Glaciers begin advancing

After 1550, the climate grew markedly colder. Glaciers began advancing and in late May or early June 1595 (there is some uncertainty about the precise date), the Gi troz Glacier in Switzerland entered the River Danse, damming it and causing a flood when the dam broke that submerged the town of Bagnes, killing 70 people. As recently as 1926 there was a house in Bagnes that still had a beam bearing the inscription Maurice Olliet had this house built in 1595, the year Bagnes was flooded by the Gi...

Ice cores

Cores are also taken from the ice sheets covering Greenland and Antarctica (see the sidebar Vostok, GISP, and GRIP on page 41). Polar ice sheets are made from compacted snow the ice is not made by freezing water, the way you make ice cubes. It is never warm enough for snow to melt in either Greenland or Antarctica, so each year's snow lies on top of the snow that fell in previous years. The weight of all that snow compresses the lower layers, packing the snowflakes tightly together. Cores...

Frost fairs

Shakespeare's description of icicles and frozen milk was clearly accurate, and there may have been occasions when he could walk across the River Thames. It froze over more than 20 times between the winters of 1564-65 and 1813-14. Admittedly, the river was more prone to freezing then. Since that time the tributaries flowing through London have been channeled through pipes, and some of the bridges have been rebuilt, allowing the tides to flow upstream more freely and vigorously, breaking any ice...

Sea levels and higher rainfall

The rise in temperatures was accompanied by a rise in sea level due partly to the expansion of the seas as the water temperature rose and partly to the melting of mountain glaciers. Measuring changes in sea level is complicated by the fact that the level of the land also changes. It can be lowered by coastal erosion and in places it is still rising as a result of removing the weight of the ice sheets of the most recent ice age (see Is the sea rising on pages 158-163). In this case, however,...

Respiration

Carbohydrate foods fats, sugars, and starches are used to supply the energy needed to power the processes that allow living things to function. Even when we are lying down quite still, our bodies require energy. The minimum amount they need is known as the basal metabolic rate (BMR), and it is measured in a person who has slept for at least eight hours and is lying motionless and who has not eaten for at least 12 hours because digestion uses energy. The BMR for an adult person is 1,200-1,800...

Radiation emission and absorption

Once the surface of the Earth becomes warmer than the interplanetary space surrounding it, its surface begins to emit radiation at a wavelength that is proportional to its temperature (see Radiation from the Sun and from the Earth on pages 128-134). Earth emits radiation in the infrared waveband, at wavelengths of approximately 3-30 pm (pm are micrometers, equal to millionths of a meter). Its radiation is most intense at about 10 pm. As the diagram on page 97 shows, water vapor absorbs...

The cyclesources and sinks

There are two principal components of the natural carbon cycle, both of which are in balance over the year. Photosynthesis removes about 132 billion tons (120 billion tonnes) of carbon from the air each year, and respiration returns a similar amount. About 99 billion tons (90 billion tonnes) of carbon dissolves into the oceans each year and a similar amount comes out of solution and enters the air as carbon dioxide. In addition to these large exchanges of carbon, there are also smaller ones....

Some clouds are more reflective than others

These differences are real and significant. A deep layer of dense cloud is much more reflective than a thin layer of more diffuse cloud. Dense cloud forms at a lower level than diffuse cloud, so cloud albedo also changes according to the height of the cloud. The table shows just how large the difference is. The surface of undulating cloud tops that covers most of the sky usually altostratus is more than twice as reflective as the thin, wispy, cirriform clouds. Heaped up cauliflower clouds...

Seasons and Tropics

If the Earth were upright, so its north-south axis of rotation intersected the plane of the ecliptic at a right angle, the plane of the ecliptic would divide the Earth exactly at the equator. The person wishing to stand directly beneath the Sun could choose any point on the equator to do so. In fact, though, the Earth's rotational axis is tilted from the vertical by 23.5 . Consequently, as the Earth travels around its orbit, the Sun appears to move north and south, and it is directly overhead...

