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Monday, July 27, 2026

Culture war

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Culture_war

A culture war is a form of cultural conflict (metaphorical war) between different social groups who struggle to politically impose their own ideology upon mainstream society, or upon the other. In political usage, culture war is a metaphor for "hot-button" politics about values and ideologies, realized with intentionally adversarial social narratives meant to provoke political polarization among the mainstream of society over economic matters, such as those of public policy, as well as of consumption. As practical politics, a culture war is about social policy wedge issues that are based on abstract arguments about values, morality, and lifestyle meant to provoke political cleavage in a multicultural society.

Etymology

Otto Von Bismarck (left) and Pope Pius IX (right), from the German satirical magazine Kladderadatsch, 1875

Kulturkampf

The Kulturkampf (German pronunciation: [kʊlˈtuːɐ̯ˌkamp͡f]; lit.'Cultural Struggle') was the seven-year political conflict (1871–1878) between the Catholic Church in Germany led by Pope Pius IX and the Kingdom of Prussia, led by Chancellor Otto von Bismarck, as well as other German states. The Prussian church-and-state political conflict was about the church's direct control over both education and ecclesiastical appointments in the Prussian kingdom. Moreover, when compared to other church-and-state conflicts about political culture, the Kulturkampf of Prussia also featured anti-Polish sentiment.

In modern political usage, the German term Kulturkampf describes any conflict (political, ideological, or social) between the secular government and the religious authorities of a society. The term also describes the great and small culture wars among political factions that hold deeply opposing values and beliefs within a nation, a community, and a cultural group.

In the English language, the term "culture war" is a calque of the German word Kulturkampf ("culture struggle"), which refers to a historical event in Germany. The term appears as the title of an 1875 British book review of a German pamphlet.

Research

Criticism and evaluation

Since the time that James Davison Hunter first applied the concept of culture wars to American life, the idea has been subject to questions about whether "culture wars" names a real phenomenon, and if so, whether the phenomenon it describes is a cause of, or merely a result of, membership in groups like political parties and religions. Culture wars have also been subject to the criticism of being artificial, imposed, or asymmetric conflicts, rather than a result of authentic differences between cultures. Researchers have differed about the scientific validity of the notion of culture war. Some claim it does not describe real behavior, or that it describes only the behavior of a small political elite. Others claim culture war is real and widespread, and even that it is fundamental to explaining Americans' political behavior and beliefs. A 2023 study on the circulation of conspiracy theories on social media noted that disinformation actors insert polarizing claims in culture wars by taking one side or the other, thus making the adherents circulate and parrot disinformation as a rhetorical ammunition against their perceived opponents.

Political scientist Alan Wolfe participated in a series of scholarly debates in the 1990s and 2000s against Hunter, claiming that Hunter's concept of culture wars did not accurately describe the opinions or behavior of Americans, which Wolfe claimed were more united than polarized. A meta-analysis of opinion data from 1992 to 2012 published in the American Political Science Review concluded that, in contrast to a common belief that political party and religious membership shape opinion on culture war topics, instead opinions on culture war topics lead people to revise their political party and religious orientations. The researchers view culture war attitudes as "foundational elements in the political and religious belief systems of ordinary citizens."

Artificiality or asymmetry

Some writers and scholars have said that culture wars are created or perpetuated by political special interest groups, by reactionary social movements, by party dynamics, or by electoral politics as a whole. These authors view culture war not as an unavoidable result of widespread cultural differences, but as a technique used to create in-groups and out-groups for a political purpose. Political commentator E. J. Dionne has written that culture war is an electoral technique to exploit differences and grievances, remarking that the real cultural division is "between those who want to have a culture war and those who don't."

Sociologist Scott Melzer says that culture wars are created by conservative, reactive organizations and movements. Members of these movements possess a "sense of victimization at the hands of a liberal culture run amok. In their eyes, immigrants, gays, women, the poor, and other groups are (undeservedly) granted special rights and privileges." Melzer writes about the example of the National Rifle Association of America, which he says intentionally created a culture war in order to unite conservative groups, particularly groups of white men, against a common perceived threat. Similarly, religion scholar Susan B. Ridgely has written that culture wars were made possible by Focus on the Family. This organization produced conservative Christian "alternative news" that began to bifurcate American media consumption, promoting a particular "traditional family" archetype to one part of the population, particularly conservative religious women. Ridgely says that this tradition was depicted as under liberal attack, seeming to necessitate a culture war to defend the tradition.

Political scientists Matt Grossmann and David A. Hopkins have written about an asymmetry between the US's two major political parties, saying the Republican party should be understood as an ideological movement built to wage political conflict, and the Democratic party as a coalition of social groups with less ability to impose ideological discipline on members. This encourages Republicans to perpetuate and to draw new issues into culture wars, because Republicans are well equipped to fight such wars. According to The Guardian, "many on the left have argued that such [culture war] battles [a]re 'distractions' from the real fight over class and economic issues."

Culture wars by country

United States

In the United States, ethnocultural politics or ethnoreligious politics refers to the pattern of certain cultural groups or religious denominations to vote heavily for one party. Groups can be based on ethnicity (such as Hispanics, Irish, Germans, etc.), race (White people, Black people, Asian Americans, etc.) or religion (Protestant and later Evangelical or Catholic, etc.) or on overlapping categories (e.g. Irish Catholics). In the Southern United States, race was the determining factor. Each of the two major parties was a coalition of ethnoreligious groups in the Second Party System (1830s–1850s) and also in the Third Party System (1850s–1890s).

Members of the American Indian Movement toppled a statue of Christopher Columbus in Saint Paul, Minnesota, on June 10, 2020.

1920s–1991: Origins

In American usage, culture war may imply a conflict between those values considered traditionalist or conservative and those considered progressive or liberal. This usage originated in the 1920s when urban and rural American values came into closer conflict. This followed several decades of immigration to the States by people who earlier European immigrants considered 'alien'. It was also a result of the cultural shifts and modernizing trends of the Roaring Twenties, culminating in the presidential campaign of Al Smith in 1928. In subsequent decades during the 20th century, the term was published occasionally in American newspapers. Historian Matthew Dallek argues the John Birch Society (JBS) was an early promoter of culture war ideas. Scholar Celestini Carmen traces the JBS's apocalyptic culture war rhetoric through the connections of Christian right leaders such as Tim LaHaye and Phyllis Schlafly to the JBS and their founding of the Moral Majority.

