefan Boltzman’s law). This means that slightly LESS energy is radiated to space than before and since the total energy must balance, the Earth warms up to radiate more heat to compensate. Don’t forget that there are windows in the IR spectrum with no absorption other water vapour allows easy extra energy loss through evaporation and IR emission. The temperature profile of the atmosphere is called the (adiabatic) lapse rate and is approximately -7 degrees per km falling to -4 degrees per km in the tropics. This is valid up to the Tropopause after which temperature rises again in the stratosphere. So greenhouse warming depends on falling temperature with height, and the anthropic enhanced greenhouse effect due to CO2 emissions is equal to the reduction of IR emissions to space in CO2 bands from the upper troposphere.

2. It is not completely true that the CO2 absorption bands are saturated as the fine structure is quite complex and in the side bands there is still energy left for the atmosphere to absorb. This is a much smaller effect than the first point. The extra absorption caused by an increase of a factor 4 is just a few percent as shown in the figure. In fact already 95% of the radiant energy is absorbed by CO2 at pre-industrial levels leaving a maximum of just 5% for any increase you like. It is often estimated  that the CO2 green house warming component of  the planet is about  3 degrees C so this extra absorption and emission to the surface  would appear to only add just 0.15 degrees of warming.

Saturation now and @ 4*CO2 levels (note LOG scale)

Therefore the main physics arguement supporting enhanced global warming caused by increasing levels of CO2 is the in height and thereby lower temperature of the effective radiating level of the atmosphere to space. The first comment to make is that we never  hear this crucial explanation in  the popular descriptions of the greenhouse effect. We just hear that more CO2 absorbs more heat radiated from the earth and radiates it back to the surface thereby heating us up just  like a thicker blanket does in bed (blankets actually work by cutting down convection losses). However the real explanation above concerns just the outermost layers of the atmosphere. The enhanced greenhouse effect depends on  a decreasing temperature gradient with height so that as the effective radiating level for IR  by CO2 rises so the energy loss falls and the earth must rise in temperature to compensate. Energy balance demands that there is a perfect match between incoming solar energy and outgoing IR energy. So lets look at this in more detail.

The effective temperature for all IR emissions is around -20 degrees C radiating at a height h of 5km. Now suppose that we double CO2 concentrations and the effective last radiating level rises to say 6 km. The temperature would now be about -27 degrees C as the decrease is almost linear in the troposphere. However the effective surface area is now also greater by an amount 8*PI*R (where R is radius of the Earth = 6350) making 1.6*10**5 sq km larger than at 5 km height.  The IR radiation falls off with temperature as T**4 which gives us a reduction of about 18% relative to before.

However if we just look at the main CO2 emission band and use the measurements from space (taken from Houghton’s book Global Warming - A complete Briefing). It would appear that the effective temperature of CO2 band alone  is -53 degrees C which is almost at the tropopause ( -60 degrees). So with all else remaining the same (water vapour, methane etc.) the drop in energy loss is just 3% in that single band.

CO2 causes the  lower atmosphere to be opaque at the main absorption bands. The mean free path is only  about 25 meters, so at these wavelengths the lower atmosphere is already like a thick fog where IR radiation is scattered in all directions. As we rise up in the atmosphere so the density falls exponentially and only at heights of 8-9 kms  does the atmosphere then become transparent in the main CO2 bands allowing energy loss direct to space. Doubling concentration rises that level nearer to the tropopause  which radiates at a lower temperature. The estimate given for the Earth’s warmng in Houghton’s book is 1.2 degrees for each doubling - so 2.4 degrees would be the heating if  CO2 concentrations were to increase by a factor 4. These figures are based on a radiation reduction of 4 watts/meter**2 caused by this effect of the effective radiation level rising to a colder level. In his book Prof. Houghton says this can easily be proved, but I have not  understood where this figure comes from nor how it has been calculated.

