View when each UN member signed the Montreal Protocol

The history of the Montreal Protocol, the only universally ratified treaty in UN history

Mario Molina and F. Sherwood Rowland discovered that chlorofluorocarbons released chlorine atoms that could break down molecules making up the protective ozone layer. Despite attempts to discredit scientists and economic concerns raised by politicians, the agreement to phase out ozone-depleting substances was signed in 1987.

How the Montreal Protocol supported developing nations in phasing out ozone-depleting substances

Established in 1991, the Multilateral Fund for the Montreal Protocol finances developing nations' transition to cleaner technologies. It has disbursed more than $4B across more than 140 countries and was the first financial mechanism created under an international treaty.

How amendments to the Montreal Protocol have expanded global ozone protections

Since 1990, five major amendments—London, Copenhagen, Montreal, Beijing, and Kigali—have accelerated chemical phase-outs, added new substances, such as hydrochlorofluorocarbons, and tightened enforcement.

The Montreal Protocol helped prevent significant quantities of greenhouse gas emissions

By phasing out ozone-depleting chemicals between 1990 and 2010, the Montreal Protocol prevented emissions equal to 135 gigatons of CO₂—avoiding an estimated 0.5 to 1 degrees Celsius of additional global warming by 2100.

Go inside the global effort that led to the Montreal Protocol in this narrative podcast

Nobel laureate Mario Molina and other key voices recount how science and diplomacy converged to develop a plan to close the ozone hole, offering insight into history's most successful environmental treaty.

A UN-led treaty may establish rules to phase out plastic globally

With support from more than 175 nations, a treaty led by the United Nations is being negotiated to establish enforceable global rules for plastic production and pollution by 2025. Negotiations come as the total amount of plastic in the ocean has increased by 50% from 2017 to 2022.

The ozone layer is on track to recover to pre-1980 levels by mid-century

Thanks to the Montreal Protocol, the ozone layer is steadily recovering and, according to a 2022 assessment, is expected to return to 1980 levels by 2040 globally, 2045 over the Arctic, and 2066 over Antarctica.

How a skin cancerous growth shifted an initially skeptical President Reagan on the ozone crisis

While a 1985 Nature study revealing the Antarctic ozone hole jolted public concern, Reagan's administration was more focused on the Cold War than on environmental policy. His health scare and the market potential for developing alternatives to chlorofluorocarbons helped turn the tide, leading to the Montreal Protocol's unanimous ratification by a bipartisan Senate in 1988.

The international agreement to address antimicrobial resistance

Antimicrobial resistance has become an increasingly glaring problem for both health and agriculture. In 2024, the United Nations announced a new suite of clear actions and targets that—taken together with existing efforts—can help address superbugs in a meaningful way and on a global scale. This page from the UN lays out these efforts, with links to additional information on the many aspects of the initiative.

Environmental regulation had bipartisan support in the 1970s

During the 1970s, Democrats and Republicans alike backed landmark environmental laws. Congress passed the Clean Air, Clean Water, and Endangered Species Acts with overwhelming bipartisan majorities—reflecting broad public agreement on protecting the environment.

193 nations are members of the United Nations

The UN's Member States webpage provides an alphabetical list of all 193 member countries, along with the exact dates they were admitted. Take a look at how the UN has expanded over time and understand each nation's place in the global organization.

Roosevelt chaired more than 3,000 hours of debate to produce the Universal Declaration of Human Rights

Roosevelt led the drafting committee for the Universal Declaration of Human Rights, guiding representatives from 18 nations through debate on conflicting ideas about rights, government, and citizenship. The General Assembly unanimously adopted the final document in December 1948.

A majority in surveyed countries approve of the UN

A 2024 Pew Research Center survey found that a median of 58% across 35 countries viewed the UN favorably, while 31% held unfavorable views. Notably, younger adults tended to view the UN more positively than older generations. The report offers a detailed, country-by-country analysis of global perceptions of the UN.

The international trademark framework is called the Madrid Protocol

Trademarks vary from country to country, but an agreement called the Madrid Protocol allows trademark protections across more than 100 participating countries. While the Madrid Protocol expands trademark access, it doesn't necessarily grant blanket protections across the participating countries, meaning each country is still in charge of its own trademark enforcement.

The GATT and its successor, the WTO, were established to lower trade barriers

Signed in 1947, the General Agreement on Tariffs and Trade began systematically reducing tariffs and trade barriers among member nations. In 1995, it was replaced by the World Trade Organization, which expanded those rules and established a formal dispute settlement system.