1991–2001: Rise in prominence

James Davison Hunter, a sociologist at the University of Virginia, introduced the expression again in his 1991 publication, Culture Wars: The Struggle to Define America. Hunter described what he saw as a dramatic realignment and polarization that had transformed American politics and culture. He argued that on an increasing number of "hot-button" defining issues—abortion, gun politics, separation of church and state, privacy, recreational drug use, homosexuality, censorship—there existed two definable polarities. Furthermore, not only were there a number of divisive issues, but society had divided along essentially the same lines on these issues, so as to constitute two warring groups, defined primarily not by nominal religion, ethnicity, social class, or even political affiliation, but rather by ideological world-views. Hunter characterized this polarity as stemming from opposite impulses, toward what he referred to as Progressivism and as Orthodoxy. Others have adopted the dichotomy with varying labels. For example, Bill O'Reilly, a conservative political commentator and former host of the Fox News Channel talk show The O'Reilly Factor, emphasizes differences between "Secular-Progressives" and "Traditionalists" in his 2006 book Culture Warrior.

Historian Kristin Kobes Du Mez attributes the 1990s emergence of culture wars to the end of the Cold War in 1991. She writes that Evangelical Christians viewed a particular Christian masculine gender role as the only defense of the United States against the threat of communism. When this threat ended upon the close of the Cold War, Evangelical leaders transferred the perceived source of threat from foreign communism to domestic changes in gender roles and sexuality.

Pat Buchanan in 2008

During the 1992 presidential election, commentator Pat Buchanan mounted a campaign for the Republican nomination for president against incumbent George H. W. Bush. In a prime-time slot at the 1992 Republican National Convention, Buchanan gave his speech on the culture war. He argued: "There is a religious war going on in our country for the soul of America. It is a cultural war, as critical to the kind of nation we will one day be as was the Cold War itself." In addition to criticizing environmentalists and feminism, he portrayed public morality as a defining issue:

The agenda [Bill] Clinton and [Hillary] Clinton would impose on America—abortion on demand, a litmus test for the Supreme Court, homosexual rights, discrimination against religious schools, women in combat units—that's change, all right. But it is not the kind of change America wants. It is not the kind of change America needs. And it is not the kind of change we can abide in a nation that we still call God's country.

A month later, Buchanan characterized the conflict as about power over society's definition of right and wrong. He named abortion, sexual orientation and popular culture as major fronts—and mentioned other controversies, including clashes over the Confederate flag, Christmas, and taxpayer-funded art. He also said that the negative attention his "culture war" speech received was itself evidence of the United States' polarization.

The culture war had significant impact on national politics in the 1990s. The rhetoric of the Christian Coalition of America may have weakened president George H. W. Bush's chances for re-election in 1992 and helped his successor, Bill Clinton, win reelection in 1996. On the other hand, the rhetoric of conservative cultural warriors helped Republicans gain control of Congress in 1994. The culture wars influenced the debate over state-school history curricula in the United States in the 1990s. In particular, debates over the development of national educational standards in 1994 revolved around whether the study of American history should be a "celebratory" or "critical" undertaking and involved such prominent public figures as Lynne Cheney, Rush Limbaugh, and historian Gary Nash.

2001–2012: Post-9/11 era

(from right to left) 43rd President George W. Bush, Donald Rumsfeld, and Paul Wolfowitz were prominent neoconservatives of the 2000s.

A political view called neoconservatism shifted the terms of the debate in the early 2000s. Neoconservatives differed from their opponents in that they interpreted problems facing the nation as moral issues rather than economic or political ones. For example, neoconservatives saw the decline of the traditional family structure as well as the decline of religion in American society as spiritual crises that required a spiritual response. Critics accused neoconservatives of confusing cause and effect.

During the 2000s, voting for Republicans began to correlate heavily with traditionalist or orthodox religious belief across diverse religious sects. Voting for Democrats became more correlated with liberal or modernist religious belief, and with being nonreligiousBelief in scientific conclusions, such as climate change, also became tightly coupled with political party affiliation in this era, causing climate scholar Andrew Hoffman to observe that climate change had "become enmeshed in the so-called culture wars."

Rally for Proposition 8, an item on the 2008 California ballot to ban same-sex marriage

Topics traditionally associated with culture war were not prominent in media coverage of the 2008 election season, with the exception of coverage of vice-presidential candidate Sarah Palin, who drew attention to her conservative religion and created a performative climate change denialism brand for herself. Palin's defeat in the election and subsequent resignation as governor of Alaska caused the Center for American Progress to predict "the coming end of the culture wars," which they attributed to demographic change, particularly high rates of acceptance of same-sex marriage among millennials.

2012–present: Broadening of the culture war

The J. E. B. Stuart Monument, defaced during protests in Richmond, Virginia, was removed on July 7, 2020.

In the early 2010s, the American right took issue with the perceived worldwide dominance of leftism in international politics and corporate activity, anti-nationalism, and secular human rights policies and activism not based on Abrahamic religious worldviews.

While traditional culture war issues, like abortion, continue to be a focal point, the issues identified with the culture war broadened and intensified in the mid-late 2010s. Jonathan Haidt, author of The Coddling of the American Mind, identified a rise in cancel culture via social media among young progressives since 2012, which he believes had "transformative effects on university life and later on politics and culture throughout the English-speaking world," in what Haidt and other commentators have called the "Great Awokening". Journalist Michael Grunwald says that "President Donald Trump has pioneered a new politics of perpetual culture war" and lists Black Lives Matter, U.S. national anthem protests, climate change, education policy, healthcare policy including Obamacare, and infrastructure policy as culture war issues in 2018. The rights of transgender people and the role of religion in lawmaking were identified as "new fronts in the culture war" by political scientist Jeremiah Castle, as the polarization of public opinion on these two topics resembles that of previous culture war issues. In 2020, during the COVID-19 pandemic, North Dakota governor Doug Burgum described opposition to wearing face masks as a "senseless" culture war issue that jeopardizes human safety.

