Are humans responsible for climate change?

Are humans driving climate change? I'll gather the latest scientific evidence to answer.

Yes - according to the overwhelming scientific evidence, modern climate change is primarily caused by human activities, although natural factors also influence climate.

What the science says

•There is unequivocal evidence that Earth is warming at an unprecedented rate and human activity is the principal cause.

•The Intergovernmental Panel on Climate Change (IPCC), the UN body that synthesizes climate science from hundreds of scientists worldwide, has steadily strengthened this conclusion:

•In its foreword it stated it is now 95 percent certain that humans are the main cause of current global warming.

•Its report said there is 95 percent certainty that humans have caused most of the warming of the planet's surface that has occurred since the 1950s.

•Its Sixth Assessment Report in 2021 issued its most definitive statement: "It is unequivocal that human influence has warmed the atmosphere, ocean, and land.". Other summaries phrase it as “It is unequivocal that human influence has warmed the atmosphere, ocean and land.” and also as it is unequivocal that human influence has warmed the atmosphere, ocean and land.

•NASA and NOAA summarize the same conclusion in plain language:

•"Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming"

•The preponderance of evidence indicates that human activities—particularly emissions of heat-trapping greenhouse gases—are mostly responsible for making our planet warmer

•Changes observed in Earth's climate since the mid-20th century are driven by human activities, particularly fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere, raising Earth's average surface temperature

How humans cause it

Human activities since the industrial revolution, especially burning coal, oil and gas and clearing land for agriculture, have increased greenhouse gas concentrations.

Burning fossil fuels such as coal, oil, and gas has increased the concentration of atmospheric carbon dioxide (CO2) from 280 parts per million to 416 parts per million. These greenhouse gases absorb and then re-radiate heat in Earth's atmosphere, which causes increased surface warming.

NASA estimates that since the pre-industrial period, human activities are estimated to have increased Earth's global average temperature by about 1 degree Celsius (1.8 degrees Fahrenheit), and that the current warming trend is unequivocally the result of human activity since the 1950s and is proceeding at an unprecedented rate over millennia.

A 2021 NASA study confirmed with direct observations that radiative forcings are increasing due to human actions, affecting the planet's energy balance and ultimately causing climate change.

Why natural causes alone don't explain it

Natural processes - such as internal variability like El Niño, volcanic activity, changes in the Sun's energy output and variations in Earth's orbit - can also contribute to climate change, but they have been overwhelmed by human activities.

Specifically:

•Natural processes driving Earth's long-term climate variability do not explain the rapid climate change observed in recent decades. The only explanation that is consistent with all available evidence is that human impacts are playing an increasing role in climate change.

•The combined influence of volcanoes and changes in solar activity would have resulted in cooling rather than warming over the past 50 years.

•Natural factors alone would have likely resulted in a slight cooling effect, not the significant warming we've seen.

Attribution studies compare observed climate data with climate models that include or exclude human emissions. Models that include human emissions reproduce the warming, but models with only natural factors do not.

Scientific consensus

The agreement among scientists is extremely high:

•The vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change.

•Large reviews of the peer-reviewed literature from 1991-2011 found 97.1% endorsed the consensus position that humans are contributing to global warming among papers expressing a position.

Leading science organizations around the world, including international and U.S. science academies and the IPCC, have issued public statements expressing this consensus.

In short, climate has always varied naturally, but the rapid warming since the mid-20th century cannot be explained without human-caused greenhouse gas emissions.

Citations (1)

1nasa.govGovernment
Climate Change - NASA Science
Backs: “Yes - according to the overwhelming scientific evidence, modern climate change is primarily caused by human activities, although natural factors also influence climate. What the science says. There is unequivocal evidence that Earth is warming at an unprecedented rate and human activity is the principal cause.”