Principal evidence for global warming

1. Global surface temperature records show a clear upward trend

Multiple global temperature datasets agree that recent decades are the warmest on record, with the 2014–2023 decade averaging about 1.19 °C above pre‑industrial levels and single‑year human‑attributed warming reaching ~1.31 °C in 2023 relative to 1850–1900, and 2024–2025 among the top warmest years ever recorded—evidence that surface warming is persistent and accelerating ^{[1] [4] [5]}.

2. The oceans have absorbed most of the excess heat, recording unprecedented warming

About 90% of the excess heat trapped by the climate system is stored in the oceans, and ocean heat content reached record highs in recent years, with large fractions of global ocean area ranking among its warmest historical conditions—this ocean warming is a fundamental indicator of a warming planet and explains why short‑term surface variations can be misleading ^{[3] [6]}.

3. Greenhouse gases and radiative forcing show the causal mechanism

Measured concentrations of greenhouse gases—chiefly carbon dioxide—have continued to rise, increasing the effective radiative forcing that traps more energy in the Earth system; monitoring reports compile GHG concentrations and use them to update radiative forcing estimates that explain why temperatures and the energy imbalance are increasing ^{[2] [1] [7]}.

4. Earth's energy imbalance, ice loss, and sea level rise provide independent confirmation

Satellites and in situ measurements document a persistent Earth energy imbalance (more incoming than outgoing energy), contemporaneous ice‑sheet and glacier mass loss, record low Arctic sea ice extents, and rising global mean sea level—these independent indicators are physically consistent with a warming world and less sensitive to short‑term weather noise than surface temperature alone ^{[2] [3] [4] [8]}.

5. Attribution: why scientists link warming to human activity

Attribution studies synthesize observed warming, greenhouse‑gas emissions, radiative forcing estimates, and models to conclude that essentially all of the recent global average warming is human‑induced; the Indicators reports quantify warming attributed to human activities and estimate shrinking remaining carbon budgets consistent with the IPCC framework ^{[1] [7]}.

6. Natural variability and recent year‑to‑year fluctuations—context, not contradiction

Natural climate drivers—El Niño/La Niña cycles, volcanic aerosols, shipping fuel rules, and solar variability—can amplify or dampen warming in the short term and help explain jumps or temporary cooling, but authoritative agencies note that transient events do not reverse the long‑term warming trend documented across multiple indicators ^{[2] [1] [9]}.

7. Uncertainties, dataset differences, and where caution is warranted

Different temperature and climate datasets use varying methods and thus produce slightly different annual rankings and uncertainty margins, and precise estimates (e.g., exact global mean temperature in °C) carry nontrivial uncertainty—but these methodological differences do not undermine the overarching, multi‑metric conclusion that the climate is warming and that greenhouse gases are the dominant driver ^{[3] [1]}.

Conclusion: convergent evidence builds the case

The principal evidence for global warming is not a single record or headline year but the convergence of multiple, independently measured indicators—surface and ocean warming, energy imbalance, greenhouse‑gas forcing, melting ice and rising seas—and robust attribution analyses tying most of the change to human emissions; short‑term variability can complicate the narrative but cannot explain away the long‑term, system‑wide signals compiled in the authoritative Indicators and WMO assessments ^{[2] [1] [3]}.