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A Timeline of the Rise of Environmentalism: 1940s–1970s

Climate and the environment are top policy issues today. In this blog post—the first in a two-part series—I trace the history of these topics. I highlight key trends and moments in history that exacerbated environmental degradation, as well as those that shaped public opinion about such destruction. I also outline key scientific advances that have allowed for a better understanding of environmental issues, particularly climate change.

The Trade-Offs of Post-War Reconstruction
World War II brought great destruction and immense casualties in Europe, Asia, and the Pacific—and a global effort in wartime production, offset by a contraction in trade.

After the war, furious efforts of economic reconstruction took place in most parts of the world. (The series of photos below depicts some of the effects of these efforts—including technological advances, increasingly crowded cities, and, of course, pollution.)

The USSR sought to rebuild after the German occupation and to face the American challenge; Western Europe grew rapidly under the U.S.-funded Marshall Plan; colonial investment in Africa meant higher taxes for African subjects; postwar Japan recovered in response to American spending during the Korean War; and other Latin American economies, including Brazil’s, grew as well.

Brazil’s economic growth—as shown in the graph below—lasted almost 30 years. (Notably, about half of this growth was under dictatorship, and it was followed by economic decline.)

The graphic here shows the rate of Brazilian growth up to 1975, followed by decline; Urban and rural degradation of environment rose with growth.

Although booming industry and development—in Brazil and elsewhere—led to economic growth; it also brought death and destruction. Many communities suffered from exposure to asbestos, lead, chemical waste, and pesticides like DDT, which increased death rates. In response, environmental social movements rose to protest the use of pesticides (in Brazil) and industrial poisons (in Japan and the United States). In India, the Green Revolution—a period of agricultural modernization—expanded grain output for wealthy farmers while dispossessing small farmers.

Burial of a new car at the inaugural Earth Day, April 12, 1970
Burial of a new car at the inaugural Earth Day, April 12, 1970

On April 12, 1970, an informal, youth-based coalition organized Earth Day in San Jose, California. It celebrated the Earth and its environment. Leader Denis Hayes, a recent Stanford University graduate, was supported in this effort by Bay Area congressman Pete McCloskey and Wisconsin Senator Gaylord Nelson. The highlight of the day, shown at left, was the burial of a new car. The car is seen in a deep pit, with celebrants gathering around it before the burial. (Denis Hayes had been a student in my course on history of the Zulu in Africa at Stanford in 1968.)

Starting around 1970, attention to the environment expanded widely. Public outcry led to organized movement and study, and the results were meaningful, including:

  • Creating programs of environmental studies—first in wealthy countries such as the U.S, UK, and Denmark, and later in other countries around the world.
  • New publications on environmental history, which traced the history of disease, agriculture, and ecology: Rachel Carson, Silent Spring (1962); William Cronon, Changes in the Land (1983), on colonial New England.
  • Locating early writers on environment, such as Swedish physicist Svante Arrhenius, who first identified the greenhouse effect in the 1890s; and Swedish biologist Carl Linnaeus, who classified great numbers of plants and animals in the 18th century; even Aristotle was seen as an environmentalist.
  • Powerful reactions against environmentalism, especially from Exxon, the world’s biggest oil firm, which supported free markets and opposed limits on petroleum consumption.

Environmental Science: Tracing Change Over Billions of Years
Chemist James Lovelock showed, beginning in 1972, that Earth’s atmosphere, previously mostly methane, became balanced almost 4 billion years ago, gaining enough oxygen to support life, and with average temperature varying no more than 10 oC (or 18 oF). This was an early and successful version of fundamentally multidisciplinary thinking.

Italian scholar Cesare Emiliani studied fossil algae recovered from Swedish cores of the ocean bottom, showing that they yielded ocean temperatures over 300,000 years. Emiliani traced the ratio of two different oxygen isotopes (the main 16O isotope and the minor 18O isotope) and found that high levels of 18O meant low temperatures. He identified Marine Isotope Stages (MIS), where the ratio of 18O/16O is high (low temperature), or low (high temperature). His 1955 results, shown here, showed oceanic temperature  in MIS stages.

Emiliani (1955). High level of oceanic 18O (compared to 16O) for low temperature. Low temperature for high 18O. MIS stages 1-14 are shown at bottom.
Emiliani (1955). High level of oceanic 18O (compared to 16O) for low temperature. Low temperature for high 18O. MIS stages 1-14 are shown at bottom

In 1967, Nicholas Shackleton identified a new factor: in cold times, lighter water (with 16O) evaporated and fell in polar areas as ice sheets, so that a high oceanic ratio of 18O/16O resulted from removal of 16O from the oceans and its deposit in ice sheets. This was a different interpretation of Emiliani’s MIS data.

