Are humans responsible for climate change?

Are humans responsible for climate change? I'll gather the latest scientific evidence on human-caused warming for you.

Yes, according to the overwhelming scientific evidence and consensus, humans are the dominant cause of the current climate change / global warming trend.

Scientific consensus

> There is scientific consensus that the Earth has been consistently warming since the start of the Industrial Revolution, that the rate of recent warming is largely unprecedented, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO2) caused by human activities.

•Nearly all actively publishing climate scientists say humans are causing climate change.

•Multiple studies published in peer-reviewed scientific journals show that climate-warming trends over the past century are extremely likely due to human activities.

•Scientific evidence continues to show that human activities (primarily the human burning of fossil fuels) have warmed Earth’s surface and its ocean basins, which in turn have continued to impact Earth’s climate.

Surveys and literature reviews consistently find high agreement:

•Widely cited surveys and institutional summaries cite ~97% agreement among actively publishing climate scientists that humans are causing warming whereas a 2021 literature survey reported greater than 99% agreement in the peer‑reviewed literature.

Leading scientific organizations worldwide have endorsed this position, stating:

> "Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver."

And:

> "Based on extensive scientific evidence, it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century."

What the IPCC and NASA conclude

The Intergovernmental Panel on Climate Change (IPCC) — the international body that assesses climate science — has strengthened its conclusion over time:

•Comparing observations with model runs that include and exclude human influence led the IPCC to state that it is unequivocal that human influence has warmed the atmosphere, ocean and land.

•In its recent summary report, the Intergovernmental Panel on Climate Change (IPCC) stated that, “It is unequivocal that human influence has warmed the atmosphere, ocean and land…

•“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.”

•The fifth Intergovernmental Panel on Climate Change (IPCC) report states with 95 percent confidence that humans are the main cause of the current global warming.

NASA similarly concludes:

> There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause.

> Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of the "greenhouse effect" — warming that results when the atmosphere traps heat radiating from Earth toward space.

Human emissions and activities have caused around 100% of the warming observed since 1950, according to the Intergovernmental Panel on Climate Change’s (IPCC) fifth assessment report.

Mechanism: How humans cause it

1.Greenhouse gas increase: Five key greenhouse gases are carbon dioxide, nitrous oxide, methane, chlorofluorocarbons, and water vapor.

2.Fossil fuels: Over the last century, burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2).

3.Scale of increase: The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750.

4.Attribution: In its Sixth Assessment Report, the Intergovernmental Panel on Climate Change concluded that it is unequivocal that the increase of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) 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.

5.“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."

Is it just natural variability or the Sun?

Climate has changed naturally in the past due to solar variation, volcanic activity, and internal cycles. However, current warming cannot be explained by those natural factors:

•While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun.

•Since 1750, the average amount of energy from the Sun either remained constant or decreased slightly.

•Climate models that include solar irradiance changes can’t reproduce the observed temperature trend over the past century or more without including a rise in greenhouse gases.

•Natural variability in the Earth’s climate is unlikely to play a major role in long-term warming.

•There is a strong consensus that natural variability cannot account for the observed global warming trend.

In short: Natural factors exist and affect climate on different timescales, but they do not explain the rapid warming observed since the mid-20th century. The human expansion of the greenhouse effect through emissions of CO2, methane, nitrous oxide and other gases is identified as the dominant and unequivocal driver.

Citations (2)

1nasa.govGovernment
Scientific Consensus - NASA Science
Backs: “There is scientific consensus that the Earth has been consistently warming since the start of the Industrial Revolution, that the rate of recent warming is largely unprecedented, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO2) caused by human activities. Nearly all…”
2nasa.govGovernment
Causes - NASA Science
Backs: “There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause. Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of the "greenhouse effect" — warming that results when the atmosphere traps heat radiating from…”