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Ought to Know




Everything has a history. The history of this primer began in 2009 - with a book. Vijay Pratap, who was standing some distance away from me, had a book in his hand, so that I could just about see its title. What I saw looked interesting, so I asked who the author was and, hearing a familiar name also asked if I could look at the book.

Engrossed in that task, I mumbled an unconsidered “Yes” when Vijay enquired, a minute or two later, whether the book was worth a review. That was my first mistake: how could I say “No” to the request to consider reviewing it that followed, without also feeling foolish!

Some months later, the job done, I showed the review to Vijay, who praised it. I accepted the praise, making, as I soon realized, my second mistake, when Vijay suggested expanding the review into a full blown article on the subject of Global Warming.

Here, in the form of a primer, is that article. Writing it has been much harder than reviewing it was. I only hope it isn’t full of mistakes!

I thank Vijay for having confidence in me. I thank members of the staff of Saded (South Asian Dialogues on Ecological Democracy) for their unstinting help. Finally, I thank Larry Lohmann for writing a fine book, with the engagingly clear title of “Carbon Trading: a critical conversation on climate change, privatization and power".

Meher Engineer

Independent Scientist and Coordinator, Ecological Democracy Project, South Asia Dialogues on Ecological Democracy, New Delhi

A Primer on Global Warming

Primer writers invariably face two questions: “Who am I writing for?” and “What do they know about the subject?”

The first question is easily answered: all primers are meant for ordinary people. The second, despite the fact that ordinary people know what Global Warming (GW) is, isn‘t. For, the answer raises further questions, like:

Do ordinary people think GW is real?

If they do, how big do they think it is?

Do they think it is man made?


The answers to these aren’t just harder to get: they raise further questions that are even harder to answer.

What, for example, should an ordinary person do with the knowledge that she gains by reading a primer on Global Warming?

Use it to alert people in her community to the problem? Join an activist group engaged in solving the problem - a global group like 350.org if she is Internet connected or a local group if she isn’t? Or leave finding a solution to the “brightest and the best”? 

Sound, readymade answers to such questions are just not available.  

 I had to keep these kinds of facts before me as firmly as possible while writing this primer. The aim and the hope behind the effort said that there was no other choice. I aimed to convince ordinary people that GW is an issue worth worrying about, something that ought to concern any functioning human being and, where conviction and concern were aroused, hoped that active and creative responses to the many threats of GW would follow.


A. What it is and why it should worry us?

The argument begins with three easy points that complement the three ways - scientific, political and Grand Narrative - of looking at GW.

Point 1

The temperature at the place you live has changed by one, or even several degrees Celsius over a single day. Do you worry?

No, and rightly so! The change is normal and easily explained. It’s raining, the sky turned cloudy, hot (or cold) wind started to blow: a legion of comforting ways explains the weather’s fickleness.

Brought up on an unvarying diet of such explanations, most people find Climate Change a hard to understand idea. Why climates are predictable, when predicting tomorrow’s weather is so hard? The winds and clouds and, for those living by the seashore the ocean currents are universally recognized as the immediate causes of the weather’s fickleness. But the forces behind those causes - the Sun’s brightness and the Earth’s daily rotation about its axis - are organized and predictable. How do predictable forces lead to unpredictable weather?

The answers lie in the fluid natures of the atmosphere and the ocean: it makes their motions organized but chaotic. The chaotic part makes the daily weather unpredictable; the organized part makes predicting a climate possible.

Point 2

The average temperature of the air at the Earth’s surface has been increasing over the last 100 years. It is now one degree Celsius more than it was then. Should we worry?

The question differs from the earlier one. The word “average” says that it is about a climate, meaning the weather, averaged over time - “usually about 30 years”; the word “planet” tells us that the climate is that of the whole Earth. Alerted by those two words, and by the one degree temperature rise, we have to wonder about the additional amounts of heat that must have entered the land, atmosphere and ocean over those years?

