2024 set new record for hottest year, passing a dangerous heat threshold

attribution: A field of research, largely used in climate studies. It seeks to test whether — and by how much — climate change may be responsible for certain extreme weather events, such as droughts, extreme flooding, hurricanes, excessive heat or odd storm trajectories.

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.

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.

degree: (in geometry) A unit of measurement for angles. Each degree equals one three-hundred-and-sixtieth of the circumference of a circle.

European Union: The confederation of 27 European countries that have agreed to work peacefully together. Residents of EU can move freely between its member countries and sell goods to them. Most members have also adopted the same currency, known as the Euro.

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.

greenhouse gas: A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.

Industrial Revolution: A period of time around 1750 that was marked by new manufacturing processes and a switch from wood to coal and other fossil fuels as a main source of energy.

milestone: An important step on the road to stated goal or achievement. The term gets its name from the stone markers that communities used to erect along the side of the road to inform travelers how far they still had to go (in miles) before reaching a town.

planet: A large celestial object that orbits a star but unlike a star does not generate any visible light.

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.

range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which values can vary (such as the highest to lowest temperatures). Also, the distance within which something can be reached or perceived.

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.

threshold: A lower limit; or the lowest level at which something occurs.

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.