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In that year the Soviet Union lost a significant portion of its winter wheat crop when the snows failed to provide adequate cover and a sharp freeze destroyed the exposed vegetation. The summer moisture that normally is carried by the westerlies did not arrive in the Ukraine or the northern Oblasts (politcial-economic districts) of the Soviet Union. Hence, the wheat harvest was delayed, and a significant portion of the ripened crop found itself blanketed by the winter snow. The rest is economic history.
Since 1972, the grain crisis has intensified. Each year the world consumes approximately 1.2 billion metric tons. Since 1969 the storage of grain has decreased from 600 million metric tons to less than 100 million metric tons-a 30-day world supply.
With global climatic-induced agricultural failures of the early 1970s, the stability of many governments has been seriously threatened. Many governments have gone to great lengths to hide their agricultural predicaments from other countries as well as from their own people. It has become increasingly imperative to determine whether 1972 was an isolated event or-as the climatologists predicted-a major shift in the world's climate.
The economic and political impact of a major climatic shift is almost beyond comprehension. Any nation with scientific knowledge of the atmospheric sciences will challenge this natural climatic change. The potential for international conflict due to controlled climate modification can be a reality in the 1970s. History has demonstrated that people and governments with nothing to lose have traditionally shown little regard for treaties and international conventions. Thus, any country could pursue a climate modification course highly detrimental to adjacent nations in order to ensure its own economic, political, or social survival.
In November of 1974 the United States will be participating in the World Food Conference in Rome, Italy. Some major issues of this conference will be the ability of the world to feed itself; how shortages will be met; and who will provide the needed food. Timely forecasting of climate and its impact on any nation is vital to the planning and execution of U.S. policy on social, economic, and political issues. The new climatic era brings a promise of famine and starvation to many areas of the world. The resultant unrest caused by the mass movement of peoples across borders as well as the attendant intelligence questions cannot be met with existing analytical tools. In addition, the Agency will be faced with tracing and anticipating climate modification undertaken by a country to relieve its own situation at the detriment of the United States. The implication of such a modification must be carefully assessed. The atmosphere is uniformly a radiative heat sink at all latitudes, while the Earth's surface-except near the poles-is a heat source. Energy must therefore be transferred from the surface to the atmosphere to keep the surface from warming and the atmosphere from cooling. The vertical heat exchange occurs mainly by evaporation of water from the surface (heat loss) and condensation in the atmosphere (heat gain) and by conduction of sensible heat from the surface and turbulent diffusion into the atmosphere (convection).
Since the late 1960s, a number of foreboding climatic predictions has appeared in various climatic, meterological, and geological periodicals, consistently following one of two themes.
Most meteorologists argued that they could not find any justification for these predictions. The climatologists who argued for the proposition could not provide definitive causal explanations for their hypothesis.
In the eastern Canadian area of the Arctic Greenland, below normal temperatures were recorded for 19 consecutive months. Nothing like this had happened in the last 100 years.
The archaeologists and the climatologists document a rather grim history of the cultural pressures instigated by changes in climatic regime. Recently, some archaeologists and historians have been revising old theories about the fall of numerous elaborate and powerful civilizations of the past, such as the Indus, the Hittites, the Mycenaean, and the Mali empire of Africa. There is considerable evidence that these empires may have been undone not by barbarian invaders but by climatic change. Bryn Mawr archaeologist, Rhys Carpenter, has tied several of these declines to specific global cool periods, major and minor, that affected the global atmospheric circulation and brought wave upon wave of drought to formerly rich agricultural lands.
Refugees from these collapsing civilizations were often able to migrate to better lands. Reid Bryson, of the University of Wisconsin's Institute for Environmental Studies, speculates that a new rainfall pattern might actually revive agriculture in some onceflourishing regions such as the northern Sahara and the Iranian plateau where Darius' armies fed. This would be of little comfort, however, to people afflicted by the southward encroachment of the Sahara. The world is too densely populated and politically divided to accommodate mass migrations.
Yet to understand the results of climatic change, we must know something of the basics of climatology and the people associated with this science.