The amounts are mind bogglingly large; they demand that we drop any explanation that is anchored in the “fickle weather” paradigm. Climate scientists, who know that the average global temperature fell by 1 to 2 degrees Celsius when the Earth entered the Little Ice Age, sometime during 16th century AD, that is, very recently compared to the 4.5 billion years that have passed since the Earth was born, and know that ice sheets that were several miles thick covered large parts of the land in the Northern Hemisphere down to latitudes of 40 degrees, when the average global temperature fell by 5 degrees Celsius 20,000 years ago, know strong the demand is. They are likely to spend many sleepless nights just thinking about it.

Point 3

Havoc stands for widespread destruction. Men, when they make havoc, do so in two ways: deliberately or blindly. Warmongers, who aim to turn opponents into mortal enemies, are engaged in creating deliberate havoc. Their many successes underline how capable they have been. GW is a blind kind of havoc for two reasons because it happened as men worked at what they saw as “development”, and because its roots are to be found in the human inability to foresee consequences.

The lack of foresight is neither criminal nor surprising. Humans aren’t primed to do science the way that children, say, are primed to speak - which parent hires a speech teacher when his or her child is born? This simple explanation carries three positive messages: that GW had to be controversial; that blaming men for it is like blaming someone blind to his faults and expecting him to change; that hope remains, once men are convinced of the havoc that GW has caused, and the much greater havoc that it is likely to cause, fairly soon.

Can they be convinced? Yes! Climate science isn’t beyond common understanding. There is a lot of it, so patience is required. But super- intelligence is not required, as Jim Hansen, who wrote ‘Storms of My Grandchildren: The Truth about the Coming Climate Catastrophe and Our Last Chance to Save Humanity’, and whose name will appear frequently in what follows, told his granddaughter Sophie recently:

‘I remember in one of my first classes in physics at the University of Iowa, the professor said "definition of the problem is 90 percent of the solution."

He was right in the case of the big climate problem, and by the big problem I mean all the things that come with it, including the need for inexpensive energy for the world. Defining the problem is a tall order, not because the concepts are difficult - they are not – rather because there are many facets to the climate story and we must "connect the dots" all the way to public policy. If we stop the problem definition a step short of defining needed policies, the final step will be defined in Washington and other capitals around the world - by the people with the most money, their paid lobbyists and paid media.

That said, we can take a quick, first look at the science behind GW.

GW science isn’t hard

The following nine bullet points are a tiny part of that science. I chose them to show readers why the science behind GW isn’t hard.

The many materials that make up the Earth’s surface include the water in its oceans, lakes and rivers; the ice and snow in the Arctic Sea, the Ocean north of Antarctica when its winter there, and on the mountain glaciers; the snow that falls on land. Then there’s rock, desert, grassland, tropical forest, savannah and, finally, the soil that covers 50% of the Earth’s land surface.

Except for the snow and ice, they all get hot when sunlight hits them, just as a car’s metal body does. We can say that they are hot without touching them: the invisible energy that we call heat that they radiate lets us to do that.

Heat - its scientific name is infrared radiation - has an interesting history. The history began when someone saw the familiar, violet to red procession of colors that Sunlight breaks up into when sent through a glass prism, and asked, “Is that all that there is”? The question was answered when William Herschel saw the mercury in a thermometer that he placed beyond the spectrum’s red end rise: Infra-red energy was present in sunlight (‘infra’ is Latin for below, under, beneath, underneath, beyond)!

Besides being invisible, infra-red energy is exactly like light. It comes in infinite varieties; matter absorbs and emits it in energy packets that we call photons; lastly, and most importantly, the Green House Gases in the atmosphere absorb it;

· The Nitrogen (N2) and Oxygen (O2) that make up 99 % of the Earth’s atmosphere neither absorb sunlight nor absorb infra red radiation;

· Six gases that humans produce are listed in The Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC) as responsible for GW: Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), the Hydrofluorocarbons (HFCs), the Perfluorocarbons (PFCs) and Sulfur hexafluoride (SF6). The list was later updated, when Nitrogen Trifluoride (NF3) 4 was added to it. Let’s call the gases the Big 7.

