September 6, 2019

This summer, unusually warm air temperatures have caused record ice melt in the North Atlantic Ocean island of Greenland. During the month of July alone, the island lost more ice than it normally does in an entire year. In just a five-day period, from July 30 to August 3, the island lost about 90 percent of the surface of its ice sheet (a massive glacier)—an estimated 55 billion tons (50 billion metric tons) of ice. The record ice loss is a result of global warming and climate change.

A Danish meteorological team travels across submerged sea ice in Greenland’s Inglefield Bredning fjord on June 13, 2019. The area is normally covered with ice and snow. Credit: Steffen M. Olsen, Danish Meteorological Institute

At the highest point of the Greenland Ice Sheet, 10,550 feet (3,216 meters) above sea level, temperatures topped freezing (32 °F or 0 °C) for more than 16 hours during July 30 and 31, melting some 12.5 billion tons (11.3 billion metric tons) of ice during that brief period. It was the first time ice had melted at that high point since July 2012, and it was just the third such ice melt there in the last 700 years.

Click to view larger image. Greenland, a self-governing territory of Denmark, stretches from the Arctic to the North Atlantic Ocean. Credit: WORLD BOOK map

The ice sheet that covers Greenland is about the size of Alaska, and it contains enough ice to raise global sea levels by more than 20 feet (6 meters). During an average summer, Greenland will lose some ice from meltwater and from icebergs that calve (break off) into the ocean. But the ice loss typically happens at the sheet’s edges at sea level—not at the highest and coldest points. The amount of ice loss is also normally much less. From 1981 to 2010, the average ice melt from July 30 to August 3 was 15 billion tons (13.6 billion metric tons).

Huge icebergs form where the Jakobshavn Glacier flows into the sea near Ilulissat, Greenland. Credit: © Radius Images, Getty Images

The drastic summer ice melt in Greenland is a continuation of an alarming and worsening trend. In 1972, Landsat satellites (a project then known as the Earth Resources Technology Satellite) began photographing and mapping Greenland’s ice sheet. Landsat, a joint mission of NASA and the United States Geological Survey, uses a series of satellites to produce detailed images of Earth from space.

From 1979 to 2006, satellite images showed a 30 percent rise in the amount of Greenland ice that melts each summer, and the ice loss continues to increase. Greenland’s ice fronts have drastically retreated, rocky peaks have become exposed, and the size and shape of the island’s many fiords have changed significantly. In August 2019, Landsat images showed wet snow and melt ponds at Greenland’s higher elevations, and large parts of the island’s shrinking glaciers appeared brownish grey. The color indicates that the surface has melted, a process that concentrates dust and rock particles and leads to a darker recrystallized ice sheet surface.

Greenland is not the only site of rapidly increasing ice melt. Warmer global temperatures are reducing glaciers and ice fields in the Arctic and Antarctica, as well as in Iceland, the Alps, the Andes, the Himalaya, the Rockies, at Kilimanjaro in Tanzania, and in the Sudirman Range in Indonesia.

July 17, 2019

To help reduce pollution in the United States, a Sierra Club program called “Ready for 100” is encouraging communities and individuals to commit to the use of 100 percent renewable energy sources. The Sierra Club, founded in 1892 by the naturalist John Muir, is an organization that works to protect the environment. Ready for 100 is asking business, civic, community, and religious leaders, as well as families and students, to help achieve the goal of complete nationwide reliance on clean, renewable energy by the year 2050.

Renewable energy comes from such sources as the sun, wind, moving water, heat beneath the ground, and plants. Such energy sources are considered “clean” because they cause little or no pollution, and they differ from fossil fuels such as coal, oil, and natural gas. Burning fossil fuels causes air pollution and acid rain, and also releases large amounts of carbon dioxide and other greenhouse gases. The gases trap heat in Earth’s atmosphere, contributing to global warming and climate change.