The climate of a region on the Earth is said to be represented by a statistical collection of its weather conditions during a specified time interval. This interval is usually at least two or three decades; for the Agency's purposes, we will be dealing with months and years. Climatology, as derived from the Greek word clima meaning inclination of the sun's rays, reflects the importance attributed by the early students of climatology to the influence of the sun. For some unknown reason, this importance was virtually ignored by climatologists until a decade ago.
Energy reaching the Earth is modulated by variations in the Earth's orbit, the inclination of the Earth's axis while in orbit, the materials in the Earth's atmosphere (dust, moisture, etc.), and energy fluctuations in the sun itself.
Parameters such as temperature, rainfall, and wind velocity can be directly related to the heterogeneous distribution of thermal energy on the surface of the Earth. They are the physical manifestations of a global system which attempts to attain a thermal equilibrium through the interchange of potential and kinetic energy between the atmosphere and the oceans.
There are two major reasons for the heterogeneous distribution of energy on the surface of the Earth:
The energy required for the physical processes taking place in the Earth-atmosphere-ocean system is almost totally provided by the sun. Each minute the sun radiates approximately 56 x 1026 calories of energy of which 2 x 103 calories per square centimeter per minute are incident upon our outer atmosphere. The exact amount of solar radiation that actually is incident depends upon the time of year, the time of day, and the latitude. Bare Earth absorbs and transforms approximately 75 percent of all visible light impinging upon it. The remainder of the energy is reflected back into space.
Figure 1 depicts the atmospheric energy as it is received from the sun. The surface of the Earth, heated by the absorption of visible or short-wave solar radiation, converts this energy to thermal or long-wave radiation which, in turn, convectively and conductively heats the atmosphere.
In a typical region of scattered clouds 2 percent of the incident visible solar energy is absorbed in the stratosphere. Fifteen percent of the remaining energy is typically absorbed in the troposphere and converted to thermal energy.
Forty-seven percent of the visual radiation eventually reaches the surface-31 percent directly and 16 percent through atmospheric diffusion. Note that 36 percent of the original energy is reflected back into space-23 percent from the tops of clouds, 6 percent through diffusion in the troposphere, and 7 percent from the surface.
It is not obvious how the Earth maintains its energy balance. The Earth's surface absorbs about 124 kilo-langleys of solar radiation each year. Energy per unit area is expressed in langleys (ly) or kilo-langleys (kly). One langley is equivalent to 1 calorie per square centimeter. The Earth effectively radiates 52 kly of long-wave energy to the atmosphere. The difference between incoming and outgoing radiation is 72 kly which is the net energy balance. The global radiation balance is zero averaged (approximately) over the year, but it will not equal zero either seasonally or annually in a given latitude
An example of energy balance is represented in Figure 1. The atmosphere can gain energy from a variety of sources. The troposphere gains 15 percent of its thermal energy through direct conversion of visual energy to thermal energy. Of the black body (thermal) radiation from the Earth's surface (98 percent), 91 percent is partially absorbed in the atmosphere, and the remaining 7 percent is radiated into space. The stratosphere provides an additional 2 percent to the troposphere; convection (22 percent) and conduction (5 percent) account for about 27 percent.
The surface, then, has two sources of energy. It gains 47 percent in visual-to-thermal energy transformation and 78 percent in back radiation. The surface loses 98 percent to the atmosphere through long (infrared) waves, and 22 percent through convection and 5 percent through conduction. The gains and losses in the atmosphere-surface system are time dependent.
A layer of clouds, snow and ice can reflect 80 to 90 percent of the visible light back into space. Because climate depends primarily upon the amount of solar radiation that is absorbed by the Earth and atmosphere, albedo becomes important. Albedo is the ratio of the energy received from the sun and reflected by the Earth. The greater the albedo, the colder the Earth.
Clouds can serve to moderate whatever climate trend is under way: if the Earth's surface temperature climbs for whatever reason, more water evaporates and may rise to form more cloud cover. This increases the albedo and lowers the rate of heating. Ice and snow, on the other hand, provide positive feedback; if the average year-round temperature decreases, the extent of ice and snow coverage increases and reflects more of the incoming sunlight back to space. The result is to lower the rate of heating still more, particularly in the regions closest to the poles.
There is yet another contributor to the planet's albedo-airborne particles, particularly the extremely fine dust particles that have been carried too high in the atmosphere to be washed out by precipitation. Many of these particles remain aloft for months or years. Thus, a heterogeneous distribution of clouds may eventually cause a heterogeneous distribution of thermal energy around the Earth.
