Introduction

Many governments are providing support and subsidies for the development of renewable sources of energy. As a result, thousands of companies, some funded by venture capital, have been founded to tackle this problem. The incentive, how­ever, is always commercial. The world runs on money, and nothing gets done without the possibility of profit. This incentive, however, is artificial. What mat­ters more is the fossil footprint of each technology. That is, how much fossil energy is used in manufacturing and maintaining the equipment, including the mining of the raw materials, their transportation, and the assembly and installa­tion of the power units.1 After all, the goal is to replace fossil fuels, not to buy more of it to buildup a new business. “Green” energy has to be self-sustaining energy-wise. This seems obvious, but only the wind people have been brave enough to calculate their fossil footprint and publicize the results. This chapter also describes new inventions and ideas which give hope for the future but are as yet untested on a large scale.

Electricity is the kind of energy that our modern lifestyle depends on. Making elec­tricity from fossil fuels requires going through a heat cycle. As explained in Chap. 2, the thermodynamics of heat cycles puts a limit on efficiency. Power plants have to be carefully designed to approach even 40% efficiency. Sixty percent of the energy in the fossil fuels that we burn up is lost in the production of electricity. Most of the renew­able energy sources, however, can generate electricity directly, without going through a heat cycle, thus avoiding that 60% loss. This is the case for hydroelectricity, wind power, and solar power. The bad news is that these sources are local, or intermittent, or have their own inefficiencies. Hydro is well established, but not everyone has it. The realities of wind and solar will be covered next. The possible backbone energy sources, fission and fusion, still have to go through a heat cycle. The second or third generation of fusion reactors, however, could possibly produce electricity directly in so-called “mirror machines.” These advanced systems will be covered in Chap. 10.

The oceans are a vast reservoir of CO2, taking up about two billion tons a year. The rate of this uptake is slowing down, although the yearly amount is increasing sim­ply because there is more and more CO2 in the atmosphere. From 1750 to 1994, 42% of CO2 released went into the sea; but from 1980 to 2005 this figure decreased to 37% as a result of the extra CO2 that we are producing. Carbon dioxide is the gas that bubbles out of soda pop and forms a weak acid when dissolved. The oceans can absorb much more CO2 than by simply dissolving it, however. That gas reacts with H2O to form positive hydrogen ions (H+) and negative carbonate (CO32-) and, mainly, bicarbonate (HCO3-) ions in a “buffering” process. This increases the uptake of CO2 by almost an order of magnitude. The possible increase is quantified by the so-called Revelle buffer factor, which depends on the partial pressure of CO2 at the ocean surface. That is, the more CO2 that is pushing back into the atmosphere, the less CO2 the ocean can absorb out of the air. It takes about a year for these pres­sures to equalize, and it takes thousands of years for carbon in different forms to circulate in the ocean. The CO32 — ion can also combine with calcium to form cal­cium carbonate (CaCO3), the material of coral and some shells. These solids sink into deeper water and stay there for millions of years. If we were to stop producing CO2, it would take 4-10 thousand years for the ocean’s partial pressure of CO2 to get back to normal.

The buffering effect injects much more H+ ions into the ocean than would be created by dissolving CO2 into carbonic acid, and this makes the ocean much more acidic. The ocean is naturally mildly alkaline, with a pH value of 7.9-8.3, and anthropogenic CO2 has decreased it by 0.1 since 1750. This does not sound like a lot, but the number of H+ ions has increased by 30%. Furthermore, computer models predict a decrease between 0.14 and 0.35 in the 21st century. Acid dissolves car­bonate matter such as coral and shells of sea animals, and it can slow or prevent their creation. We have all read about dead or dying coral reefs, though the relation to global warming is conjectural. Phytoplankton, at the bottom of the food chain, absorb almost as much CO2 as plants on land,11 and they are consumed by larger organisms which are the food source of all fishes and whales. Most crustaceans such as krill have chitin rather than carbonate shells, but those that are carbonate-based would suffer from increased acidity. The entire food chain can be upset by acidifi­cation of the oceans. However, there is so far no scientific evidence that this is happening. The 2007 IPCC report states that the effect of increased acidity on marine organisms is poorly known.