Since November 2016, solar panels and battery systems have provided 100 percent of the energy needed to power the island of Ta’u, seen here, in the U.S. Pacific territory of American Samoa. Credit: © SolarCity

There are many benefits to using clean energy sources. They can provide communities with cleaner air and water, lower energy costs, greater energy independence, and greater local ownership of energy systems. More than 50 nations around the world, including Brazil, Canada, and Norway, already get more than 50 percent of their energy supply from renewable sources. Costa Rica expects to be using 100 percent renewable energy by 2021. The U.S. state of Hawaii has promised to be Ready for 100 by 2045, and recent California legislation requires the country’s most populous state to achieve 50 percent renewable energy use by 2030. Such worldwide cities as Munich, New York, and Sydney are also well beyond the 50 percent mark, and they are fast approaching total reliance on renewable energy. To reach 100 percent, the amount of energy generated from renewable sources (for such uses as electric power, heating and cooling, and transportation) must equal or exceed the annual energy consumed.

Hoover Dam on the Colorado River has been providing renewable hydroelectric energy in the southwestern United States since 1935. Credit: U.S. Department of Transportation

So far, 182 U.S. towns and cities from coast to coast have committed to 100 percent renewable energy use by 2050. Aspen, Colorado (since 2015); Burlington, Vermont (2014); Georgetown, Texas (2018); Greensburg, Kansas (2013); Kodiak Island, Alaska (2012); and Rock Port, Missouri (2008) have already hit the 100 percent renewable energy mark, leading the push for cleaner energy and a healthier future.

April 26, 2019

Last month, in March, Tropical Cyclone Idai struck the southeastern coast of Africa. One of the strongest storms ever recorded in the Southern Hemisphere, Idai caused catastrophic landslides and flooding that killed more than 1,000 people in Mozambique and in neighboring Malawi and Zimbabwe. The storm left more than 300,000 people homeless and led to deadly outbreaks of cholera and increased cases of malaria. More than a month later, thousands of people remain missing in affected areas, and government and international aid agencies continue to struggle to provide badly needed food, water, and medical supplies.

On March 23, 2019, residents of Beira, a coastal city in central Mozambique, survey the damage done by Cyclone Idai. Credit: © Yasuyoshi Chiba, AFP/Getty Images

Cyclone Idai formed as a tropical depression over the warm waters of the southwestern Indian Ocean in early March. The storm intensified into a cyclone as it struck central Mozambique on March 4. Torrential rains and deadly winds whipped coastal areas for days as Idai spun along the Mozambique Channel between the African mainland and the island of Madagascar. Idai varied in strength, until reaching peak intensity with winds of 150 miles (240 kilometers) per hour on March 14. After 17 days of damage and deluge, the storm finally weakened and dissipated on March 21.

This satellite image shows Cyclone Idai in the Mozambique Channel on March 14, 2019. Credit: NASA

The broad and determined storm reached inland to Malawi and Zimbabwe and pelted coastal areas of Madagascar. The storm extensively damaged or destroyed vital infrastructure, including communication networks, hospitals, roads, sanitation facilities, and schools. Wide swaths of farmland were ruined, portions of forests were flattened by high winds, and flooding created a temporary inland sea in Mozambique that measured some 80 miles (130 kilometers) long and 15 miles (24 kilometers) wide. Mozambique President Filipe Nyusi called Cyclone Idai a “humanitarian disaster of great proportion.”

Mozambique. Credit: WORLD BOOK map

Mozambique’s typically able Instituto Nacional de Gestão de Calamidades (National Disasters Management Institute) was overwhelmed by the scale of Idai’s destruction, and an urgent note verbale (formal diplomatic notice) went out requesting international help. The Red Cross and Red Crescent, Doctors Without Borders, and several United Nations organizations came to the rescue, as did the European Union and the governments of Canada, France, Portugal, South Africa, and the United Kingdom.

Cyclone Idai was the seventh tropical cyclone of the Indian Ocean season, more than twice the average for this time of year. Globally, high-intensity storms have been occurring more frequently in recent years, a trend directly related to climate change. Global warming increases sea temperatures, creating more moisture and instability in the atmosphere—factors crucial to the birth of dangerous cyclones and hurricanes. Tropical cyclones need high humidity and surface water temperatures of 79 °F (26 °C ) or higher to form. Melting glaciers and ice have increased global sea levels, resulting in more frequent and intense flooding in coastal areas around the world.

March 4, 2019

Yesterday, March 3, was World Wildlife Day, an international celebration of the Earth’s flora and fauna sponsored by the United Nations (UN). This year’s theme, “Life Below Water: For People and Planet,” singled out the crucial ecosystems and marine life of the world’s oceans. Life on Earth depends on the conservation and sustainable use of the oceans.

