Global warming is caused mainly by greenhouse gases from burning fossil fuels, which trap heat in the atmosphere.
Main cause
Burning fossil fuels (coal, oil, gas) releases CO2, which traps heat.
Other causes
- Deforestation.
- Methane from agriculture and landfills.
- Industry and cement.
Numbers
CO2 is above 420 ppm, up from about 280 ppm before the industrial era. Earth has warmed about 1.1°C to 1.2°C since 1850 to 1900.
Evidence
Scientists attribute the warming to human activity (IPCC).
Records
2024 was the warmest year on record.
Warming trend in numbers
The IPCC Sixth Assessment Report (2021 to 2023) states that human influence has unequivocally warmed the atmosphere, ocean and land. Global surface temperature in 2011 to 2020 was about 1.1 C above 1850 to 1900. Atmospheric CO2 has risen from about 280 ppm before the industrial era to over 420 ppm, measured at Mauna Loa Observatory.
- Burning fossil fuels, cement production and land use change release CO2. Fossil CO2 emissions were around 37 billion tonnes in 2023, according to the Global Carbon Project.
- Methane, with about 28 times the warming effect of CO2 over 100 years, comes from livestock, rice, landfills and oil and gas.
- Nitrous oxide from fertilizers is another greenhouse gas.
Evidence
NASA and NOAA record 2023 and 2024 as the hottest years in instrument records, with 2024 the first calendar year above 1.5 C relative to preindustrial in some datasets. Evidence includes ocean heat content rise, shrinking ice sheets, sea level rise of about 3.7 mm per year recently, and earlier springs. Natural factors, such as solar variation and volcanic activity, do not explain the long-term warming.
Warming trend in numbers
NASA and NOAA report global temperature about 1.1 to 1.2 C above the late 1800s average. 2023 and 2024 were among the hottest years on record. CO2 concentration passed 420 ppm in 2023, up from about 280 ppm before industrialization.
Evidence
The IPCC concludes it is unequivocal that human influence has warmed the atmosphere, ocean and land. The main driver is burning fossil fuels.
Measured warming and its cause
NASA and NOAA data show Earth’s average surface temperature is about 1.1 to 1.2 degrees Celsius above the 1850 to 1900 level. The last decade is the warmest on record. The IPCC concludes that human activity, mainly burning fossil fuels, has unequivocally warmed the climate. Atmospheric carbon dioxide has risen from about 280 parts per million before industry to over 420 parts per million.
Effects and responses
Observed effects include sea level rise of about 20 centimeters since 1900, shrinking Arctic sea ice, glaciers retreating, and more intense heat waves and heavy rain. The Paris Agreement of 2015 aims to hold warming well below 2 degrees Celsius and pursue 1.5. Solutions include renewable electricity, efficiency, electrified transport, methane cuts and forest protection. Projected outcomes depend on future emissions scenarios.
Based on data from NASA, NOAA and the Intergovernmental Panel on Climate Change