Coal is the major problem. It supplies 27% of the world’s energy and 40% of its electricity. In the USA, coal supplies 23% of all energy and a whopping 49% of electrical energy.5 Coal is also the worst CO2 emitter. In 2007, CO2 emissions from coal burning amounted to 2.65 billion tons in China and 2.20 billion tons in the USA.6 No other nation was responsible for more than 0.54 billion tons. No wonder, since China and the USA produced 41.1 and 18.8% of the world’s energy from coal because of their large deposits.3 It is easy to see why coal is so dominant: it is cheaper than oil or gas; there is a large supply of it; and it is easy to transport by rail. The mines are not remote; no pipelines need to be built; and there is no need for tankers which occasionally crash and foul our beaches.

Coal is bad news also because it causes deaths in mining accidents, it destroys the environment when whole mountains are dug up, and it emits many pollutants such as sulfur. We all remember stories of families waiting in vain for news about their loved ones trapped miles deep in the earth with no hope of rescue. In the USA alone, 100 million tons of coal ash and sludge are stored in 200 landfills annually, and these contain dangerous contaminants such as arsenic, lead, selenium, boron, cadmium, and cobalt.7 The problems are exacerbated by the rapid development of China, where coal plants are being built at the rate of one large one in a week, while the USA has stopped building them as of 2007. Let us concentrate on this biggest problem: the unstoppable industrialization of China and India. In China, 74% of energy comes from coal, and this will increase to 90% with continued growth, though efforts to develop renewables may hold the line at 70%.8 China has about 30,000 coal mines, 24,000 of which are small ones which use antiquated equipment and are not regulated for safety. In 2006, 4,746 miners died in China, versus only 47 in the USA; both numbers are down from those in earlier years. Chinese coal generates every year 395 billion cubic meters of methane, SO2, and black soot, all of which have larger warming potential than CO2. Furthermore, the methane is what causes explosions in mines, and the SO2 causes acid rain. Of the million people in China suffering from black lung disease, 60% are miners. This disease increases the coal mining death total by 50%.8 It is not likely that other energy sources can replace coal any time soon, but we can try to mitigate its effect on global warming.

How CO2 raises the earth’s temperature is not as simple as people are led to believe. The popular notion is that the sun’s rays go through the atmosphere and are absorbed by land and water, which radiate the energy back up at a longer wave­length. GHGs prevent this radiation from getting back through the atmosphere, thus trapping the energy and heating the earth. This notion is not wrong, but it is over­simplified. Indeed, the gases in the atmosphere are quite transparent to sunlight, which has wavelengths near those we can see. When land and water absorb this light, they radiate part of the energy back to the sky at infrared wavelengths, which we cannot see. The main constituents of the air, N2 (nitrogen) and O2 (oxygen), allow the infrared to get out, but “greenhouse” gases such as CO2, CH4 (methane), and N2O (nitrous oxide) absorb the infrared and are heated up. They then re-radiate the energy both upwards and downwards. Only the downwards part is the energy “trapped” by the greenhouse effect. Actually, the energy radiated to the earth’s surface by the atmosphere is larger than the energy coming directly from the sun [5]. If it were not for GHGs, the average temperature on the earth’s surface would be -19°C (0°F) rather than 16°C (60°F) as it is now. Already we can see what a large effect CO2 has on the earth’s temperature, and why even a small change in its abundance would be worrisome.

The situation is complicated by the fact that water vapor is also a strong GHG, and its amount in the atmosphere changes constantly as water evaporates, forms clouds, and then is removed by rain and snow. But H2O is a short-lived GHG, going in and out of the atmosphere every two weeks or so, while CO2 is a long-lived GHG with an average residence time of four years.3 Furthermore, water forms clouds, which reflect sunlight strongly, and rain and cloud cover vary greatly depending on where you are. It would be impossible to predict the details of changing cloud cover, so the H2O effect has to be treated as an average. This is not as bad as it

sounds because the saturation humidity level, as we all know, increases or decreases with temperature in a predictable way.

Because the water content in the atmosphere changes constantly, climate scien­tists cannot treat H2O as a long-lived GHG like CO2 but only as a modifier of the effects caused by those gases. One can calculate that doubling the CO2 concentra­tion will cause a 1.1°C (2.1°F) rise in temperature, but the presence of H2O will cause a larger change by positive feedback. Positive feedback is a self-enhancing effect like a stock market crash. As stock prices plunge, more people will try to sell their stocks, causing the prices to fall faster. Here, as the temperature rises, more water is evaporated into the atmosphere, where it radiates energy back to earth, further increasing the temperature. It finally settles down at a high value 29°C (85°F). It is the convection of warm air upwards that brings this down to the observed value of 16°C (60°F). It is actually the stoppage of air currents that makes greenhouses work, not the trapping of radiation [5].