In 2019, the theme of World Wildlife Day is “Life Below Water: For People and Planet.” Credit: © World Wildlife Day

The first UN World Wildlife Day was celebrated on March 3, 2013, the 40th anniversary of the signing of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 1973. The treaty—which went into effect in 1975—aims to control trade in wild animals and plants, their parts, and products derived from them. Over 170 countries around the world have joined the treaty. CITES forbids commercial international trade in certain endangered species, and it regulates trade in other species that might otherwise become endangered. Nevertheless, international wildlife trade continues to put many species at risk.

This year’s World Wildlife Day theme drew particular attention to the diverse animal and plant species that inhabit the world’s oceans. It also highlighted the importance of the oceans themselves, which—aside from providing energy, food, livelihoods, medicines, natural resources, recreation, sediments, and transportation—also absorb about 30 percent of the carbon dioxide produced by humans, buffering the impacts of global warming.

Unfortunately, many ocean waters are polluted, and plastic marine debris in particular is poisoning the world’s waters and killing marine wildlife. Overfishing and other forms of exploitation are also reducing marine wildlife populations, as are the losses of coastal habitats and the effects of climate change. The goal of “Life Below Water: For People and Planet” was to raise awareness of the importance of marine life and to instruct people on responsible and sustainable behavior that can limit the many perils facing the world’s oceans.

February 11, 2019

Last week, monsoon rains dumped record amounts of water in northern  Queensland, Australia, flooding roads, swelling rivers above their banks, and causing landslides. The coastal city of Townsville received more than 3.3 feet (1.0 meters) of rain, raising the level of water held by the Ross River dam to dangerous levels far above its capacity. On February 3, city officials opened the dam’s gates, intentionally flooding several neighborhoods to ease pressure on the dam and keep it from collapsing. Crocodiles, snakes, and other wildlife followed the waters into the flooded streets, appearing in places they are not typically found. Boats and other vehicles capable of navigating high waters rescued many people and pets trapped by the flooding. Two people are known to have died in the flooding.

Floodwaters inundate the Townsville, Australia, suburb of Idalia on Feb. 4, 2019. Credit: © Ian Hitchcock, Getty Images

Some Queensland farmers welcomed the rainfall. Drought conditions have been widespread in recent months across Australia (where summer is from December to February), and the farmers hoped the rain would help their crops. The monsoon flooding came at the tail end of the hottest month ever recorded by Australia’s Bureau of Meteorology. On February 1, the agency reported that the average January temperature across the continent exceeded 86 ºF (30 ºC). The Australian Capital Territory, New South Wales, the Northern Territory, and Victoria all set new high temperature records for the month of January. Some parts of western Queensland and New South Wales had weeks of temperatures above 104 ºF (40 ºC). Numerous farm and wild animals died in the extreme heat, as did many fish in overheated lakes and rivers.

Despite the monsoon rains in Queensland, much of Australia remains in a drought. Scientists believe that such extreme weather events will become more frequent in coming years as a result of global climate change.

August 3, 2018

For many people in the Northern Hemisphere, the summer of 2018 has been touched by fire and obscured by smoke. Summers are typically fire seasons in many areas, but climate change has caused hotter and drier conditions in recent years, and wildfire outbreaks have become more frequent and more destructive. Other causes of increased fire activity include the building of more developments in fire-prone areas, a lack of proper forest management, and, of course, simple human carelessness. In the past weeks, fires have killed more than 100 people and destroyed homes and large swaths of land in Asia, Europe, and North America.

A firefighting helicopter flies over a wildfire in the Greek town of Rafina near Athens on July 23, 2018. The Greek wildfire was the deadliest yet this year, claiming the lives of 92 people. Credit: © Angelos Tzortzinis, AFP/Getty Images

In southeastern Greece, a wildfire erupted July 23, destroying or damaging some 3,500 structures and killing 96 people along the Attica coast. The giant wildfire, just 18 miles (30 kilometers) east of Athens, the Greek capital, burned out of control for several days, gutting seaside resorts and holiday homes. Fanned by high winds, the fast-moving blaze trapped and killed groups of people, including entire families as they huddled between the flames and steep cliffs overlooking the Aegean Sea. The high death toll prompted criticism of the the area’s lack of access roads, warning systems, and other civil protection measures in areas surrounded by forest and at high risk of wildfires.

