Global warming and rain.

One day when I was a boy in Hokitika (West Coast, South Island, New Zealand) it was raining when I went to school and it got worse, so I had to walk home through water lying everywhere. The water was up to my ankles everywhere, and deeper in lower lying areas. This did not come from the river, but merely from the rain falling, and in nine hours, from memory there was nine inches of rain (a little under 23 cm). This was regarded as exceptional rain then, a once in a hundred year flood.

Now we have global warming so what do we expect? You hear lots of talk about drought, and yes in some parts of the world there will be drought, but in others there will be more rain. The reason is, if the oceans get warmer more water should go into the air. By itself that may not matter too much if the air gets warmer as well, but problems arise if such warm air meets cooler air. This is the sort of thing that causes rain, but now there is more water in the air.

What happens next depends on exactly how the cause behaved. The obvious thing is the rain falls, but when the humidity collapses into rain drops, its going from the gas phase to liquid releases a lot of energy. If there is enough cold air, it might just heat it, especially if the cold came from mountains forcing the air upwards relatively slowly so that it cools and rains on one side of the mountains. That is what happens around Hokitika. Now the hot air blows a strong warm wind over the land to the east, the so-called föhn wind. If the energy cannot be dissipated that way, then stronger circular winds are generated. The tropical cyclones are examples. There was one recently in Madagascar recently that did extreme damage.

So, how will global warming affect these? The short answer is, there will be a variety of ways. Stronger cyclones, more frequent cyclones (because milder systems that get stronger enter the classification) but the more obvious one is more rain because more water has been evaporated. Which gets me back to Hokitika. They have just had a weather system pass over that lasted about a day and a half of continuous rain, and dumped 800 mm of rain in that period (about 31 ½ inches). That is as much as some places get in a year. A little way inland, in the same period they got 1,082 mm, and that is almost 43 inches.

There has been a variety of flooding around the place. A number of houses were inundated because the storm-water drains could not cope and one woman died. Apparently she was driving; she did not like the speed of the water flowing down the road, so she got out. If when driving you see rapidly flowing water of unknown depth ahead, stop and sit it out, or turn back to higher ground. Do not enter. If you are correct in your fear that a car cannot maintain its grip on the road, you walking would be in a worse position. The force of rapidly flowing water will sweep you off your feet, and if it is deep, you are lighter and therefore have less grip. Your grip depends on your weight.

Probably the most frustrating situation has been for tourists south of the Franz Josef glacier, where they are stranded. To the south, the road is apparently cut off around Haast, and to the north of the Fox Glacier, the Waiho bridge was washed out by a river carrying down quite large boulders. A little earlier there were sightseers walking on the bridge, but fortunately they all got off before the bridge went. To give some idea of the water, here are links to two videos of the bridge going: https://www.youtube.com/watch?v=ldCjVqfkKFk   and  https://www.youtube.com/watch?v=wPf49aaomYI The first one also gives a brief example of the New Zealand accent, and the vernacular. Note the bridge was a Bailey bridge and is in principle not expected to be permanent.

Once something like this happens, the blame game starts. One argument was that the river has a history of flooding and of eroding out the land and changing course, so why build a more permanent bridge? Another was the crossing is situated on a major fault and apparently the land is not good for foundations. I suspect that since it is in a very low population area, money is also a relevant issue. Where I live, there are a number of bridges across the Hutt river, and it runs along a major fault line, but being in a major metropolitan area, bridges are built. However, another more pertinent accusation came from a local who had complained a few days before that someone excavating the riverbed a little upstream had created a channel that would direct the heaviest rocks in a flood in the direction of the first supports to give way. Oops! No doubt more will follow.

When I wrote that (yesterday), the weather system was still to the south of here but working its way north. Yesterday we had wind gusts of up to 120 k/h, and while the system was working its way north, apart from some heavy rain last night, it had run out of steam. Today it is quite warm, sunny, no problem.

So is this a sign of climate change? A single incident is not, however I note that the “one in a hundred year rain event” in my youth has happened again now, and apparently in the 1980s. This time it has dumped almost four times the amount of water, and the Tasman Sea is about two Centigrade degrees above average this summer. You form your own opinion.

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Where will the Energy for Electric Vehicles come from?