Without such mitigating factors, there can be runaway feedback, in which an increase in temperature (caused by CO2) evaporates more water, which “traps” more solar energy, raising the temperature further, until all the water on the planet has been evaporated. This is apparently what happened to Venus, where the sur­face temperature is about 460°C, enough to melt lead. The runaway can also go in the other direction if the planet gets so cold that it snows everywhere, reflect­ing sunlight away so that it gets colder, causing more snow and ice to form. The planet can turn into an ice ball. In geologic times, the earth has had numerous ice ages and interim warm periods but has always escaped from catastrophic run­away feedback. We do not know why, though there are many theories. This is one of the lucky breaks that allowed life, even sentient human life, to arise in an interglacial period.

Windmills have been used for energy long before there was electricity. We are now returning to this source by building wind farms. Wind is actually a kind of solar energy, since it is produced by sunlight heating different parts of the earth differ­ently. Figure 3.1 shows a typical modern wind farm. The original concept was that these farms can be built on open land where it is usually windy and, consequently, where not many people live. Farmers can lease the land to power companies for $3,000-6,000 per turbine per year and still let their cattle graze among the towers. This seems ideal, but people began to object. The wind farm at Altamont Pass near San Francisco is notorious for the number of birds that its 5,000 turbines were killing every year. The Elk River Wind Farm in Kansas was built on a pristine prairie, the home of the sage grouse and the lesser prairie chicken.2 This habitat is now cut up by roads, transmission lines, and power stations. To get enough wind power to make a difference, the environment does have to suffer, but the benefits of this free energy far outweigh the disadvantages. China hopes to get half its electricity from wind by 2020, thus cutting its carbon emissions by 30%.3 The scenery will surely suffer, but there the objectors have less of a voice. Wind power is not free of technical problems, but these seem to be less severe than with other

green technologies. In some places, like Texas, the cost of wind energy is already competitive with that from oil.

Hurricane Katrina leveled New Orleans in 2005 and is most often cited as an example of the effects of global warming. The hurricane season in 2005 had the largest number of hurricanes, and the strongest ones, on record. It is of course not possible to ascribe any single local event, or even a season of events, to a slowly changing general condition. It takes a concatenation of unusual local conditions to produce extreme weather. More far-fetched is the linking of the 2009 wildfires in Australia to global warming.12 Yes, the tinder may have been dry, but there have been droughts before, such as that in Southeast Asia in 1998-2003, that in Australia in 2002-2003, and that in Western North America in 1999-2004. Other events named in connection with global warming are the floods in Europe in 2002 and the heat wave there in 2003. Eleven of the 12 warmest years have occurred in the past 12 years. The opposite extremes are never mentioned. The winter of 1962-1963 in Europe was so cold that the Seine froze, and oil deliveries could not reach Paris. The European winter of 2008-2009 was the coldest in 20 years. Does global warm­ing really cause heat waves, cold spells, floods, droughts, fires, and storms?

Fortunately, extreme weather events can, and have been, documented statisti­cally. In many regions of the earth, good temperature and rainfall records have been kept and published. Alexander et al. [15] have compiled these data and produced graphs from which trends can be seen. For example, Fig. 1.20 shows maps and graphs of the occurrence of temperature extremes. The figure requires some expla­nation. At the upper left, the graph below the map in panel (a) shows, for the period 1951-2003, the number of days per year when the night temperature was very cold, when compared with the average number of such days in the period near the center of the graph. We see that the number of cold nights has been decreasing recently. The map above the graph shows where these cold nights occur, averaged over the entire period, with blue showing a lesser number of cold night and red a greater number. By contrast, we can look at the number of warm nights in panel (c) at the bottom left. We see that the number of very warm nights has increased a lot recently. The map shows, for instance, that western Africa and Latin America have suffered from this the most. In panels (b) and (d), the number of unusually cold and unusually hot days is shown. These show the same trend as the nights, but not as strongly. Remember that these data are not about the general warming trend but are about the occurrence of extreme hot and cold spells. These show a trend toward fewer cold spells and more hot spells as we move into the 21st century.

