How amendments to the Montreal Protocol have expanded global ozone protections

Why a Montreal Protocol amendment cut back on the replacements for CFCs

Hydrofluorocarbons were introduced in the 1990s as ozone-safe substitutes for chlorofluorocarbons and hydrochlorofluorocarbons. However, scientists later found that they trap thousands of times more thermal energy in the atmosphere than carbon dioxide does, prompting a 2016 amendment to the Protocol to phase them out.

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.

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.

View when each UN member signed the Montreal Protocol

Adopted in 1987 to phase out ozone-depleting substances, the agreement achieved universal ratification by all 197 UN member states, making it the first and only such international treaty in the UN's history.

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 a black market for banned refrigerants still threatens ozone recovery and climate progress

Despite the Montreal Protocol's success, illegal trade in chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons persists. Driven by high profits and weak enforcement, smugglers supply banned refrigerants, causing significant ozone depletion and greenhouse gas emissions equivalent to billions of tons of carbon dioxide.

Learn why the Montreal Protocol may help prevent millions of cancer deaths

By restoring the ozone layer and reducing ultraviolet exposure, full implementation of the Montreal Protocol is expected to prevent about 443 million cases of skin cancer, 2.3 million skin cancer deaths, and 63 million cases of cataracts among Americans born from 1890 to 2100.

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.

Hear firsthand how scientists and policymakers saved the ozone layer

In this episode, atmospheric chemist Susan Solomon and Protocol architect Stephen Andersen recount how scientific discovery, diplomacy, and public pressure drove the Montreal Protocol—and share lessons for tackling climate change.

Fluorinated molecules are the most impactful, longest-lasting greenhouse gases

Developed as replacements for ozone-depleting substances in refrigeration and air conditioning systems, these compounds are released through leaks in and ongoing use of these appliances, as well as from various industrial processes. They can remain in the atmosphere for thousands of years and have warming potentials that are a thousand to tens of thousands of times greater than those of carbon dioxide.

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 Clean Air Act became the cornerstone of modern air pollution control

Passed in 1970 and strengthened through multiple amendments, the Clean Air Act authorizes the EPA to set national air quality standards, regulate industrial and vehicle emissions, and reduce pollutants such as ozone, sulfur dioxide, and lead.

Why the ozone hole altered Southern Hemisphere jet streams and rainfall patterns

Ozone depletion over Antarctica shifted jet streams southward, drying Australia while increasing rainfall in Uruguay, Brazil, Paraguay, and Argentina. Around the turn of the millennium, these trends began to slow as the Montreal Protocol phased out ozone-depleting substances.

Ozone protects against the sun's UV radiation and enhances the greenhouse effect

In the stratosphere, trioxygen molecules can absorb harmful ultraviolet radiation from the sun, preventing it from reaching Earth's surface, where it can harm organisms and raise surface temperatures. In the lower atmosphere, ozone acts as a greenhouse gas, trapping thermal radiation.

The EPA partners with other countries to strengthen environmental protection

Through bilateral programs on every continent, the EPA shares American environmental expertise with developing nations and economies in transition. These partnerships support air and water protection, chemical safety, and pollution control, while advancing US environmental priorities abroad.

More than 130 nations have enacted bans or restrictions on plastic items

Several US states have enacted similar restrictions on plastic bags, straws, food containers, and other single-use plastics, while others have prohibited plastic bans. Despite this, California’s plastic bag ban cut usage by more than 70%, showing the potential of these policies.

Why bacterial bioremediation may help counter the negative effects of past chemical solutions

Molecules such as DDT, a synthetic insecticide, and PFAS—"forever" chemicals used to make products resistant to heat, water, and grease—have historically been used across various industries but are now known to be harmful. Microbes that can convert some of these substances into nontoxic products, such as water and carbon dioxide, have already been identified, with ongoing research to find others.

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 US Constitution has been amended 27 different times since its ratification

Dive deeper into each amendment to the Constitution with resources provided by the National Constitution Center. This website features podcasts, videos, and other web resources for each of the amendments, examining their creation and their impact on today’s political and social landscape.

The five most common chemicals found in modern food

Most modern processed foods rely on a number of preservatives to stay fresh from production to our plates. The most common include citric acid (preservative and flavor), sodium benzoate (preservative), xanthan gum (thickening and stabilizing), carrageenan (thickening), and red dyes 3 and 4 (for color).

In 2016 OPEC and 10 major producers—including Russia—launched OPEC+

OPEC+ emerged in 2016 when 10 additional producers, including Russia, joined to stabilize markets amid U.S. shale growth. In 2022, OPEC alone supplied 38 % of global crude oil, but combined with OPEC+, output reached nearly 59 % of world production—significantly amplifying its market power.

In Amsterdam, planting organic flowers has increased native bee diversity by 45%

The citywide effort is an example of rethinking conventional agricultural methods, which rely on monocropping and heavy chemical use. Cover crops—plants grown to suppress weeds, prevent erosion, and attract pollinators rather than to be harvested—have also shown environmental benefits, despite not being sold for profit.

The General Agreement on Tariffs and Trade and its successor, the WTO, was formed to reduce trade barriers between nations

Data from the WTO shows that this effort was successful, resulting in a quadrupling of global trade in goods and a reduction of tariff rates of member states by 44%. This indicates that the post-World War II international efforts to create a more liberal trade environment have been successful.

Rapid environmental changes are exacerbating natural extinction processes

Human activities behind climate change, habitat destruction, pollution, and overhunting have resulted in extinction rates up to 1,000 times greater than normal, triggering massive biodiversity loss. This has led scientists to refer to the current geological age as the Anthropocene era, in which humans are the dominant force shaping nature.

The global nuclear arms regime has slowly eroded over the past few decades

Both Russia and the United States have withdrawn from key Cold War-era arms-control pacts. Russia's 2022 invasion of Ukraine marked a turning point, as it suspended its participation in inspections and data-sharing agreements.

Scientists testing how climate change affects plants found, in a years-long simulation study, that poison ivy grew 70% faster with the resulting extra carbon dioxide.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

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

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.

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.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Fish populations in the Great Barrier Reef have increased after installing waterproof speakers on the ocean floor that played recordings of sounds from healthy coral reefs.

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.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

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

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

The 2026 Ebola outbreak in the DRC is spurring new Ebola vaccine development for the Bundibugyo species.

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.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

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.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

See 33 images that became central to huge scandals, including a young Charles and Camilla, Michael Jackson's baby on a hotel balcony, and Hugh Grant's mugshot.

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.

Explore fun facts from the USPS, including unique post office buildings, a stamp that traveled past Pluto, and more.

View the ten deadliest tornadoes in US history.

Domino's Pizza's 30-minute delivery guarantee was responsible for the chain's 1980s surge, but it was discontinued after the company was found liable for delivery driver accidents.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

A small portion of The Winstons' 'Amen, Brother,' an obscure '60s gospel record, is the basis for thousands of hip-hop tracks, making it one of the most sampled records ever that's informally known as 'the Amen break.'