·The Big 7 are colourless and odourless - they don’t foul the air the way garbage fouls water. They are also rare. The most potent global warmer amongst them, CO2, occupies as little as 0.04% of the atmospheric volume; the others occupy even smaller volumes;

· Carbon dioxide (CO2), Methane (CH4) and Ozone (O3) are the three most important GHGs;

·CO2 is a GHG, even though Carbon is a solid on Earth, and Oxygen (O2), which exists as a gas, isn’t a GHG;

·Big 7 molecule, when it enters the atmosphere, absorbs a tiny bit of the heat that the Earth’s surface radiates. Many such absorptions drive the Green House Effect (GHE). All of them require a photon of heat and a GHG molecule to meet. Such meetings happen rarely in the Earth’s atmosphere. A tiny fraction of them end with a photon being absorbed;

· Different GHG molecules rarely absorb the same kind of heat photon; when they do, they absorb it unequally strongly. Given those facts, a kilogram of CH4, for example, doesn’t produce the same temperature change as a kilogram of CO2, any more than your height measured on a scale marked in inches and centimeters register the same number.

How, then, do climate scientists account for the differences between various GHGs that is reduce their effects to a common scale, so that they can be added?

The answer is that they assign each one a Global Warming Potential (GWP): the term is defined in the First Assessment Report (FAR) of The Inter-governmental Panel on Climate Change (the IPCC), of the World Meteorological Organisation, as ‘an index which allows the climate effects of the emissions of Greenhouse gases to be compared’. The GWP values depend on the positions and strengths of the absorption bands of the various gases, how long they live in the atmosphere, their molecular weights and the times over which their climate effects are of concern’.

Thus, 1 kg of CH4 and 25 kg of CO2, put into the air today, will have the same effect on the air temperature over the next 100 years. Thus, the GWP of methane (CH4), over a 100 year period, is 25. But, for times shorter than 100 years, say 20 years, methane’s GWP increases to 72.

Why? Because CH4, unlike CO2, interacts chemically with other molecules in the air (most strongly with O2), so that the initial amount of it continually decays. Taken together, the two numbers, 25 and 72, give us some idea of how long it takes before a CH4 molecule decays in the atmosphere.

The GWP idea allows us to replace the various amounts of the GHG’s that human activity produces, in one year say, to an equivalent amount of CO2 that will produce the same total climatic effect. To get that number, we simply multiply the individual GHG amounts by their relevant Global Warming Potentials (GWP’s) and add; CO2’s GWP is 1, by definition;

· Turning to the water vapour, it influences the climate system in many ways:

i) Its molecules absorb infrared photons more strongly than any of the Big 7.

ii) There is much more of it in the atmosphere than there is of the Big 7 put together: its concentration at the Earth’s surface varies from a trace over desert regions to about 4% over the Ocean. Approximately 99.13% of it stays within 12 - 16 kilometers above the Earth’s surface, unlike all the other atmospheric gases that extend to much greater heights - as the motion of the air mixes them up.

iii) By condensing into liquid water and solid ice, it makes the clouds, rain and snow that are crucial in making the weather fickle.

Why, then, isn’t it in the Kyoto Protocol’s list?

The answer is simple: men don’t produce it.

More of it does evaporate when the concentration of a man made GHG like Carbon dioxide increases, so the Earth some more, so much more that the extra CO2 induced evaporation even doubles the heating that the bare CO2 increase produces (http://www.nasa.gov/topics/ earth/features/vapor_warming.html).

Climate scientists know both those things. They separate H20 from the other GHG’s because it exists on Earth as a liquid, or a vapor or a solid. Its role in fixing the Earth’s natural (not man made) Green House Effect, on which more below, is much greater than Carbon dioxide’s. Its abundance made the Earth suitable for life. But, for man made GW, CO2 calls the shots: it contributes less to the overall greenhouse effect than water vapor does; but, added to air, it also fixes how much more water vapor is produced; in short, its amount sets the rise in temperature.

Climate science can be interesting

Stand outside your home on a cold, cloudless winter’s day and you’ll learn that a shining sun doesn’t warm the air.

Don a black winter jacket and feel its surface. It gets warm as it absorbs the Sun’s visible and infra red radiation. Land and water, but not ice and snow, are like the jacket.

Water absorbs sunlight more than land. Its larger specific heat ensures that it heats up less than land.

The atmosphere is different. It transmits sunlight, except when low clouds are around.