Isostasy and glacial rebound

Ice is very heavy and the present Greenland ice sheet is an average 10,000 feet (3,000 m) thick and the Antarctic ice sheet 6,900 feet (2,100 m). During an ice age, ice sheets of this thickness cover a much greater area. The immense weight of ice depresses the crust beneath it. The Earth's crust is made from solid rocks that lie above the hot, slightly plastic rocks of the mantle. The mantle behaves like a liquid with respect to the solid rocks of the crust, so...

The year sunspot cycle

As he worked away patiently with his examination of sunspots, Maunder found a pattern emerging. In 1843 the German astronomer Samuel Heinrich Schwabe (1789-1875) had discovered that the number of sunspots increases and decreases over a regular 11-year cycle. Maunder found that the solar latitudes in which sunspots emerge change in a regular way over the course of the sunspot cycle. The first ones appear some distance from the solar equator and later ones move gradually closer to the equator...

Adhemar and Croll

Milankovitch was not the first person to wonder whether the onset and ending of ice ages might be linked to astronomical cycles. In Les Revolutions de la Mer (1842) the French mathematician Alphonse Joseph Adhemar (1797-1862) observed that because of the eccentricity of the Earth's orbit and the obliquity of its axis, Antarctica received about 170 fewer hours of solar radiation each year than the Arctic. That, he proposed, is why it is the colder pole (he was wrong see the sidebar Why the...

Sea levels and storms

Some of the most dramatic consequences that have been predicted to accompany climate change also turn out to be exaggerated. There have been warnings of a rapid rise in sea level, of more and fiercer hurricanes, more tornadoes, and even of more blizzards. Sea levels have risen, but the rise predicted by the models, of 4.3-30 inches (0.11-0.77 m), is modest (see Is the sea rising on pages 158-163). Coastal erosion is serious in some places, but it is not due to global warming. The frequency of...

Electromagnetic radiation

Electromagnetic radiation is one of the fundamental forms of energy. It is associated with oscillating electric and magnetic fields hence the name at right angles to each other and to the direction in which the radiation is traveling. It can be regarded as pure energy traveling either in waves or as a stream of particles, called photons. Although the two descriptions sound contradictory, in fact they are not. All types of electromagnetic radiation travel at the same speed, whether it is...

Khmer Empire

Southern Asia also felt the effect of a climate change that pushed climatic zones southward. This change established a semipermanent area of high pressure (an anticyclone) over Thailand, Cambodia, Laos, and Vietnam. The climate became drier, and this may have helped the emergence of a civilization in what had been dense tropical forest. Khmer is the name of the Cambodian people and their language. The Khmer civilization reached its peak around 1200 c.e. After 1300 the climate became wetter...

Reflection and absorption

On a clear night the temperature drops rapidly as the ground surface loses by radiation the heat it absorbed during the day. Cloudy nights are much warmer. In spring and fall, meteorologists use their forecasts of cloudiness to predict whether there will be an overnight frost. Clouds that shade and therefore cool the surface by day prevent it from cooling by night. Clouds reflect and absorb the heat that is radiated from the surface and they reradiate some of the heat they absorb. This is how...

Perturbing the natural cycle

When the Industrial Revolution began, water was the principal source of power. Factories had to be sited close to a place where there was a sufficient fall of water to drive a water mill. When steam engines were introduced factories could be sited anywhere because they used coal as a fuel. With that change, from water power to steam, the process of industrialization began releasing carbon that had been stored below ground as coal. This perturbed the natural carbon cycle. At first the effect was...

Preface

Several years have passed since the publication of the first edition of the Dangerous Weather series of books. Much has happened during that time and my friends at Facts On File and I felt it would be appropriate to revise all of the books in the series in order to bring them up to date. As we began to prepare the new editions, it occurred to us that none of the books so much as mentioned climate change, yet in the minds of many people this is the single most important environmental issue of...