Feedback Effects

The IPCC predictions of future warming are based on model assumptions of positive feedback effects which are supposed to result from the initial warming caused by CO2 emissions. The main feedback effect is that of increased evaporation of the oceans leading to an increased greenhouse effect of water vapour (already 80 - 90% of greenhouse effect). However it is known that cloud cover in general leads to a net cooling effect on the Earth by blocking incident solar radiation. An increase in cloud cover of 10% would be enough to cancel out global warming effcets of increased CO2 ( Barry & Chorley).

Radiative Forcing Update: I have now found this reference to the equations used to derive the 4 watts/sq m radiative forcing by doubling the amount of CO2 in the atmosphere.

rf = f * ln([CO2]/[CO2]prein)/ln(2)    in watts/m ** 2

It would appear that in order to derive the factor f the IPCC assume that all of the 0.6 degrees warming apparently seen since the industrial revoluton is due to CO2 and thereby derive the constant

AF = 5.35 ln(C/Co)

Then we get simply  5.35*ln(2)  = 3.7 watts/sq m for the radiative forcing of  doubling CO2 !

If it is really true that this formula has been derived only by assuming that all “observed” temperature rise since 1750 is caused only by CO2 increases, then I fear this is a circular argument !  Many skeptics argue that the recent rises in temperature is dominated by a natural recovery from the little Ice Age. In order to be convinced that CO2 is the primary cause of recent warming then I would prefer  that this  formula could be derived from basic physical arguments  rather than introducing a fudge factor preset to prove a theory.

One thing that will not be addressed in Copenhagen is the damage done by an  ever growing human population on the natural balance of the Earth. This is  the real elephant in the room which eventually we must have to face up to. Even if we eliminate completely CO2 emissions from energy production by developed countries we humans will continue to degrade the earth while our numbers increase.

These are the back of the envelope calculations of Mankind’s emissions of CO2 resulting just from there being 7-9 billion of us on the planet whether we burn fossil fuels or not.

1. Breathing : People on average breath in about 7 litres a minute of air. The air we breath out contains 4% CO2. In affect we are burning food(carbon) in oxygen to provide the energy to keep warm and  active. Each one of us therefore emits about 0.3 liters of CO2 a minute weighing 0.6 gm, or 0.3 tons of CO2 per year. The current population is 7 billion and UN  forecasts a population  of 9-10 billion by 2100. Lets take a nice round figure of 10**10 people as the maximum human population. This gives:

Yearly CO2 emissions through breathing :  3 Gigatons/year

2. Domesticated Cattle breathing: Cattle are a key source of sustainance to many people throughout Africa and the rest of the world. The world populaion of domesticated cows is about 2 billion. Each cow produces about 1.5 tons of CO2 just by breathing. Methane emissions from cows humans and agricuture are completely ignored here

Yearly CO2 emissions through of domesticated cows : 3 Gigatons/year

3. Agriculture, Deforestation through burning and land clearance. As ever increasing numbers of people demand food  more from the available arable land so the pressures on natural envirnments and especialy forests increase. Forests are a key sink of the carbon cycles.

Figures resulting from deforestation from FAO : 2-4 Gigatons CO2/year

4. Finally the emissions of CO2 from Burning of Fossil fuels by developed and developing nations - Industrialisation. The agreements hoped to be reached  in  Copenhagen focus entirely on man-made (western industrial) induced emissions of CO2 high energy production. The current global figures for all CO2 emissions caused by the burning of fossil fuels  in 2008 is:

Yearly emissions fossil fuels: 5 Gtons CO2/year.

There are important measures that can be agreed in Copenhagen to reduce emissions of CO2 by industrialised countries. Yet these can only delay catastrophy while population levels increase beyond sustainable levels.

I recently heard a comment on BBC Radio 4 which compared the powerful Climate Change movement  to an inverted pyramid, because the arguments are based on just a few basic scientific measurements. The recent controversy regarding the leaked emails between the two main groups that provide global temperature data to the IPCC highlights how sensitive these core results really are. The two main people involved are Prof. Phil Jones who leads  the Climate Research Unit at the University of East Anglia and Michael Mann who is Professor at Penn State University and published the hockey stick data based on merging tree ring derived temperatures over thousands of years to CRU’s gobal data. This featured strongly in the IPCC 2001 reports and Al Gore’s film. The other famous Hockey stick shows a rise in CO2 levels since the industrial revolution following apparently steady levels over thousands of years derived from Ice cores. Taken together these two hockey stick graphs purport to show that there is overwhelming evidence that human emissions of CO2 are driving up global temperatures.

