arXiv: A website that posts research papers — often before they are formally published — in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance and statistics. Anyone can read a posted paper at no charge.
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.
Atlantic Meridional Overturning Circulation (or AMOC): Masses of water that circulate from within the Atlantic Ocean, moving warm saline water from south to north near the surface and returning cooler freshwater from north to south along the seafloor. It’s part of a “conveyor belt” of circulation that helps move water — including heat and nutrients — through the globe’s interconnected system of seas. The AMOC’s circulation is slow, taking some 1,000 years for any particular mass of water to complete one circuit.
atmosphere: The envelope of gases surrounding Earth, another planet or a moon.
average: (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
circulation: (adj. circulatory) A term that refers to the pumping of some fluid repeatedly throughout a system of vessels or pathways.
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.
colleague: Someone who works with another; a co-worker or team member.
computer model: A program that runs on a computer that creates a model, or simulation, of a real-world feature, phenomenon or event.
consensus: An opinion or conclusion shared by most, if not all, of a specific group.
constant: Continuous or uninterrupted.
convection: The rising and falling of material in a fluid or gas due to uneven temperatures. This process occurs in the outer layers of some stars.
current: A fluid — such as of water or air — that moves in a recognizable direction.
density: The measure of how condensed some object is, found by dividing its mass by its volume.
dilute: To make something thinner or less concentrated by adding a liquid to it.
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.
engineering: The field of research that uses math and science to solve practical problems. Someone who works in this field is known as an engineer.
factor: Something that plays a role in a particular condition or event; a contributor.
focus: To look or concentrate intently on some particular point or thing.
fossil fuel: Any fuel — such as coal, petroleum (crude oil) or natural gas — that has developed within the Earth over millions of years from the decayed remains of bacteria, plants or animals.
freshwater: A noun or adjective that describes bodies of water with very low concentrations of salt. It’s the type of water used for drinking and making up most inland lakes, ponds, rivers and streams, as well as groundwater.
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. Indeed, Vikings arrived in Greenland around the 10th century, and for a time the island was a colony of Denmark. In June 2009, Greenland became an independent nation. 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: (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents. (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 age: Earth has experienced at least five major ice ages, which are prolonged periods of unusually cold weather experienced by much of the planet. During that time, which can last hundreds to thousands of years, glaciers and ice sheets expand in size and depth. The most recent ice age peaked 21,500 years ago, but continued until about 13,000 years ago.
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.
Intergovernmental Panel on Climate Change: , or IPCC. This international group keeps tabs on the newest published research on climate and on how ecosystems are responding to it. The United Nations Environment Programme and the World Meteorological Organization jointly created the IPCC in 1988. Their aim was to provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and social impacts.
land bridge: A narrow region of land linking two large masses of land. In prehistoric times, a major land bridge connected Asia and North America across the Bering Strait. Scientists believe early humans and other animals used it to migrate between the continents.
mean: One of several measures of the “average size” of a data set. Most commonly used is the arithmetic mean, obtained by adding the data and dividing by the number of data points.
meltwater: The water that comes from melting ice. The quantities can be large and show up quickly when it comes from melting glaciers, ice sheets and snow-capped mountains.
meteorology: (adj. meteorological) The study of weather as it pertains to future projects or an understanding of long-term trends (climate). People who work in this field are called meteorologists.
migrate: To move long distances (often across many countries) in search of a new home. (in biology) To travel from one place to another at regular times of the year to find food or more hospitable conditions (such as better weather). Species that migrate each year are referred to as being migratory. (in chemistry) To move from one material, usually a solid, into a neighboring liquid, such as water. (in science) To travel from one place to another in an attempt to achieve new conditions that may afford stability.
model: A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.
Nordic Seas Overturning Circulation (or NOC): A northern European branch of the AMOC (short for Atlantic Meridional Overturning Circulation). NOC’s water flows between a path between Greenland and Scotland (known as the Greenland-Scotland Ridge) and into the Nordic Seas.
oceanographer: Someone who works in the branch of science that deals with the physical and biological properties and phenomena of the oceans.
Paris Agreement: A United Nations treaty that was negotiated in Paris, France, on Dec. 12, 2015. Its key 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). As of January 2026, 194 nations had signed onto (agreed to the provisions of) this treaty.
physical: (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another). (in biology and medicine) The term can refer to the body, as in a physical exam or physical activity. (in job titles) It can refer to a type of research that focuses on attributes grounded in the physical sciences (chemistry, physics or materials science).
precipitation: (in chemistry) The creation of a solid from a solution. This can occur if there is too much of a chemical to dissolve completely into a solution. It also can be a sign that some chemical reaction is taking place. (in meteorology) A term for water falling from the sky. It can be in any form, from rain and sleet to snow or hail.
projection: Some feature that extends out (or projects) from the body of a structure. (in cartography) The depiction of some three-dimensional area (on land or in space) as a two-dimensional map.
salt: A compound made by combining an acid with a base (in a reaction that also creates water). The ocean contains many different salts — collectively called “sea salt.” Common table salt is a made of sodium and chlorine.
scenario: A possible (or likely) sequence of events and how they might play out.
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.
simulation: (v. simulate) An analysis, often made using a computer, of some conditions, functions or appearance of a physical system. A computer program would do this by using mathematical operations that can describe the system and how it might change over time or in response to different anticipated situations.
standard deviation: (in statistics) The amount that each a set of data varies from the mean.
statistics: The practice or science of collecting and analyzing numerical data in large quantities and interpreting their meaning. Much of this work involves reducing errors that might be attributable to random variation. A professional who works in this field is called a statistician.
strait: (in geography) A narrow passage between two big bodies of water (often used in the plural form).
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.
tipping point: A point at which some action leads to a disproportionately large or irreversible change in a process, impact or attitude.
treaty: A formal agreement that two or more sovereign powers (usually countries or tribal nations) have adopted, giving its provisions the force of law.
tropics: The region near Earth’s equator. Temperatures here are generally warm to hot, year-round.
uncertainty: (in statistics) A range of how much measurements of something will vary around an already-measured value.
variable: (in mathematics) A letter used in a mathematical expression that may take on different values. (in experiments) A factor that can be changed, especially one allowed to change in a scientific experiment. For instance, when researchers measure how much insecticide it might take to kill a fly, they might change the dose or the age at which the insect is exposed. Both the dose and age would be variables in this experiment.
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.