Low clouds are usually thick and have lots of water vapor, so they - along with the free water vapour, ozone and aerosols (tiny particles in the atmosphere that get there either naturally or via human activities) in the air - directly absorb 23 percent of incoming solar energy (http://earthobservatory.nasa.gov/Features/EnergyBalance/page6.php).

Next, the water in the low clouds exists as tiny droplets; that makes those clouds potent reflectors of sunlight. High clouds are thin: they transmit sunlight, as anyone can see.

Man made aerosols can have spectacular impacts. The brownish haze that covers a large area of India just south of Mt. Everest is the best example of such an impact. Similar hazes exist over many industrial regions, and over those rural areas in the tropics and the subtropics where large amounts of biomass (dung, for example) are burnt. Winds that blow over large distances transform local hazes into regional aerosol layers. Well-known examples are the Arctic haze, the Indo-Asian haze, the East Asian dust and haze traveling across the Pacific, and the biomass burning and dust plumes from North Africa (Sahara and Sahel regions) that spread over most of the subtropical Atlantic. Unlike the long-lived Big7 that are distributed uniformly over the globe, aerosols last for a week or less, so their distribution is non-uniform and concentrated near their sources, that is, the places that burn coal or biomass.

The land and water at the Earth’s hot surface radiate energy. Humans, who can’t see that energy, feel it as heat. The invisible radiant heat makes its way to space: the Earth would get hotter and hotter if that didn’t happen;

Does the atmosphere transmit radiant heat passively? “No”. It is actually the major source of the Earth’s outgoing heat: data recorded by instruments mounted on satellites have revealed that it radiates, in the form of heat, as much as 59 % of the incoming solar energy to space. Where does it get the energy to do that?

More on that, later! For now, and I hope reader’s agree, the above list says that climate science can be interesting.

Is Climate science accurate?

What happens to sunlight as it enters the Earth? 29% of its energy is reflected back to space, directly; the remaining 71% is absorbed, partly in the atmosphere (23%) and partly at the Earth’s surface (48%); the materials at the surface absorb solar energy more than twice as fast as the gases in the atmosphere do, so they heat up more than the atmosphere does.

Is the 48 % to 23 % ratio between the surface and atmospheric absorptions maintained in the outgoing heat energy? The satellite based instruments that have been monitoring the outgoing heat energy since the late 1970’s say “No”. They report that 59% of the outgoing energy originates in the atmosphere; only 12% comes from the Earth’s surface!

The surface of the Earth’s absorbs incoming solar energy twice as fast as its atmosphere. But the atmosphere sends energy to space more than four times faster than the surface.

We shall see how that happens, after looking at Table 1.

The Table ranks the 4 major gases that contribute to the Natural Greenhouse Effect:

Gas                                           Contribution (%)

Water vapor                            36-72%

Carbon dioxide                       9 - 26 %

Methane                                  4-9%


Ozone                                      3-7%

Water vapour is present because we are speaking about the Natural Greenhouse Effect and not about man-made Global Warming. It contributes the most, by a huge margin. More than any other substance, it made Earthly life possible. Without it, the planet’s Global Mean Surface Temperature (GMST) would have been an impossible-for-living-things-to-bear minus 18 degrees Celsius; with it, the GMST rose, by 33 degrees, to the comfortable +15 degrees Celsius that we know. The increase was first computed over a 100 years ago by the Swedish scientist Svante Arrheinus.

Next, How, more exactly, does the Green House Effect happen?

The Earth’s surface

The Sun radiates energy, all by itself. No earthly substance, apart from the radioactive chemicals, e.g. Uranium Oxide, tiny amounts of which are present on its surface, does that. The land, water, snow and ice on the surface, and the gases in its atmosphere, radiate energy after absorbing some of the energy that comes their way. The absorbed energy makes then radiate heat, as coal in a fire that is warm but not glowing does.

Two things fix the rate at which hot bodies radiate:

  1. Their areas: double them and the rates double; and
  2. Their Absolute Temperatures that are got by adding 273 to degrees Celsius: double them and the rates go up sixteen times.

What the surfaces are like, whether they are solid or liquid, grassland or wetland or forest, ice or snow or water, etc., makes very little difference!

