Are humans responsible for climate change?

I'll gather the latest scientific evidence on humanity's role in climate change.

Yes, according to the overwhelming scientific consensus, humans are responsible for modern climate change.

What the science says

•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.

•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.

•The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over many recent millennia.

•According to the Intergovernmental Panel on Climate Change (IPCC), "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."

IPCC Assessment - "Unequivocal"

The IPCC Sixth Assessment Report (AR6, 2021-2023), synthesizing thousands of peer-reviewed studies from scientific experts from countries all over the world, concluded:

> It is unequivocal that human influence has warmed the global climate system since pre-industrial times

And more specifically:

> 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 authors conclude that it is "unequivocal" that humans have warmed the planet, causing "widespread and rapid" changes to Earth's oceans, ice and land surface

It also notes that global surface temperature was about 1.1°C higher in 2011-2020 than in 1850-1900 due to human activities.

How humans are causing it

•Greenhouse gas increase: The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750. This is due to burning fossil fuels like coal and oil, deforestation, agriculture, and industrial processes, combined with distinctive isotopic fingerprints in the atmosphere showing a human origin.

•Evidence excludes natural causes alone:

•Earth's climate has changed throughout history. Just in the last 800,000 years, there have been eight cycles of ice ages and warmer periods, with most attributed to very small variations in Earth's orbit.

•However, 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, and models that include solar irradiance changes can't reproduce the observed temperature trend without including a rise in greenhouse gases.

Scientific Consensus

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

•Nearly all actively publishing climate scientists say humans are causing climate change, with quantitative literature reviews finding 97% to >99% agreement depending on sampling and definitions.

•Every major U.S. and international scientific academy, the IPCC, NASA and leading research organizations state that humans—primarily burning oil, gas and coal—are the dominant cause of recent warming.

Statements include:

> "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. There is no alterative explanation supported by convincing evidence." - American Geophysical Union

> "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." - Statement from 18 Scientific Associations (2009)

In summary: While climate has varied naturally in the past due to orbital changes, volcanic activity and solar variability, the rapid warming observed since the mid-20th century is dominated by human-caused emissions of greenhouse gases. Natural factors alone cannot explain it.

Citations (1)

1nasa.govGovernment
Causes - NASA Science
Backs: “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. Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of…”