The scientific evidence for human induced climate changed is based on 3 main pillars:

1. Global temperatures are rising since the industrial revolution and particulary in recent decades. It is assumed this rise is due to increases in man made greenhouse gases particularly CO2

2. CO2 measurements at Maona Loa and elsewhere clearly show that CO2 concetrations are increasing caused by fossil fuel emmissions. CO2 is the most important anthropgenic greenhouse gas and drives the climate.

3. Global Circulation models predict a rise in temperaturs of between 1-6 degrees by the end of this century. These models have many unknown parameters. The predictions depend on these  parameters being  fined tuned to agree with the above temperature trends.

So lets look at these one by one.

1. Is it really beyond doubt that global temperatures have risen in recent decades? Mann’s graph would appear to make this clear. However his analysis is  based just on only one long term source for historic temperatures namely tree ring data. It ignores other historical measurements or derived data including estimates of falls during  the little Ice Age, rises during the the Warm Roman period. The flat tree ring data  are merged with the CRU/Hadley with the  (now challenged) global tempretature data for the last 20 years.

The hockey stick relies on the tree data to give the impression of a long flat and stable climate. Many reputable scientists think however that the climate was not that stable over the last thousand years. In particular the little Ice Age and the medieval warm periods with reports of Romans growing wine in York etc. Michael Manns hockey stick graph succeeds in eliminating both these periods. Did they really exist or  have they been deliberately suppressed in order to have a bigger political impact ? Tempretaure measurements using isotope concentrations in Ice cores in Greenland show detail of temperatures back to the last Ice age and support the historic evidence of medieval warm period and the little Ice Age.

The second graph above shows satellite global average temperatures of the earth’s near surface based on thermal microwave emission of oxygen. Note that the excessive rise recently is not apparent, but fine details like  the cooling during Mount Pinatoubo erruptions show up nicely.  This graph does not support the accentuated  hockey stick effect.

2. CO2 emissions. Data from Maona Loa and elsewhere show that CO2 concentrations have been rising since the 1950s. They are currently around 380 ppm having risen steadily from 316 ppm in 1959.  This is actually still a tiny number as it represents just 38 molecules of CO2 in every 100,000 molecules of air. On average there are 100 times more H2O molecules in air than CO2. Since both molecules vibrate to absorb infrared in a similar way you can see that it is actually water vapour which dominates the greenhouse affect on earth.  This is obvious to anyone who has spent the night in the desert where the air is so dry that heat loss can cool the air to freezing point over night. CO2 does not do much good for you in the desert in keeping you warm.

CO2 dissolves in water. The oceans contain large amounts of dissolved CO2 and more CO2 dissolves the colder it gets. Likewise the Oceans emit CO2 as they warm up thus increasing the concentration in the air. The effect is known to all of us. If you take a fizzy drink and leave it in the sunshine then it loses its fix fast, whereas put it in the fridge and it remains fizzy overnight as the water losses CO2 much slower.Al Gore seems not to know this fact because in his film he made the exagerated claim that a correlation of CO2 levels with previous Ice Ages proved that CO2 concentrations drive the Earth’s temperature. It is of course exactly the opposite way round. Ice ages are caused by astronomical effects related to slow changes in the Earth’s orbit and direction of spin. As the Ocean cools so it dissolves more CO2 out of the atmosphere and levels fall. In fact there is a clear time delay between the two signals of 1-2  thousand years.

Solubility of CO₂ at a partial pressure for CO₂ of 1 bar abs.

A 5 degree rise in ocean temperatures would seem to imply about a 15% decrease in CO2 concentration in the Ocean, causing a significant increase in the atmosphere.

Effect or Cause ?

