Human-caused climate change
The IPCC Sixth Assessment Report (2021-2023) concludes it is unequivocal that human influence has warmed the atmosphere, ocean, and land. More than 97% of actively publishing climate scientists and over 99% of peer-reviewed climate papers endorse anthropogenic climate change.
What we know
Multiple independent lines of evidence support the conclusion that human activities, primarily the burning of fossil fuels and land-use change, are the dominant cause of observed global warming since the mid-20th century. These include direct measurements of atmospheric CO2, isotopic fingerprinting linking the carbon increase to fossil fuel combustion, satellite measurements of declining outgoing long-wave radiation consistent with increased greenhouse gas concentrations, and attribution studies comparing observed warming with natural-only climate models.
The IPCC Sixth Assessment Report (AR6), published 2021-2023, states: 'Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming.' The AR6 Working Group I report finds it is 'extremely likely' that human influence caused more than half of the observed increase in global mean surface temperature from 1951 to 2010, and 'virtually certain' that human-induced greenhouse gas forcing is the main driver of observed increases in heat extremes.
Multiple surveys of the scientific literature and of climate scientists consistently find that 97-100% of climate experts agree that recent global warming is primarily caused by humans. A 2021 study examining 88,125 climate-related papers found that more than 99.9% of peer-reviewed scientific literature agrees with anthropogenic causation.
Claims that current warming is natural, that the sun is responsible, or that CO2 is too minor a gas to matter have been examined and found inconsistent with observational data. Solar output has not increased over the period of strongest warming (since ~1980), and models that include only natural forcings cannot reproduce the observed pattern of warming.
Common claims
- Current climate change is driven by natural cycles, not humansNot supported, natural forcings cannot explain observed warming pattern
- Scientists disagree significantly about whether humans cause warmingFalse, 97-100% of actively publishing climate scientists agree
- The sun is responsible for recent warmingNot supported, solar output has not increased during the period of strongest warming
- CO2 is such a tiny fraction of the atmosphere it can't matterNot supported, CO2's infrared absorption properties are well-established physics