Are humans responsible for climate change?

Your question on human responsibility for climate change deserves the clearest evidence — I'll gather the latest assessments from the major scientific bodies.

Yes, according to the overwhelming scientific evidence assessed by major scientific bodies - humans are responsible for the modern climate change, particularly the warming observed since the mid-20th century.

1. Scientific consensus is that recent warming is human-caused

> Scientific evidence continues to show that human activities (primarily the human burning of fossil fuels) have warmed Earth's surface and its ocean basins

> Scientists know that recent climate change is largely caused by human activities from an understanding of basic physics, comparing observations with models, and fingerprinting the detailed patterns of climate change caused by different human and natural influences

> In its Sixth Assessment Report, the Intergovernmental Panel on Climate Change, composed of scientific experts from countries all over the world, concluded that it is unequivocal that the increase of CO2, methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere and biosphere

The IPCC also states:

> "It is unequivocal that the increase of CO2, methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere, and biosphere."

> "Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact."

NASA notes that:

> Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of the "greenhouse effect"

And:

> Yes, the vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change

2. How scientists know

a) Greenhouse gas increase is human-caused:

> Over the last century, burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2)
> The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750

> Direct measurements of CO2 in the atmosphere and in air trapped in ice show that atmospheric CO2 increased by 50% from 1800 to 2025. Measurements of different forms of carbon (isotopes, see Question 3) reveal that this increase is due to human activities

b) Natural causes alone cannot explain observed warming:

> But several lines of evidence show that current global warming cannot be explained by changes in energy from the Sun
> Since 1750, the average amount of energy from the Sun either remained constant or decreased slightly

> Calculations using climate models have been used to simulate what would have happened to global temperatures if only natural factors were influencing the climate system. These simulations yield little surface warming, or even a slight cooling, over the 20th century and into the 21st. Only when models include human influences on the composition of the atmosphere are the resulting temperature changes consistent with observed changes

3. Degree of certainty

The IPCC's Fifth Assessment Report expressed this as it is "extremely likely," with 95-100% certainty, that human activity has been the dominant cause of observed warming since the mid-20th century, and its Fifth and Sixth Assessment Reports concluded humans have caused around 100% of the warming observed since 1950 and that warming is unequivocally human-driven.

Natural factors - solar variability, volcanic eruptions, orbital changes, and internal variability like El Niño - have driven climate changes in the distant past, but they do not explain the rapid, globally coherent warming of the last ~150 years. The observed patterns of surface warming, upper-atmosphere cooling, ocean heat content increase, and sea level rise match the fingerprint expected from human greenhouse gas emissions, not from natural drivers alone