global warming policy

global warming policy, the process by which key decisions regarding the mitigation of global warming and its effects on climate change are made or influenced by central governments. Leading climate scientists agree that many of the ongoing changes to the global climate system are largely caused by the release into the atmosphere of greenhouse gases—that is, gases that enhance Earth’s natural greenhouse effect. Although opponents of this view have often stressed the role of natural factors in past climatic variation and have accentuated the scientific uncertainties associated with data on global warming and climate change, a consensus of scientists has called upon governments, industries, and citizens to reduce their emissions of greenhouse gases.

Since the 19th century, many researchers working across a wide range of academic disciplines have contributed to an enhanced understanding of the atmosphere and the global climate system. Concern among prominent climate scientists about global warming and human-induced (or “anthropogenic”) climate change arose in the mid-20th century, but most scientific and political debate over the issue did not begin until the 1980s. Since then, scientific studies have traced increases in the concentrations of greenhouse gases (such as carbon dioxide, methane, nitrous oxide, and other chemical compounds) in Earth’s atmosphere to the burning of fossil fuels for heating, cooking, electrical generation, transportation, and manufacturing combined with the natural decomposition of organic materials, wildfires, deforestation, and land-clearing activities. For a detailed description of the phenomenon of global warming, see global warming.

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All countries on Earth emit greenhouse gases, but highly industrialized countries and more populous countries emit significantly greater quantities than others. Countries in North America and Europe that were the first to undergo the process of industrialization have been responsible for releasing most greenhouse gases in absolute cumulative terms since the beginning of the Industrial Revolution in the mid-18th century. Today these countries are being joined by large developing countries such as China and India, where rapid industrialization has been accompanied by a growing release of greenhouse gases. According to the World Resources Institute, in 2019 China and India, whose combined populations totaled more than 36 percent of the world’s human population, accounted for 26.4 percent and 7.1 percent of global greenhouse emissions, respectively. In contrast, the United States, which possessed approximately 4.25 percent of the global population, emitted almost 12.5 percent of global greenhouse gases in 2019. The same year, the 27 member states of the European Union (EU; excluding the United Kingdom, which formally left the EU in 2020), which possessed about 5.8 percent of the global population, emitted 7.0 percent of all anthropogenic greenhouse gases.

In terms of per capita emissions, however, citizens of highly industrialized countries continue to produce more greenhouse gas emissions than those of developing ones. According to the World Bank, in 2000 the average American emitted 20.5 tons of greenhouse gases, the average person living in the EU released 7.8 tons, and the average person living in China discharged only 2.65 tons. Although China’s per capita greenhouse gas emissions were significantly lower than those of the EU and the United States, it became the largest greenhouse gas emitter in 2006 in absolute terms. By 2019 per capita emissions in the United States and the EU had peaked and fallen to about 14.7 tons and 6.1 tons, respectively, whereas per capita emissions in China more than doubled, increasing to about 7.6 tons that same year.

The IPCC and the scientific consensus

An important first step in formulating public policy on global warming and climate change is the gathering of relevant scientific and socioeconomic data. In 1988 the Intergovernmental Panel on Climate Change (IPCC) was established by the World Meteorological Organization and the United Nations Environment Programme. The IPCC is mandated to assess and summarize the latest scientific, technical, and socioeconomic data on climate change and to publish its findings in reports presented to international organizations and national governments all over the world. Many thousands of the world’s leading scientists and experts in the areas of global warming and climate change have worked under the IPCC, producing major sets of assessments in 1990, 1995, 2001, 2007, 2014, and 2021. Those reports evaluated the scientific basis of global warming and climate change, the major issues relating to the reduction of greenhouse gas emissions, and the process of adjusting to a changing climate.

The first IPCC report, published in 1990, stated that a good deal of data showed that human activity affected the variability of the climate system; nevertheless, the authors of the report could not reach a consensus on the causes and effects of global warming and climate change at that time. The 1995 IPCC report stated that the balance of evidence suggested “a discernible human influence on the climate.” The 2001 IPCC report confirmed earlier findings and presented stronger evidence that most of the warming over the previous 50 years was attributable to human activities. The 2001 report also noted that observed changes in regional climates were beginning to affect many physical and biological systems and that there were indications that social and economic systems were also being affected.

The IPCC’s fourth assessment, issued in 2007, reaffirmed the main conclusions of earlier reports, but the authors also stated—in what was regarded as a conservative judgment—that they were at least 90 percent certain that most of the warming observed over the previous half century had been caused by the release of greenhouse gases through a multitude of human activities. Both the 2001 and 2007 reports stated that during the 20th century there had been an increase in global average surface temperature of 0.6 °C (1.1 °F), within a margin of error of ±0.2 °C (0.4 °F). Whereas the 2001 report forecast an additional rise in average temperature by 1.4 to 5.8 °C (2.5 to 10.4 °F) by 2100, the 2007 report refined this forecast to an increase of 1.8–4.0 °C (3.2–7.2 °F) by the end of the 21st century. Those forecasts were based on examinations of a range of scenarios that characterized future trends in greenhouse gas emissions.