Early CO2 measurement data

It turns out that there were also regular CO2 measurements made before 1960 which have been dismissed as inaccurate and ignored (see above). So what are we to make of all this? Maybe the old CO2 measurement data were biased by local polution at the time. Maybe the temperature data are themselves  biased by their proximity to urbanisation. My strong feeling is  that the case for CO2 to be a primary driving force for climate change has not yet been made. Water Vapour and clouds are between one and two orders of magnitude more important. Several estimates place water vapour as being 95% of the greenhouse effect on Earth with CO2 providing about 3%. Human additions to CO2 concentrations on this scale are < 1%  of greenhouse gas effects. This does not mean to say that it is not important to curb emissions,  but the doomsday scaremongering on climate which sometimes seems more politically motivated than justified is miss directed. The best way to curb CO2 emissions is anyway to expand dramatically Nuclear Power rather than industrialise yet more of the countryside for very little return.

3. Climate Models. These predict future climate based on complex theoretical interpretaion of how earth systems work. they attempt to model, solar heating, radiation balance, atmosphere/Ocean interactions, Ice dynamincs, Cloud dynamics, Carbon cycle, solar variation, albedo changes, phytoplancton feedback etc. The variables are endless with many unknowns. Only by fitting to past climates is it hoped that some of these parameters be pinned down to give reliable future predictions of climate. Currently models that correctly follow the observed past temperature profiles of recent years need to include CO2 effects to some degree. This would appear to support that CO2 has begun to effect temperatures. However if there are natural variations at play which are causing warming such as a continuing recovery from the little ice age, these effects are of course not included in the models.

The Earth’s climate is such a complex system that I doubt whether anyone can be 100% certain one way or the other. Human damage to the Earth’s environment is self evident and we don’t need the one issue of climate change to dominate all others for political reasons. One thing is for certain is that the next 10 years of  data will decide  one way or the other. I think a far greater threat to the Earth and to the natural environment is human over-population with the consequent destruction of the natural environment. James Lovelock estimates that the  world population which the Earth can sustain long term is about 1 billion people. On the same timescale as the IPCC predictions of a 1-6 degree rise in global temperatures the world population will rise to 9 billion.  So I would like to see a IPPC - Intergovernmental Panel on Population Control, although I doubt whether this will ever happen.

The current emissions of CO2 from burning fossil fuels is about 5 Giga tons per year.  A back of the envelope calculation estimates that  9 billion people will emit 3 Giga Tons of CO2 a year just by breathing ! Is it not time for a reality check ?

references:

1. http://www.drroyspencer.com/latest-global-temperatures/

2. http://en.wikipedia.org/wiki/Hockey_stick_controversy

We all know the theory. The average temperature of the Earth would  only be about 6 degrees C. if it had no atmosphere. This temperature can be derived from Stefan Boltzman’s law assuming that the Earth is a perfect Black Body in thermal equilibrium with the Sun’s radiant energy. Luckily greenhouse gases in the Earth’s atmosphere actually keep the Earth’s temperature at a more comfortable ~ 15 degrees C. Human activity has led to an increase of about 25% in CO2 concentration in the Earth’s atmosphere  and this is now predicted to increase average temperaturesby a couple of degrees over the next century. Glaciers will melt, sea levels will rise, people will migrate, our way of life is to blame - we must repent etc.  So if all this is now accepted as factual evidence, then how come the desert is so cold at night ?

Temperatures in the Sahara and other deserts can reach 45 degrees during the day but then magically fall to below freezing at night. Now the CO2 concentration in the air is exactly the same over the Sahara as it is anywhere else e.g. in Hawaii where long term  measurements are made. How does this magic work? - surely human additions to CO2 that we are so alarmed about must also cause greenhouse warming in deserts.  The greenhouse effect acts like a blanket helping  block infra red radiation losses to space and thereby keeps the Earth warm. So what is going wrong and why is it that the greenhouse effect simply  doesn’t seem to work at all deserts ?  The answer to this question is not only interesting  scientifically but because it exposes a flaw in the selective use of data to overstate the climate change issue for political reasons.