Some gases, ozone and water vapor being the most prominent, absorb Sunlight. The absorptions account for a small proportion of the heat that the atmosphere radiates.

Solar energy at the Earth

Power is energy per second. The power that the Sun sends out into space, which is not only enormous, but is also a tiny fraction of the far greater energy that the Sun produces in a second amounts to 360 trillion trillion Watts their temperatures in measured

The Earth has a radius of 6, 400 kilometers and is 150 million kilometers away from the Sun. Seen from the Sun as a tiny disc; it intercepts a tiny fraction of the power that the Sun sends out in all directions. The fraction is also enormous: it amounts to 0.17 million trillion Watts at the top of the Earth’s atmosphere (TOA power), an amount that is many thousands of times larger than the mere 13 trillion Watts that humanity consumes, today (see: Ray Pierrehumbert Phys Today?).


The need to tame those wild numbers, leads to power per square meter that enters the top of the Earth’s atmosphere (TOA). Modeling the top as to be a sphere concentric with the spherical Earth, the power per square meter depends on how the square meter is oriented (does it face the Sun’s rays, or is it inclined to them); larger, whatever the hemisphere, in summer than winter; and larger, when it is noon at the equator than when it is noon at either pole etc.

The North-South axis that the Earth spins on is not perpendicular to the direction of the Sun’s rays, so the sun’s rays strike its surface more directly at the equator than at the poles. The unequal amounts of power received at those three places raises the temperatures in the air above those places unequally. The global circulation of air that transports heat from the warmer, low-latitudes to the cooler poles is the main result of those inequalities.

The perpendicular-to-Sunlight TOA power is 1360 watts. The global average of the power, again at the TOA, is one quarter of that, i.e., around 340 watts (http://physics.info/power/).

The power arriving at the Earth’s surface is even smaller: average it over the entire globe and it amounts to 240 watts per square meter.

The difference between the TOA power and that absorbed at the surface arises because sunlight is:

i) Reflected - by land, water, snow, ice and the upper surfaces of low lying clouds, and,

ii) Scattered by the molecules of air;

Scattering and reflection send as much as % of the Sunlight back to space. The upper surfaces of low lying clouds are particularly strong reflectors; think of the top surfaces of thick monsoon clouds in India, for example, which are a brilliant white. Reflection also occurs at the land, water, snow and ice that make up the Earth’s surface. Scattering, on the other hand, occurs throughout the atmosphere. Air molecules scatter blue light much more strongly than red light, in all directions: that’s why the sky is blue. Regarding absorption, air’s major molecules - O2, O3, N2 and H20 – absorb negligibly small amounts of Sunlight.


How much Sunlight hits different parts of the Earth’s surface at the same time of day?

The amounts aren’t identical because the Earth’s surface is round: a patch at the equator gets more than a patch of the same area near a pole. Its easy to see why. Imagine facing a light source directly with your eyes open. Tilt your face backwards. Will the light seem as strong? No.


The Earth rotates about an internal axis that is tilted with respect to the direction of the Sun’s rays. It also revolves, in an elliptic orbit, around the Sun. The first motion gives us day and night; the second, the cycle of the seasons.


How hot does the surface get?

Knowing the rate at which energy arrives at different latitudes throughout the year, we can calculate the temperature of the Earth’s surface. The details, which are complicated, are routinely done by digital computers, nowadays. The basic ideas involved are, however, easily explained.

Imagine a planet that gets energy at the same rate everywhere on its surface, that the “Sun” is equally far from you wherever you are on the Earth’s surface or, in other words, a “Sun” that surround the Earth.

Imagine, next, an “Earth” whose surface is the same everywhere (all water, or all land). Finally, imagine an “atmosphere” that ignores the heat coming from the “Earth’s” surface i. e., one that is devoid of any GHG. What temperature will the surface of our imaginary planet reach?

The procedure for finding the answer is simple. You know the planet’s surface area, and the rate at which every square meter of its surface absorbs solar energy (the surface is uniform, so every bit of it gets energy at the same rate), so you know the total energy that the planet absorbs every second. Equate that energy to the rate at which it’s uniform surface radiates heat into space, using the “fourth power of the absolute temperature” law and the known surface area. The sought for temperature is the solution to that equation.