From top: anti-abortion protesters in 1986; members of the Proud Boys protest a drag queen story hour; Representative Marjorie Taylor Greene of Georgia and Libs of TikTok creator Chaya Raichik hold up an anti-transgender sign; "Save Our Children" graffiti near downtown Lufkin, Texas in relation to the LGBT grooming conspiracy theory.

This broader understanding of culture war issues in the mid-late 2010s and 2020s is associated with a political strategy called "owning the libs." Conservative media figures employing this strategy emphasize and expand upon culture war issues with the goal of upsetting liberals. According to Nicole Hemmer of Columbia University, this strategy is a substitute for the cohesive conservative ideology that existed during the Cold War. It holds a conservative voting bloc together in the absence of shared policy preferences among the bloc's members.

Hundreds of participants at the Unite the Right rally in Charlottesville, Virginia, in August 2017; an event associated with the alt-right and neo-Nazi movements, regarded as a battleground in the culture wars.

A number of conflicts about diversity in popular culture occurring in the 2010s, such as the Gamergate controversy, Comicsgate and the Sad Puppies science fiction voting campaign, were identified in the media as being examples of the culture war. Journalist Caitlin Dewey described Gamergate as a "proxy war" for a larger culture war between those who want greater inclusion of women and minorities in cultural institutions versus anti-feminists and traditionalists who do not. The perception that culture war conflict had been demoted from electoral politics to popular culture led writer Jack Meserve to call popular movies, games, and writing the "last front in the culture war" in 2015.

These conflicts about representation in popular culture re-emerged into electoral politics via the alt-right and alt-lite movements. According to media scholar Whitney Phillips, Gamergate "prototyped" strategies of harassment and controversy-stoking that proved useful in political strategy. For example, Republican political strategist Steve Bannon publicized pop-culture conflicts during the 2016 presidential campaign of Donald Trump, encouraging a young audience to "come in through Gamergate or whatever and then get turned onto politics and Trump."

Canada

The empty pedestal of the former John A. Macdonald monument in Montreal, left vacant after the statue of Canada's first Prime Minister was toppled during a 2020 protest and later removed

Some observers in Canada have used the term "culture war" to refer to differing values between Western versus Eastern Canada, urban versus rural Canada, as well as conservatism versus liberalism and progressivism. The phrase has also been used to describe the Harper government's attitude towards the arts community. Andrew Coyne termed this negative policy towards the arts community as "class warfare."

Australia

During the tenure of the Liberal–National Coalition government of 1996 to 2007, interpretations of Aboriginal history became a part of a wider political debate regarding Australian national pride and symbolism occasionally called the "culture wars", more often the "history wars". This debate extended into a controversy over the presentation of history in the National Museum of Australia and in high-school history curricula. It also migrated into the general Australian media, with major broadsheets such as The Australian, The Sydney Morning Herald and The Age regularly publishing opinion pieces on the topic. Marcia Langton has referred to much of this wider debate as "war porn" and as an "intellectual dead end".

Two Australian Prime Ministers, Paul Keating (in office 1991–1996) and John Howard (in office 1996–2007), became major participants in the "wars". According to Mark McKenna's analysis for the Australian Parliamentary Library, Howard believed that Keating portrayed Australia pre-Whitlam (PM 1972–1975) in an unduly negative light, while Keating sought to distance the modern Labor movement from its historical support for the monarchy and for the White Australia policy by arguing that it was the conservative Australian parties which had been barriers to national progress. He accused Britain of having abandoned Australia during the Second World War. Keating staunchly supported a symbolic apology to Aboriginal Australians for their mistreatment at the hands of previous administrations, and outlined his view of the origins and potential solutions to contemporary Aboriginal disadvantage in his Redfern Park Speech of December 10, 1992 (drafted with the assistance of historian Don Watson). In 1999, following the release of the 1998 Bringing Them Home Report, Howard passed a parliamentary Motion of Reconciliation describing treatment of Aboriginal people as the "most blemished chapter" in Australian history, but declined to issue an official apology. Howard saw an apology as inappropriate as it would imply "intergeneration guilt", saying measures were a better response to contemporary Aboriginal disadvantage. Keating argued for the eradication of remaining symbols linked to colonial origins, including deference for ANZAC Day, for the Australian flag, and for the monarchy in Australia, while Howard supported these institutions. Unlike fellow Labor leaders and contemporaries, Bob Hawke (PM 1983–1991) and Kim Beazley (Labor Party leader 2005–2006), Keating never travelled to Gallipoli for ANZAC Day ceremonies. In 2008 he described those who gathered there as "misguided".

The defeat of the Howard government in the 2007 Australian federal election and its replacement by the Rudd Labor government altered the dynamic of the debate. Rudd made an official apology to the Aboriginal Stolen Generations with bi-partisan support. Like Keating, Rudd supported an Australian republic, but in contrast to Keating, Rudd declared support for the Australian flag and supported the commemoration of ANZAC Day; he also expressed admiration for Liberal Party founder Robert Menzies. Subsequent to the 2007 change of government, and prior to the passage of the official apology, historian Richard Nile argued: "the culture and history wars are over and with them should also go the adversarial nature of intellectual debate", a view contested by others, including conservative commentator Janet Albrechtsen.

Climate change in Australia is also considered a highly divisive or politically controversial topic, to the point it is sometimes called a "culture war".

The 2017 Same Sex Marriage Plebiscite was also a divisive topic within Australia with many supporters of marriage equality were targeted with Homophobic vandalism in the lead up to the Plebiscite.

Since the defeat of the 2023 Australian Indigenous Voice referendum, there has been a significant calls reignited from conservative politicians and commentators, including former federal opposition leader Peter Dutton to oppose or scale down Indigenous Reconciliation, viewing customs such as Welcome to Country ceremonies and placing the Aboriginal and Torres Strait Islander flags alongside the national flag as "divisive".

African continent

According to political scientist Constance G. Anthony, American culture war perspectives on human sexuality were exported to Africa as a form of neocolonialism. In his view, this began during the AIDS epidemic in Africa, with the United States government first tying HIV/AIDS assistance money to evangelical leadership and the Christian right during the Bush administration, then to LGBTQ tolerance during the administration of Barack Obama. This stoked a culture war that resulted in (among others) the Uganda Anti-Homosexuality Act of 2014.