In the previous post, I looked at the issues involved with replacing all motor vehicles with electric vehicles, and noted that is impossible with what we know now because the necessary materials are just not there. Of course there may be new battery technology developed, but there is another issue: from whence the energy? From international energy statistics, petroleum liquids have the equivalent energy of 53 trillion kWh. Since the electric vehicle is more efficient we can divide that number by about three, so we need almost 18 trillion kWh. (The issue is more complicated by whether we are trying to replace petroleum or solve the transport issue, since some petroleum products are used for heating, but for simplicity I am going to stick with that figure.) If we were going to do that by solar energy, the sunlight gives according to Wikipedia, on average about 3.5 – 7 kWh/m2per day. That needs about five trillion square meters devoted to solar energy to replace petroleum products. The Earth’s area is 510 trillion square meters, so we need about 1% of the surface area devoted solely to this, if the cells are 100% efficient. The highest efficiencies so far (Data from NREL) come from four junctions, gallium arsenide, and a concentrator where 46.6% has been reached. For single junction cells using gallium arsenide, we get 35% efficiency, while silicon cells have reached 27.6%. If silicon, we need 4% of the world’s area.

It is, of course, a bit worse than this because 70% of the world’s surface is ocean, and we can eliminate the polar regions, and we can eliminate the farmland, and we should eliminate the wild-life habitats, and we can probably assume that places like the Sahara or the Himalayas are not available and anyway would be too dusty, too windy, too snowy. Solar energy drops efficiency quite dramatically if the collectors get covered in dust or snow. So, before we get all enthusiastic about solar, note that while it can contribute, equally there are problems. One issue that is seldom mentioned is how we find the materials to make such a huge number of panels. In this context, the world supply of gallium is 180 tonne/a, so basically we should be back to silicon, which is one of the most plentiful elements. (In one of my novels I made a lot of someone finding a source of gallium otherwise overlooked. I feel good about that!). We don’t know how critical element supply would be because currently there is a lot of development work going on on solar conversion and we cannot tell what we will find. The final problem is that latitude also plays a part; in southern England we would be struggling to get the bottom of the range listed above on a sunny day, and of course there are many cloudy days. Accordingly, assuming we do not put the collectors on floats, the required area is starting to get up to 10% of the land area, including highly unsuitable land. We just cannot do it.

That does not mean solar in of no use. One place to put solar panels is on the roof of your house. Superficially, if every motorist did this, the problem is solved, apart from the long-distance driving, at least in the low latitude areas. The difficulty here is that the sun shines in the day, when the commuter uses his car. The energy could be stored, but we have just doubled the battery requirements, and they were already out of hand. You could sell to the power to the grid, and buy power back at night, and there is merit in this as it helps with daylight loads, except that the power companies have to make money, and of course, the greatest normal power requirements are in winter at the beginning and end of the day, when solar is not contributing. So yes, solar power can help, but it is not a single fix. Also, peak power loads are a problem. If the company needs capacity for that, where does it come from? Right now, burning gas or coal. If your electric vehicle is purchased to save the environment from greenhouse gas emission, that is pointless if extra power has to be generated from coal or oil.

My personal view on this is that while renewables are going to be helpful, if we want to stop emitting carbon dioxide when making energy, we have to go partially either nuclear or thermonuclear. My personal preference is for fusion reactors, but we do not know how to make them yet. The main problem with fission reactors is the disposal of waste, and the potential for making materials for bombs. We can get around that if we restrict ourselves to thorium reactors, because the products, while still radioactive, decay much more quickly, and finally you cannot make a thorium bomb. Another benefit of thorium reactors is they cannot get the runaway problems as seen at Chernobyl and Fukushima; they really are very much safer. The problem now is we have not developed thorium fission reactors because everyone uses uranium to make plutonium for bombs.