You might, alternatively, think of a glowing light bulb, whose filament gets energy from an electric current. The filament gets hot and begins to radiate, first heat and then light, as its temperature increases.

The process reaches a steady state when the rate at which the filament gets electrical energy and the rate at which it radiates heat and light are equal.

How the Green House Effect works

The simple explanations available for the greenhouse effect on the internet are often so wrong that reader’s end up confused about what GW is: are the GHG’s that men are obviously adding to the atmosphere behind it?

The correct explanation begins with three facts:

The Earth’s atmosphere and its surface both receive two kinds of radiant energy: heat and light.

The surface receives both heat and light from above; the atmosphere, being situated differently, receives Sunlight from above and heat from below.

The Big Six GHG’s are almost totally transparent to Sunlight, but are strong absorbers of radiant heat.


Put together, these facts lead to the Green House Effect. The effect says that any change in the GHG concentration raises the temperature at the Earth’s surface. How? John Tyndall, who discovered that water vapour and CO2 absorbed heat, described it by saying:

“As a dam built across a river causes a local deepening of the stream, so our atmosphere, thrown as a barrier across the terrestrial rays, produces a local heightening of the temperature at the Earth's surface".

He was partly correct. The “flowing river” captures the flow of radiant heat from the Earth’s surface to the atmosphere perfectly. But the “dam” thrown across it doesn’t model the interaction between heat radiation and the CO2 molecules in air as well because:

i) Dams stop a river’s flow all at one place, GHG molecules, because they are present at all heights above the Earth’s surface, stop the Earth’s heat from escaping into space at many places.

ii) A dam’s wall turns every bit of the water reaching it back, but doesn’t destroy any of it. A GHG molecule, wherever it is in the air, destroys the photons oh heat that it absorbs, but doesn’t absorb every photon that it meets!

Can we improve upon the “dam” analogy? Here’s how:

Recall two things about the atmosphere:

i) Its density decreases with altitude. Darjeeling and Siliguri are neighbors, but the air in Siliguri is denser than it is in Darjeeling. Two things make it denser: the fact that the atmospheric pressure decreases with altitude, and the dharma of a perfect gas, which says: “My temperature being fixed, a lower pressure on me will make my density will fall”.

ii) Its temperature decreases with altitude: Darjeeling is colder than Siliguri (the rate at which the atmosphere’s temperature decreases is, typically, 6.5° Celsius per kilometer).

Next, imagine slicing the atmosphere into layers, as you slice a cake, only do it horizontally. Keep each slice so thin and the air in it will have the same density.

What happens to the infrared radiation that the Earth’s hot surface emits? Focus on a particular slice, remembering that radiant heat consists of infinitely many kinds of photons. Each of the GHG’s in the slice will absorb some fraction of some of those photons. The fractions absorbed depend on the relative concentrations of the GHG’s. But, all of the concentrations are smaller than the corresponding concentrations in the slices that are below our slice, so the fractions absorbed will, all, be smaller than the corresponding fractions absorbed in the slices below our slice (the slice in contact with the Earth’s surface is an obvious exception to the rule, there being no air below it). Thus, a smaller number of the photons that the Earth’s surface emits will reach our slice than will reach any of the in between slices.

Finally, the Earth’s surface isn’t the only source of infra red photons. Each slice, once it absorbs photons and gets hot, becomes such a source that emits photons to the slices above and below it, and to the Earth’s surface.

It’s a grand tangle. But we’ve sorted it out, so we know the rates at which radiation enters and leaves any slice. Once they are known, the temperature in each slice can be calculated, when they are all in a state of energy balance. Each air slice, with one exception, gets heat from, and sends heat to, below it. The exceptional slice is located at the height from where heat escapes directly into space: it sends photons to the layers below it but doesn’t, by definition, receive photons from any of them.

Are we concerned here with where that height is? No! What we want to know is: “Does the exceptional slice move up or down when the GHG concentration is increased?” The answer is easy: the slice must be at the Earth’s surface when no GHG’s are present, so it must shift upwards when they are present! But: Upward is always colder place in the atmosphere, so the rate at which heat escapes from the Earth into space decreases whenever the GHG concentration increase.