The IPCC’s fifth assessment report, released in 2014, further refined projected increases in global average temperature and sea level. The 2014 report stated that the interval between 1880 and 2012 saw an increase in global average temperature of approximately 0.85 °C (1.5 °F) and that the interval between 1901 and 2010 saw an increase in global average sea level of about 19–21 cm (7.5–8.3 inches). The report predicted that by the end of the 21st century surface temperatures across the globe would increase between 0.3 and 4.8 °C (0.5 and 8.6 °F), and sea level could rise between 26 and 82 cm (10.2 and 32.3 inches) relative to the 1986–2005 average. This assessment was followed by a special report in 2018 that noted that human beings and their activities have been responsible for a worldwide average temperature increase between 0.8 and 1.2 °C (1.4 and 2.2 °F) since preindustrial times and that most of the warming over the second half of the 20th century could be attributed to human activities.

The IPCC’s sixth assessment report, published in 2021, noted that the best estimate of the increase in global average surface temperature between 1850 and 2019 was 1.07 °C (1.9 °F). The report provided a series of global climate predictions based on scientific models of five greenhouse gas emission scenarios that accounted for future emissions, mitigation (severity reduction) measures, and uncertainties in the model projections. Some of the main uncertainties include the precise role of feedback processes and the impacts of industrial pollutants known as aerosols, which may offset some warming. The lowest-emissions scenario, which assumed steep cuts in greenhouse gas emissions starting in 2015, predicted that the global mean surface temperature would increase between 1.0 and 1.8 °C (1.8 and 3.2 °F) by 2100 relative to the 1850–1900 average. This range stood in stark contrast to the highest-emissions scenario, which predicted that the mean surface temperature would rise between 3.3 and 5.7 °C (5.9 and 10.3 °F) by 2100, assuming that greenhouse gas emissions would continue to increase throughout the 21st century. The intermediate-emissions scenario, which speculated that emissions would stabilize by 2050 before declining gradually, projected an increase of between 2.1 and 3.5 °C (3.8 and 6.3 °F) by 2100.

Each IPCC report has helped to build a scientific consensus that elevated concentrations of greenhouse gases in the atmosphere are the major drivers of rising near-surface air temperatures, sea level rise, and other associated ongoing climatic changes. In this respect, the current episode of climatic change, which began about the middle of the 20th century, is seen to be fundamentally different from earlier periods in that critical adjustments have been caused by activities resulting from human behaviour rather than nonanthropogenic factors. The IPCC’s 2007 assessment projected that future climatic changes could be expected to include continued warming, modifications to precipitation patterns and amounts, elevated sea levels, and “changes in the frequency and intensity of some extreme events.” Such changes would have significant effects on many societies and on ecological systems around the world.

The UN Framework Convention and the Kyoto Protocol

The reports of the IPCC and the scientific consensus they reflect have provided one of the most prominent bases for the formulation of climate-change policy. On a global scale, climate-change policy is guided by two major treaties: the United Nations Framework Convention on Climate Change (UNFCCC) of 1992 and the associated 1997 Kyoto Protocol to the UNFCCC (named for the city in Japan where it was concluded).

The UNFCCC was negotiated between 1991 and 1992. It was adopted at the United Nations Conference on Environment and Development in Rio de Janeiro in June 1992 and became legally binding in March 1994. In Article 2 the UNFCCC set the long-term objective of “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” Article 3 established that the world’s countries have “common but differentiated responsibilities,” meaning that all countries share an obligation to act—though industrialized countries have a particular responsibility to take the lead in reducing emissions because of their relative contribution to the problem in the past. To this end, by 2013 the UNFCCC Annex I listed 42 specific industrialized countries and countries with economies in transition plus the European Economic Community (EEC; formally succeeded by the EU in 2009), and Article 4 stated that these countries should work to reduce their anthropogenic emissions to 1990 levels. However, no deadline was set for this target. Moreover, the UNFCCC did not assign any specific reduction commitments to non-Annex I countries (that is, developing countries).