Even if we manage to get sufficient electricity, the next problem is transmission of this huge increase in electricity. In most countries, the major transmission lines will not take it, and would have to be replaced or supplemented. Not impossible, butat the cost of a lot of carbon dioxide being emitted in making the metals, and transferring them, because massive electric vehicles cannot precede the ability to shift electricity. Again, this is not a problem per se, but it is if we do not get organised quickly. The next problem is to get it to houses. “Slow charging” overnight is probably adequate, even for a tesla. If you can charge it fully in an hour at just over 40 amps, you should need only 3 amps overnight. Not difficult. However, the retail sale of electricity for vehicles travelling is not so easy. It is hard to put figures on this because I don’t know what the demand will be, but charging a vehicle for over an hour means no more than about ten vehicles per day per outlet. It is hard to make money out of that, so you need a lot of outlets. If you have a hundred outlets, you service a thousand cars, say, per day. Still not a lot of profit there and you need a parking lot and some excellent organization. You are also drawing 4,000 amps, so you need a fairly good power supply. Not an enticing proposition for investment.

The point I am trying to make here is that the problem is very large. We have built a monstrous infrastructure around oil, and in the normal circumstances, when we have to change, that industry would go slowly and another would slowly take its place. We don’t have that luxury if we want to save our coastal cities. Yes, everyone can “do their bit”, and that buys time if we all do it, but we also need some bigger help, in organization, research, development and money. It is time for the politicians to stop thinking about the next election, insulting the opposition, and start thinking about their country.

Climate Change: the Potential for Electric Vehicles

In my last post, I discussed the need for action over climate change. Suppose we decide to be more responsible, what can we do? There are several issues, but the main ones include is a solution fit for purpose, which includes will the general population see it as such and does it achieve a useful goal, and is it actually possible? To illustrate what I mean, consider the “easy option”: scrap motor cars and replace with electric vehicles. At first sight, that is easy and you will probably think there is no technological advance needed. Well, think again on both of those. Let’s put numbers on the problem: according to Wikipedia, the number of motor vehicles in the world is 1.015 billion.

Now, to consider the issue, “fit for purpose”, in New Zealand, anyway, and I suspect North America will be worse, people drive fairly long distances at least some of the time. One solution to that problem is to make people stop doing that. This is from the “sacrifices have to be made” school. As it happens, energy consumption probably will have to be reduced, but that does not mean that we need some politicians to say which form of energy consumption is forbidden to you. If people must use less, they should have a choice in what form they give it up.

There are two “niches” of electric vehicle, and as examples I shall pick on the Tesla and the Nissan Leaf. The Tesla currently claims a 400 km range (and intends to provide a 500 km range) per charge, while what you get from the Leaf is highly dependent on driving conditions, but it reaches a little over 100 km with average city driving. Basically, the Leaf would be great for someone wishing to commute daily, but not use it for distance driving. As an aside, the dependency on conditions will affect all such cars; we know about this aspect of the Leaf because there is more information available as more Leafs have been sold. The difference in range is simply because the Leaf’s battery is much smaller (198 cells compared with Tesla’s 7,104).

So why doesn’t the Leaf put in more cells? That is partly because of the problem of charging, and partly because of price and suitability for a chosen niche. A review of electric vehicles in our local paper brought up these facts. There are statements that the 400 k type car be charged at home overnight, “just like your mobile phone”. Well, not quite. While that sounds easy enough, where are you going to do it? Your home may have a garage, so maybe there. The mobile connector comes with adaptors that permit charging at 40 amps. Um, does your house have 40 amp rating to your garage, or maybe 50 amp to be on the safe side because you don’t want to accidentally throw the fuse and be walking to wherever next morning? Our reviewer found that to fully charge such a vehicle with 400 km range using his garage power rating took the best part of two days. Using a fast charger as available here, it took 75 minutes. Yes, you can charge these batteries relatively quickly if you can deliver the required current. The reason the Leaf has such a small battery capacity is so that it can be charged overnight with the average domestic power supply, and it can also be recharged while at work if the owner can “graze” on some power supply. Needless to say, once someone published figures like that, someone else challenged them, and pointed out that a steady 7 kW overnight would do it and “nearly two days” was wrong. Unfortunately, power itself is not the whole story because the current has to be rectified and voltage has to be kept to within a specific range. Apply an over-voltage, and different chemistry starts up in the battery that is not reversible, which means you greatly shorten your battery life.

There is some good news on batteries, though. The batteries do decay with time, and while details are not available, one estimate is that Tesla batteries should still be 90% effective after 8 years, which is quite respectable, while the Leaf claims its batteries should last ten years in a workable condition. Thus we have two types of vehicles: an expensive vehicle that can do anything a current vehicle can do on the open highway, provided there are adequate rapid charging sites. Here “adequate” takes on significance; refilling with petrol takes a few minutes and sometimes there is overcrowding. Will there be enough cables if it takes 75 minutes? How much will “site time” charge?