Zambian scholar Kapya Kaoma notes that because "the demographic center of Christianity is shifting from the global North to the global South" Africa's influence on Christianity worldwide is increasing. American conservatives export their culture wars to Africa, Kaoma says, particularly when they realize they may be losing the battle back home. US Christians have framed their anti-LGBT initiatives in Africa as standing in opposition to a "Western gay agenda", a framing which Kaoma finds ironic.

North American and European conspiracy theories have become widespread in West Africa via social media, according to 2021 survey by First Draft News. COVID-19 misinformation, New World Order conspiracy thinking, QAnon and other conspiracy theories associated with culture war topics are spread by American, Pro-Russian, French-language, and local disinformation websites and social media accounts, including prominent politicians in Nigeria. This has contributed to vaccine hesitancy in West Africa, with 60 percent of survey respondents saying they were unlikely to try to get vaccinated, and an erosion of trust in institutions in the region.

United Kingdom

The statue of Robert Milligan on June 9, 2020, the day of its removal

A 2021 report from King's College London argued that many people's views on cultural issues in Britain had become tied up with the side of the Brexit debate with which they identify, while the public party-political identities, although not as strong, show similar alignments and that around half the country held relatively strong views on "culture war" issues such as debates on Britain's colonial history or Black Lives Matter; however, the report concluded Britain's cultural and political divide was not as stark as the Republican–Democratic divide in the US and that a sizeable section of the public can be categorised as having either moderate views or as being disengaged from social debates. It also found that The Guardian, as opposed to the centre-right newspapers, was more likely to talk about the culture wars.

The Conservative Party have been described as attempting to ignite culture wars in regard to "conservative values" under the tenure of Prime Minister Boris Johnson. Others argue that it is the left who are engaging in "culture wars", particularly against liberal values, accepted words, and British institutions. Observers such as Johns Hopkins University professor Yascha Mounk and journalist and author Louise Perry have argued that the collapse in support for the Labour Party during the 2019 United Kingdom general election came as a result of both a media-induced public perception and a deliberate strategy of Labour of pursuing messages and policy ideas based on cultural issues that resonated with more university educated grassroots activists on the left of the party but alienated Labour's traditional working class voters.

An April 2022 survey found evidence that Britons are less divided on "culture war" issues than has often been portrayed in the media. The greatest predictor of opinion was how people voted in the UK's referendum on membership of the European Union, Brexit, yet even among those who voted Leave, 75% agreed "it is important to be attentive to issues of race and social justice". Similarly, even among Remainers and those who last voted for the Labour Party, there was moderately strong support for several socially conservative positions.

Europe

Statue of Ivan Konev in Prague was removed in 2020.

In 2020, French President Emmanuel Macron promised that France would not erase elements of its history or remove statues of controversial public figures, saying "The Republic won't erase any name from its history. It will forget none of its artworks, it won't take down statues."

Several politicians, such as Poland's Law and Justice party, Hungary's Viktor Orbán, Serbia's Aleksandar Vučić, and Slovenia's Janez Janša, have been often accused of fomenting culture wars in their respective countries by encouraging dissent, resistance to LGBT rights, and restrictions on abortion. One facet of the controversy in Poland is the removal of Soviet War Memorials, which is divisive because some Poles viewed the memorials positively as commemorations of their ancestors who died during World War II, while others felt negatively due to the oppression that some Poles experienced under the Soviet-backed Polish People's Republic. Culture war in Hungary is alleged by Kim Scheppele to be a disguise for democratic backsliding by Orbán. Ukraine also experienced a decades-long culture war pitting the eastern, predominately Russian-speaking, regions against the western Ukrainian-speaking areas of the country. LGBT rights are controversial in Poland, as exemplified by President Andrzej Duda's vow in 2020 to oppose both same-sex marriage and LGBT adoption.

Different interpretations of bitter events during World War II have become especially contentious in Poland since 2015, shortly after the start of the Russo-Ukrainian War. One disputed issue is whether Poland bears any responsibility for the Holocaust, or whether Poland was entirely a victim of Nazi Germany. This dispute is embodied by the "Polish death camp" controversy (involving concentration camps that had been built by Nazi Germany during World War II on German-occupied Polish soil) and an attempt to address that controversy with a now partly repealed law.

A second issue, also addressed by the partly repealed law, revolves around Poland–Ukraine relations. In the region, in passing a law to criminalize negative interpretations of the country's collaborationist nationalist movements during World War II, Poland is not alone, and Poland–Ukraine relations have suffered as a result of a similar law in Ukraine that was criticized in Poland for deflecting blame away from the Ukrainian Insurgent Army and their massacres of Poles in Volhynia and Eastern Galicia.

The empty plinth of a statue dedicated to Alexander Pushkin in Ternopil, Ukraine, April 11, 2022

Derussification in Ukraine is a process of removing Russian influence from the post-Soviet country of Ukraine. This derussification started after the collapse of the Soviet Union in 1991 and intensified with the demolition of monuments to Lenin during Euromaidan in 2014 and the further systemic process of decommunization in Ukraine. The Russian invasion of Ukraine gave a strong impetus to the process.

In 2024, the city of Vienna rejected a monument to Polish King John III Sobieski due to concerns about Islamophobia and anti-Turkish sentiment.

Global dimming

From Wikipedia, the free encyclopedia
Hotspots of sulfate aerosol pollution in 2005–2007 are highlighted in orange. Such sulfates rarely occur naturally outside of volcanic activity, and their increased levels are the main cause of global dimming.

Global dimming is a decline in the amount of sunlight reaching the Earth's surface. It is caused by atmospheric particulate matter, predominantly sulfate aerosols, which are components of air pollution. Global dimming was observed soon after the first systematic measurements of solar irradiance began in the 1950s. This weakening of visible sunlight proceeded at the rate of 4–5% per decade until the 1980s. During these years, air pollution increased due to post-war industrialization. Solar activity did not vary more than the usual during this period.

Aerosols have a cooling effect on the earth's atmosphere, and global dimming has masked the extent of global warming experienced to date, with the most polluted regions even experiencing cooling in the 1970s. The opposite effects it has on global warming appears to be beneficial to the environment. Global dimming has interfered with the water cycle by lowering evaporation, and thus has probably reduced rainfall in certain areas. It may have weakened the Monsoon of South Asia and caused the entire tropical rain belt to shift southwards between 1950 and 1985, with a limited recovery afterwards. Record levels of particulate pollution in the Northern Hemisphere caused or at least exacerbated the monsoon failure behind the 1984 Ethiopian famine.

