The scientific consensus is expressed most clearly in the Fourth Assessment Report in 2007 by the United Nations-sponsored Intergovernmental Panel on Climate

Change (IPCC), the fourth in a series of reports since 1990 (1). The IPCC began as a group of scientists meeting in Geneva in November 1988 to discuss global climate issues under the auspices of the World Meteorological Organization and the United Nations Environment Program. But it had its genesis in the hot sum­mer of 1988. On a sweltering June day in Washington, DC, Senator Tim Wirth of Colorado chaired a committee hearing on climate change. The lead witness was James Hansen, an atmospheric physicist and head of NASA’s Goddard Institute for Space Studies. He proclaimed that global temperature was rising as his com­puter models predicted and that global warming was being caused by greenhouse gases released by human activities. The hearing got a lot of press and began a dialogue between scientists and policy makers. The World Conference on a Changing Atmosphere met in Toronto shortly after the Wirth hearing and called for coordinated policies among countries to reduce CO2 emissions. But public interest flagged as the hot summer faded into fall (2).

Lack of public interest didn’t stop the science, though. The IPCC meeting and subsequent workshops and reviews of what was known scientifically about cli­mate and its control was coordinated by a Swedish meteorologist, Bert Bolin, who was very careful not to let speculation get ahead of the science. The IPCC gave its First Assessment Report to the UN in the fall of 1990 and concluded that the earth was indeed warming and that humans were “substantially increasing the atmospheric concentrations of the greenhouse gases carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide.” Furthermore, “the main green­house gas, water vapour, will increase in response to global warming and further enhance it.” But it also concluded that the global warming could be caused by either man-made greenhouse gases or natural climate variability (3).

There was sufficient reason to worry, though, that the United Nations General Assembly called for an international agreement to limit CO2. This was to be ham­mered out at an Earth Summit to be held in Rio de Janeiro in 1992. After a fractious meeting filled with plenty of demagoguery, an agreement was finally signed—the United Nations Framework Convention on Climate Change. It committed devel­oped countries to control their greenhouse gas emissions and to provide financial resources for developing countries to reduce their emissions. It called for devel­oped countries to reduce emissions in 2000 to 1990 levels on a voluntary basis (2).

This was just the beginning. The IPCC prepared a second scientific assessment report in 1995 by even more scientists, again under the careful leadership of Bert Bolin, which built on the conclusions of the first report. The second report sub­stantiated the general conclusions of the first report with more precise data but made an important new conclusion—that there was now “a discernible human influence on global climate” (4)

And then came the infamous meeting in Kyoto in 1997, which aimed to put teeth in the Rio conference agreement. Greenhouse gas emissions had in fact gone up substantially since 1990, so specific targets were to be set. The United States and the European Union had divergent views on emissions targets, but the deadlock was broken by the arrival of Vice President Al Gore. He had already written a seri­ous book, Earth in the Balance, discussing greenhouse gases and global warming (5), and his presence at Kyoto seemed to indicate that the United States was serious about reducing greenhouse gas emissions. The United States, Europe, and Japan agreed to binding targets to reduce CO2 emissions by 6-8% by 2008-2012 com­pared to 1990, with an overall goal of reducing global greenhouse gas emissions by 5% below 1990 levels (6). The second big dispute was between developed and devel­oping countries. Developing countries such as China, India, and Brazil refused to make binding commitments to reduce greenhouse gases since they (rightly) claimed that they had not caused the problem with greenhouse gases. However, as they grew they would become a bigger contributor to the problem. The problem was that the US Senate had made it clear in the Byrd-Hagen Resolution of 1992 that it would not accept a treaty that exempted developing countries. The third dispute arose over how to pay for emissions reductions. The United States had suc­cessfully implemented a cap and trade system to reduce acid rain from coal-fired power plants and wanted that market-oriented model; Europe wanted mandates and governmental intervention. The United States won the argument, and the Kyoto Protocol was signed. But the disagreement over the role of developing coun­tries meant that it could never clear the US Senate. President Bill Clinton never even submitted the treaty for consideration, knowing it would be defeated (2).

The third Scientific Assessment Report for the IPCCin2001 continued to refine the conclusions of previous reports with increasingly accurate data and modeling. It also began to give statistical values to its conclusions. The evidence pointing to the human contribution to global warming was even stronger, with the report concluding that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”(7)

And the political meetings continued. Political leaders from all over the world met in Copenhagen in late 2009 to discuss global climate change and what can be done to prevent or mitigate it, though they were not able to decide on any course of action (8). They met again in Cancun in late 2010 and signed a modest agreement to begin to tackle global warming. “For the first time all countries are committed to cutting car­bon emissions under an official UN agreement. Rich nations also have to pay a total of £60 billion [$92 billion] annually from 2020 into a “green fund” to help poor countries adapt to floods and droughts. The money will also help developing countries, includ­ing China and India, switch to renewable energy sources including wind and solar power”(9) Also, in late 2009 the US Environmental Protection Agency (EPA) ruled that greenhouse gases pose a danger to the environment and to human health, open­ing the door to regulation of CO2 emissions from automobiles, power plants, factories, and other anthropogenic sources.

But signing agreements and actually doing something about it are two differ­ent things. So far the action to mitigate CO2 emissions has been minimal, espe­cially in the United States. Europe, however, established a cap and trade market in 2003—the European Union’s Emission Trading Scheme—and adopted an ambi­tious goal to reduce CO2 emissions by 20% of 1990 levels by 2020 (2). The United States, meanwhile, failed to get any legislation passed that would establish a cap and trade market to reduce CO2 emissions, and the whole issue became a political hot potato because of widespread Republican opposition.

It is well beyond the scope of this chapter to discuss all of the issues fully, but it is important to consider the science behind the controversy, since the premise of this book is that global climate change is occurring due in large part to anthropo­genic contributions to atmospheric CO2 from burning fossil fuels. So, is it or isn’t it? That is the question.