Then there is the question of how you use it. Do you carry big loads? Ferry lots of children? Go off road, or go camping? If so, the current electric vehicle is not for you. So the question then is, for those who see the electric vehicle as all you have to do to solve the transport problem, are they advocating no off-road activity, no camping, no serious loads? The answer is probably, yes. So, do we want to give up our lifestyle? If the answer is no. are there options? Of course not everyone wants to do those sort of things, so there will most certainly be quite sizable niches that can be filled with electric vehicles. Finally, there will be one further problem: the poorer people cannot afford new Teslas, or even new Leafs. They own second hand cars and cannot afford to simply throw that investment away. The liquid fuel transport economy will be with us for a lot longer yet.

The next question is, is it feasible to replace all cars with electric vehicles? For the purpose of analysis, I shall assume everyone wants a Tesla type driving capacity, as the next step is to put numbers on the problem. The battery weight is listed as 540 kg, which means to do the replacement, we would need something approaching half a billion tonne of batteries. That is not all lithium, but it includes “a small amount of cobalt and nickel”. If we interpret that as about 2% the weight each of the batteries, we need about ten million tonne of cobalt and nickel. World production of cobalt in 2017 was about 110,000 tonne, while nickel was over ten times this. Both metals, however, are fully used now, and the cobalt supply is deficient by about two orders of magnitude if all cobalt was devoted to electric vehicles. Unlikely. Oops! That is more than a small problem. It is not a problem right now because electric vehicles comprise only a very small fraction of the market, but it is insoluble. There is a strict limit on the possible supply of cobalt because as far as I know, there are no cobalt ores. Most cobalt comes from the Democratic Republic of Congo, as a by-product of copper mining. There would also be a significant demand for copper. The Tesla has two motors, one of which is 300 kW, so considerable amount of copper would be used, but world production of copper is about 24,000 Mt annually, so that is not an immediate problem, but may be in the long term. The annual supply of graphite is 126,000 t. Given that there will be more graphite used than lithium, this is a serious problem, however there is no shortage of carbon; the problem is converting carbon to graphite. That is quite a subtle problem; as it happens I know how to get close to the required fraction of graphite, but as yet, not economically.

So there are technological problems. Maybe they are soluble, but doing so introduces another problem, as exemplified by finding an alternative to cobalt. Cobalt is needed to give the non-graphitic electrode enough strength that the battery will have adequate lifetimes with good charging rates. So that is probably non-negotiable. There are alternatives, but so far none match the current battery type used by Tesla. Further, to develop a new battery and test its lifetime over ten years takes: you guessed it; the last part alone takes ten years, assuming your first pick works. Therein lies the overall problem; politicians have wasted nearly 30 years on the basis that it was not urgent. However, technical development does take a long time. For that reason it is wrong to lazily say, electric vehicles, or some other solution, will solve the problem. They will most certainly help, but we have to back many more options.

Science and Climate Change

In the previous post, I questioned whether science is being carried out properly. You may well wonder, then, when this week the Intergovernmental Panel on Climate Change issued a rather depressing report, and a rather awkward challenge: according to their report, the world needed to limit the temperature rise to 1.5 degrees C between now and 2050, and to do that, it needed to cut carbon emissions by 45% by 2030, and net zero by 2050. Even then significant amounts of carbon have to be removed from the atmosphere. The first question is, then, is this real, and if so, why has the IPCC suddenly reduced the tolerable emissions? If their scientists previously predicted seriously lower requirements, why should these be considered better? There are two simple answers. The first is the lesser requirements were based on the assumption that nations would promptly reduce emissions. Most actually increased them. The second is more complicated.

The physics have been verified many times. However, predicting the effects is another matter. The qualitative effects are easily predicted, but to put numbers on them requires very complicated modelling. The planet is not an ideal object, and the calculation is best thought of as an estimate. What has probably happened is their modelling made a projection of what would happen, and they did this long enough ago that now that they can compare prediction with where we are now. That tells them how good the various constants they put into the model were. Such a comparison is somewhat difficult, but there are clear signs in our observations, and things are worse than we might hope for.

