I am Thomas Gale Moore, an economist and a Senior Fellow at the Hoover Institution. Recently I have published two papers based on historical evidence that earlier warm periods were good for mankind. My current research deals with health effects and amenity benefits of a less cold climate.
If warming occurs, it is more likely to bring net benefits than losses to Americans and most of the world. Warmer periods in the past have brought benign weather. Milder temperatures will induce more evaporation from oceans and very likely more rainfall -- where it will fall we cannot be sure but the earth as a whole should receive greater precipitation. Meteorologists now believe that any rise in sea levels over the next century will be at most a foot or two, not twenty. History shows that around 6,000 years ago the earth sustained temperatures that were probably more than four degrees Fahrenheit hotter than those of the twentieth century, yet mankind flourished. The Sahara desert bloomed with plants, and water loving animals such as hippopotamuses wallowed in rivers and lakes. Dense forests carpeted Europe from the Alps to Scandinavia.
History shows that the world has shifted from periods that were considerably warmer -- during the Mesozoic era when the dinosaurs thrived the earth appears to have been about 18deg. Fahrenheit warmer than now -- to spells that were substantially colder, such as the Ice Ages when huge glaciers submerged much of the Northern Hemisphere. During the last interglacial, about 130,000 years ago or about when modern man was first exploring the globe, the average temperature in Europe was at least 2deg. to 5deg.F warmer than at present. Hippopotamuses, lions, rhinoceroses and elephants roamed the English countryside. Areas watered today by the monsoons in Africa and east Asia enjoyed even more rainfall then. Indeed during the last 12,000 years, that is since the end of the last glacial period, the globe has alternated between times substantially warmer and epochs that were noticeably cooler.
An examination of the record of the last twelve millennia reveals that mankind prospered during the warm periods and suffered during the cold ones. Transitions from a warm to a cold period or vice-versa were difficult for people who lived in climates that were adversely affected yet benefited others who inhabited regions in which the weather improved. On average, however, humans gained during the centuries in which the earth enjoyed higher temperatures.
A warmer climate could, however, change the nature and location of tourism. Many ski resorts, for example, might face less reliably cold weather and shorter seasons.
A number of articles in the popular press as well as some pieces in more scientific journals have raised alarms about the spread of tropical diseases that might accompany warming. Concern about tropical and insect-spread diseases seems overblown. Inhabitants of Singapore, which lies almost on the equator, and of Hong Kong and Hawaii, also in the tropics, enjoy life spans as long as or longer than those of people living in Western Europe, Japan, and North America. Modern sanitation in advanced countries prevents the spread of many scourges found in hot climates.
Moreover, deaths from disease peak in the winter; overall mortality is 17 percent greater when it is cold than in the warm season. Respiratory problems, such as pneumonia and influenza, are a particular problem in cold months, but even the leading causes of death -- diseases of the circulatory system -- kill more people in the winter. Rather than increasing mortality, these data suggest that warmer weather should reduce it, but this possibility is rarely discussed.
Over the last few months, I have been exploring the relationship between climate and death rates. After holding constant the proportion of the population that is elderly, the racial composition of the area, and the income or education of the people, the warmer the climate the lower the death rate. Based on nationwide data for some 89 major counties I find that a warming of 2.5deg. Celsius would reduce deaths by nearly 40,000 annually.
A rise in world-wide temperatures will go virtually unnoticed by inhabitants of the advanced industrial countries. In his 1991 address to its members, the President of the American Economic Association asserted: "I conclude that in the United States, and probably Japan, Western Europe and other developed countries, the impact on economic output [of global warming] will be negligible and unlikely to be noticed." As modern societies have developed a larger industrial base and become more service oriented, they have grown less dependent on farming, thus boosting their immunity to temperature variations.
A warmer climate would produce the greatest gain in temperatures at northern latitudes and much less change near the equator. Not only would this foster a longer growing season and open up new territory for farming but it would mitigate harsh weather. As a result of more evaporation from the oceans, a warmer climate should intensify cloudiness. More cloud cover will moderate daytime temperatures while acting at night as an insulating blanket to retain heat. The Intergovernmental Panel on Climate Change has found exactly this pattern both for the last 40 years, indeed for the whole of the twentieth century. For the Northern Hemisphere in summer months, daytime high temperatures have actually fallen; but in the fall, winter and spring, both the maximum and especially the minimum temperatures (nighttime) have climbed.
Warmer nighttime temperatures, particularly in the spring and fall, create longer growing seasons, which should enhance agricultural productivity. Moreover, the enrichment of the atmosphere with CO2 will fertilize plants and make for more vigorous growth. Agricultural economists studying the relationship of higher temperatures and additional CO2 to crop yields in Canada, Australia, Japan, northern Russia, Finland, and Iceland found not only that a warmer climate would push up yields, but also that the added boost from enriched CO2 would enhance output by 17 percent. Researchers have attributed a burgeoning of forests in Europe to the increased CO2 and the fertilizing effect of nitrogen oxides.
There have been two periods since the last ice age during which the climate was significantly warmer than it is today. During the first period, sometimes called the Climatic Optimum Period, the earth was much warmer than today; perhaps 4deg.F hotter, about the average of the various predictions for global warming after a doubling of CO2. Although the climate cooled a bit after 3000 B.C., it stayed relatively warmer than the modern world until sometime after 1000 B.C., when chilly temperatures became more common. During this Climatic Optimum epoch, Europe enjoyed mild winters and warm summers with a storm belt far to the north. Not only was the country less subject to severe storms, but the skies were less cloudy and the days sunnier.