Many mechanisms are employed by the Earth to bring itself into thermal equilibrium. When thermal radiation from land surfaces heats the air directly above it, the rising air causes a change in the local atmospheric pressure. The spinning of the Earth and the resultant pressure differentials are physically manifested by the gaseous currents known as "wind." Thermal radiation from the Earth also causes the evaporation-condensation cycle that forces moisture from land and ocean sources to enter the atmosphere (Figure 2). Thus, the atmosphere becomes one of the major means of equalizing the thermal energy distribution around the world.
For evaporation to occur, both a driving force and a source of energy in the transformation phase are required. Radiation is the main energy source. In the presence of an adequate supply of energy, most precipitation evaporates before it has a chance to run off. The oceans lose more water by evaporation (84 percent) than they gain by precipitation (77 percent). The deficit is made up by run off from the continents (7 percent) over which precipitation exceeds evaporation.
The oceans provide about 84 percent of global evaporation, while the continents provide the remaining 16 percent. The change of phase from a liquid state to a vapor requires that energy be provided to overcome the intermolecular attractions between water molecules. The latent heat required to evaporate one gram of water at 0°C. is 600 calories. Condensation is responsible for releasing this energy. Thus the 7 percent horizontal advection of water vapor to the land mass contributes significantly to the transfer of energy to the continents. The normal dynamic movement of air and vapor masses is continuously directed at the equalization of energy in the oceans as well as land
Since 80 percent of the Earth's surface is water, principally the oceans, it would seem reasonable that mechanisms had to exist in the oceans to offset the heterogeneous distribution of thermal energy. Throughout all the major oceans, great currents of water flow between energy sinks and sumps. The winds created by the ocean's radiated energy form atmospheric tides. As an example, the greatest mass of water on the Earth-the Pacific Ocean-is constantly depressed one meter on the east side as compared with the west due to an atmospheric pressure anomaly.
Figure 3 shows that the most dangerous effect of the global cooling trend has been a change in atmospheric circulation and rainfall. The change centers on the behavior of the circumpolar vortex, the great cap of high-altitude winds revolving about the poles from west to east. The broad band across the Northern Hemisphere marks the approximate southern edge of the wind system as it was during the summertime in the early 1960s. Its southern edge determines the location of the prominent high-pressure regions, indicated here by narrow clockwise-spiraling arrows representing winds flowing outward. The highs
result from dry winds that descend after traveling at high altitudes from the equator. They created the world's great deserts and determine the northern limit of penetration by rain-bearing summer monsoons (indicated by heavy, northward-trending arrows). The limit is known as the "intertropical convergence zone."
Because of the global cooling trend, the lower edge of the circumpolar vortex has in recent years stayed farther south during the summer, in the position shown by the smaller band near the equator. It has kept the high pressure zones farther south too, blocking the monsoons out of regions where they are vital to the survival of hundreds of millions of people. At the same time, the vortex's semistationary wave patterns have altered, affecting rainfall patterns in temperate regions and making the climate more variable. The deeper wave over the U.S., for example, is believed responsible for recent cold winters in the West and mild ones in the East. The West has been subjected to north winds; the East, the return flow. Although some evidence exists that the cooling trend has affected wind patterns in the Southern Hemisphere as well, weather statistics are scanty.
There are three basic schools or philosophies of climatology. The first is centered around Professor H. H. Lamb, who is currently the Director of the Climatic Research Unit at the University of East Anglia in the United Kingdom. This school contends that if a climatologist is to project future climates, he must understand what has occurred in the past. The second is characterized by Dr. Joseph Smagorinsky, who is the Director of the Geophysical Fluid Dynamics Laboratory at Princeton University. This center believes that a complete understanding of atmospheric circulation is sufficient for climatic forecasting. The third is best represented by Dr. M. I. Budyko, an eminent Soviet climatological theoretician. He pursues the hypothesis that an understanding of the total distribution of thermal energy is necessary for climatic forecasting.