The 5 permanent Security Council members can veto resolutions

The UN Security Council veto is a power held by its five permanent members—China, France, Russia, the UK, and the US—allowing any one of them to block resolutions, regardless of international consensus. It has been used over 300 times since the UN's founding.

Watch the historic treaty signing that established NATO in 1949

NATO was created with the signing of the North Atlantic Treaty on April 4, 1949, in Washington, DC. The clip embedded in the webpage includes a newsreel with an excerpt from US President Harry Truman’s speech celebrating the historic day.

Earth Day has become the largest civic event in the world

What began in 1970 with 20 million Americans now involves more than 1 billion participants across over 190 countries each year. Earth Day now encompasses rallies, cleanups, and climate actions worldwide.

The Non‑Proliferation Treaty was designed to prevent new states from developing nuclear bombs

The Treaty on the Non‑Proliferation of Nuclear Weapons (created in 1968, effective 1970) binds non-nuclear states to forgo nuclear weapons and commits nuclear powers to share peaceful technology and pursue disarmament—forming the core of the global non-proliferation regime.

The 1951 Refugee Convention established international refugee rights and state obligations amid mass World War II displacement

The international treaty defines refugee status and outlines refugees' entitled rights while establishing state obligations to protect them. The UNHCR explains the convention's significance in creating the legal framework governing refugee protection worldwide.

David Attenborough received the 2021 Champions of the Earth Lifetime Achievement Award

The UN's highest environmental honor celebrated Attenborough as "one of the leading voices of the global environmental movement." For at least four decades, he collaborated with the UN Environment Programme by advocating for "efforts to counter the climate crisis, biodiversity loss and pollution" and addressing "world leaders at the UN Climate Change Conference" in 2021.

A look at Mauna Loa, which produces the gold standard of global CO2 measurements.

Mauna Loa Observatory is a station that measures the elements in the atmosphere that contribute to climate change. It is located on the side of the Mauna Loa volcano in Hawaii. 

Explore the world's oldest constitutions

The 1789 US Constitution remains the oldest active written national constitution. Older systems exist—such as San Marino’s statutes or the Magna Carta—but they are not single, codified constitutions. See how other countries compare in this visualization.

The legacy of Agent Orange: a photo gallery

An herbicide sprayed over the Vietnamese jungles during the war had a far greater impact than its supposed role as a defoliant, a chemical used to remove greenery. Agent Orange’s deleterious nature quickly impacted exposed people – and their children. This photo gallery, which includes graphic images, follows a photographer as they report on those affected by the chemical.

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

Explaining the unified atomic mass units, which quantifies the mass of atoms and molecules

Until 1961, the atomic mass unit was defined based on oxygen-16, but it was later replaced by the unified atomic mass unit, defined as 1/12th the mass of a carbon-12 atom. Today, the term "atomic mass unit" often refers to the "unified atomic mass unit," denoted by the symbol u.

Meet the 56 signers of the Declaration of Independence—most of whom didn't put pen to paper until August 2, 1776—and see their original signatures.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

The most expensive ad of all time was for Chanel No. 5 perfume and cost roughly $33M to produce in 2004—about $57M in today's dollars.

See the 25 of the best photos of auroras from around the world.

Jimmy Carter signed a 1978 bill that legalized home brewing, a move credited with kick-starting the craft beer industry.

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

In preparation for this weekend's Eurovision finale, which is something like the World Cup of pop music, here's a young Céline Dion performing (for Switzerland?) at the 1988 competition.

Watch how deep-sea mining equipment collects and processes polymetallic nodules—metal-rich, potato-shaped rocks—from the ocean floor and creates environmentally damaging plumes of sediments.

'Grand Canyon of the Yellowstone,' a work by American painter Thomas Moran, inspired Congress to establish Yellowstone National Park.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

See the evolution of Ebola vaccine and treatment development.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

During the French Revolution, a botanist's letter asking about "dear Rhus" (poison ivy) was intercepted, leading authorities to suspect he was conspiring with the Russians.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

70 years ago today, city officials in Santa Cruz, California, banned rock 'n' roll to protect its youth from corruption after witnessing a 'provocative' concert the night before.

Double world record holder Hunter Ewen helped conquer his fear of balloons, called globophobia, by training to win Guinness World Record titles for balloon inflation.

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

The identity of the Tank Man in the iconic photo from the 1989 Tiananmen Square protests remains unknown and was possibly killed.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Comedy legend Catherine O'Hara, star of 'Schitt's Creek' and 'Home Alone,' quit 'Saturday Night Live' after just one week to return to her old job.