Will there be more ice ages

Snowball Earth, if it existed, ended many millions of years ago. No one suggests that the world could freeze over again to that extent, but most scientists agree that there will be more ice ages. When Louis Agassiz proposed it, the Great Ice Age was believed to have been a single event that ended once and for all it was confined to the Pleistocene epoch, and we now live under quite different conditions, in the Holocene. Then, as geologists unraveled more of the Earth's recent history, it became...

How oxygen accumulated

At that time the Sun was young and weak. The thermonuclear reaction in its core had made it start to shine, but it was about 25 percent to 30 percent dim mer and cooler than it is today. Nevertheless, this was enough to warm the surface layers of water and to provide light for the first cells to begin manufacturing sugars by photosynthesis. Those cells were cyanobacteria and they lived in microbial mats the fossil remains of those mats are called stromatolites. Oxygen is a by-product of...

The Medieval Optimum

Cahokia is an archaeological site covering 2,200 acres (890 hectares). It is located in southern Illinois, about eight miles (13 km) to the northeast of St. Louis, Missouri. One of its principal features is Monks Mound, a four-sided pyramid rising in four terraces to a height of 100 feet (30.5 m) and covering 12 acres (5 hectares). A temple once stood at the top. Monks Mound is the largest prehistoric earthwork anywhere in the Americas, and it is just one of about 120 mounds at Cahokia. In...

Models have limitations

Climate models are now very detailed, but they still have limitations. Some climate processes are not yet fully understood and so assumptions have to be made about the way they function. Models are also limited by computing power. This affects the size of the grid. At present, the best models of the atmosphere over land use a grid with a side that is about 155 miles (250 km) long. Above the boundary layer the lowest layer of air, extending to about 1,700 feet (519 m), in which the air is...

Warm weather everywhere

The benign conditions were not confined to Greenland and Iceland, of course. During the early Middle Ages the climate was warmer over most of the Northern Hemisphere. A prolonged period of weather that is warmer than the weather before or after it is known as a climatic optimum. This period is the medieval optimum. For about 200 years, beginning around 880, farmers were growing wheat around Trondheim, Norway, and they grew barley as far north as about 69.5 N. This is north of Narvik and well...

Heat islands and urban domes

Lysocline Layer

Air escaping from heated buildings, atmospheric particles absorbing infrared radiation at night, the reduction in wind speed, and the heat from thousands of engines combine to make the city into an island of warmth surrounded by a cool, rural sea. It is a heat island. During the day the temperature rises rapidly. On a sunny day in summer it may rise by as much as 31 F 17 C between dawn and the middle of the afternoon. It falls again at night, but in the early part of the night the city center...

Trade winds and Hadley cells

Southern Hemisphere Trade Winds

Air over the equator is heated strongly by contact with the warm surface. The warm air rises all the way to the tropopause. There, trapped beneath the tropopause, it moves away from the equator. Cooler air flows toward the equator at low level, to take its place. Moving air tends to turn in a circle. This is called vorticity and it is why the water usually forms a spiral, or vortex, when it flows out of a bathtub. As the cool air moves toward the equator its vorticity swings it to the right in...

Tree rings and isotopes

We know now that the Maunder Minimum is real. Maunder's data were reliable and a period when there were very few sunspots did indeed coincide with a period of very cold weather. We know he was right because there is other evidence to support him, evidence that was not available in his own day. The supporting evidence comes from studies of tree rings and ice cores see Climates of the Past on pages 37-43 . Tree rings are made from the cells surrounding the trunk that are produced as new growth...

City air is drier but rainfall is higher

This is the first and most obvious difference between the urban and rural environments. It means that rain does not soak into the ground, but is removed by storm drains. When the rain ceases the streets dry very quickly. Rainwater is removed too quickly for much of it to evaporate and there are fewer areas of standing water ponds and lakes than there are outside the city. Consequently, there is less evaporation in the city than there is in the countryside....

Cities are less sunny

One reason people find the countryside attractive may be that they believe it to be sunnier. They are quite right. On average, city dwellers experience 5 percent to 15 percent fewer hours of sunshine over the year, 15 percent to 20 percent less solar radiation in total, and 5 percent less ultraviolet radiation in summer and 30 percent in winter. The drawing shows why this is so. Buildings shade the ground and the taller the buildings are, the deeper the shade that they cast. The extent of the...