So, what are we going to do? Nothing dramatic is going to happen on 2040, or 2050. Change will be gradual, but its progress will be unstoppable unless very dramatic changes in our behaviour are made. The technical challenges here are immense. However, there are a number of important decisions to be taken because we are running short of time due to previous inaction. Do we want to defend what we have? Do we want to attempt to do it through sacrificing our life style, or do we want to attempt a more aggressive approach? Can we get sufficient agreement that anything we try will be properly implemented? Worst of all, do we know what our options are? Of these questions, I am convinced that through inaction, and in part the structural defects of academic science, the answer to the last question is no.

The original factor of required emissions reduction was set at 1990 as a reference point. What eventuated was that very few countries actually reduced any emissions, and most increased them. The few that did reduce them did that by closing coal-fired electricity generation and opted for burning natural gas. This really achieves little, and would have happened anyway. Europe did that, although France is a notable exception to this in that it has had significant nuclear power for a long time. Nuclear power has its problems, but carbon emissions are not one of them. The countries of the Soviet Union have also actually had emission reductions, although this is as much as anything due to the collapse of their economies as they made the rather stupid attempt to convert to “free market economics” which permitted a small number of oligarchs to cream the economy, sell off what they could, use what was usable, pay negligible wages and export their profits so they could purchase foreign football clubs. That reduced carbon emissions, but it is hardly a model to follow.

There is worse news. Most people by now have recognized that Donald Trump and the Republican party do not believe in global warming, while a number of other countries that are only beginning to industrialize want the right to emit their share of CO2 and are on a path to burn coal. Some equatorial countries are hell-bent on tearing down their rain forest, while warming in Siberia will release huge amounts of methane, which is about thirty times more potent than CO2. Further, if we are to totally change our way of life, we shall have to dismantle the energy-related infrastructure from the last fifty years or so (earlier material has probably already been retired) and replace it, which, at the very least will require billions of tonnes of carbon to make the required metals.

There will be some fairly predictable cries. Vegetarians will tell everyone to give up meat. Cyclists will tell everyone they should stop driving cars. In short, everyone will have ideas where someone else gives up whatever. One problem is that people tend to want to go for “the magic bullet”, the one fix to fix them all. Thus everyone should switch to driving electric vehicles. In the long term, yes, but you cannot take all those current vehicles off the road, and despite what some say, heavy trucks, major farm and construction equipment, and aircraft are going to run on hydrocarbons for the foreseeable future. People talk about hydrogen, but hydrogen currently requires massive steel bottles (unless you are NASA, or unless you can get hydrides to act reversibly). And, of course, there is a shortage of material to make enough batteries. Yes, electric vehicles, cycling, public transport and being a vegetarian are all noble contributions, but they are just that. Wind and solar power, together with some other sources, are highly desirable, but I suspect that something else, such as nuclear power must be adopted more aggressively. In this context, Germany closing down such reactors is not helpful either.

Removing CO2 from the atmosphere is not that easy either. There have been proposals to absorb it from the effluent gases of coal-fired power stations. Such scrubbing is not 100% efficient, but even if it were, it is not dealing with what is already there. My guess is, that can only be managed by plants in sufficient scale. While not extremely efficient, once going they look after themselves. Eventually you have to do something with the biomass, but restoring all the tropical rain forests would achieve something in the short term. My personal view is the best chances are to grow algae. The sea has a huge area and while we still have to learn how to do it, it is plausible, and the resultant biomass could be used to make biofuel.

No, it is not going to be easy. The real question is, can we be bothered trying to save what we have?

Can We Feed an Expanded Population?

One argument you often see is that our farmland can easily feed even more people and that our technology will see that famines are a thing of the past. I am going to suggest that this may be an overenthusiastic view of our ability. First, the world is losing a surprising amount of good soil every year, to water and wind erosion. Seawater rising will remove a lot of prime agricultural land, but there is a much worse problem that needs attention. The 18th May edition of Science had some information that might give cause to rethink any optimistic view. Our high intensity agriculture depends on keeping pests, weeds and fungi at bay, and much of that currently depends on the heavy use of certain chemicals. The problem is what we are trying to keep at bay are gradually evolving resistance to our agents.