The Lambian school is based on the establishment of climatic statistical trends. A great deal of effort has been expended by the followers of this philosophy in quantifying the qualitative descriptions provided by historical sources (ancient court scribes, ship's logs, and scholars). Their reconstruction of climatic conditions has reached back 5,000 years. This particular approach was almost totally dependent upon man-made records. In recent years, the use of geophysical indicators such as tree rings, sedimentary deposits, and Arctic ice layering has added substantially to the global data pool.
Unique scientific methods have been developed which allow the climatologist to determine the historical intensity and distribution of solar radiation and precipitation on a worldwide bases. Before these developments, it was necessary for the scientist to infer climatic variability based on many indirect factors. Though this work is still quite incomplete, preliminary reports by Dr. John Imbrie (Brown University) have provided a fascinating portrayal of the Earth's climatology over the last 50 million years.
Current evidence indicates that the continental areas which were once in the tropical climatic regions of this planet, for some reason, underwent a rapid climatic change. Beginning approximately 20 million years ago (miocene period), large climatic variations characterized by what is known as the Ice Ages began to make appearances. Dr Imbrie's group has been able to establish that these Ice Ages are cyclic in nature and consist of approximately a 90,000-year glacial period followed by a relatively brief warming peak for 10,000 to 12,500 years, called the interglacial periods. Thus, as we see in Figure 4 based upon a sample space of 20 million years, this rather narrow period of the interglacial span is a consistent feature.
Investigations indicate interglacial periods never extended beyond 12,500 years nor has the period ever been less than 10,000 years (Figure 5). The glacial periods may be characterized by large continental ice sheets that extended across vast regions of Europe, North America, and Asia. This phenomena is well documented on the North American continent and came to an end approximately 10,000 years ago. The present interglacial era is characterized by a thermal maximum which occurred about 5,000 to 3,000 B.C. During this time, many major deserts in the world-as we know them-were formed, such as the Sahara, the Arabian, and great Mongolian deserts.
Climate change at the end of these interglacial time periods is rather sharp and dramatic. Excellent historical evidence exists from areas on the European plains which once were oak forests and were later transformed into poplar, then into birch, and finally into tundra within a 100-year span. Thus, the researchers of the CLIMAP group (CLImatic MAPing) hypothesize that the change from an interglacial to glacial time period could take place in less than 200 years. An example of rapid climatic changes are the remains of frozen mastodons completely preserved in Siberian and North American ice packs.
Scientists are confident that unless man is able to effectively modify the climate, the northern regions, such as Canada, the European part of the Soviet Union, and major areas in northern China, will again be covered with 100 to 200 feet of ice and snow. That this will occur within the next 2,500 years they are quite positive; that it may occur sooner is open to speculation.
The Smagorinsky-ian school of climatology is based upon the meteorologist's attempts to extend the predictive capabilities of the equations of fluid motion. Meteorology deals principally with the forecasting of atmospheric pressure differentials and the propensity for given patterns to result in rain, snow, ice, high winds, etc. It does not take into account solar or Earth radiation nor hydrological (i.e., evaporation) variables.
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Air temperatures in the lowlands of central England. Trends of the supposed 1000-year and 100-year averages since 10,000 B.C. (the latter calculated for the last millennium) (after Lamb, 1966). Shaded ovals indicate the approximate ranges within which the temperature estimates lie and error margins of the radiocarbon dates. Note that the pre-boreal phase begins about 8300 B.C. following the end of the Glacial Period.
models describe the effects of large-scale atmospheric motion and are treated explicitly by numerical integration. For almost 30 years the meteorologist has tried unsuccessfully to extend his predictive capability past a 24-hour forecast. The Smagorinsky-ian approach, however, is the currently accepted methodology within the United States Government and receives more than 90 percent of all the research and development funding available therein.
The Budyko-ian school is based upon the theoretical work of Dr. M. I. Budyko, who is associated with the Global Meterological Institute in Leningrad. The basis of this approach to the climatological problem is Dr. Budyko's 1955 paper entitled, "The Heat Balance of the Earth's Surface." This paper advances the hypothesis that all atmospheric motions are dependent upon the thermodynamic effect of a nonhomogeneous distribution of energy on the Earth's surface. Though this work originally met with opposition from the world's meteorologists, it is now accepted as a more reasonable basis for developing a successful climatic prediction model. The earlier, simplistic explanation of climate was basically Budyko-ian.
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