The Record That Started the Questions
1The weather club at Harrow Hill Middle School runs a rooftop weather station that measures air temperature, humidity, wind and rain. Its readings feed a forecast app that students and teachers check every morning. The station has been running since 2012. In January 2025, the app reported that 2024 had been the warmest year at the school since the station was set up. It also reported that 2024 was the warmest year on record for Earth as a whole. Club adviser Mr. Lorenzo Gatti asked members Sakura Endo and Darius Mensah to prepare questions for a video call with a climate scientist about what has caused Earth's temperature to rise over the past century.
2Darius learned that 2024 was also an El Niño year. El Niño is a pattern in which the surface water of the eastern tropical Pacific Ocean becomes warmer than usual for several months. During El Niño, the ocean gives off extra energy to the air, so the planet as a whole tends to be warmer than in the years around it. La Niña, the opposite pattern, brings cooler-than-usual water to the same area and tends to make a year a little cooler. The two patterns come and go every few years.
3Sakura looked into the Sun. The energy the Sun gives off rises and falls slightly in a cycle that lasts about 11 years. At solar maximum, the Sun has many sunspots and sends out a little more energy; at solar minimum, it sends out a little less. Satellites measure the energy arriving at the top of Earth's air.
4Mr. Gatti added that greenhouse gases, such as carbon dioxide (CO₂), absorb energy given off by Earth's surface and send some of it back down. Burning coal, oil and natural gas adds CO₂ to the air. He also explained one way scientists tell these factors apart. Extra energy from the Sun would warm the whole atmosphere, from the ground up to the thin, high layer called the stratosphere. Extra greenhouse gases trap energy in the lower air, and the stratosphere tends to cool.
5The global data in the tables are based on real measurements, rounded. Temp change means how much warmer the year was than the average for 1951–1980.