Milankovitch on Mars

The cycles that Milankovitch proposed are much more clearly evident on Mars than on Earth. This is because Mars is closer to the outer giant planets and has no large moon. Consequently, its orbital eccentricity varies from 0.00 circular orbit to 0.13 more than twice that of Earth over the course of 95,000-99,000 years. Obliquity changes even more dramatically, from about 13 to 47 , over 120,000 years. The Martian equinoxes also pre-cess, returning to an initial position over a period of about...

Transport Of Heat By The Oceans

Edmonton, Alberta, and Dublin, Ireland are in almost the same latitude 53.58 N and 53.37 N respectively . July is the warmest month in Edmonton, with an average daytime temperature of 74 F 23 C , and January is the coldest month. The average nighttime coldest temperature in January is -4 F -20 C . July is also the warmest month in Dublin, with an average daytime temperature of 67 F 20 C , and January is the coldest month, with nighttime temperatures of 34 F 1 C . Edmonton is warmer than Dublin...

Obliquity

Obliquity Seasons

The greater the obliquity, the greater the intensity of solar radiation over polar regions. The rotational axis of the Earth is tilted from the vertical, but the angle of tilt called the obliquity also varies. This affects the way sunlight strikes the Earth. At present, the angle between the rotational axis and the plane of the ecliptic is about 23.45 , but over a period of about 42,000 years the obliquity changes from 22.1 to 24.5 and back again. The change is significant...

Sunspots and cloud formation

Even so, it seems unlikely that so small a change, never amounting to as much as 1 percent, could produce such a big effect. The answer is that the climatic effect is not due to direct heating. Solar astronomers believe that sunspots are magnetic disturbances. They occur in pairs, with magnetic field lines emerging from one sunspot Solar constant. The Sun subtends an angle of 0.5' at the Earth's surface. Solar radiation is emitted in all directions, but the Earth is exposed to only a tiny...

Potential temperature

There is an apparent paradox, however. When a fluid cools, its molecules move closer together, increasing its density. If a rising fluid, such as air, grows colder it must become denser, and it cannot rise above fluid that is less dense. Yet temperature decreases with height throughout the troposphere see the section Composition and structure of the atmosphere, on page 1 . It seems to follow that air at the top of the troposphere must be Cold air is denser than warm air, because its molecules...

Cloud condensation nuclei

Water vapor will not condense very readily unless there are small particles onto which it can form droplets. These particles were first identified by John Aitken see the sidebar and they are known as Aitken nuclei or cloud condensation nuclei. The air contains large quantities of them, especially over land. Cloud condensation nuclei are of a particular size and the air contains particles of many other sizes. Some are solid and some liquid. The bigger ones are visible to the naked eye. You can...

The Sporer Minimum Dalton Minimum and Maunder Minimum

Then, in 1889, Maunder read an article by another German astronomer, Friedrich Wilhelm Gustav Sporer 1822-95 . Sporer was also studying sunspots and he had discovered something very interesting. Astronomers had been observing and recording sunspot activity for centuries, but Sporer found that very few had been observed between approximately 1400 and 1520. This period came to be known as the Sporer Minimum. It was a time of very cold weather. People called it a Little Ice Age. The Baltic Sea...

The Mongol Empire

In the 13 th century the Mongolians eventually established what may have been the biggest empire the world has ever seen. The story began during a prolonged period when the climate was moist. Traces of earlier shorelines show that sea level in the Caspian Sea was much higher then than it is now, and that it was rising. The steppe pastures grew dense and rich under the increased rainfall and warmer weather associated with it. The people flourished and the population increased, but around 1200...