Still another interpretation came. Serbian astronomer Milutin Milankovitch’s calculations, originally published in 1927, show 200,000 years of the Earth’s  orbital fluctuations and the resulting “insolation”—the varying force of solar radiation on the surface of the Earth.

Milankovitch’s calculations depict eccentricity, obliquity, and precession, which combine to predict changes in insolation on the Earth.
Milankovitch’s calculations depict eccentricity, obliquity, and precession, which combine to predict changes in insolation on the Earth.

Milankovitch’s cycles (pictured left) show three types of fluctuations: eccentricity (with a cycle of 100,000 years), obliquity (cycle of 40,000 years), and precession (cycle of 20,000 years). The combination of these fluctuations brought predictable levels of overall insolation for the various regions of the Earth over time.

Not until the 1970s was insolation recognized as the main cause of climate change, as it provokes ice ages as well as changing oceanic temperature.

UNESCO, the United Nations scientific organization, sponsored programs of global research, especially the International Geophysical Year (IGY), 1957-58. The IGY quickly found that the mid-ocean ridges—shown as dark lines in the map on the right—formed lines along which magma rose from below, forcing the seafloor to widen.

International Geophysical Year (IGY), 1957-58. The IGY quickly found that the mid-ocean ridges—shown as dark lines in the map on the right—formed lines along which magma rose from below, forcing the seafloor to widen.

The research also revealed that the Earth’s magnetic pole shifted, after many million years—from North to South and back again—with a record preserved in the spreading seafloor. (This is shown in dark and light green layers in the graphic at right.)

By 1965-67, generalization of ocean-floor studies clarified plate tectonics. Soon, the history of the movement of plates, in these patterns, revealed millions of years of movement of the continents.


In the 1950s, Charles Keeling, a new PhD in physics, was greatly concerned that the level of atmospheric CO2 might be growing rapidly, with changes in only decades. He proposed an experiment to gather accurate data at one of the highest and most isolated points in the world: the top of Mauna Kea on Hawaii.

Keeling gained support for the project and started collecting data in 1958. By 1965, it was clear that the overall rate of growth of atmospheric CO2 was significant—and frightening.

Other scholars began to model the impact of growing CO2 on climate. Data could come from satellites and from ice-core data.

Mauna Loa Observatory, Hawaii. Monthly Average Carbon Dioxide Concentration.

The study that provided the best early answer on the seriousness of rising atmospheric CO2 came from Syukoro Manabe’s 1967 model of the atmosphere. He showed that doubling the level of CO2 (from 150 to 300 parts per million) would add 3 oC to average temperature.

Manabe, another new physics PhD, hailed from Tokyo University and was working at Princeton University. He created a one-dimensional model: an atmospheric column, from the Earth’s surface to 40 km high, showing a decline in atmospheric pressure from 1,000 millibars at the surface to 2.3 millibars at 40 km high.

Assuming a doubling in atmospheric CO2 concentration shows the rising temperature in the troposphere and the declining temperature in the stratosphere. Temperature (across the bottom) is in degrees Kelvin, where 273 oK is freezing point of water and 295 oK is 71 oF. (Triangles show figures for initial 150 ppm of CO2; x’s show figures for 300 ppm of CO2.)

Manabe’s results showed that a doubling of CO2 concentration would raise Earth’s surface temperature by 3 oC (or 5 oF).

Manabe’s 2021 Nobel Prize lecture is a clear and brilliant statement of his original 1967 work—showing how simple analysis can sometimes reveal fundamental principles. His lecture also traces the resulting expansion of collaborative work in climate modeling, which was summarized in reports by a United Nations commission beginning in 1988.

Public Policy Change in the 1970s
Japan’s Basic Law for Environmental Pollution Control, adopted in 1967, was the first national law regulating environmental pollution. In response to public demand, this law placed serious restrictions on pollution and remained in place until the 1990s.

In 1970, the United States established its Environmental Protection Agency (EPA), which initiated an active program of restricting environmental pollution. But by 1973, corporate opposition to environmental regulation had already limited the EPA’s effectiveness.

Worldwide interest in environmental protection rose, however, and the Stockholm Environment Conference of 1972 was widely attended. In its wake, the UN Environmental Program formed, and it was effective in conveying the interaction and significance of environmental issues.

Environmental impact reports, beginning about 1970, were one practical result of public reform for environmental protection, in the U.S. and worldwide. These reports required that any new construction project specify the various types of environmental change likely to result from the project. This valuable tool, while not always used, raised the standards for anticipating and limiting environmental destruction.

By 1985, remarkable new data had become available on the oceans, temperature change, continental drift, and short-term temperature rise. Collaborative work to model and predict global warming had succeeded.  Efforts moved ahead to document environmental decline and to set policies that protect the environment. But as I will argue in my next posting, despite this expanded knowledge and public support for action, new environmental problems would soon arise.

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