In far northern Europe, dozens of wildfires have consumed more than 62,000 acres (25,000 hectares) this summer in Sweden, which is experiencing an abnormally lengthy and intense heat wave. Neighboring Finland and Norway are also suffering from unusual heat and wildfire outbreaks, as are Estonia, Latvia, and Lithuania on the other side of the Baltic Sea. Wildfires also torched drought-stricken areas of Germany, the Netherlands, and Poland.

This week in northern California, firefighters continued to battle the Carr Fire that has killed 8 people, destroyed over 1,500 buildings, and consumed some 125,000 acres (50,000 hectares) of land. The wildfire started on July 23 along Carr Powerhouse Road in Shasta County near the city of Redding. The “mechanical failure of a vehicle” ignited dried grasses and trees, and soon flames were roaring through the forested hills around Whiskeytown Lake west of Redding. The wildfire, aided by hot and dry weather, high winds, an abundance of natural fuel, and steep terrain, has since been chased westward by more than 4,200 firefighters—2 of whom have died fighting the blaze. Reports of  “firenados” (huge, rotating whorls of smoke, flame, and ash) encouraged nearly 40,000 people to obey evacuation orders and leave the fire area (which included parts of nearby Trinity County). Many people will return to find their homes and property in ashes.

The Carr Fire is the largest of 17 wildfires currently burning throughout the state of California. Collectively, wildfires in the western United States have scorched 4.6 million acres (1.86 million hectares) so far this year, a 24 percent increase over the annual average for the past decade. Wildfires have also stricken large areas of western Canada and parts of Mexico this summer.

Wildfires have also consumed vast amounts of territory in Siberia of eastern Russia. Since May, firefighters have been battling immense wildfires in the Amur Oblast region along the Chinese border, where towering pyrocumulus clouds have injected smoke and pollutants high into Earth’s atmosphere. Pyrocumulus clouds are formed by rising heat from wildfires or by plume emissions from fossil fuel-burning industrial plants, and they sharply increase the levels of carbon dioxide and harmful aerosols in the atmosphere.

July 26, 2018

The baobab, one of the world’s most unusual and iconic trees, is in danger. The gigantic baobab, known as the “tree of life,” can live as long as 3,000 years. But the hardy trees are suddenly dying in unusual numbers, many long before their expected life spans. Climate change has increased the occurrence of such weather anomalies as droughts, floods, and lightning storms, all of which can harm or kill baobab trees. A destructive mold called black fungus is also appearing more frequently on baobab trees. The tree is further threatened by the loss of its natural habitat to agriculture and development. Habitat loss and illegal hunting have also greatly reduced the population of African elephants, the animals largely responsible for spreading the tree’s seeds. If no action is taken to protect the baobab and its environment, certain species of the tree could be extinct within 100 years.

These giant baobabs form part of the magnificent Avenue of the Baobabs in the Megabe region of western Madagascar. Credit: © Monika Hrdinova, Shutterstock

Baobab is the name of a group of trees that grow in tropical and subtropical regions of the Eastern Hemisphere, especially in Madagascar. The best-known type of baobab is found on the African mainland. It has an extremely thick, often bulging, trunk. This tree may grow to 80 feet (24 meters) tall with a trunk from 30 to 50 feet (9 to 15 meters) in diameter. The tree has white flowers that open at night and are pollinated by bats. The fruit, called monkey bread, is almost 1 foot (30 centimeters) long. It dangles from the tree like a lantern from a long, ropy stem. The fruit holds many seeds buried in a mealy pulp. The pulp, which is rich in vitamin C, serves as food for both animals and people, and it is also used to flavor cool drinks. People sometimes use the leaves and bark in medicines. They make paper, cloth, and rope from the bark fibers. The giant trees also provide shade in the hot climates where they grow, serving as cool gathering places for animals and humans alike.