Looking at fungicides first, there are basically four classes of fungicides licensed for use, and some of these, such as the azoles, have a number of variations, but the variations tend to be those to differentiate the compounds from someone else’s, and to get around patents. The fundamental activity usually comes from one chemical group. As an example from antibiotics, there are a large number of variation on penicillin, but they all have beta lactams, and it is the beta lactams that give the functionality, so when bugs evolve that can tolerate beta lactams, the whole set of such penicillin-like drugs becomes ineffective. For fungi, the industrial scale production of single crops in some regions optimises the chance of a fungus developing a resistance, and there appears to be the possibility of gene transfer between fungi.

This has some other downstream issues. Thus medical advances lead to people having a much better chance of survival through cancer treatments, but they then become more susceptible to fungi. Apparently Candida auris is now resistant to all clinical antifungals, and is a worse threat in hospitals because it can survive most standard decontamination procedures. A number of other fungi are very threatening in clinical situations.

So what can be done about fungi? Obviously, seeking new antifungals is desirable, but this is a slow process because before letting such new chemicals out into the environment, we have to be confident that there will really be benefits and the chemicals are sufficiently effective under all circumstances, and we also need to know there are no unintended consequences.

Insecticides and herbicides (and following the article in Science, these will be collectively termed pesticides) have the same problem. It was estimated that even now the evolution of such resistance costs billions of dollars in the US. With regard to weeds, in 1996 plants were produced that were not harmed by glyphosate, and the effectiveness of this led to over 90% of US maize, soy and cotton being planted with such plants. (Some will recall the fact that some were bred so the plants did not produce viable seed, and further seed had to be purchased from the company that developed the plant.) Now there are at least forty serious weeds that have developed resistance to glyphosate. Plants have been engineered that are resistant to chemicals mimicking previous herbicides but the weeds are defeating that. Weed species have evolved to resist every known herbicide, and no herbicide has been developed with a new mode of action over the last thirty years.

In agriculture, it is easy to see how this situation could arise. When you spray a crop, not every part of every plant gets the same amount of spray. Some of what you don’t want will survive in places where the dose was less than enough. From the farmer’s point of view, this does not matter because enough of the pests have been dealt with that his return is not hurt by the few that survive. However, the fact that some always survive is just what evolution needs to develop life forms capable of resisting the chemicals.

So, what to do? Obviously, more effort is required, but here we meet some problems that might be intractable. Major companies have to invest large amounts of money to provide a possible solution, and they will only do so when there are likely to be guaranteed very large sales. However, to defeat resistance, it is most desirable to pulse agents, thus using agent A one year, agent B the next, and no repeat for a number of years. That maximises the chance of avoiding the generation of further resistance, but what company wants to participate in the sort of sales future? We could try natural procedures and live with the fact that yields are lower, but that implies we really do not want to eat that much more, which in turn suggests population growth needs to be curbed. Unfortunately, there are no easy answers.

Agricultural Fix for Climate Change?

One of the sadder aspects of our problem with climate change is that the politicians simply do not appreciate the magnitude of the problem, which is illustrated by a briefing in the journal Nature (554, 404). It is all very well to say that emissions must be curbed, and fast, but there is a further problem. What is there is still there. The Intergovernmental Panel on Climate Change has argued that carbon emissions must peak in the next couple of decades, and then fall steeply if we want to avoid a 2 Centigrade degree rise in average temperatures. So how do we get a steep decline?

The 2015 Paris agreement settled on negative emissions. That sounds good, until you start putting numbers on what has to be done. Consider the simple approach of putting silicates onto the land, where they will be weathered to produce silica and calcium/magnesium/iron bicarbonate or carbonate.

In an experiment (Beerling et al. 2018. Nature Plants: 4: 138 – 147) applied 3.5 t/ha of wollastonite powder (calcium silicate) to some New Hampshire land, which led to a 50% increase in the delivery of weathered calcium and silica to a stream. This was accompanied by a decrease in soil acidity and a decreased release of soil aluminium. So, carbon dioxide was taken from the atmosphere while improving the soil quality. Global cropland totals 12 million square km and additionally 1 – 10 million square km of marginal land is available.

