Climate change refers to long-term shifts in temperatures and weather patterns. These shifts may be natural, but since the 1800s, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels (like coal, oil, and gas), which produces heat-trapping gases. These gases, known as greenhouse gases, trap the sun's heat and raise the planet's average temperature. The most significant greenhouse gas is carbon dioxide (CO2), which has increased by about 50% since the Industrial Revolution. This has led to an increase in the global average temperature of about 1.2°C (2.2°F) since the pre-industrial era.
The scientific understanding of climate change began in the early 19th century when scientists first began to suspect that the Earth's climate had changed over time. In the 1820s, Joseph Fourier proposed the greenhouse effect. In 1856, Eunice Newton Foote demonstrated the warming effect of carbon dioxide. In the late 19th century, Svante Arrhenius calculated that carbon dioxide emissions from burning fossil fuels could cause global warming. However, it was not until the 1950s that scientists began to collect systematic data on the Earth's climate, with Charles David Keeling's measurements of atmospheric CO2 concentrations at Mauna Loa Observatory being a key turning point. It was not until the 1980s that the issue of climate change began to receive widespread attention.
Climate change is a major global issue, and it is having a significant impact on the environment and on human society. The effects of climate change include rising sea levels, more extreme weather events (such as heatwaves, droughts, floods, and wildfires), and changes in agricultural yields. The issue is the subject of intense debate, and there is a great deal of disagreement about how to address it. However, there is a broad consensus among scientists that climate change is real and that it is caused by human activity. International agreements such as the Paris Agreement have been established to address the issue, with the goal of limiting global warming to well below 2°C, preferably to 1.5°C, compared to pre-industrial levels.