Specific heat capacity

When any substance absorbs heat, its temperature rises. The amount of heat that must be absorbed to produce a one-degree rise in temperature varies from one substance to another. It is known as the specific heat capac- ity of the substance, usually denoted by the symbol c, and is measured as the units of heat that must be absorbed for a one-degree increase in temperature. The scientific units are joules per gram per kelvin and are written as J g-1 K-1. Alternatively, the units can be given as...

Out of the steppes of Central Asia

Central Asia is a vast region of grasslands called steppe. Traditionally, its inhabitants were nomadic pastoralists, driving their herds and flocks from one seasonal pasture to another. Many Mongolians still live a seminomadic life. Drought is a common occurrence in the dry climate. It makes farming unreliable, but only occasionally does it seriously injure the nomads. Droughts in Central and Western Asia around 300 c.e. forced people known as the Hunni, or Huns, out of their homelands. They...

Oxygen isotopes and heavy water

Water molecules from ice cores and shells taken from sediments have another story to tell. They contain oxygen of two different types and two different types of hydrogen. Most chemical elements exist as two or more isotopes. Different isotopes of an element are identical chemically, but they have different atomic masses. Oxygen has three isotopes, two of which are important 16O and 18O. Seawater contains 99.76 percent H216O and 0.2 percent H218O. It also contains 0.03 percent HDO the remainder...

Reading stalagmites

Victor Polyak and Yemane Asmerom, scientists at the University of New Mexico, used uranium-thorium dating to determine the age of the bands in stalagmites taken from caves in the Carlsbad Caverns National Park and Hidden Cave in the Guadalupe Mountains National Park, both in southwestern New Mexico. What they found was a clear link between changes in the local climate and the way of life of the people living there at the time. They found evidence of climate changes that had changed the course...

Siting the thermometer

No matter how accurate it may be, a thermometer will give very inaccurate readings if it is incorrectly sited. If a glass thermometer is placed in direct sunlight, for example, the mercury or alcohol in the bulb will absorb solar radiation and its temperature will rise for that reason. The thermometer will then display the temperature inside the bulb, but this will be quite different from the temperature of the surrounding air. This is why the air temperature must always be taken in the shade....

Hipparchus and the precession of the equinoxes

The axial wobble was another effect Milankovitch studied, but he was not the first person to notice it. That person was the Greek astronomer and mathematician Hipparchus c. 190 b.c.e.-c. 120 b.c.e. . Hipparchus was the greatest of all Greek astronomers, and some of the discoveries he made and the deductions he made from them are still important today the axial wobble is one of them. He also calculated the length of the year as 365.25 days, diminishing by 0.003 day each year, and the lunar...

Ocean gyres and boundary currents

Global Maps Gyres

Ocean currents are like rivers that flow through the water around them. They are quite distinct. Kuroshio means black water and the Kuroshio Current is clearly visible as a stream less than 50 miles 80 km wide moving at up to 7 MPH 11 km h . When an ocean current moves toward or away from the equator, the Coriolis effect influences its direction. Currents start to turn as they approach continents. The Coriolis effect intensifies as currents move farther from the equator. This makes them turn...

Glacials interglacials and geologic time

Glacials And Interglacials

As well as classifying rocks, geologists were also dividing the history of the Earth into episodes they called eras, periods, and epochs. The table Geologic Time Scale below lists the present divisions of geologic time the history of the Earth with the approximate dates when they began. The Great Ice Age occurred recently, so the period of time that encompassed it was called the most new epoch, but using the Greek words pleistos most and kainos new to make the word Pleistocene. The Great Ice...

Polar and Ferrel cells

Hadley Ferrel Polar

Extremely cold, dense air also subsides over the North and South Poles. It produces the two polar high-pressure regions. Air flows out from them and is deflected to become the polar easterly winds. Any object moving toward or away from the equator and not firmly attached to the surface does not travel in a straight line. As the diagram illustrates. It is deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Moving air and water tend to follow a clockwise...