The follow-up agreement to the UNFCCC, the Kyoto Protocol, was negotiated between 1995 and 1997 and was adopted in December 1997. The Kyoto Protocol regulated six greenhouse gases released through human activities: carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF₆). Under the Kyoto Protocol, Annex I countries were required to reduce their aggregate emissions of greenhouse gases to 5.2 percent below their 1990 levels by no later than 2012. Toward this goal, the protocol set individual reduction targets for each Annex I country. These targets required the reduction of greenhouse gases in most countries, but they also allowed increased emissions from others. For example, the protocol required the then 15 member states of the EU and 11 other European countries to reduce their emissions to 8 percent below their 1990 emission levels, whereas Iceland, a country that produces relatively small amounts of greenhouse gases, could increase its emissions as much as 10 percent above its 1990 level. In addition, the Kyoto Protocol required three countries—New Zealand, Ukraine, and Russia—to freeze their emissions at 1990 levels.

The Kyoto Protocol outlined five requisites by which Annex I parties can choose to meet their 2012 emission targets. First, it required the development of national policies and measures that lowered domestic greenhouse gas emissions. Second, countries could calculate the benefits from domestic carbon sinks that soak up more carbon than they emit. Third, countries could participate in schemes that trade emissions with other Annex I countries. Fourth, signatory countries could create joint implementation programs with other Annex I parties and receive credit for such projects that lower emissions. Fifth, countries could receive credit for lowering the emissions in non-Annex I countries through a “clean development” mechanism, such as investing in the building of a new wind power project.

In order to go into effect, the Kyoto Protocol had to be ratified by at least 55 countries, including enough Annex I countries to account for at least 55 percent of that group’s total greenhouse gas emissions. More than 55 countries quickly ratified the protocol, including all the Annex I countries except for Russia, the United States, and Australia. (Russia and Australia ratified the protocol in 2005 and 2007, respectively.) It was not until Russia, under heavy pressure from the EU, ratified the protocol that it became legally binding in February 2005.

The most-developed regional climate-change policy to date was formulated by the EU in part to meet its commitments under the Kyoto Protocol. By 2005 the 15 EU countries that have a collective commitment under the protocol reduced their greenhouse gas emissions to 2 percent below their 1990 levels. In 2007 the EU set a collective goal for all 27 member states to reduce their greenhouse gas emissions by 20 percent below 1990 levels by the year 2020. In anticipation of this goal, the EU in 2005 established the world’s first multilateral trading scheme for carbon dioxide emissions, covering more than 11,500 large installations across its member states.

In the United States, by contrast, Pres. George W. Bush and a majority of senators rejected the Kyoto Protocol, citing the lack of compulsory emission reductions for developing countries as a particular grievance. At the same time, U.S. federal policy did not set any mandatory restrictions on greenhouse gas emissions, and U.S. emissions increased more than 16 percent between 1990 and 2005. Partly to make up for a lack of direction at the federal level, many individual U.S. states formulated their own action plans to address global warming and climate change and took a host of legal and political initiatives to curb emissions. These initiatives include: capping emissions from power plants, establishing renewable portfolio standards requiring electricity providers to obtain a minimum percentage of their power from renewable sources, developing vehicle emissions and fuel standards, and adopting “green building” standards.

The Paris Agreement and future climate-change policy

Countries differ in opinion on how to proceed with international policy with respect to climate agreements. Long-term goals formulated in Europe and the United States seek to reduce greenhouse gas emissions by up to 80 percent by the middle of the 21st century. Related to these efforts, the EU set a goal of limiting temperature rises to a maximum of 2 °C (3.6 °F) above preindustrial levels. (Many climate scientists and other experts agree that significant economic and ecological damage will result should the global average of near-surface air temperatures rise more than 2 °C [3.6 °F] above preindustrial temperatures.)

Despite differences in approach, countries launched negotiations on a new treaty, based on an agreement made at the United Nations Climate Change Conference in 2007 in Bali, Indonesia, that would replace the Kyoto Protocol after it expired. At the 17th UNFCCC Conference of the Parties (COP17) held in Durban, South Africa, in 2011, the international community committed to the development of a comprehensive legally binding climate treaty that would replace the Kyoto Protocol by 2015. Such a treaty would require all greenhouse-gas-producing countries—including major carbon emitters not abiding by the Kyoto Protocol (such as China, India, and the United States)—to limit and reduce their emissions of carbon dioxide and other greenhouse gases. This commitment was reaffirmed by the international community at the 18th Conference of the Parties (COP18) held in Doha, Qatar, in 2012. Since the terms of the Kyoto Protocol were set to terminate in 2012, the COP17 and COP18 delegates agreed to extend the Kyoto Protocol to bridge the gap between the original expiration date and the date that the new climate treaty would become legally binding. Consequently, COP18 delegates decided that the Kyoto Protocol would terminate in 2020, the year in which the new climate treaty was expected to come into force. This extension had the added benefit of providing additional time for countries to meet their 2012 emission targets.

