June 22, 2017

In May 2017, scientists watched anxiously as an enormous crack in Larsen C, one of Antarctica’s largest ice shelves, grew by more than 11 miles (18 kilometers) in just a few days. Scientists have been closely monitoring the Larsen C ice shelf, where a large fissure in the ice has been advancing and widening in rapid bursts in recent years. When it eventually breaks away, it will form one of the largest icebergs ever seen.

An airplane passes above the giant crack in Antarctica’s Larsen Ice Shelf in late 2016. Credit: NASA/John Sonntag

The Larsen Ice Shelf is a broad, flat, floating mass of ice in the northwest part of the Weddell Sea. It extends along the east end of the Antarctic Peninsula. Researchers who work in the area originally labeled three segments of the massive ice shelf as Larsen A, Larsen B, and Larsen C (running north to south). The Larsen A ice shelf broke away and disintegrated in 1995. The Larsen B ice shelf disintegrated in 2002. Researchers fear the disintegration of Larsen C, the largest of the three and the fourth largest in Antarctica, will leave the continent’s whole system vulnerable to future break-up.

This airborne photograph shows a detail of the massive 300-foot- (100-meter-) wide rift in Larsen C in late 2016. Credit: NASA Goddard Space Flight Center

Larsen C is substantially larger than its former neighbors Larsen A and B, and its loss would be a huge blow to ice on the Antarctic Peninsula. When the shelf breaks away as an iceberg, it will weaken or destroy key areas where ice overlaps nearby islands. The ice shelf helps keep larger ice masses nearby from falling apart. Losing Larsen C would destabilize and even threaten the existence of the area’s larger ice masses.

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This map shows the rift on Larsen C on May 31, 2017, and its growth since 2010. The shelf is larger than Wales in the United Kingdom. Credit: © A. Luckman, MIDAS project/Swansea University

Antarctica has about 90 percent of the world’s ice with a volume of about 7.25 million cubic miles (30 million cubic kilometers). The average thickness of the ice is over 7,100 feet (2,200 meters), and the masses contain about 70 percent of the world’s fresh water. Most of this ice lies in two massive sheets that can be as thick as 11,500 feet (3,500 meters). If all that ice melted, Earth’s oceans would rise nearly 230 feet (70 meters), flooding coastal cities around the world.

Antarctica’s Larsen B Ice Shelf broke apart in 2002, forming these icebergs that have since melted and disappeared. Credit: Ted Scambos, NSIDC

Scientists blame the disintegration of the Larsen Ice Shelf on global warming. The ice destruction has destabilized the entire eastern Antarctic Peninsula and raised sea levels. Scientists note that global warming does not affect all parts of the world equally. Average temperatures in Antarctica have jumped 5 Fahrenheit degrees (2.8 Celsius degrees) since the 1950′s, a faster rate of increase compared to other parts of the Earth. Climate scientists think that temperatures could increase up to 7 Fahrenheit degrees (3.9 Celsius degrees) further in the coming decades, putting ever more stress on the ice.

Ice shelves themselves do not contribute directly to sea level rise because they are floating on the ocean and they already displace the same volume of water. But scientists are still deeply troubled by the collapse of Larsen C. In Antarctica, ice shelves act as doorstops to the land-based glaciers that feed them. As ice shelves disappear, the glaciers move faster and flatten out, pushing ever more ice into the ocean and raising sea levels.

Although cycles of cooling and warming as well as other natural processes affect Antarctica’s climate, scientists are largely in agreement that human activities, particularly emissions of heat-trapping greenhouse gases, are the main driving force behind the area’s temperature increases and the resulting loss of the ice shelves. The most significant greenhouse gas is carbon dioxide, which is produced by the burning of such fossil fuels as coal and oil. A number of other atmospheric, oceanic, and glaciological factors are also involved.

June 21, 2017

On June 10, the Expo 2017 international exhibition opened in Astana, the capital city of Kazakhstan, a country in west-central Asia. Expo 2017—like so many exhibitions and fairs before it—is a celebration of international commerce, industry, and science. The theme for Expo 2017 is “Future Energy,” concentrating on clean energy innovations as well as creative ideas for the future. The expo stresses the importance of moving from polluting fossil fuels to such green technologies as wind and solar power and providing “solutions for tackling humankind’s greatest challenge”—climate change.