Since the 1980s, a decrease in air pollution has led to a partial reversal of the dimming trend, sometimes referred to as global brightening. This global brightening had contributed to the acceleration of global warming, which began in the 1990s. According to climate models, the dimming effect of aerosols most likely offsets around 0.5 °C (0.9 °F) of warming as of 2021. As nations act to reduce the toll of air pollution on the health of their citizens, the masking effect on global warming is expected to decline further. The scenarios for climate action required to meet 1.5 °C (2.7 °F) and 2 °C (3.6 °F) targets incorporate the predicted decrease in aerosol levels. However, model simulations of the effects of aerosols on weather systems remain uncertain.

The processes behind global dimming are similar to stratospheric aerosol injection. This is a proposed solar geoengineering intervention which aims to counteract global warming through intentional releases of reflective aerosols. Stratospheric aerosol injection could be very effective at stopping or reversing warming but it would also have substantial effects on the global water cycle, regional weather, and ecosystems. Furthermore, it would have to be carried out over centuries to prevent a rapid and violent return of the warming.

History

The observed trends of global dimming and brightening in four major geographic regions. The dimming was greater on the average cloud-free days (red line) than on the average of all days (purple line), strongly suggesting that sulfate aerosols were the cause.

In the 1970s, numerous studies showed that atmospheric aerosols could affect the propagation of sunlight through the atmosphere, a measure also known as direct solar irradiance. One study showed that less sunlight was filtering through at the height of 1.7 km (1.1 mi) above Los Angeles, even on those days when there was no visible smog. Another suggested that sulfate pollution or a volcano eruption could provoke the onset of an ice age. In the 1980s, Atsumu Ohmura, a geography researcher at the Swiss Federal Institute of Technology, found that solar radiation striking the Earth's surface had declined by more than 10% over the three previous decades, even as the global temperature had been generally rising since the 1970s. In the 1990s, this was followed by the papers describing multi-decade declines in Estonia, Germany, Israel and across the former Soviet Union.

Subsequent research estimated an average reduction in sunlight striking the terrestrial surface of around 4–5% per decade over the late 1950s–1980s, and 2–3% per decade when 1990s were included. Notably, solar radiation at the top of the atmosphere did not vary by more than 0.1–0.3% in all that time, strongly suggesting that the reasons for the dimming were on Earth. Additionally, only visible light and infrared radiation were dimmed, rather than the ultraviolet part of the spectrum. Further, the dimming had occurred even when the skies were clear, and it was in fact stronger than during the cloudy days, proving that it was not caused by changes in cloud cover alone.

Causes

Anthropogenic sulfates

Satellite snapshot of atmospheric sulfur dioxide on 15 April 2017. Sulfur dioxide forms highly reflective sulfates, which are considered the main cause of global dimming.

Global dimming is primarily caused by the presence of sulfate particles which hang in the Earth's atmosphere as aerosols. These aerosols have both a direct contribution to dimming, as they reflect sunlight like tiny mirrors. They also have an indirect effect as nuclei, meaning that water droplets in clouds coalesce around the particles. Increased pollution causes more particulates and thereby creates clouds consisting of a greater number of smaller droplets (that is, the same amount of water is spread over more droplets). The smaller droplets make clouds more reflective, so that more incoming sunlight is reflected back into space and less reaches the Earth's surface. In models, these smaller droplets also decrease rainfall.

Before the Industrial Revolution, the main source of sulfate aerosols was dimethyl sulfide produced by some types of oceanic plankton. Emissions from volcano activity were the second largest source, although large volcanic eruptions, such as the 1991 eruption of Mount Pinatubo, dominate in the years when they occur. In 1990, the IPCC First Assessment Report estimated dimethyl sulfide emissions at 40 million tons per year, while volcano emissions were estimated at 10 million tons. These annual levels have been largely stable for a long time. On the other hand, global human-caused emissions of sulfur into the atmosphere increased from less than 3 million tons per year in 1860 to 15 million tonnes in 1900, 40 million tonnes in 1940 and about 80 million tonnes in 1980. This meant that by 1980, the human-caused emissions from the burning of sulfur-containing fuels (mostly coal and bunker fuel) became at least as large as all natural emissions of sulfur-containing compounds. The report also concluded that "in the industrialized regions of Europe and North America, anthropogenic emissions dominate over natural emissions by about a factor of ten or even more".

Black carbon

If smoke from wildfires mixes into clouds, it darkens them, decreasing their albedo. If there are no clouds, then smoke can increase albedo, particularly over oceans.

Another important type of aerosol is black carbon, colloquially known as soot. It is formed due to incomplete combustion of fossil fuels, as well as of wood and other plant matter. Globally, the single largest source of black carbon is from grassland and forest fires, including both wildfires and intentional burning. However, coal use is responsible for the majority (60 to 80%) of black carbon emissions in Asia and Africa, while diesel combustion produces 70% of black carbon in Europe and The Americas.

Black carbon in the lower atmosphere is a major contributor to 7 million premature deaths caused by air pollution every year. Its presence is particularly visible, as the so-called "brown clouds" appear in heavily polluted areas. In fact, it was 1970s research into the Denver brown cloud which had first found that black carbon particles absorb solar energy and so can affect the amount of visible sunlight. Later research found that black carbon is 190 times more effective at absorbing sunlight within clouds than the regular dust from soil particles. At worst, all clouds within an atmospheric layer 3–5 km (1.9–3.1 mi) thick are visibly darkened, and the plume can reach transcontinental scale (i.e. the Asian brown cloud.) Even so, the overall dimming from black carbon is much lower than that from the sulfate particles.

Reversal

Sun-blocking aerosols around the world steadily declined (red line) since the 1991 eruption of Mount Pinatubo, according to satellite estimates.