Wollastonite is not the most readily available rock, but there is unlimited basalt. There are massive amounts of olivine, and this is potentially able to capture 0.8 – 0.9 t CO2 per tonne of applied rock, but olivines also tend to have higher levels of nickel and chromium. The authors suggest continental flood basalts, which have lower amounts of nickel and chromium and higher amounts of phosphorus, but now the carbon capture potential is about 0.3 t CO2 per tonne of applied rock. This suggests that applying 10 – 50 t /ha/y of rock to an area of farmland about the size of Texas could sequester 0.2 – 1.1 billion tonne (Gt) of CO2. That is a significant reduction, but of course about 1/3 of that would currently be emitted in the grinding/transportation. Suppose we wanted to put it on all agricultural land? There is a hundred hectares to a square kilometre, so in the worst case we would need to grind and apply 60 Gt of basalt per year.

The problem could be lessened if the 7 – 17 Gt of silicate waste were used. For example, it is estimated that quarrying for construction generates an estimated 3 Gt of “fines” that are too small to be used. There is about 1.4 – 5.9 Gt of construction/demolition waste dumped each year. Cement in particular is particularly suitable. Up to half a Gt of steel slag is produced each year, and this contains weatherable elements plus some fertiliser, such as phosphate. Besides these wastes, in some places there are historically accumulated dumps of material, although these materials are probably already sequestering CO2, so perhaps they should not be counted

A further benefit from this is that the silica will replenish eroded soil and aid replacement of further soil organic carbon, as the world’s cropland soil is eroding far faster than it can be replaced (about 5 t/ha/y). Such weathered material provides silicic acid for plants, which strengthens stems, and it is suggested that this might reduce the effect of pests.

To summarise, here is a method that could in theory take CO2 from the air, but think of the problems. Let us assume the most encouraging figures. Humanity currently burns about 9 Gt of carbon a year. To absorb all of that, we would have to apply 109 Gt of powdered basalt a year, and burn no carbon while we are doing it. That is 109 billion tonne of basalt, which is not a soft rock, and do that while running the risk of some serious adverse environmental issues, and try to avoid having a lot of silicosis amongst the workers. All of this is not going to be easy. Worse, as far as CO2 levels are concerned, that is merely standing still.

There is one other related option. The rock peridotite is a mantle rock, but occasionally there are large surface deposits. It is a relatively soft rock on the surface, and it is one of the faster rocks for sequestering carbon dioxide. For that reason, it tends to be rather rare because when it does get to the surface, it weathers and erodes relatively quickly under the effect of water and carbon dioxide. However, one proposal is to drill into a deposit and fracture hydraulically, and force CO2 in, where it will form dolomite. The problem here tends to be with location. One of the bigger masses of peridotite is in the Oman desert, which is not rich in water, nor in local CO2.

Thinking about this shows some of the problems of modifying a planet. People seem to think changing Mars into somewhere pleasant to live in would be easy. In my novel Red Gold I offered the suggestion that to do that you would need a dead minimum of at least a petatonne (a million billion tonne) of nitrogen to have enough pressure to have a tolerable outside air pressure that would last through the winter. Where do you find that?

Another small commercial break: from May 3 – 10, for those in the US and the UK, A Face on Cydonia will be at 99c or 99p respectively. For everyone else, Amazon requires it to be $2.99 – still a bargain!

How Earth Cools

As you may have seen at the end of my last post, I received an objection to the existence of a greenhouse effect on the grounds that it violated the thermodynamics of heat transfer, and if you read what it says it is essentially focused on heat conduction. The reason I am bothering with this post is that it is an opportunity to consider how theories and explanations should be formed. We start by noting that mathematics does not determine what happens; it calculates what happens provided the background premises are correct.

The objection mentioned convection as a complicating feature. Actually, the transfer of heat in the lower atmosphere is largely dependent on the evaporation and condensation of water, and wind transferring the heat from one place to another, and it is these, and ocean currents, that are the problems for the ice caps. Further, as I shall show, heat conduction cannot be relevant to the major cooling of the upper atmosphere. But first, let me show you how complicated heat conduction is. The correct equation for one-dimensional heat conduction is represented by a partial differential equation of the Laplace type, (which I would quote if I knew how to get such an equation into this limited htm formatting) and the simplest form only works as written when the medium is homogenous. Since the atmosphere thins out with height, this clearly needs modification, and for those who know anything about partial differential equations, they become a nightmare once the system becomes anything but absolutely simple. Such equations also apply to convection and evaporative transfer, once corrected for the nightmare of non-homogeneity and motion in three dimensions. Good luck with that!