African elephants, who are themselves in danger, help propagate baobabs by eating the tree’s fruit and seeds (antelopes, baboons, and other animals also contribute). The seeds pass through the animal’s digestive system, and they are then dropped in ready-made fertilizer. Elephants tend to walk great distances in search of food and water, and a single tree’s seeds can thus be spread out over many miles. Ironically, elephants are also known to damage or kill baobab trees in times of severe drought. Elephants sometimes rip apart a baobab’s trunk to get at the tree’s bountiful water supply inside.

Adrian Patrut, a chemist at Babeș-Bolyai University in Romania, has led an international research study on baobab trees since 2005. Patrut pioneered a radiocarbon technique to date baobabs, which do not have the tell-tale age rings found in most trees. Patrut and his team have kept close tabs on the largest and oldest baobabs in southern Africa. They found that 9 of the 13 oldest recorded baobabs (between 1,100 and 2,500 years old) and 5 of the 6 largest have died in the past 12 years—an alarming death rate among these long-living trees. Parts of many other baobabs have also died. The trees have multiple core systems within their massive trunks, allowing parts of the tree to die while the rest lives on.

Of the nine species of baobab trees, six are endemic to the African island of Madagascar. Of those six, half are on the Red List of Threatened Species compiled by the International Union for the Conservation of Nature and Natural Resources (IUCN). The numbers of three Madagascar baobabs—Adansonia grandidieri, Adansonia perrieri, and Adansonia suarezensis—have dropped more than a 50 percent since the 1950′s. A. perrieri and A. suarezensis are considered critically endangered. The numbers of the remaining baobab species that live in mainland Africa, the Arabian peninsula, and Australia are also on the decline.

July 12, 2017

Last month, in June, an international team of researchers and scientists braved heavy snows, freezing winds, and thin air to extract ice core samples from the Illimani glacier high in the Andes Mountains of Bolivia. The samples were the latest collected by teams from Ice Memory, a project aiming to gather ice samples from endangered glaciers around the world. The archive—which will be stored in a sanctuary in Antarctica—will allow future studies of glaciers that will soon fall victim to global warming. Ice Memory is managed by the University of Grenoble Alps Foundation in France and supported by the French and Italian national commissions for the United Nations Educational, Scientific and Cultural Organization (UNESCO).

On June 6, 2017, the Ice Memory team drills near their camp on the Illimani glacier in the Andes Mountains of Bolivia. Credit: © Sarah Del Ben, Wiltouch/Fondation UGA

At 21,004 feet (6,402 meters), Illimani is the highest mountain in the Cordillera Real range of western Bolivia. Glaciers on Illimani have existed for many thousands of years, but they are rapidly melting and retreating as climate change increases Earth’s temperatures. Glacier ice reads like a historical record of climate and environment, preserving ancient animal, plant, and mineral samples as well as showing glacial growth over millennia. They also show variations in temperatures and more recent concentrations of greenhouse gases and other pollutants. Saving Illimani cores will allow scientists to study the ice long after the host glaciers have disappeared.

Scientists remove ice from the drilling core on the Illimani glacier in Bolivia on June 9, 2017. Credit: © Sarah Del Ben, Wiltouch/Fondation UGA

It took several weeks for the Illimani team to drill through the ice and extract the core samples, both of which were more than 440 feet (135 meters) long. Dangerous weather forced the team to abandon the planned retrieval of a third sample. The glacier cores were then cut into smaller pieces, stored in tubes, and catalogued. The samples will eventually make their way to the archive at Concordia Station in Antarctica, where they will join the first core samples extracted from France’s Mont Blanc in 2016. The Concordia glacier archive is meant to store hundreds of ice core samples in a protected snow cave at -65° Fahrenheit (-54° Celsius).

An Ice Memory researcher stacks tubed sections of ice core in an improvised snow cave on the Illimani glacier on June 5, 2017. The samples will eventually be stored in Antarctica. Credit: © Sarah Del Ben, Wiltouch/Fondation UGA

Future core extractions are planned for such threatened glacier areas as Mera Peak in Nepal, Mount Elbrus in Russia, Mount Kilimanjaro in Tanzania, and sites in the Swiss Alps and the Altai Mountains in Asia. Ideally, three glacier samples from each area will provide one sample for immediate analysis and two for storage and archiving. Aside from providing clues about the past, the samples help scientists understand the current effects of climate change and predict future environmental events.

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.

Click to view larger image
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 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.