The desert temperature falls dramatically at night simply  because the air is dry. There is little water vapour in the air and it is water vapour which dominates all other greenhouse gasses thereby contributing  about  75% of the greenhouse effect on planet Earth, while CO2 causes only  10% of the warming. The  main reason for this discrepancy is that there is a tiny amount of CO2 in the atmosphere compared with the amount of water vapour.  This is not about clouds which are another story - it is just about the number of H2O molecules in clear air  compared to the number of CO2 molecules. The amount of water vapour in the air varies dramatically from the tropics to arctic and desert regions but on average it is about 1-4 % at the surface. CO2 is just 0.038% so at the surface there are about 100 water molecules for every CO2 molecules and averaged over the entire atmosphere there are at least 10 times more water molecules. Without water vapour  the greenhouse effect would be at least one order of magnitude smaller, and the direct evidence for this are those very cold nights with sub zero tempreatures in the desert where the air is dry.

Water vapour is often taken out of the equation  because it is a supposed feedback greenhouse gas. The air can hold more water vapour the warmer it gets so the argument goes that CO2 is the real driver for warming so that as the atmosphere warms it holds more water vapour thereby warming even more - a positive feedback. As air rises so it cools and given sufficient concentration water vapour condenses out as clouds at a certain height once it reaches the dew point. Clouds then can  have two separate effects : 1) They reflect incoming sunlight back to space thereby cooling the land and 2) They reflect infra-red back to the earth thereby warming. During the day the former usually wins which is why it feels cold when the cloud blocks the sun and at night the second effect dominates keeping the land warmer than it otherwise would be. So it is not clear whether clouds warm or cool the Earth or whether they produce a negative or positive feedback. Imagine a world completely covered in white clouds. Would the temperature at the surface be higher or lower than today. My gut feeling is that it would be cooler as more of the sun’s energy would be reflected back to space.

Earth recovering from Little Ice Age versus IPCC predictions

Global measurements show that 2008 was 0.2 degrees colder than the hottest year so far recorded, which was in  1998 -  the red dot pointed to by the green arrow in the above graph is the measured 2008 global temperature. This value follows a trend of several cooler years this milenium. As a result of this recent data the IPCC predictions of temperature rise due to increasing CO2 are beginning to look a little in disagreement. My thanks to Prof. Hukui for bringng my attention to the work of Prof. Akasofu at the University of Alaska who argues that most of the observed rise since 1800 is actually due to the earth recovering from the little Ice Age in  the middle ages superimposed with a  natural multi-decadel variation. Selective global temperature plots used by the climate change scientists  data usually argue that the significant rise of temperature since industrialisation is direct evidence that  increases in CO2 emissions are the cause. While CO2 has a proven greenhouse gas effect the modellers still have large uncertainties as to its global quantititative effect and actually tune the parameters in the models assuming that all the observed temperature rises are due to  CO2 alone. They ignore the possibility that other natural effects may be at work. This then leads to future large temperature rise predictions of 2-3 degrees by the end of this century.

Akasufo’s paper can be downloaded here . He brings together a large range of independent data as evidence that the world has anyway been slowly warming since around 1800 after the end of the little Ice Age which lasted from around 1500 until 1800. In medieval times from the Roman era to around 1200 a much warmer climate existed on earth. Circumstantial evidence for this is well known e.g.  wine was grown in northern England during the Roman period, while the Thames used to  freeze over  during the middle ages.  Superimposed on these longer term trends are, he proposes, a multi-decadal oscillation, which although not explained here has been previously associated with things like sun spot activity. If these ideas are right then the next 5-10 years will continue to see cooler temperatures  by which time the IPCC predictions will then be looking in serious trouble.

Humans are having a huge effect on the planet mainly because there are too many of us. We have already transformed much of the arable land coverage to feed ourselves. However the idea that one single issue - burning fossil fuels and the associated  increase in  CO2  dominates all others has always seemed to me a little simplistic. Good science will always prevail, so if CO2 emissions really is the dominant  driver for global warming then predictions must be validated experimentally. Interestingly it just maybe that the evidence is starting to hint at something else. The next 10 years should decide.