Are humans driving climate change? I'll gather the latest scientific consensus and evidence.
Yes, according to overwhelming scientific evidence and consensus, humans are the principal cause of the climate change observed in recent decades.
Scientific consensus
•The vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change.
•Based on well-established evidence, about 97% of climate scientists have concluded that human-caused climate change is happening.
•Multiple independent analyses show overwhelming consensus that recent warming is anthropogenic, with agreement in the high-90s percentiles to greater than 99%.
•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.
Endorsed by major scientific organizations:
> "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", a statement on climate change from 18 scientific associations reads, according to NASA.
Evidence from NASA and the IPCC
NASA states:
> There is unequivocal evidence that Earth is warming at an unprecedented rate. Human activity is the principal cause.
•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 greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.
•Scientific evidence continues to show that human activities (primarily the human burning of fossil fuels) have warmed Earth's surface.
Greenhouse gas increase:
•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, because scientists can see a distinctive isotopic fingerprint in the atmosphere confirming the source as human activity.
> In its Sixth Assessment Report, the Intergovernmental Panel on Climate Change ... 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.
IPCC assessments have increased certainty over time:
•Fifth Assessment Report (AR5) ... concluded that it is 95% certain that human activities, primarily the emission of greenhouse gases, are the dominant cause of global warming since the mid-20th century.
•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 AR6 concludes that it is unequivocal that humans have caused the earth's climate to warm, with a likely human contribution of 0.8 to 1.3 degrees Celsius to global mean temperature since the late 1800s.
Why natural causes do not explain current warming
Climate has changed naturally in the past due to solar cycles, volcanic activity and orbital changes, but:
•While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun.
•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, consistent with greenhouse gases trapping heat in the lower atmosphere.
•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 summary, natural variability exists, but multiple lines of evidence indicate that human influences have had an increasingly dominant effect on global climate warming observed since the mid-twentieth century.