In 1896, a Swedish chemist named Svante Arrhenius suggested that the coal-fired Industrial Revolution was adding carbon dioxide gas to the atmosphere and that the gas might raise the temperature of the earth. Arrhenius went on to win the Nobel Prize for his other work in chemistry, but his ideas about climate change didn’t get much support.

He didn’t get much support – until the 1970s.

In the last third of the 20th century, the weight of scientific research has now strongly suggested that our worldwide climate is changing because of manmade processes and those changes will have significant impacts on agriculture. On the one hand, the world’s food supplies could be threatened as global warming progresses [and we have more on that in the Crops section]. On the other hand, farmers could help reduce climate changes by changing their farming practices.

Actually, life on Earth wouldn’t exist without some global warming from the Sun. Space is a very cold place. The Sun’s energy passes through the Earth’s atmosphere and heats the surface. The surface, in turn, radiates heat back to the atmosphere. Some of that heat energy passes through the atmosphere and dissipates back out in space. But some is trapped and reflected back to the surface by the water vapor in clouds and by gasses like carbon dioxide, nitrous oxide and methane.

It’s called the “greenhouse effect” because the atmosphere acts like the glass in a greenhouse, letting the Sun’s heat in and keeping the warm air inside. The global climate system is in a very delicate balance and there is now evidence that human activities are throwing the climate out of balance.

In the 1950s, an amateur British scientist named G.S. Callendar charted increasingly higher levels of carbon dioxide in the air and showed that a rise in fossil fuel emissions from cars and power plants paralleled the rise in CO₂. Then, Callendar suggested that the rising level of carbon dioxide could be causing a startling rise in the average global temperature. What became known as greenhouse gases – CO₂, Nitrous Oxide (N₂O) and methane (CH₄, a major component of natural gas) – reflect heat back to the surface of the earth, and as those gas levels rise the Earth heats up. More and more scientists examined Callendar’s work and expanded on it.

• In the 1950s, geophysicist Roger Revelle demonstrated that carbon dioxide levels in the air had increased because of the burning of fossil fuels.
• In 1965, Revelle was serving on the President’s Science Advisory Committee and wrote the first mention of global warming in a high-level governmental report.
• In 1968, studies suggested that a collapse of Antarctic ice sheets could raise sea levels catastrophically.
• In 1970, in the same year as the first Earth Day, the National Oceanic and Atmospheric Administration was created. NOAA became the world’s leading funder of climate research.
• In 1971, an international conference organized by MIT and Swedish scientific bodies reported a danger of rapid and serious global climate change caused by humans.
• In 1977, the nonpartisan National Academy of Sciences issued a study that said carbon dioxide is one of the primary greenhouse gases that contributes to global warming and that, once released, it remains in the atmosphere for a century.
• In 1982, Roger Revelle published a widely-read article in Scientific American addressing the rise in global sea levels. In the meantime, Revelle and (then) Representative Al Gore became close and Gore organized the first Congressional hearings on global warming.
• In 1988, NASA told Congress that “greenhouse warming should be clearly identifiable in the 1990s.” As global warming became a hot topic, the United Nations set up the Intergovernmental Panel on Climate Change (IPCC) to keep track of the scientific studies and make recommendations.
• In 1990, Congress passed and Pres. George Bush signed the “Global Change Research Act” to study climate change.
• In 1992, the “Earth Summit” brought together 30,000 leaders and scientists from 170 countries to discuss climate change. The conference produced a call to deal with global warming, but the U.S. blocked any serious actions.
• In 1995, the IPCC reported that measurements were detecting rising CO₂ levels and that serious global warming is likely in the coming century. In the meantime, the press reported the break up of Antarctic ice sheets and other signs of actual global warming. The public began to take serious note.
• In 1997, representatives of 160 nations met in Kyoto, Japan, and negotiated binding limitations on greenhouse gases for developed nations. But the U.S. Senate blocked the ratification of the treaty unless the same emission limitations were imposed on poorer nations. A majority in Congress were concerned that greenhouse gas limitations would seriously hurt our economy. The Kyoto Protocol was in limbo until 2005.
• In 2001, a third IPCC report stated baldly that global warming is happening and is unprecedented since the end of the last ice age. The debate about global warming among all but a few scientists was effectively over.
• In 2005, the Kyoto Protocol went into effect, signed by 149 nations, including all major industrial nations except the United States. The protocol committed developed nations to reduce their combined emissions to 5 percent below 1990 levels by 2008-2012.
• In February 2009, the Environmental Proection Agency (EPA) officially designated carbon dioxide and five other heat trapping gases to be pollutants dangerous to the environment. The Obama administration made the determination after the U.S. Supreme Court ordered the Bush administration to look at greenhouse gases. The Bush administration ignored the ruling. The determination was the first step in a process that could lead to the regulation of the gases for the first time in the United States, and that could have profound affects on transportation, manufacturing costs and power generation.

By 2009, worldwide CO₂ levels reached over 380 parts per million (ppm), up from levels of 290 ppm measured in ancient ice. And the global average temperature keeps rising.

Written by Bill Ganzel, the Ganzel Group. First published in 2009. A partial bibliography of sources is here.