The sprawling Expo 2017 complex centers on the large sphere of the National Pavilion of Kazakhstan. The international exhibition runs from June into September in Astana, Kazakhstan. Credit: © Nick Melnichenko, Shutterstock

Expo 2017 kicked off with elaborate opening ceremonies and a speech by longtime Kazakhstan President Nursultan Nazarbayev. “The most advanced technologies in the field of clean energy will be showcased here,” he said. “And I hope that the results of the Astana Expo 2017 will bring tangible benefits to all.” The expo runs through the summer until September 10. More than 130 countries and numerous global organizations are taking part in the fair. Between 3 million and 5 million people are expected to visit the expo’s sprawling 430-acre (174-hectare) complex, a busy mix of international pavilions clustered around the giant sphere-shaped National Pavilion of Kazakhstan.

Astana, Kazakhstan, is known for its unusual architecture and futuristic appearance. Credit: © Shutterstock

The expo’s Energy Best Practices Area Pavilion features innovative energy-related ideas and projects dealing with the creation, distribution, storage, and use of renewable and alternative energy. The new technologies include plant-powered biological fuel cells, the harnessing of bioluminescent microorganisms to produce light, inflatable solar collectors, the use of ice to power cooling and heating systems, and electric-powered zero-emission race cars and scooters. The expo also includes a full schedule of concerts and cultural programs, as well as food and drink from around the world and numerous shops and other diversions.

The Space Needle in Seattle is one of the most recognizable buildings in the United States. The 605-foot (184-meter) tower served as the centerpiece for a 1962 world’s fair called Century 21. Credit: © Shutterstock

World’s fairs and expositions have a long tradition dating back to London’s Great Exhibition of 1851. Over the years, world’s fairs have been a showcase for new inventions, unfamiliar peoples, and new kinds of art. The newly invented telephone wowed audiences at the Philadelphia exhibition in 1876, and the Eiffel Tower changed the skyline of Paris for the world’s fair of 1889. Automobiles impressed people and scared horses as they rumbled through the 1904 expo in St. Louis, and early television broadcasts showed the future of entertainment at the famous Century of Progress Exhibition in Chicago in 1933-1934. The 1962 Century 21 fair in Seattle introduced the Space Needle at the dawn of the space age.

June 2, 2017

Yesterday, June 1, United States President Donald Trump announced that the United States would formally withdraw from the Paris Agreement, an international treaty designed to combat global warming. The decision to withdraw from the treaty represented a sharp break with leaders of nearly all nations and went against the wishes of thousands of corporate executives, economists, environmentalists, other U.S. politicians, scientists, and even members of the president’s own Cabinet. Trump’s decision to withdraw from the treaty met with immediate international and domestic scorn and spurred numerous protests.

On June 1, 2017, protesters gather outside the White House in Washington, D.C., moments after President Donald Trump announced that the United States would withdraw from the Paris Climate Agreement. Credit: Kellybdc (licensed under CC BY 2.0)

By joining the Paris Agreement in 2015 and ratifying it in 2016, the United States had voluntarily committed to cut back on the use of polluting fossil fuels, develop more green (environmentally friendly) technology, and raise funds to help poorer countries reduce their greenhouse gas emissions. Trump, who has previously called climate change a “hoax,” sees these commitments as an unfair economic burden on the United States. Most evidence, however, shows that climate change is real and that moving to green technology actually stimulates economic growth.

The goal of the Paris Agreement is to slow and eventually cease the rise in global temperatures that has sharply increased in the last few decades. Scientists predict that, if global warming continues unchecked, it will damage human society and the environment. For example, global warming could melt enough of the ice near Earth’s poles to raise sea levels, flooding many coastal cities. Global warming could lead to more widespread droughts. It could also raise the risk of extinction for many plant and animal species. Already, global warming has greatly reduced glaciers at the North and South poles, harmed the world’s coral reefs, and created ever more erratic and extreme weather patterns.

Withdrawing from the Paris Agreement is a lengthy process that will take until November 2020 to complete, leaving time for the United States to rejoin the treaty. A number of U.S. cities and states have already announced they will continue to comply with the provisions of the Paris Agreement whether the federal government does or not.

May 18, 2017

Glacier National Park in northwestern Montana may soon be without any of its trademark glaciers. Many of the park’s largest glaciers have lost much of their former size in the last 50 years, according to surveys published by the United States Geological Service (USGS) and Portland State University in Oregon. Steadily rising temperatures have dramatically reduced 37 of the park’s glaciers that are large enough to have individual names. Some have lost as much as 85 percent of their bulk.

