Are humans responsible for climate change?

Yes — the overwhelming scientific evidence and consensus show that humans are the primary driver of current climate change.

What the science says:

The Intergovernmental Panel on Climate Change (IPCC), the leading international body on climate science, stated in its most recent major assessment that "It is unequivocal that human influence has warmed the atmosphere, ocean and land." Its 2023 Synthesis Report went further, with the UN noting that the IPCC "categorically confirmed that human activity is the overwhelming cause of climate change."

The mechanism:

Human activities—burning fossil fuels and changes in land use—release greenhouse gases that trap heat in the atmosphere, with carbon dioxide responsible for most of global warming, although methane and other greenhouse gases also contribute. NASA echoes this, stating plainly that human activity is the principal cause of current warming, and that the current warming trend is clearly the result of human activities since the mid-1800s, proceeding at a rate not seen over many recent millennia.

How scientists know it's not natural causes:

Climate scientists have tested whether natural factors (like solar cycles or volcanic activity) could explain the observed warming. As the Union of Concerned Scientists explains, when climate scientists focus only on natural climate drivers, their models cannot accurately reproduce the observed warming of the past half century, but when the models also include human-induced climate drivers, they accurately capture recent temperature increases in the atmosphere and in the oceans. In fact, studies show that human activity is responsible for more than half of the warming observed since 1951. The UN similarly notes that natural changes in the sun's activity or large volcanic eruptions have caused ancient shifts in Earth's temperatures, but over the last 200 years, these natural causes have not significantly affected global temperatures.

The level of scientific agreement:

This isn't a fringe view—it represents near-universal consensus among climate experts. A comprehensive 2021 study found between 91% (all scientists) to 100% (climate scientists with high levels of expertise) agreed human activity is causing climate change, with 98.7% agreement among the broader group of climate scientists. NOAA summarizes it simply: "there is no real disagreement among climate experts that humans are the primary cause of recent global warming."

Bottom line: While natural factors have influenced Earth's climate throughout history, the current, rapid warming trend is driven overwhelmingly by human activities—primarily the burning of fossil fuels—according to virtually unanimous scientific consensus backed by physical evidence, climate modeling, and decades of research.