After 1990, the global dimming trend had clearly switched to global brightening. This followed measures taken to combat air pollution by the developed nations, typically through flue-gas desulfurization installations at thermal power plants, such as wet scrubbers or fluidized bed combustion. In the United States, sulfate aerosols have declined significantly since 1970 with the passage of the Clean Air Act, which was strengthened in 1977 and 1990. According to the EPA, from 1970 to 2005, total emissions of the six principal air pollutants, including sulfates, dropped by 53% in the US. By 2010, this reduction in sulfate pollution led to estimated healthcare cost savings valued at $50 billion annually. Similar measures were taken in Europe, such as the 1985 Helsinki Protocol on the Reduction of Sulfur Emissions under the Convention on Long-Range Transboundary Air Pollution, and with similar improvements.

Satellite photo showing a thick pall of smoke and haze from forest fires in Eastern China. Such smoke is full of black carbon, which contributes to dimming trends but has an overall warming effect.

On the other hand, a 2009 review found that dimming continued to increase in China after stabilizing in the 1990s and intensified in India, consistent with their continued industrialization, while the US, Europe, and South Korea continued to brighten. Evidence from Zimbabwe, Chile and Venezuela also pointed to increased dimming during that period, albeit at a lower confidence level due to the lower number of observations. Later research found that over China, the dimming trend continued at a slower rate after 1990, and did not begin to reverse until around 2005. Due to these contrasting trends, no statistically significant change had occurred on a global scale from 2001 to 2012. Post-2010 observations indicate that the global decline in aerosol concentrations and global dimming continued, with pollution controls on the global shipping industry playing a substantial role in the recent years. Since nearly 90% of the human population lives in the Northern Hemisphere, clouds there are far more affected by aerosols than in the Southern Hemisphere, but these differences have halved in the two decades since 2000, providing further evidence for the ongoing global brightening.

Relationship to climate change

Cooling from sulfate aerosols

Air pollution, including from large-scale land clearing, has substantially increased the presence of aerosols in the atmosphere when compared to the preindustrial background levels. Different types of particles have different effects, and there is a variety of interactions in different atmospheric layers. Overall, they provide cooling, but complexity makes the exact strength of cooling very difficult to estimate.

Aerosols have a cooling effect, which has masked the total extent of global warming experienced to date.

It has been understood for a long time that any effect on solar irradiance from aerosols would necessarily impact Earth's radiation balance. Reductions in atmospheric temperatures have already been observed after large volcanic eruptions such as the 1963 eruption of Mount Agung in Bali, 1982 El Chichón eruption in Mexico, 1985 Nevado del Ruiz eruption in Colombia and 1991 eruption of Mount Pinatubo in the Philippines. However, even the major eruptions only result in temporary jumps of sulfur particles, unlike the more sustained increases caused by anthropogenic pollution.

In 1990, the IPCC First Assessment Report acknowledged that "Human-made aerosols, from sulphur emitted largely in fossil fuel combustion can modify clouds and this may act to lower temperatures", while "a decrease in emissions of sulphur might be expected to increase global temperatures". However, lack of observational data and difficulties in calculating indirect effects on clouds left the report unable to estimate whether the total impact of all anthropogenic aerosols on the global temperature amounted to cooling or warming. By 1995, the IPCC Second Assessment Report had confidently assessed the overall impact of aerosols as negative (cooling); however, aerosols were recognized as the largest source of uncertainty in future projections in that report and the subsequent ones.

Warming from black carbon

Unlike sulfate pollution, black carbon contributes to both global dimming and global warming, since its particles absorb sunlight and heat up instead of reflecting it away. These particles also develop thick coatings over time, which can increase the initial absorption by up to 40%. Because the rate at which these coatings are formed varies depending on the season, the warming from black carbon varies seasonally as well.

Though this warming is weaker than the CO2-induced warming or the cooling from sulfates, it can be regionally significant when black carbon is deposited over ice masses like mountain glaciers and the Greenland ice sheet. There, it reduces their albedo and increases their absorption of solar radiation, which accelerates their melting. Black carbon also has an outsized contribution to local warming inside polluted cities. Even the indirect effect of soot particles acting as cloud nuclei is not strong enough to provide cooling: the "brown clouds" formed around soot particles were known to have a net warming effect since the 2000s. Black carbon pollution is particularly strong over India: thus, it is considered to be one of the few regions where cleaning up air pollution would reduce, rather than increase, warming.

Minor role of aircraft contrails

Aircraft contrails (white lines) and natural clouds.

Aircraft leave behind visible contrails (also known as vapor trails) as they travel. These contrails both reflect incoming solar radiation and trap outgoing longwave radiation that is emitted by the Earth. Because contrails reflect sunlight only during the day, but trap heat day and night, they are normally considered to cause net warming, albeit very small. A 1992 estimate was between 3.5 mW/m2 and 17 mW/m2 – hundreds of times smaller than the radiative forcing from major greenhouse gases.

However, some scientists argued that the daytime cooling effect from contrails was much stronger than usually estimated, and this argument attracted attention following the September 11 attacks. Because no commercial aircraft flew across the US in the immediate aftermath of the attacks, this period was considered a real-world demonstration of contrail-free weather. Across 4,000 weather stations in the continental United States, the diurnal temperature variation (the difference in the day's highs and lows at a fixed station) was widened by 1.1 °C (2.0 °F) – the largest recorded increase in 30 years. In the southern US, the difference was diminished by about 3.3 °C (6 °F), and by 2.8 °C (5 °F) in the US midwest. This was interpreted by some scientists as a proof of a strong cooling influence of aircraft contrails.

Ultimately, follow-up studies found that a natural change in cloud cover which occurred at the time was sufficient to explain these findings. When the global response to the 2020 coronavirus pandemic led to a reduction in global air traffic of nearly 70% relative to 2019, multiple studies found "no significant response of diurnal surface air temperature range" as the result of contrail changes, and either "no net significant global ERF" (effective radiative forcing) or a very small warming effect.

Historical cooling

This chart shows how much various physical factors affect climate change. For example, sulfur dioxide causes cooling because it reacts to form a variety of sunlight-reflecting sulfates. Its large error bar shows that there is a lot of uncertainty regarding the strength of cooling caused by sulfur dioxide in the atmosphere.

At the peak of global dimming, sulfur dioxide was able to counteract the warming trend completely. By 1975, the continually increasing concentrations of greenhouse gases had overcome the masking effect, and have dominated ever since. Even then, regions with high concentrations of sulfate aerosols due to air pollution had initially experienced cooling, in contradiction to the overall warming trend. The eastern United States was a prominent example: the temperatures there declined by 0.7 °C (1.3 °F) between 1970 and 1980, and by up to 1 °C (1.8 °F) in the Arkansas and Missouri.