Transferor he Latent heat and the Bowen ratio

The absorption and release of latent heat see the sidebar Latent heat and dew point on page 32 also transfer energy from one part of the Earth to another through the movement of clouds. When water evaporates over the ocean, absorbing latent heat, and condenses when it crosses the coast, releasing latent heat, energy has been transported from the ocean to the land. This is an important component of the overall movement of heat. Latent heat does not affect the temperature the heat is hidden,...

Cold weather during the Dark Ages

The abandonment of Cahokia marked the end of a period when the climate was relatively warm and moist over all of the Northern Hemisphere. That warm period followed a period of cold weather lasting from the second half of the third century until the ninth century c.e. There was heavy snow over much of Europe in the winter of 763-64, and the intense cold killed many olive and fig trees. The winter of 859-60 was so cold that the ice was thick enough to bear the weight of horse-drawn wagons on the...

Carbonate lysocline and carbonate compensation depth

The fate of dissolved carbon depends on the temperature and pressure under which it is held. Carbon dioxide is more soluble at low temperatures and high pressures. The fizz in a can of soda is produced by carbon dioxide that is held in solution under pressure and usually chilled. Opening the can releases the pressure, and the carbon dioxide escapes into the air as a mass of tiny bubbles. Warm the can before opening it and the escaping carbon dioxide will eject a froth of liquid. When carbon...

Changing land use alters the albedo

Other changes do alter the surface albedo, however. Felling a broad-leaved, deciduous forest to provide farmland increases albedo, and converting a coniferous forest to meadow has an even larger effect. As albedo increases, more solar radiation is reflected and the surface temperature decreases. Changing forest to farmland has a cooling effect. Planting forests, on the other hand, may have a warming effect, because it reduces albedo, although the warming this caused would not be sufficient to...

Layers of the atmosphere

Height Layers Atmosphere

There is no clearly defined top to our atmosphere. About 90 percent of it lies between the surface and a height of about 10 miles 16 km . Above COMPOSITION OF THE PRESENT ATMOSPHERE ammonia nitrogen dioxide sulfur dioxide hydrogen sulfide 365 p.p.m.v. 18 p.p.m.v. 5 p.p.m.v. 2 p.p.m.v. 1 p.p.m.v. 0.5 p.p.m.v. 0.3 p.p.m.v. 0.05-0.2 p.p.m.v. 0.08 p.p.m.v. variable 4 p.p.b.v. 1 p.p.b.v. 1 p.p.b.v. 0.05 p.p.b.v. p.p.m.v. means parts per million by volume 1 p.p.m. 0.0001 percent. p.p.b.v. means parts...

Radiometric dating

All radiometric dating methods work in the same way as radiocarbon dating, by measuring the proportions of a radioactive element and the stable element into which it decays. One of the two isotopes of rubidium 87Rb decays to an isotope of strontium 87Sr with a half-life of 48 billion years 10 times the age of the solar system . Radioactive potassium 40K decays to argon 40Ar with a half-life of 1.277 billion years. The most widely used dating methods, however, are based on the decay of uranium U...

Weather balloons and satellites

Weather balloons are free from such types of interference. They use standard instruments, calibrated to recognized standards, and they measure temperature and pressure in air that is well clear of the surface. The measurements are very reliable, but their global coverage is poor and there have been changes in the instruments used and the way their data is processed that have left gaps in the record. Balloons are released from land-based stations and there are far more in North America and...

The axial wobble

There is a third, more subtle cycle that takes place over about 25,800 years. It concerns the way the Earth's rotational axis wobbles. This is not the same thing as the way its obliquity changes the two motions are at right angles to each other. Earth behaves like a spinning top, and a spinning top has certain properties. As long as it maintains a high enough angular velocity, or rotational speed, and it experiences no outside force, the top is stable. It will remain upright, spinning on its...

The faint Sun paradox and the Gaia hypothesis

This is because of the faint Sun paradox. Stars slowly grow hotter as they age. This means that in the distant past the Sun was cooler than it is today. Svante August Arrhenius 1859-1927 , a Swedish physical chemist, was the first scientist to calculate the influence of atmospheric carbon dioxide on the air temperature. He published the results in 1896, in a paper, On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground Philosophical Magazine, vol. 41, pp. 237-71 ....