Melt water from the Gem, Grinnell, and Salamander glaciers feeds the lakes of Grinnell Valley in Montana’s Glacier National Park. Credit: Tim Rains, National Park Service

A glacier is a large mass of ice that flows slowly under the influence of gravity. Glaciers consist of packed snow that has built up over many years. The snow’s weight eventually compresses its lower layers into ice. Glaciers scrape the ground as they move over it, eroding old landforms and creating new ones. They range in thickness from several feet or meters to 10,000 feet (3,000 meters) or more.

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The retreat of a mountain glacier can provide visible evidence of global warming. These photographs show two late-summer views of Grinnell Glacier in Glacier National Park, Montana. In the photo taken around 1940, top, Upper Grinnell Lake had only begun to form at the glacier’s end. By 2006, bottom, melting ice had caused the lake to swell in size. Researchers predict that warming will melt all of the park’s glaciers by 2030. Credit: Glacier National Park Archives, top,U.S. Geological Survey, photograph by Karen Holtzer, bottom

Glacier National Park was named for the large number of glaciers found there. In 1850, the area had about 150 glaciers. Large glaciers in the park today include the Grinnell and Blackfoot glaciers. Over the past 50 years, scientists used digital maps from aerial photography and satellites to measure the glaciers in late summer when seasonal snow has melted to reveal the boundaries of the glacial ice. Surveys were conducted in 1966, 1998, 2005, and 2016. Since the first survey in 1966, the glaciers have shrunk by an average of 39 percent. Today, the park has just 26 ice masses large enough to qualify as glaciers.

Scientists blame this dramatic glacier melt on global warming, and they predict Glacier National Park will be without any glaciers at all by 2030. This is troubling news for the state of Montana, where more than 2 million tourists take in the scenic views at Glacier National Park each year. Experts worry that the glacier loss will also have serious damaging effects on the ecosystems of the park and surrounding Rocky Mountain habitats.

May 2, 2017

In Canada’s Yukon territory, increased melting of the vast Kaskawulsh Glacier has caused the nearby Slims River to run dry. The Slims, once a gushing channel of glacial melt water, is now a waterless expanse of mud and dust. In recent decades, increased temperatures caused by global warming shrank the Kaskawulsh Glacier to the point that its melt water found an alternate route out of the Saint Elias Mountains, cutting off water to the Slims.

Parts of Kluane Lake, which received much of its water from the disappeared Slims River, have dried up, leaving behind these small pinnacles of hardened sediment. Credit: Jim Best, University of Illinois/University of Washington (licensed under CC BY 2.0)

For centuries, Kaskawulsh melt water fed the Slims River (as well as the Kaskawulsh River), which in turn fed Kluane Lake as well as the Kluane River. In 2016, however, a scientific expedition into the remote area found that the Slims had changed dramatically. In place of the river’s wide, rushing waters, the expedition found a narrow stream running down a path of mucky and treacherous sediment. The scientists learned that melt water from the shrinking Kaskawulsh Glacier had shifted outlets and was now feeding only the Kaskawulsh River—which had grown in size. In geology, the diversion of water from one river to another is called river piracy. River piracy occurred in ancient times—such as during and after the last ice age—but the theft of Kaskawulsh waters is the first modern case known to science.

Kluane National Park and Reserve is in southwestern Yukon, a territory of Canada. Global warming has reduced the park’s Kaskawulsh Glacier, shown here, and shifted the flow of its melt water. Credit: © Parks Canada

Between 1956 and 2007, the Kaskawulsh Glacier retreated some 2,300 feet (700 meters). In recent years, however, the retreat greatly accelerated, ultimately resulting in a sudden and radical water diversion in 2016. New melt water channels were carved in a matter of days, and the glacial waters found their way only to the Kaskawulsh River—leaving the Slims River high and dry.

Yukon is a northern Canadian territory known for its magnificent scenery. Kluane National Park, shown here, features the Wrangell and Saint Elias mountain ranges. Credit: © Thinkstock

The sudden shift in geological landscape altered much more than the view: fish and other wildlife populations either moved, migrated, or died, and entire plant populations withered and died. A statistical analysis, published in the journal Nature Geoscience in April 2017, blamed the Kaskawulsh river piracy squarely on anthropogenic (human caused) climate change. The analysis warned that river piracy could become a common event as glaciers retreat around the world. Few people live in the Kaskawulsh area, but sudden river piracy in heavily populated regions dependent on glacial melt for water—such as the Himalaya in Asia or the Andes in South America—could have catastrophic effects on human populations.

