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Grok 4.5Oct 26, 2026x-ai/grok-4.5-20260708

Are humans responsible for climate change?

Yes, humans are the primary cause of recent (modern) climate change. This is the overwhelming scientific consensus, based on multiple independent lines of evidence from observations, physics, chemistry, and climate models.[1]

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.” Observed increases in well-mixed greenhouse gases (GHGs) since around 1750 are unequivocally caused by human activities. The likely range of total human-caused global surface temperature increase from 1850–1900 to 2010–2019 is 0.8°C to 1.3°C (best estimate 1.07°C). Well-mixed GHGs contributed 1.0–2.0°C of warming, other human drivers (mainly aerosols) contributed 0.0–0.8°C of cooling, natural drivers (solar + volcanic) changed temperature by only –0.1°C to +0.1°C, and internal variability by –0.2°C to +0.2°C.[2]

Key Evidence

•Greenhouse gas increases: Burning fossil fuels (coal, oil, gas), deforestation, agriculture, and industry have raised atmospheric CO₂ by nearly 50% since 1750 (from ~280 ppm to over 410–420 ppm), with methane and nitrous oxide also rising sharply. The isotopic “fingerprint” of the added carbon matches fossil fuels, not natural sources. Human emissions far exceed natural ones (e.g., volcanoes release <<1 billion tonnes of CO₂/year vs. >35 billion from fossil fuels and cement).[3]
•Basic physics: GHGs trap heat (the greenhouse effect). Increasing their concentrations must warm the planet unless offset by larger cooling factors—which have not occurred.
•Climate models and attribution: Simulations including only natural factors (solar variability, volcanoes, internal variability like El Niño) cannot reproduce the observed warming since the mid-20th century; they often show slight cooling or flat trends. Models that include human GHG emissions and other forcings match observations closely. Patterns (“fingerprints”) such as tropospheric warming combined with stratospheric cooling, greater Arctic warming, and ocean heat uptake align with GHG forcing, not solar or other natural drivers.[4]
•Rate and paleoclimate context: Current warming is occurring at a rate unprecedented in at least the last 2,000 years (and much faster than post-ice-age natural recoveries). CO₂ levels are higher than at any point in at least the last 800,000 years. Earth’s climate has always varied naturally (orbital cycles, solar changes, volcanoes, etc.), but these operate too slowly or are too small in magnitude to explain the rapid post-Industrial Revolution changes.[5]

Scientific Consensus

•Surveys and literature reviews show extremely high agreement: ~97% of climate scientists (and higher among the most actively publishing experts) agree that humans are the main cause. A 2021 analysis of >88,000 peer-reviewed climate papers found >99.9% consensus that climate change is mainly human-caused (updating earlier ~97% figures).[6]
•Major scientific organizations (NASA, NOAA, AAAS, Royal Society, National Academies of Sciences, and others worldwide) endorse this position. NASA states that human activities are driving the global warming trend observed since the mid-20th century.[7]

Natural factors continue to play a role in short-term variability (e.g., weather, El Niño/La Niña, volcanic eruptions), but they do not account for the long-term global warming trend. Continued human GHG emissions will drive further warming, with impacts already observed in extreme weather, sea-level rise, ice melt, ocean acidification, and more.

This conclusion rests on decades of accumulating evidence and has strengthened over successive IPCC assessments (from “discernible human influence” in 1995 to “unequivocal” today).

Citations (7)

  1. 1climate.govGovernment
    https://www.climate.gov/news-features/climate-qa/isnt-there-lot-disagreement-among-climate-scientists-about-global-warming

    Backs: “This is the overwhelming scientific consensus, based on multiple independent lines of evidence from observations, physics, chemistry, and climate models.”

  2. 2ipcc.chGovernment
    https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-3/

    Backs: “Well-mixed GHGs contributed 1.0–2.0°C of warming, other human drivers (mainly aerosols) contributed 0.0–0.8°C of cooling, natural drivers (solar + volcanic) changed temperature by only –0.1°C to +0.1°C, and internal variability by –0.2°C to +0.2°C.”

  3. 3nasa.govGovernment
    https://science.nasa.gov/climate-change/causes/

    Backs: “Human emissions far exceed natural ones (e.g., volcanoes release <<1 billion tonnes of CO₂/year vs. >35 billion from fossil fuels and cement).”

  4. 4royalsociety.orgAcademic
    https://royalsociety.org/news-resources/projects/climate-change-evidence-causes/

    Backs: “Patterns (“fingerprints”) such as tropospheric warming combined with stratospheric cooling, greater Arctic warming, and ocean heat uptake align with GHG forcing, not solar or other natural drivers.”

  5. 5nasa.govGovernment
    https://science.nasa.gov/climate-change/evidence/

    Backs: “Earth’s climate has always varied naturally (orbital cycles, solar changes, volcanoes, etc.), but these operate too slowly or are too small in magnitude to explain the rapid post-Industrial Revolution changes.”

  6. 6eurekalert.orgAcademic
    https://www.eurekalert.org/news-releases/931811

    Backs: “A 2021 analysis of >88,000 peer-reviewed climate papers found >99.9% consensus that climate change is mainly human-caused (updating earlier ~97% figures).”

  7. 7nasa.govGovernment
    https://science.nasa.gov/climate-change/scientific-consensus/?mod=article_inline

    Backs: “NASA states that human activities are driving the global warming trend observed since the mid-20th century.”