Latent heat and adiabatic cooling and warming

Latent Heat Condensation Water

Water also absorbs heat when it evaporates. This heat supplies the energy needed to break the hydrogen bonds that hold molecules together. Because it is used to break the hydrogen bonds between individual molecules, this heat does not raise the temperature of the liquid water. It is known as latent heat, because it appears to be hidden see the sidebar Latent heat and dew point below . Heat energy that is absorbed when water evaporates is released when the hydrogen bonds form once again and the...

Mesosphere and mesopause

The stratopause is a region where temperature remains constant with height. The atmospheric layer above it is the mesosphere, extending to a height of about 50 miles 80 km . At the top of the mesosphere the air pressure is about 0.00015 lb. in.-2 1 Pa 0.01 mb one-millionth of the pressure at sea level. Temperature remains constant with height at the stratopause, but then decreases. The temperature at the upper boundary, the mesopause, varies widely. In winter it can be as low as -148 F -100 C ,...

Erik the Red and settlements in Greenland

Around 980 or 982, Erik Thorvaldsson, nicknamed Erik the Red because of the color of his hair, discovered the eastern coast of Greenland. Erik lived in Iceland, but he had quarreled with his neighbors and the quarrel had deteriorated into a fight in which two men were killed. Erik was convicted of manslaughter and exiled for three years on pain of death. Having little choice, he set sail, heading west toward where his friend Gunnbjorn Ulfsson claimed to have sighted land. He settled near the...

Breaking the bond evaporation

A molecule in a mass of liquid water is pulled by the molecules around it, but it is pulled equally strongly from every direction. If it is at the surface of a body of liquid, however, it is pulled from the sides and from below, but not from above, so it is not quite so securely held. If it can acquire a little more energy, the molecule will move faster and faster until the hydrogen bonds linking it to its neighbors break and the molecule is free to enter the air. It then enters the layer of...

Jean Baptiste Fourier John Tyndall and the greenhouse effect

The absorption of outgoing radiation that warms the Earth is usually likened to the effect of a greenhouse rather than a blanket. It is called the greenhouse effect, a name it acquired in 1822, when Jean-Baptiste Joseph Fourier 1768-1830 first used that metaphor. Fourier was a French mathematician and physicist who made many important contributions to science and had an interesting and exciting life. A supporter of the French Revolution, he was later arrested and narrowly escaped the...

Louis Agassiz and the Great Ice

The debate was at its height when one of the most talented scientists of his generation turned his attention to it. Louis Agassiz see the sidebar Louis Agassiz and the Great Ice Age on page 62 had already made a reputation based on his studies of fossil fish. In Recherches sur lespoissons fossiles Studies of fossil fishes he classified more than 1,700 species. Agassiz was born in Switzerland of French parents and was very familiar with Swiss glaciers. He was also in search of attractive places...

Thermohaline circulation and North Atlantic Deep Water

North Atlantic Deep Circulation

At the edge of the Arctic Circle, where water freezes at the ocean surface, it is the process of freezing that drives the Great Conveyor. Ice is less dense than liquid water that is why ice floats. Water becomes denser as its temperature decreases and it reaches its maximum density at a little above freezing. Freshwater is densest at 39.2 F 4 C and seawater is densest at 35.6 F 2 C . The sea loses heat into the very cold air. This chills the sea surface and increases the density of the...

Stratosphere and stratopause

The layer above the tropopause is called the stratosphere because L on-Philippe Teisserenc de Bort 1855-1913 , the French meteorologist who discovered and named it, thought that at this height the atmospheric gases separated into layers, or strata, according to their masses. This was incorrect, but the name stuck. Temperature remains constant with height through the lower stratosphere, but it begins to increase with height above about 12 miles 19 km and the rate of increase accelerates above 20...