April 14, 2017

An unusually high number of dangerous icebergs have drifted into busy shipping lanes of the North Atlantic Ocean over the past month, prompting warnings from the U.S. Coast Guard (USCG) and other international agencies. More than 450 icebergs, many large enough to sink a ship, have been sighted in the past weeks, about five times the average for this time of year. Ships are warned to sail well south of their normal course to avoid the huge iceberg field.

Icebergs like these are crowding shipping lanes in the North Atlantic Ocean. Credit: © Thinkstock

An iceberg is a huge mass of ice that has calved (broken off) from a glacier or ice shelf and is floating in water. Icebergs are much larger below the water than above it, and they can pose a great danger to ships that come too close. The hard ice can easily tear open the steel hull of a ship that strikes it. At least one cargo ship has already reported a close encounter with an iceberg this month.

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Icebergs form where chunks of ice break away from a glacier as it flows into the sea. The sun and wind melt the top of an iceberg. The bottom, which is under water, melts much more slowly. As the top melts away, leaving the bottom hidden beneath the surface, the iceberg becomes extremely dangerous to ships. Credit: WORLD BOOK diagrams by Marion Pahl

The unusual iceberg hazard in the North Atlantic recalls the conditions that led to the sinking of the Titanic on April 14, 1912—105 years ago today. The Titanic sank after colliding with a large iceberg in the same region. More than 1,500 people, including many wealthy and famous passengers, went down with the ship.

The Titanic struck an iceberg in the North Atlantic Ocean on April 14, 1912, and sank within hours. Credit: © AP/Wide World

The USCG International Ice Patrol, which was created in the aftermath of the Titanic disaster, uses satellites to track large icebergs in the region. The agency has observed that the icebergs clogging the North Atlantic shipping lanes today mostly calved from glaciers in Greenland. Many climate scientists think the dramatic increase in icebergs may be a result of climate change. Warmer conditions than normal have weakened ice fields in Greenland, leading to an increased rate of iceberg calving. Strong winds and currents then push the icebergs about, causing some to drift into the heavily trafficked shipping lanes.

January 27, 2017

Last week, the United States National Aeronautics and Space Administration (NASA) and the U.S. National Oceanic and Atmospheric Administration (NOAA) announced that 2016 was the hottest year on record, setting a new record for the third consecutive year. The average land and ocean surface temperature was 58.69 ˚F (14.83 ˚C), 1.69 Fahrenheit (0.94 Celsius) degrees warmer than the global average during the 1900’s. Sixteen out of the 17 warmest years on record have occurred since 2001, one of many clear indicators that the planet is warming.

This global heat map covering 2012 through 2016 shows areas with the sharpest temperature increases in red. White areas indicate Earth’s few remaining “cool” spots.  Credit: NASA

Global warming is an increase in the average temperature at Earth’s surface. People often use the term global warming to refer specifically to the warming observed since the mid-1800’s. Scientists estimate that Earth’s average surface temperature has risen by about 1.4 Fahrenheit (0.78 Celsius) degrees since 1880. Researchers have also found that most of the temperature increase occurred from the mid-1900’s to the 2000’s.

This chart clearly shows the sharp rise in global temperatures since 1980. Note the temperature spike coinciding with World War II (1939-1945). Credit: NOAA/NESDIS/NCEI

The record heat of 2014 topped the previous high by just 0.07 Fahrenheit (0.4 Celsius) degrees. Since then, however, record temperatures jumped by 0.29 Fahrenheit (0.16 Celsius) degrees in 2015 and 0.36 Fahrenheit (0.20 Celsius) degrees in 2016. The recent strong El Niño event, which began in mid-2014, contributed to the record-shattering heat. An El Niño is a part of the interaction between Earth’s atmosphere and the tropical waters of the Pacific Ocean. An El Niño occurs about every two to seven years, and it can affect the climate throughout the world.

El Niño was not the primary cause for the record heat, however. Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, estimated that the El Niño effect contributed just 0.09 Fahrenheit (0.05 Celsius) degrees to 2015′s record 1.62 Fahrenheit (0.90 Celsius) degrees increase and only 0.22 Fahrenheit (0.12 Celsius) degrees of 2016′s 1.69 Fahrenheit (0.94 Celsius) degrees record. Climate scientists agree that human activities, such as the release of carbon dioxide and other gases into the atmosphere, are responsible for the warming trend seen over the last several decades.