Brightening and accelerated warming

Since the 1980s, the reduction in global dimming has contributed to higher global temperatures. Hot extremes have accelerated as global dimming has abated. It has been estimated that since the mid-1990s, peak daily temperatures in northeast Asia and hottest days of the year in Western Europe would have been substantially cooler if aerosol concentrations had stayed the same as before. Some of the acceleration of sea level rise, as well as Arctic amplification and the associated Arctic sea ice decline, was also attributed to the reduction in aerosol masking.

In Europe, the declines in aerosol concentrations since the 1980s had also reduced the associated fog, mist and haze: altogether, it was responsible for about 10–20% of daytime warming across Europe, and about 50% of the warming over the more polluted Eastern Europe. Because aerosol cooling depends on reflecting sunlight, air quality improvements had a negligible impact on wintertime temperatures, but had increased temperatures from April to September by around 1 °C (1.8 °F) in Central and Eastern Europe. The central and eastern United States experienced warming of 0.3 °C (0.54 °F) between 1980 and 2010 as sulfate pollution was reduced, even as sulfate particles still accounted for around 25% of all particulates. By 2021, the northeastern coast of the United States was one of the fastest-warming regions of North America, as the slowdown of the Atlantic Meridional Overturning Circulation increased temperatures in that part of the North Atlantic Ocean.

Rapid decline in air pollution caused by the COVID-19 lockdowns in China was responsible for up to 40% of the regional temperature changes in January–March 2020, relative to January–March 2019

In 2020, COVID-19 lockdowns provided a notable "natural experiment", as there had been a marked decline in sulfate and black carbon emissions caused by the curtailed road traffic and industrial output. That decline did have a detectable warming impact: it was estimated to have increased global temperatures by 0.01–0.02 °C (0.018–0.036 °F) initially and up to 0.03 °C (0.054 °F) by 2023, before disappearing. Regionally, the lockdowns were estimated to increase temperatures by 0.05–0.15 °C (0.090–0.270 °F) in eastern China over January–March, and then by 0.04–0.07 °C (0.072–0.126 °F) over Europe, eastern United States, and South Asia in March–May, with the peak impact of 0.3 °C (0.54 °F) in some regions of the United States and Russia. In the city of Wuhan, the urban heat island effect was found to have decreased by 0.24 °C (0.43 °F) at night and by 0.12 °C (0.22 °F) overall during the strictest lockdowns.

Future

Since changes in aerosol concentrations already have an impact on the global climate, they would necessarily influence future projections as well. In fact, it is impossible to fully estimate the warming impact of all greenhouse gases without accounting for the counteracting cooling from aerosols.

Early 2010s estimates of past and future anthropogenic global sulfur dioxide emissions, including the Representative Concentration Pathways. While no climate change scenario may reach Maximum Feasible Reductions (MFRs), all assume steep declines from today's levels. By 2019, sulfate emission reductions were confirmed to proceed at a very fast rate.

Climate models started to account for the effects of sulfate aerosols around the IPCC Second Assessment Report; when the IPCC Fourth Assessment Report was published in 2007, every climate model had integrated sulfates, but only 5 were able to account for less impactful particulates like black carbon. By 2021, CMIP6 models estimated total aerosol cooling in the range from 0.1 °C (0.18 °F) to 0.7 °C (1.3 °F); The IPCC Sixth Assessment Report selected the best estimate of a 0.5 °C (0.90 °F) cooling provided by sulfate aerosols, while black carbon amounts to about 0.1 °C (0.18 °F) of warming. While these values are based on combining model estimates with observational constraints, including those on ocean heat content, the matter is not yet fully settled. The difference between model estimates mainly stems from disagreements over the indirect effects of aerosols on clouds.

Regardless of the current strength of aerosol cooling, all future climate change scenarios project decreases in particulates and this includes the scenarios where 1.5 °C (2.7 °F) and 2 °C (3.6 °F) targets are met: their specific emission reduction targets assume the need to make up for lower dimming. Since models estimate that the cooling caused by sulfates is largely equivalent to the warming caused by atmospheric methane (and since methane is a relatively short-lived greenhouse gas), it is believed that simultaneous reductions in both would effectively cancel each other out. Yet, in the recent years, methane concentrations had been increasing at rates exceeding their previous period of peak growth in the 1980s, with wetland methane emissions driving much of the recent growth, while air pollution is getting cleaned up aggressively. These trends are some of the main reasons why 1.5 °C (2.7 °F) warming is now expected around 2030, as opposed to the mid-2010s estimates where it would not occur until 2040.

Addressing air pollution in Europe line with the current policies (blue line) is likely to increase the frequency of hot days and reduce the frequency of cold ones. Those increases will be even faster with maximum possible reductions (red line), unless the GHG emissions are addressed at the same rate. Similar trends will be seen in China

It has also been suggested that aerosols are not given sufficient attention in regional risk assessments, in spite of being more influential on a regional scale than globally. For instance, a climate change scenario with high greenhouse gas emissions but strong reductions in air pollution would see 0.2 °C (0.36 °F) more global warming by 2050 than the same scenario with little improvement in air quality, but regionally, the difference would add 5 more tropical nights per year in northern China and substantially increase precipitation in northern China and northern India. Likewise, a paper comparing current level of clean air policies with a hypothetical maximum technically feasible action under otherwise the same climate change scenario found that the latter would increase the risk of temperature extremes by 30–50% in China and in Europe.

Unfortunately, because historical records of aerosols are sparser in some regions than in others, accurate regional projections of aerosol impacts are difficult. Even the latest CMIP6 climate models can only accurately represent aerosol trends over Europe, but struggle with representing North America and Asia. This means that their near-future projections of regional impacts are likely to contain errors as well.

Relationship with water cycle

Sulfate aerosols have decreased precipitation over most of Asia (red), but increased it over some parts of Central Asia (blue).

On regional and global scale, air pollution can affect the water cycle, in a manner similar to some natural processes. One example is the impact of Sahara dust on hurricane formation: air laden with sand and mineral particles moves over the Atlantic Ocean, where they block some of the sunlight from reaching the water surface, slightly cooling it and dampening the development of hurricanes. Likewise, it has been suggested since the early 2000s that since aerosols decrease solar radiation over the ocean and hence reduce evaporation from it, they would be "spinning down the hydrological cycle of the planet."