That done, we are ready for the last step. The temperature at the surface of an Earth that radiates less heat when CO2 (in general, any GHG) is added must, if the rate at which solar energy entering it doesn’t change, increase compared to what it was in the “no GHG” case. Only then can the planet move back into a state at which it loses heat energy at the same rate at which it gets solar energy.


A capacity to absorb solar radiation and an ability to generate infra red radiation are, we have just learned, a big driver of the Earth’s climate. Both properties require experimental confirmation. Space based measurements of the Earth’s radiation budget are central to providing us with that confirmation.

Such measurements do, fortunately, exist. The road leading to them opened up in the mid-960’s, as artificial satellites began circling the planet. Two decades, and much hard work later, a coordinated network of satellites, the Earth Radiation Budget Experiment or ERBE, was launched, in 1984. ERBE has provided us with comprehensive measurements of the flows of three kinds of radiative energy – the incoming solar radiation and the outgoing part of it that comes from reflection within the Earth, and the Earth’s infra red radiation - all measured at the top of the atmosphere.

The evidence for and against Global Warming

Things to write about: Stratospheric cooling, the hockey stick, sea level rise, arctic ice melts, the tropospheric hotspot and Earth’s thermal inertia about which Hansen et. Al., 2005, Science, say “The primary symptom of Earth’s thermal inertia, in the presence of an increasing climate forcing, is an imbalance between the energy absorbed and emitted by the planet. This imbalance provides an invaluable measure of the net climate forcing acting on Earth. Improved ocean temperature measurements in the past decade, along with high precision satellite altimetry measurements of the ocean surface, permit an indirect but precise quantification of Earth‘s energy imbalance.”

More facts and questions

Carbon dioxide (CO2) and Methane (CH4) are the two most important GHG’s. CO2 is a GHG despite the fact that Carbon is a solid on Earth and Oxygen (O2), while it is a gas, isn’t a GHG.

One tonne (T) of CO2 contains a little more than 250 kgs of Carbon (1T = 1000 kilograms).

Currently, men send about 32 Gigatonnes of CO2 into the air every year, amounts that are much larger than the smaller amounts were emitted towards the end of the 19th century. Thus, the proportion of CO2 in the atmosphere was about 285 parts per million in 1880, the year that the Goddard Institute of Space Studies’ (GISS) global temperature record begins. By 1960, it had risen to 315 parts per million. Today it exceeds 390 parts per million and continues to rise (‘G’ stands for Giga, meaning a billion). (ME: add a bit on ‘About half + the oceans absorb..’97% of those 33 GT’s are produced when the three fossil fuels, petroleum, coal and natural gas (the Big 3) are burnt, for various reasons.

The Big 3 are fossil fuels. Nature produced them under the ground, millions of years ago. They don’t contain identical amounts of carbon, nor do they produce equal amounts of CO2 when equal amounts of them are burnt. Lignite and anthracite are coals; but 60% of lignite is carbon as against 80% of anthracite. (Source:http://www.eia.doe.gov/cneaf/coal/quarterly/co2_article/co2.html).

Cement manufacture accounts for the remaining 3% of the 33 GigaTonnes produced every year, worldwide. Cement is mostly a mixture of calcium silicates. Heat limestone plus other stuff to around 1,500 degrees Celsius and you will get it. The process is the third largest source of greenhouse gas pollution in the U.S.A, the U.S. Environmental Protection Agency says. 1 MT of

CO2 is emitted when 1 MT of cement is made. About half of the emitted CO2 originates from the fuel; the rest comes from the conversion of the raw material [7]. The steam locomotives used in 19th Century England to transport coal offer a telling comparison: they burned 1 MT of coal to transport 1 MT of coal, [8]! Moss Landing, [9], a power plant on the California coast, burns natural gas to run turbines that produce more than 1,000 megawatts of electric power. The 370- degree Celsius fumes that the plant emits contain at least 30,000 parts per million (ppm) of CO 2.

The current CO2 concentration in the atmosphere (392 ppm) is 100 times smaller!


Next Issue: Solving Global Warming