Are humans responsible for climate change?

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

Yes - according to the major scientific assessments, human activity is the principal and dominant cause of observed climate change since the mid-20th century, though natural variability also plays a smaller role.

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

•While natural variability plays some part, the preponderance of evidence indicates that human activities—particularly emissions of heat-trapping greenhouse gases—are mostly responsible for making our planet warmer.

•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.

Scientific consensus and attribution:

•Nearly all actively publishing climate scientists (97–100%) say humans are causing climate change. The vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change.

•The report by the Intergovernmental Panel on Climate Change (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.

•The IPCC (2013), USGCRP (2017), and USGCRP (2018) indicate that it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-twentieth century.

•In its Sixth Assessment Report, the IPCC concluded that it is unequivocal that human influence has warmed the atmosphere, ocean and land, and 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.

Why scientists attribute warming to humans:

•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.

•Analysis of samples collected by NOAA's Global Greenhouse Gas Reference Network provides a measure of excess heat trapped, and "the conclusion that humans are nearly 100 percent responsible for their increase is inescapable".

•Current warming cannot be explained by natural solar changes: Since 1750, the average amount of energy from the Sun either remained constant or decreased slightly. The greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.

In summary, natural factors including solar variability and volcanic activity have influenced climate in the past, but they cannot explain the observed warming trend since the mid-20th century without including the rise in human-caused greenhouse gases.

Citations (3)

1nasa.govGovernment
Climate Change - NASA Science
Backs: “There is unequivocal evidence that Earth is warming at an unprecedented rate.”
2nasa.govGovernment
World of Change: Global Temperatures - NASA Science
Backs: “There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause. While natural variability plays some part, the preponderance of evidence indicates that human activities—particularly emissions of heat-trapping greenhouse gases—are mostly responsible for making our…”
3nasa.govGovernment
Causes - NASA Science
Backs: “While natural variability plays some part, the preponderance of evidence indicates that human activities—particularly emissions of heat-trapping greenhouse gases—are mostly responsible for making our planet warmer. Scientists attribute the global warming trend observed since the mid-20th century to the human expansion…”