Milutin Milankovitch And His Astronomical Cycles

Milutin Milankovitch was born on May 28, 1879, in the village of Dalj, on the Croatian side of the border between Croatia and Serbia, near the Croatian town of Osijek. At that time Serbia was an independent nation and Croatia was part of Austria-Hungary. He studied at the Vienna Institute of Technology and in 1904 he was awarded a doctorate in technical science. Dr. Milankovitch worked for a time as the chief engineer for a construction company, but in 1909 he accepted an offer to teach applied...

The complete electromagnetic spectrum

Blackbody radiation is not confined to a particular wavelength or even waveband a range of wavelengths. The amount of energy a blackbody radiates is proportional to its temperature, and its temperature determines the wavelength at which it radiates most intensely, but to either side of this peak the radiation tails off toward longer and shorter wavelengths. Visible light forms only a part of the electromagnetic spectrum, but it is the region at which the Sun radiates most intensely, in the...

The water molecule and the hydrogen bond

Movement requires energy and it is the Sun that supplies the energy for the movement of water from the ocean to the land the hydrologic cycle. Once the water is moving, particular physical properties of air and water interact to produce our weather. A water molecule comprises one atom of oxygen and two of hydrogen H2O . The three atoms share electrons. That is what binds them together, but it does so in such a way that lines drawn from the two hydrogen atoms to the center of the oxygen atom...

Diurnal and seasonal changes

Seasonal Changes Weather

The budget is complicated still further by the Earth's rotation and by its tilted axis. Obviously, the surface absorbs no solar energy at night, when it is dark. There is a very large variation in energy gain and loss over the 24hour cycle. In the tropics this can amount to a net gain of about 1,000 W m-2 at noon and a net loss of about 70 W m-2 at midnight. As the illustration shows, the Earth's axial tilt produces the seasons by turning first one hemisphere and then the other to face the Sun....

Troposphere and tropopause

The lowest layer, extending to about 10 miles 16 km over the equator, seven miles 11 km over middle latitudes, and five miles 8 km over the poles, is the troposphere. This is the region where the air is constantly being mixed and where all the world's weather happens. It is also the layer in which the temperature decreases with height. Its upper boundary, known as the tropopause, is the height at which the temperature ceases to decrease as you climb higher. This means that air that is rising...

Ocean currents

Ocean Currents Normal And Nino

Like the atmosphere, ocean currents transport heat. Instead of transporting it by means of vertical cells, in which air rises, moves horizontally, and subsides again, the oceans transport it by a system of surface and deep currents. Ocean currents have names, many of which are familiar. Most people have heard of the Gulf Stream, for example, and perhaps of the California and Labrador Currents. There are also the Kuroshio and Oyashio Currents which affect the weather in Japan, and the Peru...

The Radiation Balance

Earth receives energy from the Sun in the form of solar radiation. It then radiates the energy it has received back into space in the form of terrestrial radiation see Radiation from the Sun and from the Earth on pages 128-134 . The two are in balance the amount of outgoing energy from the Earth is equal to the amount of incoming energy from the Sun. If this were not so, the Earth would grow steadily hotter or colder. The global climate does change over time, of course, and at present many...

Outgoing radiation

Terrestrial Radiation

The Earth then radiates away the energy it has absorbed. The diagram summarizes the global energy budget. The numbers in the drawing refer to the percentages of the total energy budget. Those with a plus sign represent incoming solar energy and those with a minus sign represent outgoing terrestrial radiation. Other numbers indicate the movement of energy between the Earth and atmosphere. The table shows the budget in more detail. The surface of land and sea receive 51 percent of the solar...

Incoming radiation and the ozone layer

Incoming Radiation

Solar radiation enters the atmosphere. About 18 percent of the incoming shortwave radiation is absorbed by ozone near the top of the stratosphere and in the troposphere by clouds, water vapor, and aerosols. Absorption by oxygen O2 and ozone O3 produces the ozone layer by the reactions 03 photon O2 O O3 O 2O2 M is a molecule of any substance, but usually nitrogen. This sequence of reactions absorbs ultraviolet radiation and when governments acted to halt and reverse the depletion of the ozone...