Discovering the greenhouse effect
Earth's climate has always changed: ice ages and interglacials have alternated over tens of thousands of years, partly due to small changes in Earth's orbit, and abrupt past changes are linked to mass extinctions. In 1824 Joseph Fourier reasoned that the atmosphere acts like a warming blanket. In 1856 the American Eunice Foote reported that a glass jar of carbon dioxide heated more in sunlight, and in 1859–61 John Tyndall precisely measured how water vapour and CO₂ absorb infrared (heat). Sunlight passes through the air and warms the ground, and greenhouse gases trap the infrared electromagnetic waves the ground emits. In 1896 Svante Arrhenius calculated that doubling CO₂ would raise temperatures by several degrees.
Evidence accumulates
In 1938 Guy Callendar argued that fossil-fuel CO₂ was already warming the planet, though many were sceptical at first. From 1958 Charles David Keeling's measurements at Mauna Loa, Hawaii, showed CO₂ rising every year — the Keeling curve. Concentrations of about 280 ppm before industrialisation have recently passed 420 ppm. In 1967 Syukuro Manabe and Richard Wetherald built a climate model combining radiation and convection; Manabe shared the 2021 Nobel Prize in Physics. The Intergovernmental Panel on Climate Change (IPCC), founded in 1988, concluded in 2021 that it is "unequivocal" that human influence has warmed the atmosphere, ocean and land. Shrinking glaciers and sea ice, sea-level rise and ocean acidification are all observed.
Impacts and responses
Warming can make heatwaves, droughts, heavy rain and wildfires more frequent and intense. Health concerns include heatstroke and heat illness, worsening heart and lung disease, shifting ranges of mosquito-borne diseases, and food and water shortages. In heatwaves, limit midday outdoor activity, drink water often, and check on older people, children and those with chronic illness. The 2015 Paris Agreement aims to hold warming well below 2 °C above pre-industrial levels and pursue 1.5 °C. Responses include mitigation — cutting emissions through renewables and efficiency — and adaptation, such as flood defences and water management. Protecting forests and oceans that absorb CO₂ through photosynthesis also matters. The future temperature of the Earth depends largely on emissions from here on.
FAQ
- How is weather different from climate?
- Weather is the day-to-day state of the atmosphere; climate is the pattern of weather averaged over typically 30 years or more. One cold winter day does not disprove global warming.
- Do individual actions matter?
- Saving energy, using public transport and cutting food waste all help reduce emissions, though large cuts are generally judged to also require changes in energy systems and policy.
Sources reviewed: 2026-10-26
References
- Fourier, J. (1824). Remarques générales sur les températures du globe terrestre et des espaces planétaires. Annales de Chimie et de Physique, 27, 136–167.
- Foote, E. (1856). Circumstances affecting the heat of the sun's rays. American Journal of Science and Arts, 22, 382–383.
- Tyndall, J. (1861). On the absorption and radiation of heat by gases and vapours. Philosophical Transactions of the Royal Society of London, 151, 1–36.
- Arrhenius, S. (1896). On the influence of carbonic acid in the air upon the temperature of the ground. Philosophical Magazine, 41(251), 237–276.
- Callendar, G. S. (1938). The artificial production of carbon dioxide and its influence on temperature. Quarterly Journal of the Royal Meteorological Society, 64(275), 223–240.
- Keeling, C. D. (1960). The concentration and isotopic abundances of carbon dioxide in the atmosphere. Tellus, 12(2), 200–203.
- Manabe, S., & Wetherald, R. T. (1967). Thermal equilibrium of the atmosphere with a given distribution of relative humidity. Journal of the Atmospheric Sciences, 24(3), 241–259.
- Hansen, J., et al. (1981). Climate impact of increasing atmospheric carbon dioxide. Science, 213(4511), 957–966.
- IPCC. (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report. Cambridge: Cambridge University Press.