The shift of cold and hot spells can be seen more clearly in the bell-shaped probability curves in Fig. 1.21. The blue curves are for the 1950s-1970s, and the red curves for the recent period. The horizontal axis is the number of days per year that have the probability corresponding to the height of the curve. Thus, the peak of the blue curve in panel (a) says that there was a probability of 0.12 (12%) that there were 11 unusually cold nights in any year in that period. The plots (a) and (c) of Fig. 1.21 show the red curves to the left of the blue ones, meaning that there are

Fig. 1.21 Bell-shaped curves showing the probability of having the number of days per year (plotted on the horizontal axis) with unusually cold nights (a), warm nights (b), cold days (c), and warm days (d) [6]. The blue curves are for 1951-1978, and the red curves are for 1979-2003 [15]

now fewer cold spells; and the plots (b) and (d), with the red curves shifted to the right, show that there are more hot spells in recent years.

The occurrences of unusually heavy rainfall have also been recorded. These extremes are shown in Fig. 1.22. Though there is considerable variation from year to year, a trend toward more rain falling in big storms since 1990 can be seen.

The coal industry will not do anything that lowers its profits without government intervention. What is being done in most developed countries is to legislate a decrease in carbon emissions by a certain deadline. The Cap and Trade system allows large utilities to meet these standards without a sudden capital expenditure. However, Cap and Trade does not directly lower total CO2 emissions. It works as follows. An emissions cap is legislated for each industry, and this cap is divided into credits, in terms of tons of CO2, that that sector is allowed to emit. Credits are then auctioned off. Heavy emitters, such as a large utility, may find it less expensive to buy credits than to build equipment to reduce emissions, while light emitters, such as a modern, efficient plant, can sell the credits that they do not need. Both utilities would gain financially. To make this work, the government has to establish a fraud-proof monitoring system and assess severe penalties for noncompliance.

Unfortunately, Cap and Trade does not actually decrease carbon emissions because, in the example above, both utilities would emit the same amount of CO2 that they would without trading credits. It actually allows the large utility to delay investing in the equipment for capturing CO2, when it should be forced to do it as soon as possible. New power plants using solar or wind energy can sell their credits to coal plants, but these producers of green power are being built anyway because they are profitable, not because of Cap and Trade. Cap and Trade does not force industries to lower their emissions if they are already taking steps to do this because of societal concerns or because it is profitable publicity-wise. Only additional low-carbon plants should be counted, not those that already exist or are planned.

Loopholes in the scheme allow accounting tricks to get around doing anything constructive. The only advantage of Cap and Trade is to make large polluters aware of what is coming and begin to worry about it.

Predicting how the earth’s climate will change is a huge job, even with the help of the largest, most advanced computers. Here, we wish to give some idea of how the problem is being tackled. Each factor that can change the earth’s average tempera­ture ( T) is evaluated for its ability to change T. This ability, called a “forcing,” is expressed in watts per square meter (W/m2), as if sunshine intensity were increased by that many W/m2, all else staying the same. Forcings have to be computed using a model. For instance, to compute the forcing due to CO2, one has to take into account the amount of CO2 in the atmosphere and how long it stays, its rate of absorption and emission of radiation, and feedback effects such as the rise in T due to the increase in water vapor caused by the temperature rise that the CO2 caused initially. Obviously, the result is only as good as the computer model used to calcu­late it, but these models are carefully checked, and the uncertainties are clearly stated. More on this will come later. For the GHGs, the forcing is known within ±10% with 90% confidence, but other effects (the small ones) can have errors of

±100% or so. Figure 1.3a compares the major radiative forcings; that is, the effectiveness of the main agents that can change T by altering the absorption of solar radiation.

