Are humans responsible for climate change?

I'll gather the current science on human-caused climate change to give you a full, evidence-based answer.

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

1. What the scientific bodies say

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

Key assessments:

•The Intergovernmental Panel on Climate Change (IPCC) Synthesis Report of its Sixth Assessment cycle confirms that human activities, mainly through emissions of greenhouse gases, have unequivocally caused global warming. These include unsustainable energy use, land use and land-use change, as well as consumption and production patterns.

•The IPCC says there is 95 percent certainty that humans have caused most of the warming of the planet's surface that has occurred since the 1950s. More recent language describes it as extremely likely (95-100% probability) that most of the warming since 1950 has been due to human influence.

•In its Sixth Assessment Report, the IPCC 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 synthesis is described as: the scientific consensus is that the Earth's climate system is unequivocally warming, and that it is extremely likely (meaning 95% probability or higher) that this warming is predominantly caused by humans.

2. How strong is the consensus?

Multiple independent efforts to quantify expert agreement show overwhelming consensus that recent warming is anthropogenic: surveys and literature reviews find agreement in the high‑90s percentiles.

Today 97% to 99.9% of climate scientists agree that climate change is happening and that human activity is the primary cause. Scientific consensus identifying humans as primarily responsible for climate change was already forming in the 1980s and is not new.

3. How are humans causing it?

•The greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.

•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.

•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. This increase is due to human activities, because scientists can see a distinctive isotopic fingerprint in the atmosphere.

•To a lesser extent, clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases.

Five key greenhouse gases are carbon dioxide, nitrous oxide, methane, chlorofluorocarbons, and water vapor, with CO2, methane, nitrous oxide and chlorofluorocarbons being directly increased by human activity.

> Human Activity Is the Cause of Increased Greenhouse Gas Concentrations

4. Why not natural causes like the Sun?

Climate has changed naturally in the past due to solar variation, volcanic activity and orbital cycles. Scientists explicitly test for this:

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

•While the Sun has played a role in past climate changes, the evidence shows... Wait - specific evidence:

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

•If a more active Sun caused the warming, scientists would expect warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere and a warming at the surface.

•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.

In other words, natural factors alone would not produce the warming observed; when human greenhouse gas emissions are included, models match observations.

Bottom line

•Climate change itself is natural and has happened throughout Earth's history, but the rapid warming observed since the mid-20th century — about 1.1-1.2°C since the late 19th century — and the increase in heat extremes, heavy precipitation, droughts and other impacts, is dominated by human activity, primarily burning fossil fuels and deforestation.

The IPCC describes human-induced greenhouse gas forcing as the main driver behind observed changes in hot and cold extremes on the global scale, with some recent hot events being extremely unlikely without human influence.

If you want, I can explain how much warming is attributed to humans vs. natural factors, or what the evidence looks like for your region.

Citations (3)

1nasa.govGovernment
Global warming consensus – Climate Change: Vital Signs of the Planet
Backs: “What the scientific bodies say. There is unequivocal evidence that Earth is warming at an unprecedented rate.”
2fao.orgGovernment
News | FAO in North America | Food and Agriculture Organization of the United Nations
Backs: “There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause. Key assessments: The Intergovernmental Panel on Climate Change (IPCC) Synthesis Report of its Sixth Assessment cycle confirms that human activities, mainly through emissions of greenhouse gases, have…”
3nasa.govGovernment
Causes - NASA Science
Backs: “More recent language describes it as extremely likely (95-100% probability) that most of the warming since 1950 has been due to human influence. In its Sixth Assessment Report, the IPCC concluded that it is unequivocal that the increase of CO2, methane, and nitrous oxide in the atmosphere over the industrial era is…”