The recent El Niño ended in in the spring of 2016, and a La Niña cooling event emerged at the end of the year. Because of this development, almost all climate scientists agree that 2017 will not be as hot as 2016. But La Niña conditions are already declining, and some models predict another El Niño could begin as early as the middle of 2017.

The 2016 election of Donald Trump as president of the United States created new problems for climate scientists and environmentalists trying to slow global warming. Much of the momentum gained by last year’s Paris Climate Agreement has been halted by Trump, who has claimed that climate change is a hoax and has vowed to back out of the agreement. Working with Trump, the Republican-controlled U.S. Congress is preparing to dismantle many of the environmental regulations put in place or strengthened by former President Barack Obama. China and the other signatories of the Paris Agreement may have to act without the United States to try to prevent the direst effects of global warming. Trump’s administration has already removed climate change websites from numerous government agencies, and on Jan. 24, 2017, Trump banned government agencies from mentioning climate change on press releases and social media posts and from discussing the issue with other public officials.

January 10, 2017

Last week, Australia’s Bureau of Meteorology (BOM) released its annual climate statement, and it was filled with bad news. Extreme weather lashed Australia throughout 2016, harming fragile landscapes and ecosystems both on land and in the sea. The BOM blamed the damaging weather extremes on climate change as well as an unusually strong El Niño, a periodic variation in ocean currents and temperatures that can affect climate throughout the world.

This photo taken on Feb. 12, 2016, shows the charred remains of rare alpine flora after bush fires raged through the Tasmanian Wilderness World Heritage Area. Credit: Rob Blakers (licensed under CC BY-SA 3.0)

The BOM listed a number of weather events that devastated parts of Australia in 2016. The cities of Darwin and Sydney saw their hottest years on record, while hot and dry conditions and large numbers of lightning strikes led to raging bushfires in Tasmania, Victoria, and Western Australia. Fires destroyed much of the unique alpine flora—including rare, 1,000-year-old cushion plants and King Billy pine trees—found in the Tasmanian Wilderness World Heritage Area. The seas around Australia also reached record high temperatures, causing unprecedented bleaching of the Great Barrier Reef and other coral systems. Around Tasmania, hot sea temperatures damaged fragile kelp forests as well as the abalone, oyster, and salmon populations.

This photo of Uluru, also known Ayers Rock, shows its typically hot and dry environment. Heavy rains in late 2016 caused waterfalls to cascade down the sides of the giant sandstone formation. Credit: © Steve Vidler, SuperStock

Australia’s extreme weather in 2016 included both drought and heavy rains that caused unprecedented flooding. The areas around Darwin and Brisbane saw significantly less rainfall during the year, while heavier than usual rains soaked Adelaide, Canberra, Hobart, and Sydney. In central Australia, dangerous flash floods took out roads, washed away cars, and forced the evacuations of several communities. At Christmastime, record rains and floods forced the closure of Uluru-Kata Tjuta National Park. Uluru itself, a giant sandstone formation among sand dune plains, was awash with waterfalls.

The BOM climate statement warned that such extreme weather events will become more common, even become normal, as global warming continues to reshape Earth’s climate.

December 22, 2016

Last month, a new dawn rose over a small island in American Samoa. The island of Tau (also spelled Ta’u), home to less than 1,000 people, now gets all of its electric power from the sun. It is a small but significant step in the global push toward renewable energy. American Samoa is a United States territory in the Pacific Ocean, about 2,300 miles (3,700 kilometers) southwest of Hawaii. It consists of seven tropical islands with a combined population of about 55,000 people.

Solar panels and battery storage systems on the island of Ta’u, seen here, have provided all the island’s electric power since November 2016. Credit: © SolarCity

Tau worked with the company SolarCity, which was recently acquired by the electric car manufacturer Tesla, to convert its small electrical grid to run entirely on solar energy. (Both companies were founded by Elon Musk, a South African-born business developer.) About 5,000 solar panels and 60 battery storage systems were installed on the island over the course of two years. The battery systems store electric energy for nights and cloudy days. With the battery backups, the island can operate without sun for several days in a row.

Prior to the solar conversion, Tau’s power came from costly and polluting electric generators. Diesel fuel had to be shipped to the island over long stretches of ocean, an expensive process that itself used a lot of fuel. The new solar energy system will save some 110,000 gallons (415,000 liters) of diesel fuel each year, thereby preventing about 2.5 million pounds (1.1 million kilograms) of carbon dioxide emissions—a main cause of global warming and climate change—from entering the atmosphere.