These forcing numbers seem very small, less than 2 W/m2, compared with the peak solar irradiance of about 1,300 W/m2, or even the 342 W/m2 averaged over a hemisphere or the 240 W/m2 that reaches the earth’s surface. But a small change in T can have catastrophic effects, as we shall see. The man-made forcings have both positive (warming) and negative (cooling) values. Let us see where these figures come from. The three main GHGs dominate the warming effects. CH4 has 26 times the warming potential of CO2 and N2O, 216 times; but their concentrations are much lower than CO2’s, and CO2 is dominant. The ozone-depleting chlorine-containing gases which were banned by the Montreal protocol are lumped under the rubric CFCs. That value comes from 60 different gases which were evaluated one by one in the IPCC report of 2007 [6]. The value for ozone does not depend on the state of the ozone hole, because high-altitude ozone has a small role here. The ozone that contributes to warming is in the lower atmosphere and is generated on the ground by natural processes such as rotting of biological matter. What we have called “dust” is the sum of all aerosols emitted by factories and volcanoes. Industrial aerosols are mainly sulfate and carbon particles of varying sizes and reflectivities. You would think that black carbon would absorb well, but remember that black not only absorbs well but also emits well. More importantly, particulate matter can seed cloud forma­tion, and clouds reflect sunlight efficiently. The net result is that aerosols have a large negative forcing and give a cooling effect. Albedo is the change in the reflectivity of the earth’s surface, and this small effect comes from the balance between two effects. Black dust on snow will reduce the albedo of the snow and cause warming.

Deforestation and other land modifications by man will replace trees with farms or buildings, thus increasing the albedo. In this case, land use wins, and changes in albedo are a negative forcing. The result is very uncertain, but it is small in any case.

The natural forcings come from volcanoes and solar variability. Volcano dust stays in the atmosphere only a few years, and eruptions are rare and unpredictable. On the other hand, solar variability follows the 11-year sunspot cycle closely, and this 8% effect is accurately predictable. However, what concerns us is not the 11-year cycle but the long-term trend. Changes in the earth’s orbit or the tilt of its axis occur over tens of thousands of years, so only a very small part of these changes could have occurred in modern times. Recently obtained data on solar irradiance from 1,750 to the present yield a forcing of +0.12 W/m2, with a 90% chance of the exact value’s being within 50% of this. Figure 1.3b compares the net anthropogenic forcing with the natural forcing caused by solar variability. The man­made part is 13 times larger. Skeptics1 who say that present global warming is a natural phenomenon would imply that climate scientists are wrong by over an order of magnitude. Even if that were true, it is irrelevant. The present rate of CO2 emis­sions by man is not conjectural, and their effect on temperature can be calculated with ± 10% accuracy.

In spite of its economic efficiency, wind power has encountered considerable oppo­sition. Initially, many bats and raptors were found to be killed in wind farms. At Altamont Pass, the count was 1,300 raptors a year, including more than 100 golden eagles.4 This wind farm was located on a bird flyway, and the obvious solution was to avoid these flyways. Apparently, the raptors would land on top of the turbine and look for rodents on the ground. Once they saw one, they would dive right through the whirling blades. There was such concern that the state of California issued guidelines for the treatment of birds in the development of wind power.5 This report did not say how to avoid bird kills, but did outline the procedures for licensing and monitoring. Bats are not the most lovable creatures, but they do eat a lot of insects. Golden eagles have a regal name, but they have practically hunted the island fox of California’s Channel Islands to extinction. Wind power’s impact on wildlife is monitored by various organizations.6

This problem has not surfaced with modern turbines such as those shown in Fig. 3.1. These are much taller than first-generation turbines and turn at much slower speeds. But the clinching argument lies in the numbers. Ten to 40 thousand birds and bats are killed per year in wind farms. Compared to this, 100 million are killed per year by cats, and 60 million by cars and windows (which they fly into).4 It is just that no one goes around counting these carcasses the way they do on wind farms. If global warming is not controlled by eliminating fossil fuels, many more birds and animals will die and even become extinct, as we saw in Chap. 1.

There are other environmental objections. Wind farms cannot always be built where there are no people. The noise can be bothersome, and the effect on scenery, even of offshore turbines, often cannot be tolerated. There is a NIMBY (Not In My Back Yard) sentiment. Objectors have their own website.7 The technical problems have to do with time and place. Since wind speed fluctuates, the excess energy generated in periods of strong wind has to be stored, and there is no easy way to store that much energy. Wind farms are usually built far from population centers where the energy is needed. This involves modifying the power grid with new transmission lines. This presents a chicken-and-egg problem: neither the wind farm companies nor the transmission line companies want to proceed without the other.