Convening in Paris in 2015, world leaders and other delegates at COP21 signed a global but nonbinding agreement to limit the increase of the world’s average temperature to no more than 2 °C (3.6 °F) above preindustrial levels while at the same time striving to keep this increase to 1.5 °C (2.7 °F) above preindustrial levels. The Paris Agreement was a landmark accord that mandated a progress review every five years and the development of a fund containing $100 billion by 2020—which would be replenished annually—to help developing countries adopt non-greenhouse-gas-producing technologies. The number of parties (signatories) to the convention stood at 197 by 2019, and 185 countries had ratified the agreement. Despite the United States having ratified the agreement in September 2016, the inauguration of Donald J. Trump as president in January 2017 heralded a new era in U.S. climate policy, and on June 1, 2017, Trump signaled his intention to pull the U.S. out of the climate agreement after the formal exiting process concluded, which occurred on November 4, 2020. The United States’ absence was short-lived, however. On January 20, 2021, the first day of his term, Pres. Joe Biden reentered the agreement on behalf of the United States, which opened the way for the country’s formal reinstatement in February 2021. By February 2022, 195 countries had signed and 193 countries had ratified the agreement.

Mitigation and adaptation

As public policies relative to global warming and climate change continue to develop globally, regionally, nationally, and locally, they fall into two major types. The first type, mitigation policy, focuses on different ways to reduce emissions of greenhouse gases. As most emissions come from the burning of fossil fuels for energy and transportation, much of the mitigation policy focuses on switching to less carbon-intensive energy sources (such as wind, solar, and hydropower), improving energy efficiency for vehicles, and supporting the development of new technology (including carbon capture and storage). In contrast, the second type, adaptation policy, seeks to improve the ability of various societies to face the challenges of a changing climate. For example, some adaptation policies are devised to encourage groups to change agricultural practices in response to seasonal changes, whereas other policies are designed to prepare cities located in coastal areas for elevated sea levels.

In either case, long-term reductions in greenhouse gas discharges will require the participation of both industrial countries and major developing countries. In particular, the release of greenhouse gases from Chinese and Indian sources is rising quickly in parallel with the rapid industrialization of those countries. In 2006 China overtook the United States as the world’s leading emitter of greenhouse gases in absolute terms (though not in per capita terms), largely because of China’s increased use of coal and other fossil fuels. Indeed, all the world’s countries are faced with the challenge of finding ways to reduce their greenhouse gas emissions while promoting environmentally and socially desirable economic development (known as “sustainable development” or “smart growth”). Whereas some opponents of those calling for corrective action continue to argue that short-term mitigation costs will be too high, a growing number of economists and policy makers argue that it will be less costly, and possibly more profitable, for societies to take early preventive action than to address severe climatic changes in the future. Many of the most harmful effects of a warming climate are likely to take place in developing countries. Combating the harmful effects of global warming in developing countries will be especially difficult, as many of these countries are already struggling and possess a limited capacity to meet challenges from a changing climate.

It is expected that each country will be affected differently by the expanding effort to reduce global greenhouse gas emissions. Countries that are relatively large emitters will face greater reduction demands than will smaller emitters. Similarly, countries experiencing rapid economic growth are expected to face growing demands to control their greenhouse gas emissions as they consume increasing amounts of energy. Differences will also occur across industrial sectors and even between individual companies. For example, producers of oil, coal, and natural gas—which in some cases represent significant portions of national export revenues—may see reduced demand or falling prices for their goods as their clients decrease their use of fossil fuels, whereas producers of new, more climate-friendly technologies and products may see increases in demand. This process appears to be playing out around the world. In U.S. energy markets, for example, as the cost of coal-generated electricity increased during the early 21st century, the cost of solar- and wind-generated energy fell; by 2023 the cost to produce one megawatt of coal-generated electricity was 50 percent higher than the cost to produce one megawatt of electricity produced by solar and wind. In addition, renewable energy, which generated only 10 percent of electricity in the U.S. in 2010, had risen to nearly 24 percent by 2023.

To address global warming and climate change, societies must find ways to fundamentally change their patterns of energy use in favour of less carbon-intensive energy generation, transportation, and forest and land use management. A growing number of countries have taken on this challenge, incentivizing less carbon-intensive energy use through carbon taxes, transitioning the energy sources that power public transportation and electrical generation from fossil fuels to renewables, and providing incentives to manufacturing and public utilities to capture and store the carbon they produce. In addition, there are many things individuals too can do, including purchasing household electricity generated from renewable sources, reducing personal emissions of greenhouse gases through energy conservation in the home, operating more energy-efficient vehicles (such as electric and hybrid-electric vehicles), using public transportation when available, and transitioning to more energy-efficient household appliances and other products. Individuals might also improve their household insulation, learn to heat and cool their residences more effectively, and purchase and recycle more environmentally sustainable products.