The conversion is the latest step in the slow but steady trend toward renewable energy. Not only are such power systems better for the environment, but they are also becoming cheaper than fossil fuel-burning systems in a growing number of situations. Prices for solar cells continue to fall while their efficiency at capturing the sun’s energy slowly improves. Manufacturers are producing larger and more efficient wind turbines as well. Earlier this month, the first offshore wind farm in the United States began delivering power to an island within the state of Rhode Island. Offshore wind farms are more expensive and complicated to build than wind turbines on land, but they take advantage of strong, steady winds off the coasts to deliver cheap, consistent power.

Pacific islands like Tau are prime targets for switching to solar energy. Many are close to the equator and have few cloudy days. Therefore, they receive a strong, constant supply of sunlight year-round. Furthermore, the remote locations of these islands make shipping fossil fuels to them extremely expensive. Residents of Tau saw their electric bills remain the same after the switch and will now be insulated from oil’s fluctuating (rapidly changing) prices that, in the past, often caused energy costs to spike.

SolarCity is now working with the Hawaiian island of Kauai to improve distribution and storage of solar energy there. Kauai is significantly larger than Tau, with a population of over 70,000, but the Hawaiian state government is committed to switching to entirely renewable energy. Such islands as Kauai and Tau are likely to bear the brunt of global warming through rising sea levels and greater numbers of extreme weather events. Renewable energy, often considered the best environmental choice, may soon become the best economic choice as well.

November 8, 2016

Yesterday, November 7, officials from around the world gathered in Marrakech, Morocco, for the 2016 United Nations (UN) Climate Change Conference, or COP22. COP22 is an acronym for the 22nd annual session of the Conference of the Parties. The meetings come on the heels of the Friday, November 4, entry into force of COP21’s Paris Climate Agreement. One hundred countries—including the two considered to be the greatest polluters, China and the United States—have ratified the agreement for nations to report their greenhouse gas emissions.

UN Secretary General Ban Ki-moon (second left); Christiana Figueres (left), executive secretary of the UN Framework Convention on Climate Change; Laurent Fabius (second right), minister for foreign affairs of France and president of the UN Climate Change Conference in Paris (COP21); and French President François Hollande (right) celebrate the signing of the historic Paris Climate Agreement in April 2016. The agreement went into effect on Nov. 4, 2016. Credit: © Mark Garten, UN Photo

Most scientists believe that greenhouse gas emissions contribute to global warming. Global warming is an increase in the average temperature at Earth’s surface, specifically the warming observed since the mid-1800’s. If it continues unchecked, it may melt ice on land near Earth’s poles, raising sea levels; lead to widespread droughts; and cause certain plant and animal species to become extinct. Natural processes have caused Earth’s climate to change in the distant past. But scientists have found strong evidence that human activities have caused most of the warming since the mid-1900’s. These activities include the release of such greenhouse gases as carbon dioxide into the atmosphere, where the gases trap heat like a blanket around Earth.

Countries that have ratified the Paris Climate Agreement must assess and report their emissions levels every five years. However, they are not obligated to lower emission levels. Officials hope that such “name and shame” practices will encourage countries to do their best to reduce emissions. Now that the agreement has entered into force, the Marrakech conference is being called the “COP of Action.” Talk has shifted from finger-pointing and negotiation to working out action plans to slash greenhouse gas emissions.

In some cases, action plans have already been developed. A few weeks ago, in the African country of Rwanda, officials agreed to phase out the production of hydrofluorocarbons (HFC’s). HFC’s are a type of molecule used as a refrigerant in air conditioning and refrigeration systems. They were originally designed as a replacement for chlorofluorocarbons (CFC’s), which were found to damage the Earth’s protective ozone layer. Unfortunately, HFC’s were later discovered to be incredibly potent greenhouse gases, up to 12,000 times more powerful than carbon dioxide. Scientists estimate that the phase-out will prevent 0.9 °F (0.5 °C) of warming during the next century alone. Also last month, aviation industry officials met in Montreal, Canada, and agreed to cap the emissions of greenhouse gases on international flights.  The pact is not as strict as many scientists had hoped, and will only take effect in 2021. Nevertheless, it serves as a first step in controlling the greenhouse gas output of an industry that has largely resisted regulation.