Extreme events like hurricanes cannot be predicted, and even the statistics are less certain because it is hard to define what constitutes a hurricane, a cyclone, or a typhoon. A useful definition is ACE (accumulated cyclone energy), an index which takes into account both the wind velocities and how long they persevere. The ACE value can be used to tell what is a hurricane and what is just a bad storm. Statistics are gathered for each region and year. Perhaps the most interest­ing are the data for the Atlantic region. In the 1970-1994 period, there were on average 8.6 tropical storms, 5 hurricanes, and 1.5 major hurricanes; and their average ACE value was only 70% of normal. By contrast, the period 1995-2004 had 13.6 tropical storms, 7.8 hurricanes, and 3.8 major hurricanes, with an aver­age ACE value 159% of normal [6]. In fact, only two years in that period, 1997 and 2002, had fewer hurricanes than normal, and those were El Nino years. It is well known that El Nino produces more severe storms in the Pacific but the oppo­site in the Atlantic.

Although these statistics show an increase in destructive storms, no direct cause-and-effect relation with global warming can be proved. Nonetheless, there are physical reasons why hurricanes arise, and these are being used in attempts to model hurricanes. When the sea surface temperature rises, more moisture is evaporated into the atmosphere. The water vapor has a greenhouse effect that increases the temperature further. The heated air rises, creating an upward flow of air. When the temperature reaches 26°C (79°F) locally, the air current is strong enough to create a hurricane. Whether this happens or not depends on the wind shear in the atmosphere. If the cross-winds are weak, the upward air currents become very strong in one place, seeded by some random fluctuation there. By Bernoulli’s Law, a flowing fluid has less pressure than one that is not moving. This is the same effect that causes a baseball to curve if given a spin such that the air flows on opposite sides of the ball are not equal. The incipient hurricane then has less pressure, and air flows into the column from all sides. The Coriolis force then causes the column to spin and develop into a cyclonic vortex. We described the Coriolis force briefly in Footnote 8. How this force causes winds and spins is interesting and often misunderstood, so we have added a detailed explanation in Box 1.2.

Tropical storms have a cooling effect on surface temperature. Evaporation of seawater cools the surface just as the evaporation of sweat cools our skin. Eventually, the moisture in the atmosphere condenses into rain, reversing the process and carrying the heat back into the ocean; and there is no net cooling. Storms, however, stir up the atmosphere so that this heat is carried up to higher altitudes, where it can be radiated into space before it comes back to earth. This may be a way for nature to stabilize the ocean’s temperature. Lightning-lit forest fires renew our forests by burning the undergrowth and allowing new trees to grow. Hurricanes and forest fires may be natural mechanisms that stabilize the present conditions on the planet. Both are catastrophic for mankind, but humans are only a minuscule part of life on earth.

Box 1.2 Why Do Northern Hurricanes Rotate Counter-Clockwise?

Hurricanes have been observed to rotate clockwise in the Southern Hemisphere and counter-clockwise in the Northern Hemisphere, and this has been attributed to the Coriolis force, illustrated in Fig. 1.23. The earth is shown rotating from west to east, causing the sun to rise in the east and set in the west. Several latitude lines are shown. Since these circles are smaller at higher latitudes, the ground speed of the rotation is highest at the equator and diminishes as one moves toward the poles. The atmosphere is dragged by the ground, and therefore the air has a different speed at each latitude, as shown by the lengths of the orange arrows at the left. Nothing happens until the air masses move north-south. Looking at the northern hemisphere in the left diagram, we see that if the air mass at the equator, say, moves northward from A to B, the large velocity of the air at A is brought into a region where the normal velocity is smaller. This motion is indi­cated by the wiggly blue arrows. The difference between the velocities is shown by the thick blue arrow. The people at latitude B, therefore, feel a wind blowing from west to east. The same happens in the Southern Hemisphere if the air moves south out of the tropics. Now suppose the air flow is toward the tropics, south­ward in the north and northward in the south. This is shown in the right diagram. Then the air masses move into regions where the normal velocity is larger. This slowing down of the normal speed appears as a wind going in the opposite direction, namely westward. This is shown by the thick blue arrows in the right diagram. The Coriolis force is the imaginary force that causes that wind.

Whether air moves north or south depends on other conditions, such as temperature or barometric pressure differences at different latitudes. It turns out that for latitudes between 30° and 60° N the motion is northward, as at B,

Fig. 1.23 Illustration of Coriolis force causing westerly (left) and easterly (right) winds