Global coral die-offs signal Earth’s first climate tipping point

accord: A formal agreement between two or more groups, usually nations.

annual: Adjective for something that happens every year. (in botany) A plant that lives only one year, so it usually has a showy flower and produces many seeds.

Atlantic: One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.

atmosphere: The envelope of gases surrounding Earth, another planet or a moon.

battery: A device that can convert chemical energy into electrical energy.

carbon: A chemical element that is the physical basis of all life on Earth. Carbon is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules. (in climate studies) The term carbon sometimes will be used almost interchangeably with carbon dioxide to connote the potential impacts that some action, product, policy or process may have on long-term atmospheric warming.

carbon dioxide: (or CO₂) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.

CEO: An acronym for Chief Executive Officer, which is typically the person who runs a company.

circulation: (adj. circulatory) A term that refers to the pumping of some fluid repeatedly throughout a system of vessels. (in medicine) The pumping of blood through the arteries and smaller types of vessels (and from there into other organs and tissues).

climate: The weather conditions that typically exist in one area, in general, or over a long period.

climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

coauthor: One of a group (two or more people) who together had prepared a written work, such as a book, report or research paper. Not all coauthors may have contributed equally.

consortium: A group or association of independent organizations.

coral: Marine animals that often produce a hard and stony exoskeleton and tend to live on reefs (the exoskeletons of dead ancestor corals).

deforestation: The intentional removal of all trees from notable pieces of forested land. Sometimes this has been done to make way for roads or towns. It may also be done to harvest trees for income from lumber.

develop: To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing.

dire: An adjective that means grave, or hard to survive.

drought: An extended period of abnormally low rainfall; a shortage of water resulting from this.

ecological: An adjective that refers to a branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

forest: An area of land covered mostly with trees and other woody plants.

geographer: A scientist who studies Earth’s features and how the living and nonliving parts of the planet affect one another.

global warming: The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

Greenland: The world’s largest island, Greenland sits between the Arctic Ocean and North Atlantic. Although it is technically part of North America (sitting just east of Northern Canada), Greenland has been linked more politically to Europe. Ice covers roughly 80 percent of Greenland. Indeed, the Greenland ice sheet is the world’s largest. If its frozen water were to melt, it could raise sea levels around the world by 6 meters (about 20 feet). Although this is the 12th biggest nation (based on surface area), Greenland averages the fewest people per square kilometer of its surface area.

host: (v.) The act of providing a home or environment for something. A website, for instance, could host photos, news or other types of information.

ice sheet: A broad blanket of ice, often kilometers deep. Ice sheets currently cover most of Antarctica. An ice sheet also blankets most of Greenland. During the last glaciation, ice sheets also covered much of North America and Europe.

media: A term for the ways information is delivered and shared within a society. It encompasses not only the traditional media — newspapers, magazines, radio and television — but also digital outlets, such as Twitter, Facebook, Instagram, TikTok and WhatsApp. The newer, digital media are sometimes referred to as social media. The singular form of this term is medium.

methane: A hydrocarbon with the chemical formula CH₄ (meaning there are four hydrogen atoms bound to one carbon atom). It’s a natural constituent of what’s known as natural gas. It’s also emitted by decomposing plant material in wetlands and is belched out by cows and other ruminant livestock. From a climate perspective, methane is 80 times more potent than carbon dioxide is in trapping heat in Earth’s atmosphere, making it a very important greenhouse gas.

Paris Accord: The language for a United Nations treaty that was negotiated in Paris, France, on Dec. 12, 2015. Its key, stated aim was to strengthen the response of nations around the world to the threat of climate change by keeping the average global rise in temperature by 2100 under 2 degrees Celsius (3.6 degrees Fahrenheit), as compared to pre-industrial levels. It would also work toward (if possible) holding the temperature rise to less than 1.5 degrees Celsius (2.7 degrees Fahrenheit).

political: (n. politics) An adjective that refers to the activities of people charged with governing towns, states, nations or other groups of people. It can involve deliberations over whether to create or change laws, the setting of policies for governed communities, and attempts to resolve conflicts between people or groups that want to change rules or taxes or the interpretation of laws. The people who take on these tasks as a job (profession) are known as politicians.

political scientist: Someone who studies or deals with the governing of people, largely by elected officials and governments. 

preindustrial: An adjective that refers to the period before societies had begun to industrialize, using machines and fossil fuels to build products, often with assembly lines or big teams of workers. In the United States, that period began in the mid- to late-1700s.

rainforest: Dense forest rich in biodiversity found in tropical areas with consistent heavy rainfall.

reef: A ridge of rock, coral or sand. It rises up from the seafloor and may come to just above or just under the water’s surface.

risk: The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

sea: An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

sea level: The overall level of the ocean over the entire globe when all tides and other short-term changes are averaged out.

soot: Also known as black carbon, it’s the sometimes oily residues of incompletely burned materials, from plastics, leaves and wood to coal, oil and other fossil fuels. Soot particles can be quite small — nanometers in diameter. If inhaled, they can end up deep within the lung.

sustainable: (n. sustainability) An adjective to describe the use of resources in a such a way that they will continue to be available long into the future.

system: A network of parts that together work to achieve some function. For instance, the blood, vessels and heart are primary components of the human body’s circulatory system. Similarly, trains, platforms, tracks, roadway signals and overpasses are among the potential components of a nation’s railway system. System can even be applied to the processes or ideas that are part of some method or ordered set of procedures for getting a task done.

tactic: An action or plan of action to accomplish a particular feat.

threatened: (in conservation biology) A designation given to species that are at high risk of going extinct. These species are not as imperiled however, as those considered “endangered.”

tipping point: A point at which some action leads to a disproportionately large or irreversible change in a process, impact or attitude.

United Kingdom: Land encompassing the four “countries” of England, Scotland, Wales and Northern Ireland. More than 80 percent of the United Kingdom’s inhabitants live in England. Many people — including U.K. residents — argue whether the United Kingdom is a country or instead a confederation of four separate countries. The United Nations and most foreign governments treat the United Kingdom as a single nation.

weather: Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.