Are humans responsible for climate change?

Are humans driving climate change? I'll gather the latest scientific evidence on our responsibility.

Yes — according to the overwhelming weight of scientific evidence, modern climate change is primarily caused by human activity.

What the major scientific bodies say

> "It is unequivocal that human influence has warmed the atmosphere, ocean and land."

That is the conclusion of the Intergovernmental Panel on Climate Change (IPCC) in its Sixth Assessment Report (2021-2023), which was described as the most comprehensive climate assessment ever produced and stated with "unequivocal" certainty that human activities are the primary cause of global warming.

In its Sixth Assessment Report, the IPCC also 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.

Earlier assessments already stated the same conclusion with high confidence:

•"the IPCC is now 95 percent certain that humans are the main cause of current global warming"

•"human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history"

•"there is a 95 per cent probability that most of the warming since 1950 has been caused by human influence."

The IPCC's Fifth Assessment Report estimated that:

> Humans emissions and activities have caused around 100% of the warming observed since 1950

NASA summarizes the same finding:

> 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.

And:

> 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.

How humans are causing it

1.Burning fossil fuels and deforestation: Human activities contributing to climate change primarily include burning fossil fuels (e.g., coal, oil, and natural gas) and deforestation. Burning fossil fuels releases large amounts of carbon dioxide (CO2) and other greenhouse gases into the atmosphere, which trap heat and cause global warming.

2.Dominant share of emissions: Multiple authoritative sources converge: fossil fuel combustion for energy, transport and industry accounts for the dominant share of greenhouse‑gas emissions and is identified as the main contributor to modern global warming, producing nearly 90% of anthropogenic CO2 and roughly three‑quarters of total human‑caused greenhouse emissions.

3.Greenhouse effect amplification: The greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.

4.Measurable rise in CO2: 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.

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

How much warming is human-caused?

•The IPCC AR6 presents a strong body of scientific evidence 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.

•The combined effects of human activity have already increased the global average temperature by about 1.1 degrees Celsius above the late 19th-century average. The contribution to global warming of natural factors, such as the sun and volcanoes, is estimated to be close to zero.

Why natural causes alone don't explain current warming

Scientists acknowledge past climate changes had natural causes, but:

> While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun.

Evidence includes:

•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 and lower parts of the 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

NASA's synthesis also notes that paleoclimate records, modern instrumental records, and satellite data show a coherent warming signal consistent with increased CO2 and other greenhouse gases, and that human activities, especially the burning of fossil fuels, may be the main cause of global warming.

Scientific consensus

> Yes, the vast majority of actively publishing climate scientists – 97 percent – agree that humans are causing global warming and climate change.

Different methods have been used to estimate consensus — including surveys of experts and reviews of the peer-reviewed literature — and both methods converge on the conclusion: 97% or more of climate scientists are convinced that human-caused climate change is happening.

Comprehensive reviews cited by NASA, IPCC and national academies state that human activities, especially emissions of CO2 and other greenhouse gases, are the primary cause of the global warming trend observed over recent decades.

In short, while the climate has changed naturally in the distant past, the rapid warming since the mid-20th century — and the unprecedented rise in greenhouse gases — is unequivocally attributed by the IPCC, NASA, and the vast majority of publishing climate scientists to human activities, principally the burning of fossil fuels, deforestation, agriculture and industrial processes.

Citations (3)

1nasa.govGovernment
Causes - NASA Science
Backs: “That is the conclusion of the Intergovernmental Panel on Climate Change (IPCC) in its Sixth Assessment Report (2021-2023), which was described as the most comprehensive climate assessment ever produced and stated with "unequivocal" certainty that human activities are the primary cause of global warming. In its Sixth…”
2nasa.govGovernment
Climate Change - 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. And: There is unequivocal evidence that Earth is warming at an unprecedented rate.”
3phys.orgNews and mediaquality 0.85
Climate scientists reach 'unequivocal' consensus on human-made warming in landmark report
Backs: “The combined effects of human activity have already increased the global average temperature by about 1.1 degrees Celsius above the late 19th-century average. The contribution to global warming of natural factors, such as the sun and volcanoes, is estimated to be close to zero.”