Are humans responsible for climate change?

Yes, the overwhelming scientific consensus is that human activities are the primary driver of the observed climate change since the mid-20th century.[1][2]Yes, humans are the primary (and dominant) cause of the rapid climate change observed since the mid-20th century (and more broadly since the Industrial Revolution). This is the overwhelming scientific consensus, described by the IPCC as “unequivocal.”[3]

Scientific Consensus

•The Intergovernmental Panel on Climate Change (IPCC) 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 of the observed warming (~1.1°C). Natural drivers (solar and volcanic) contributed roughly –0.1 to +0.1°C, and internal variability a similarly small amount.[1][4]

•Analyses of the peer-reviewed literature find greater than 99% consensus that recent climate change is mainly human-caused (e.g., >99.9% in a survey of ~88,000 papers from 2012–2020; earlier studies often cited ~97%).[2][5]

•Major scientific bodies—including NASA, NOAA, the U.S. National Academies, and numerous national academies and professional societies—endorse this conclusion.[6][7][8]

Climate has always varied naturally (e.g., due to orbital cycles, solar output, volcanoes, and internal variability like El Niño). However, the current rate and pattern of warming cannot be explained by natural factors alone.

Key Evidence

Multiple independent lines of evidence converge on human responsibility:

1.Greenhouse gas increases: Atmospheric CO₂ has risen from ~280 ppm pre-industrially to over 420 ppm today, with methane and nitrous oxide also sharply elevated. These rates are unprecedented in at least the last 800,000 years (from ice cores). The isotopic “fingerprint” (e.g., depleted ¹³C/¹²C ratios) matches fossil fuel combustion and land-use change, not natural sources like volcanoes or the ocean.[3][7]

2.Physics and the greenhouse effect: These gases trap outgoing infrared radiation. Basic radiative physics (established since the 19th century) predicts warming from higher concentrations. Human activities (primarily burning coal, oil, and gas; also deforestation and agriculture) are the source.

3.Climate models and attribution: Simulations that include only natural forcings (solar, volcanoes) produce little to no long-term warming and fail to match observations. Models that include human greenhouse gas emissions (plus aerosols) closely reproduce the observed global temperature rise, ocean heat content increase, tropospheric warming + stratospheric cooling pattern, and other changes.[3][9]

4.Observed patterns and rate:

•Global surface temperature has risen ~1.1–1.5°C since the late 1800s, with the last decade the warmest on record. The rate over recent decades exceeds anything in at least the past 2,000 years.[10]

•Warming is stronger at the surface and lower atmosphere; the stratosphere is cooling (consistent with greenhouse forcing, not solar).

•Oceans have absorbed most of the excess heat; sea levels are rising; ice sheets/glaciers are losing mass; extremes (heatwaves, etc.) are increasing—all attributable primarily to human influence.[4][11]

5.Paleoclimate context: Past warm periods existed, but the current combination of speed, magnitude, and CO₂ levels (higher than in at least 2 million years) is exceptional on human timescales.[12]

Nuances

•Humans are responsible for virtually all of the net warming since pre-industrial times. Aerosols from pollution have a partial cooling effect that offsets some greenhouse warming.

•Natural variability still causes year-to-year and decade-to-decade fluctuations (e.g., temporary pauses or accelerations), but the long-term trend is anthropogenic.

•“Climate change” here refers to the modern, human-driven global warming and associated shifts, not all historical climate variations.

In short, the evidence from observations, physics, chemistry, models, and paleoclimate records is robust, multi-decadal, and independently confirmed by agencies and researchers worldwide. Reducing greenhouse gas emissions is the primary lever to limit further warming.

Citations (12)

1icj-cij.orgGovernment
https://www.icj-cij.org/node/202879
Backs: “Yes, the overwhelming scientific consensus”
2iop.orgAcademic
https://iopscience.iop.org/article/10.1088/1748-9326/ac2966
Backs: “Yes, the overwhelming scientific consensus is that human activities are the primary driver of the observed climate”
3ipcc.chGovernment
https://www.ipcc.ch/report/ar6/wg1/downloads/faqs/IPCC_AR6_WGI_FAQ_Chapter_03.pdf
Backs: “mid-20th century (and more broadly since the Industrial Revolution). This is the overwhelming scientific consensus, described by the IPCC as “unequivocal.””
4carbonbrief.orgNews and mediaquality 0.85
https://www.carbonbrief.org/in-depth-qa-the-ipccs-sixth-assessment-report-on-climate-science
Backs: “Natural drivers (solar and volcanic) contributed roughly –0.1 to +0.1°C, and internal variability a similarly small amount.”
5cornell.eduAcademic
https://news.cornell.edu/stories/2021/10/more-999-studies-agree-humans-caused-climate-change
Backs: “Analyses of the peer-reviewed literature find greater than 99% consensus that recent climate change is mainly human-caused (e.g., >99.”
6nasa.govGovernment
https://science.nasa.gov/climate-change/scientific-consensus/?mod=article_inline
Backs: “Major scientific bodies—including NASA, NOAA, the U.S. National Academies, and numerous national academies and professional societies—endorse this conclusion.”
7climate.govGovernment
https://www.climate.gov/news-features/climate-qa/what-evidence-exists-earth-warming-and-humans-are-main-cause
Backs: “Major scientific bodies—including NASA, NOAA, the U.S. National Academies, and numerous national”
8nasa.govGovernment
https://science.nasa.gov/climate-change/causes/
Backs: “National Academies, and numerous national academies and professional societies—endorse this conclusion.[[6]](https://science.nasa.gov/climate-change/scientif”
9nasa.govGovernment
https://science.nasa.gov/resource/human-and-natural-drivers-of-climate-change-1850-2018/
Backs: “Models that include human greenhouse gas emissions (plus aerosols) closely reproduce the observed global temperature rise, ocean heat content increase, tropospheri”
10un.orgGovernment
https://www.un.org/en/climatechange/what-is-climate-change
Backs: “Global surface temperature has risen ~1.1–1.5°C since the late 1800s, with the last decade the warmest on record.”
11ipcc.chGovernment
https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-3
Backs: “Oceans have absorbed most of the excess heat; sea levels are rising; ice sheets/glaciers are losing mass; extremes (heatwaves, etc.) are increasing—all attributable primarily to human influence.”
12archive.phData and tools
https://archive.ph/2024.10.06-154745/https://science.nasa.gov/climate-change/evidence/
Backs: “Paleoclimate context: Past warm periods existed, but the current combination of speed, magnitude, and CO₂ levels (higher than in at least 2 million years) is exceptional on human timescales.”