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

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.

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 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.

How sunlight helps chlorofluorocarbons destroy the ozone molecules that block solar radiation

CFCs, which are used in old refrigerants, air conditioners, and aerosol sprays, do not react with atmospheric molecules. Once they reach the stratosphere, ultraviolet radiation breaks chlorine atoms off of them, which can each break apart more than 100,000 ozone molecules, thinning Earth's protective layer against ultraviolet radiation.

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.

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 the Montreal Protocol made CFCs the most valuable Miami contraband after cocaine

Following the 1990s production ban, smugglers flooded Miami with illegal chlorofluorocarbons used in air conditioning. A 15-kilogram cylinder bought for $70 in Europe could sell for $242 in the US, fueling multimillion-dollar black-market trade. (Some users may experience a paywall.)

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.

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.

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.

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.

Carbon markets incentivize companies to cut emissions but require high carbon prices

To reduce greenhouse gas emissions, a cap-and-trade system issues a limited number of emissions permits—carbon credits—that decrease each year, cutting into a company's profits if it does not reduce emissions and must buy permits from others. However, cheap permits and minimal fines for lacking permits have reduced the system's effectiveness.

Why helium helped preserve the US' founding documents, but was later replaced

In 1951, the Charters of Freedom were stored in glass and metal cases filled with helium, which would not chemically react with the documents. After microscopic cracks were identified in the glass through which helium could leak out of and—experts feared—pollutants could infiltrate, new encasements made of aluminum, titanium, and argon replaced the old system in 2003.

As of 2024, 13 states have plans to phase out gas-powered cars

In 2022, California adopted the Advanced Clean Cars II Act, which requires all new passenger cars, trucks, and SUVs sold to produce zero emissions by 2035. Other states adopted similar laws, joining more than 50 countries with phaseout plans.

Project STORMFURY explored modifying hurricanes with silver iodide

Between 1962 and 1983, researchers at the National Oceanic and Atmospheric Administration investigated whether weakening and controlling hurricanes was possible. The investigation showed very few hurricanes met the criteria for modification, despite successfully weakening two storms.

Revelations that apples were sprayed with the chemical Alar led to its ban in the 1980s

Almost three decades after Rachel Carson’s “Silent Spring,” a “60 Minutes” segment on the use of Alar, a chemical sprayed on apples, drew national attention and inspired supermarkets and schools to remove apples from their shelves and cafeterias. That same year, the Environmental Protection Agency took action against the use of the chemical in food.

The Office of Air and Radiation oversees America's clean air and climate programs

The office develops and enforces national standards for air quality, vehicle emissions, and radiation protection. In 2025, the EPA announced the closure of two key divisions under the office responsible for regulating climate and air pollution: the Office of Atmospheric Protection and the Office of Air Quality Planning and Standards.

Climate tipping points are irreversible changes to Earth's environment

Earth's natural systems have prevented these events—including the mass death of coral reefs, loss of the Amazon rainforest, and shutdown of Atlantic currents—but scientists believe they are unlikely to withstand continued stressors from climate change.

Research shows Venus would be hotter if some of its CO₂ were swapped out

The planet's atmosphere—whose density is 92 times that of Earth's—is 96.5% carbon dioxide. Since these molecules all capture the same subset of infrared radiation emitted from Venus's surface, radiation outside this range escapes, demonstrating the increased impact that diverse greenhouse gas composition has on planetary warming.

The 22nd Amendment was a reaction to Roosevelt's four terms

After Franklin D. Roosevelt won four elections, Congress moved to prevent future presidents from holding power indefinitely. Ratified in 1951, the 22nd Amendment set a firm two-term limit as a safeguard against extended presidencies.

Chemtrails are formed from condensing water vapor and soot from jet fuel

Conspiracy theories about the phenomenon—also known as contrails—began circulating in the 1990s, but have gained significant traction on social media platforms. Chemtrails are more common in high-humidity conditions, where they persist and form cirrus clouds.

Plant based milk is good for the planet, but not quite as good for you

Rising in popularity, plant-based milks are a practical alternative for consumers concerned about sustainability and climate change. Plant-based milks, such as oat, almond, rice, and soy milk, generate about one-third of the greenhouse gases and use...

Since 2022, two-thirds of data centers have been built in water-stressed areas

In residential evaporative cooling systems, 10% of consumed water is lost to evaporation compared to 80% in data centers. Although some companies have pledged to become water-positive—replenishing more freshwater than they consume—by 2030 through a transition to air cooling, only 10% of data center operators track water use across all their facilities.

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 history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

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.

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.

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

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

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.

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.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Despite being favored by 87% of Americans, Congress does not have term limits.

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.

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.

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.

'Silent' fireworks have gained more interest in recent years as a quieter celebratory option.

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.

See the evolution of Ebola vaccine and treatment development.

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.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

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.

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.

Hotels in Cannes, the glamorous city on the French Riviera, hire hawks to ward off seagulls during the city's famous film festival.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO