Are humans responsible for climate change?

Yes, humans are the primary cause of recent climate change (global warming since the Industrial Revolution, especially since the mid-20th century). This is the overwhelming scientific consensus, backed by multiple independent lines of evidence from observations, physics, paleoclimate records, and climate models.[1]

Scientific Consensus

•The Intergovernmental Panel on Climate Change (IPCC), in its Sixth Assessment Report (AR6, 2021), states it is unequivocal that human influence has warmed the atmosphere, ocean, and land. The best estimate of human-caused global surface temperature increase from 1850–1900 to 2010–2019 is 1.07°C (likely range 0.8–1.3°C), which accounts for essentially all the observed warming. Natural drivers (solar and volcanic) contributed roughly –0.1°C to +0.1°C, and internal variability ±0.2°C.[1]

•Surveys of the peer-reviewed literature show greater than 99% consensus that humans are the main cause of contemporary climate change. A 2021 analysis of over 88,000 climate-related papers found only a tiny fraction skeptical, updating earlier ~97% figures.[2]

•Major scientific organizations (NASA, NOAA, Royal Society, AAAS, national academies, and others) endorse this position. NASA notes that multiple studies show warming trends over the past century are extremely likely due to human activities.[3]

Key Evidence

•Greenhouse gas increases: Atmospheric CO₂, methane, and nitrous oxide have risen sharply since ~1750 due to human activities (primarily burning fossil fuels, plus land-use changes like deforestation and agriculture). CO₂ is now ~50% higher than pre-industrial levels—higher than at any time in at least the last 800,000 years (from ice cores). The isotopic “fingerprint” of the extra CO₂ matches fossil fuels, not natural sources.[4]

•Physics of the greenhouse effect: These gases trap heat. Basic radiative physics, known since the 19th century, predicts warming from increased GHGs.

•Fingerprinting and patterns: Observations show warming of the lower atmosphere (troposphere) and cooling of the upper atmosphere (stratosphere)—a signature of greenhouse gases, not increased solar output (which would warm all layers). Ocean heat content has risen, ice sheets and glaciers are losing mass, sea levels are rising, and extreme weather patterns are shifting in ways consistent with human forcing.[5]

•Climate models: Simulations that include only natural factors (solar variability, volcanoes) cannot reproduce the observed warming since the mid-20th century. Models including human GHG emissions and aerosols match the observations closely. Human aerosols have a partial cooling effect that has offset some GHG warming.[6]

•Rate and context: The recent rate of warming is unusually rapid compared to natural changes over the past 2,000+ years (and longer). Earth’s climate has always varied naturally (orbital cycles, etc.), but those do not explain the current rapid changes.[7]

Natural factors continue to play roles in year-to-year or regional variability (e.g., El Niño, volcanic eruptions), but they are not the drivers of the long-term global warming trend. Human activities—especially CO₂ from fossil fuels—are the dominant cause.

This conclusion has strengthened over successive IPCC assessments as data and methods improved. For primary sources, see the IPCC AR6 Summary for Policymakers, NASA’s climate pages, and consensus studies in journals like Environmental Research Letters.

Citations (7)

1ipcc.chGovernment
https://www.ipcc.ch/report/ar6/wg1/chapter/summary-for-policymakers/
Backs: “This is the overwhelming scientific consensus, backed by multiple independent lines of evidence from observations, physics, paleoclimate records, and climate models.”
2iop.orgAcademic
https://iopscience.iop.org/article/10.1088/1748-9326/ac2966
Backs: “A 2021 analysis of over 88,000 climate-related papers found only a tiny fraction skeptical, updating earlier ~97% figures.”
3nasa.govGovernment
https://science.nasa.gov/climate-change/scientific-consensus/
Backs: “NASA notes that multiple studies show warming trends over the past century are extremely likely due to human activities.”
4nasa.govGovernment
https://science.nasa.gov/climate-change/causes/
Backs: “The isotopic “fingerprint” of the extra CO₂ matches fossil fuels, not natural sources.”
5royalsociety.orgAcademic
https://royalsociety.org/news-resources/projects/climate-change-evidence-causes/
Backs: “Ocean heat content has risen, ice sheets and glaciers are losing mass, sea levels are rising, and extreme weather patterns are shifting in ways consistent with human forcing.”
6metlink.orgNot yet classified
https://www.metlink.org/resource/ipcc-2021-the-evidence-for-climate-change/
Backs: “Human aerosols have a partial cooling effect that has offset some GHG warming.”
7archive.isData and tools
https://archive.is/2025.11.13-121149/https://science.nasa.gov/climate-change/evidence/
Backs: “Earth’s climate has always varied naturally (orbital cycles, etc.), but those do not explain the current rapid changes.”