Concept 45.6: Ecological Challenges Can Be Addressed through Science and International Cooperation

The current period of climate change is not unprecedented. Throughout the history of life on Earth, wobble in the planet’s orbit around the sun, continental drift, volcanic activity, sunspots, and even asteroid impacts have caused Earth’s climates to change, precipitating five major episodes of mass extinction (see Figure 18.12). There is even precedent for organism-caused change in the atmosphere. The first photosynthetic microbes increased atmospheric oxygen concentrations to a level that was toxic to the anaerobic prokaryotes that inhabited Earth at the time, and the first land plants raised oxygen concentrations even more about 250 million years ago. What is unprecedented about the present climate change is that it has been precipitated by diverse activities of a single species: Homo sapiens.

It is sobering to realize that one species can wield such power. However, it is encouraging to realize that, of all species on Earth, humans are uniquely able to address the problems they have caused—not only because science equips us to understand the natural world and to solve problems, but also because Homo sapiens has a remarkable capacity for cooperative action. We certainly are capable of selfishness and conflict too, but cooperative interactions are central features of all functional human societies. Other group-living animals cooperate as well, but scientific studies show that cooperation with unrelated individuals is especially highly developed in humans—even as infants we routinely offer help to another individual in need. We support cooperative societal ventures of all sorts, we police “bad” behaviors that can undermine cooperation—and we are unique, as far as we now know, in caring about the other species with which we share planet Earth.

The scale of cooperative human groups has gradually expanded through human history from prehistoric hunter–gatherer family groups to the United Nations, which spans the planet. It is encouraging that governments of separate nations have been cooperating in several global-scale initiatives to tackle complex environmental issues, from the IGY, which supported the first years of Dave Keeling’s work, to the United Nations’ Intergovernmental Panel on Climate Change and World Meteorological Organization, which operate today. Earth’s nations have also negotiated international agreements to achieve environmental goals, including the Montreal Protocol to prevent depletion of UV-absorbing atmospheric ozone, the Kyoto Protocol to reduce emissions of greenhouse gases, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which seeks to conserve species by eliminating the economic benefits of exploiting them.

Nonetheless, humans face huge challenges to achieving effective cooperation on a global scale. A major challenge is that the economic policies of virtually every nation are structured to achieve continual economic growth—ever-increasing production and consumption of goods and services—despite the fact that Earth has a finite capacity to provide those goods and services. We will need to make the transition to sustainable, steadystate economies, and that will require an overhaul of economic models and institutions. Another, related, challenge is the continued multiplicative growth of the human population (see Concept 42.4). On a crowded planet, with competition among societies for limited resources, cooperation inevitably becomes more difficult. Addressing both challenges will require us to devise international systems for establishing—and enforcing—rules of acceptable behavior among groups and nations.

ANSWER Dave Keeling’s four decades of research left an important legacy, the Keeling curve (see Figure 45.12A), which documents the ongoing increase in atmospheric CO₂ (Concept 45.4). Almost immediately, Keeling discovered that CO₂ concentrations do not vary erratically, as earlier crude methods of measurement suggested, but instead change seasonally as summer warmth, and the primary productivity that goes with it, shifts from the Northern Hemisphere (where most of Earth’s land mass lies) to the Southern Hemisphere (see Figure 45.12A inset).

Keeling’s measurements quickly contributed to a better understanding of the pools and fluxes of the global carbon cycle (Concept 45.3), including the influence of fossil fuel burning and cement production (which together added 9.5 × 10¹⁵ g of carbon—and 34.7 × 10¹⁵ g of carbon dioxide—to the atmosphere in 2011). Measurements on Mauna Loa and elsewhere continue to the present day, and they show that CO₂ increased from 315 parts per million (ppm) in the atmosphere in 1958 to 399 ppm in July 2013. Better understanding of the carbon cycle has contributed to greatly improved global climate models.

Keeling’s results were noticed almost immediately. In 1965 the U.S. President’s Science Advisory Committee warned of the increasing greenhouse effect, and in 1966 the National Academy of Sciences issued a scholarly report on the topic. The first World Climate Conference was held in Geneva, Switzerland, in 1979, at a time when there was growing scientific consensus that climate change poses a critical environmental challenge (Concept 45.5). The number of scientists studying climate change, and the sophistication of their experiments and models, grew rapidly. At the end of the twentieth century, measurements showed that the average temperature of the planet had increased by 0.7°C since 1900—an increase very close to the predictions of global climate models.

The Keeling curve forms a crucial part of our understanding of the Earth system. It is an example of the carefully documented scientific information used by the Intergovernmental Panel on Climate Change (IPCC). The IPCC was formed in 1988 by another scientific collaboration of governments—a sort of “grandchild” of IGY—and its many scientists continue to summarize and report on the latest evidence for natural and human-caused climate change. The 2009 IPCC report predicted a further human-caused increase in the global average temperature of between 1.8°C and 4.0°C by the year 2100.