How do greenhouse gases drive climate change?

Greenhouse gases drive climate change by altering Earth’s energy balance. Incoming solar radiation passes largely unimpeded through the atmosphere and warms the surface. That warmed surface emits infrared radiation. Greenhouse gases absorb a portion of this outgoing longwave radiation and re-emit it in all directions, including back toward the surface, raising the equilibrium temperature. Gavin Schmidt at the NASA Goddard Institute for Space Studies explains this radiative forcing mechanism as the primary physical process behind recent global warming.

How greenhouse gases trap heat
Molecules such as carbon dioxide, methane, nitrous oxide, and fluorinated gases have vibrational modes that interact with infrared wavelengths. This molecular absorption increases the atmosphere’s opacity to outgoing heat, so more energy is retained in the climate system. The Intergovernmental Panel on Climate Change co-chair Valérie Masson-Delmotte at the Laboratoire des Sciences du Climat et de l'Environnement summarizes the science in the IPCC assessment: net positive radiative forcing from increased greenhouse gas concentrations has warmed the atmosphere and oceans. Observational records and satellite measurements document the growing imbalance that drives temperature rise.

Sources and human influence
Human activities raise atmospheric greenhouse gas concentrations, chiefly by burning fossil fuels and altering land cover. Continuous atmospheric monitoring initiated by Charles David Keeling at the Scripps Institution of Oceanography shows carbon dioxide climbing from preindustrial levels near 280 parts per million to values above 400 parts per million in the modern era. Pieter Tans at the National Oceanic and Atmospheric Administration tracks these concentrations and attributes the steady upward trend to fossil fuel emissions and land-use changes. Methane from agriculture, wetlands, and fossil fuel extraction and nitrous oxide from fertilized soils contribute additional warming per unit mass, while industrial fluorinated gases, although less abundant, are potent long-lived contributors to radiative forcing.

Consequences for people, places, and ecosystems
The physical increase in greenhouse forcing produces measurable consequences: global average temperature rise, sea-level rise from thermal expansion and land ice loss, and changes in precipitation patterns and extreme weather frequency. Michael E. Mann at Pennsylvania State University and other climate scientists link many observed changes to anthropogenic greenhouse gas increases through detection and attribution studies. These changes have uneven geographic and cultural impacts. Low-lying island nations face existential threats from sea-level rise; Arctic indigenous communities confront permafrost thaw, coastal erosion, and altered subsistence resources; and agricultural regions experience shifting growing seasons and increased heat stress on crops and laborers.

Policy relevance and environmental nuance
Because greenhouse gases differ in atmospheric lifetime and radiative potency, mitigation strategies combine rapid reductions in methane alongside deep, sustained cuts in carbon dioxide emissions. The IPCC assessment and researchers at NASA and NOAA emphasize that cutting emissions now limits long-term warming and reduces risks to vulnerable territories and ecosystems. Effective responses must integrate scientific monitoring, emissions accounting, and attention to social justice, since communities that contributed least to historical emissions often face the greatest harms from a changed climate.