Carbon dioxide directly influences global temperatures by altering Earth’s radiative balance. Carbon dioxide molecules absorb and re-emit longwave infrared radiation emitted by the surface, reducing the rate at which heat escapes to space. This greenhouse effect is a well-established physical process first quantified by Svante Arrhenius of the Royal Swedish Academy of Sciences and refined by later atmospheric scientists. Laboratory spectroscopy and satellite measurements confirm that increasing atmospheric CO2 raises the downward infrared flux at the surface, producing a positive radiative forcing that drives surface warming.
How CO2 changes the energy budget
Radiative forcing from CO2 grows approximately logarithmically with concentration, meaning each doubling of CO2 produces a roughly constant additional forcing. Valérie Masson-Delmotte, Laboratoire des Sciences du Climat et de l'Environnement and co-chair of the Intergovernmental Panel on Climate Change Working Group I, reports in the IPCC Sixth Assessment that this forcing, when combined with climate feedbacks such as water vapor, clouds, and surface albedo, results in an equilibrium climate sensitivity most likely between 2.5 and 4 degrees Celsius per CO2 doubling. Observational studies by Gavin Schmidt at the NASA Goddard Institute for Space Studies and others document that the current rise from preindustrial levels near 280 parts per million to over 400 parts per million observed at Mauna Loa by Pieter Tans of the National Oceanic and Atmospheric Administration is already producing measurable warming trends.
Evidence from past climates and modern records
Paleoclimate reconstructions by Michael Mann at Pennsylvania State University and colleagues show strong correlations between atmospheric CO2 and global temperature across glacial-interglacial cycles, reinforcing causality beyond coincidence. Instrumental records analyzed by James Hansen at Columbia University show that the spatial and seasonal patterns of warming match expectations from increased greenhouse forcing rather than alternative drivers such as solar variability or volcanic aerosol changes. Multiple independent lines of evidence — ice core gas records, tree-ring and sediment proxies, satellite radiative flux measurements, and direct atmospheric monitoring — converge on the conclusion that rising CO2 is a dominant driver of the observed global temperature increase.
Consequences and regional nuances
Global temperature rise driven by CO2 induces diverse consequences. Sea-level rise from thermal expansion and melting land ice threatens low-lying coastal territories and island nations, with disproportionate impacts on communities in the Global South and on indigenous peoples whose livelihoods and cultural sites are tied to specific landscapes. Changes in temperature and precipitation patterns alter agricultural suitability, exacerbate heat extremes in urban areas, and shift ecosystems, with cascading effects on food security and biodiversity. Policymaking must account for territorial vulnerabilities; for example, small island states advocate for stringent emissions reductions because even modest additional warming greatly increases their flood and erosion risks.
Limiting future warming requires stabilizing CO2 concentrations through rapid emissions reductions and carbon removal where necessary. Scientific assessments led by multidisciplinary teams across institutions such as the IPCC, NASA, NOAA, and major universities provide the basis for understanding the magnitude and pace of change, enabling societies to weigh mitigation and adaptation choices in light of regional and cultural priorities.