The invention of agriculture coincided with the end of the last Ice Age and the melting of the glaciers. Archaeologists have found the earliest evidence for husbandry and farming in Mesopotamia around 9000 B.C. The domestication of plants appears to have occurred around the world at about the same time: from 10,000 YBP to 7,500 YBP.
The development of agriculture and the establishment of fixed communities led to a population explosion and the founding of cities. Agricultural societies produce enough surplus to support such urban developments, including the evolution of trades and new occupations. A large community could afford to have specialists who made farm tools, crafted pots, and traded within the village and between the locals and outsiders.
In Europe, the Optimum period produced an expansion of civilization with the construction of cities and a technological revolution. The Bronze Age replaced the New Stone Age. The more benign climate with less severe storms encouraged travel by sea. Trade flourished during this warm period.
During the second warm period from around 800 A.D. to 1200 or 1300, the globe warmed considerably and civilization prospered. Virtually all of northern Europe, the British Isles, Scandinavia, Greenland, and Iceland were considerably warmer than at present. The Mediterranean, the Near East, and North Africa, including the Sahara, received more rainfall than they do today. North America enjoyed better weather during most of this period. China during the early part of this epoch experienced higher temperatures and a more clement climate. From Western Europe to China, East Asia, India, and the Americas, mankind flourished as never before.
The warm period coincided with an upsurge of population almost everywhere, but the best data are for Europe. For centuries during the cold damp "dark ages" the population of Europe had been relatively stagnant. Towns shrank to a few houses clustered behind city walls. Although we lack census figures, the numbers from Western Europe after the climate improved show that cities grew in size; new towns were founded; and colonists moved into relatively unpopulated areas.
The warmth of the Little Climate Optimum made territory farther north cultivable. In Scandinavia, Iceland, Scotland, and the high country of England and Wales, farming became common in regions which neither before nor since have yielded crops reliably. In Iceland, oats and barley were cultivated. In Norway, farmers were planting further north and higher up hillsides than at any time for centuries. Greenland was 4deg. to 7deg.F warmer than at present and settlers could bury their dead in ground which is now permanently frozen. Scotland flourished during this warm period with increased prosperity and construction. Greater crop production meant that more people could be fed, and the population of Scandinavia exploded.
Farmers and peasants in medieval England launched a thriving wine industry south of Manchester. Good wines demand warm springs free of frosts, substantial summer warmth and sunshine without too much rain, and sunny days in the fall. Winters cannot be too cold -- not below zero Fahrenheit for any significant period. The northern limit for grapes during the Middle Ages was about 300 miles above the current commercial wine areas in France and Germany. These wines were not simply marginal supplies, but of sufficient quality and quantity that, after the Norman conquest, the French monarchy tried to prohibit British wine production.
All across Europe, the population went on an unparalleled building spree erecting at huge cost spectacular cathedrals and public edifices. Byzantine churches gave way to Romanesque, to be replaced in the twelfth century by Gothic cathedrals. Virtually all the magnificent religious edifices that we visit in awe today were started by the optimistic populations of the eleventh through the thirteenth centuries, although many were not finished for centuries. In southern Spain, the Moors laid the cornerstone in 1248 for perhaps the world's most beautiful fortress, the Alhambra.
Economic activity blossomed throughout the continent. Banking, insurance, and finance developed; a money economy became well established; manufacturing of textiles expanded to levels never seen before. Farmers were clearing forests, draining swamps and expanding food production to new areas. Starting in the eleventh century European traders developed great fairs that brought together merchants from all over Europe. At their peak in the thirteenth century they were located on all the main trade routes and served not only to facilitate the buying and selling of all types of goods but also functioned as major money markets and clearing houses for financial transactions.
The warming in the Far East seems to have preceded that in Europe by about two centuries. Chinese Economist Kang Chao has studied the economic performance of China since 200 B.C. In his careful investigation, he discovers that real earnings rose from the Han period (206 B.C. to 220 A.D.) to a peak during the Northern Sung Dynasty (961 A.D. to 1127). The wealth of this period gave rise to a great flowering of art, writing, and science. The Little Climate Optimum witnessed the highest rate of technological advance in Chinese history.
Over the four hundred years between 800 A.D. and 1200, the peoples of South Asia prospered as well. Society was rich enough to produce colossal and impressive temples, beautiful sculpture, elaborate carvings, many of which survive to this day. In India, the Lingaraja Temple, one of the finest Hindu shrines, as well as the Shiva Temple date from this period. Seafaring empires existed in Java and Sumatra, which reached its height around 1180. Ninth century Java erected the vast stupa of Borobudur; other temples -- the Medut, Pawon, Kelasan and Prambanan -- originate in this era. In the early twelfth century, the predecessors of the Cambodians, the Khmers, built the magnificent temple of Angkor Wat. In the eleventh century Burmese civilization reached a pinnacle.
Starting around 800 to 900 A.D., the indigenous peoples of North America extended their agriculture northward up the Mississippi, Missouri, and Illinois river basins. By 1000 they were farming in southwestern and western Wisconsin and eastern Minnesota. They grew corn in northwestern Iowa prior to 1200 in an area which is now marginal for rainfall. In the Southwest, which received more rainfall during the warm period, the Anasazi civilization of Mesa Verde flourished until the climate cooled and became drier near the end of the thirteenth century..
As noted, not all regions or all peoples benefit from a shift to a warmer climate. Some locales may become too dry or too wet; others may become too warm. Certain areas may be subject to high pressure systems which block storms and rains. Other parts may experience the reverse. On the whole, though, mankind should benefit from an upward tick in the thermometer. Warmer weather means longer growing seasons, more rainfall overall, and fewer and less violent storms. The optimal way to deal with potential climate change is not to strive to prevent it, a useless activity in any case, but to promote growth and prosperity so that people will have the resources to deal with any shift.