In 2011, it was found that anthropogenic aerosols had been the predominant factor behind 20th century changes in rainfall over the Atlantic Ocean sector, when the entire tropical rain belt shifted southwards between 1950 and 1985, with a limited northwards shift afterwards. Future reductions in aerosol emissions are expected to result in a more rapid northwards shift, with limited impact in the Atlantic but a substantially greater impact in the Pacific. Some research also suggests that these reductions would affect the AMOC (already expected to weaken due to climate change). Reductions from the stronger air quality policies could exacerbate this expected decline by around 10%, unless methane emissions are reduced by an equivalent amount.

Most notably, multiple studies connect aerosols from the Northern Hemisphere to the failed monsoon in sub-Saharan Africa during the 1970s and 1980s, which then led to the Sahel drought and the associated famine. However, model simulations of Sahel climate are very inconsistent, so it's difficult to prove that the drought would not have occurred without aerosol pollution, although it would have clearly been less severe. Some research indicates that those models which demonstrate warming alone driving strong precipitation increases in the Sahel are the most accurate, making it more likely that sulfate pollution was to blame for overpowering this response and sending the region into drought.

In the United States, aerosols generally reduce both mean and extreme precipitation across all four seasons, which has cancelled out the increases caused by greenhouse gas warming

Another dramatic finding had connected the impact of aerosols with the weakening of the Monsoon of South Asia. It was first advanced in 2006, yet it also remained difficult to prove. In particular, some research suggested that warming itself increases the risk of monsoon failure, potentially pushing it past a tipping point. By 2021, however, it was concluded that global warming consistently strengthened the monsoon, and some strengthening was already observed in the aftermath of lockdown-caused aerosol reductions.

In 2009, an analysis of 50 years of data found that light rains had decreased over eastern China, even though there was no significant change in the amount of water held by the atmosphere. This was attributed to aerosols reducing droplet size within clouds, which led to those clouds retaining water for a longer time without raining. The phenomenon of aerosols suppressing rainfall through reducing cloud droplet size has been confirmed by subsequent studies. Later research found that aerosol pollution over South and East Asia didn't just suppress rainfall there, but also resulted in more moisture transferred to Central Asia, where summer rainfall had increased as the result. In the United States, effects of climate change on the water cycle would typically increase both mean and extreme precipitation across the country, but these effects have so far been "masked" by the drying due to historically strong aerosol concentrations. The IPCC Sixth Assessment Report had also linked changes in aerosol concentrations to altered precipitation in the Mediterranean region.

Relevance for solar geoengineering

This graph shows that if stratospheric aerosol injection were to be deployed starting from 2034, then it could be finely scaled to either halve the speed of warming by 2100, to halt it, or to reverse it entirely. The same degree of control is available under the scenarios of low, medium and high greenhouse gas emissions

Global dimming is also relevant for certain proposals about slowing, halting, or reversing global warming. An increase in planetary albedo of 1% would eliminate most of radiative forcing from anthropogenic greenhouse gas emissions and thereby global warming, while a 2% albedo increase would negate the warming effect of doubling the atmospheric carbon dioxide concentration. This is the theory behind solar radiation modification (or solar geoengineering), and the high reflective potential of sulfate aerosols means that they were considered in this capacity starting from the 1970s.

Because the historical levels of global dimming were associated with high mortality from air pollution and issues such as acid rain, the concept of relying on cooling directly from pollution has been described as a "Faustian bargain" and is not seriously considered by modern research. Instead, the seminal 2006 paper by Paul Crutzen suggested that the way to avoid increased warming as the sulfate pollution decreased was to revisit the 1974 proposal by the Soviet researcher Mikhail Budyko. The proposal involved releasing sulfates from the airplanes flying in the upper layers of the atmosphere, in what is now described as stratospheric aerosol injection, or SAI. In comparison, most air pollution is in the lower atmospheric layer (the troposphere), and only resides there for weeks. Because aerosols deposited in the stratosphere would last for years, far less sulfur would have to be emitted to produce the same amount of cooling.

While Crutzen's initial proposal focused on avoiding the warming caused by the reductions in air pollution, it was immediately understood that scaling up this proposal could slow, stop, or reverse warming. It has been estimated that the amount of sulfur needed to offset a warming of around 4 °C (7.2 °F) relative to now (and 5 °C (9.0 °F) relative to the preindustrial), under the highest-emission scenario RCP 8.5 would be less than what is already emitted through air pollution today, and that reductions in sulfur pollution from future air quality improvements already expected under that scenario would offset the sulfur used for geoengineering. The trade-off is increased cost. Although there's a popular narrative that stratospheric aerosol injection can be carried out by individuals, small states, or other non-state rogue actors, scientific estimates suggest that cooling the atmosphere by 1 °C (1.8 °F) through stratospheric aerosol injection would cost at least $18 billion annually (at 2020 USD value), meaning that only the largest economies or economic blocs could afford this intervention. Even so, these approaches would still be "orders of magnitude" cheaper than greenhouse gas mitigation, let alone the costs of unmitigated effects of climate change.

Even if SAI were to stop or outright reverse global warming, weather patterns in many areas would still change substantially. The habitat of mosquitoes and other disease vectors would shift. However, it's unclear how it would compare to the shifts that are otherwise likely to occur from climate change. Lower sunlight would affect crop yields and carbon sinks due to reduced photosynthesis, but this would likely be offset by lack of thermal stress from warming and the greater CO2 fertilization effect relative to now. Most importantly, the warming from CO2 emissions lasts for hundreds to thousands of years, while the cooling from SAI stops 1–3 years after the last aerosol injection. This means that neither stratospheric aerosol injection nor other forms of solar geoengineering can be used as a substitute for reducing greenhouse gas emissions. In contrast, if greenhouse gas levels remained high, it would lead to "large and extremely rapid" warming and similarly abrupt changes to the water cycle. Many thousands of species would likely go extinct as a result. Instead, any solar geoengineering would act as a temporary measure to limit warming. At the same time, emissions of greenhouse gases are reduced and carbon dioxide is removed, which may well take hundreds of years.

Operator (physics)

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