This form of heat transfer is irrelevant to the so-called greenhouse effect. To show why, I start by considering what heat is, and that is random kinetic energy. The molecules are bouncing around, colliding with each other, and the collisions are elastic, which means energy is conserved, as is momentum. Most of the collisions are glancing, and that means from momentum conservation that we get a range of velocities distributed about an “average”. Heat is transferred because fast moving molecules collide with slower ones, and speed them up. The objection noted heat does not flow from cold to hot spontaneously. That is true because momentum is conserved in collisions. A molecule does not speed up when hit by a slower molecule. That is why that equation has heat going only in one way.

Now, suppose with this mechanism, we get to the top of the atmosphere. What happens then? No more heat can be transferred because there are no molecules to collide with in space. If heat pours in, and nothing goes out, eventually we become infinitely hot. Obviously that does not happen, and the reason becomes obvious when we ask how the heat gets in in the first place. The heat from the sun comes from the effects of solar radiation. Something like 1.36 kW/m^2 comes in on a surface in space at right angles to the line from the sun, but the average is much less on the surface of earth as the angle is at best normal only at noon, and if the sun is overhead. About a quarter of that is directly reflected to space, and that may increase if the cloud cover increases. The important point here is that light is not heat. When it is absorbed, it will direct an electronic transition, but that energy will eventually decay into heat. Initially, however, the material goes to an excited state, but its temperature remains constant, because the energy has not been randomised. Now we see that if energy comes in as radiation, it follows to get an equilibrium, equivalent energy must go out, and as radiation, not heat, because that is the only way it can get out in a vacuum.

The ground continuously sends radiation (mainly infrared) upwards and the intensity is proportional to the fourth power of the temperature. The average temperature is thus determined through radiant energy in equals radiant out. The radiance for a given material, which is described as a grey body radiator, is also dependent on its nature. The radiation occurs because any change of dipole moment leads to electromagnetic radiation, but the dipoles must change between quantised energy states. What that means is they come from motion that can be described in one way or another as a wave, and the waves change to longer wavelengths when they radiate. The reason the waves representing ground states switch to shorter wavelengths is that the heat energy from collisions can excite them, similar in a way to when you pluck a guitar string. Thus the body cools by heat exciting some vibratory states, which collapse by radiation leaving them. (This is similar to the guitar string losing energy by emitting sound, except that the guitar string emits continuous decaying sound; the quantised state lets it go all at once as one photon.)

Such changes are reversible; if the wave has collapsed to a longer wavelength when energy is radiated away, then if a photon of the same frequency is returned, that excites the state. That slows cooling because the next photon emitted from the ground did not need heat to excite it, and hence that same heat remains. The reason there is back radiation is that certain frequencies of infrared radiation leaving the ground get absorbed by molecules in the atmosphere when their molecular vibrational or rotational excited states have a different electric moment from the ground state. Carbon dioxide has two such vibrational states that absorb mildly, and one that does not. Water is a much stronger absorber, and methane has more states available to it. Agriculture offers N2O, which is bad because it is harder to remove than carbon dioxide, and the worst are chlorocarbons and fluorocarbons, because the vibrations have stronger dipole moment changes. Each of these different materials has vibrations at different frequencies, which make them even more problematical as radiation at more frequencies are slowed in their escape to space. The excited states decay and emit photons in random directions, hence only about half of that continues on it way to space, the rest returning to the ground. Of that that goes upwards, it will be absorbed by more molecules, and the same will happen, and of course some coming back from up there with be absorbed at a lower level and half of that will go back up. In detail, there is some rather difficult calculus, but the effect could be described as a field of oscillators.

So the take-away message is the physics are well understood, the effect of the greenhouse gases is it slows the cooling process, so the ground stays warmer than it would if they were not there. Now the good thing about a theory is that it should predict things. Here we can make a prediction. In winter, in the absence of wind, the night should be warmer if there is cloud cover, because water is a strong greenhouse material. Go outside one evening and see.