Are humans responsible for climate change?

Are humans driving recent climate change? I'll pull the latest scientific consensus to answer.

Yes, according to the overwhelming scientific evidence, modern climate change is primarily caused by human activities.

•The Intergovernmental Panel on Climate Change (IPCC) headline finding is that climate change is "unequivocally" caused by human activities.

•The IPCC firmly states that human actors are the primary driver of global warming, and that "it is unequivocal and indisputable that humans are warming the" climate.

The evidence for human responsibility includes:

1.Dominant cause since mid-20th century: 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.

2.Greenhouse gas increase is human-caused: 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.

The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750. This increase happens because burning fossil fuels like coal and oil combines carbon with oxygen to make CO2, with clearing land for agriculture and other human activities also increasing concentrations.

3.Quantification of human contribution: Humans emissions and activities have caused around 100% of the warming observed since 1950, according to the IPCC's fifth assessment report.

•In its 2013 fifth assessment report, the IPCC stated it is "extremely likely that more than half of the observed increase in global average surface temperature" from 1951 to 2010 was caused by human activity. By "extremely likely", it meant that there was between a 95% and 100% probability.

•A 2013 UN report summarized by NASA 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 — up from 90 percent certainty in the last assessment report in 2007.

•Detailed analysis finds about 104% of the total since the start of the "modern" period in 1950 comes from human activities (and 103% since 1850). A human contribution greater than 100% is possible because natural climate change associated with volcanoes and solar activity would most likely have resulted in a slight cooling over the past 50 years, offsetting some of the warming.

4.Natural factors cannot explain current warming: 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, but instead they have observed a cooling in the upper atmosphere and a warming at the surface.

5.Scientific consensus: Multiple independent analyses of the peer-reviewed literature and surveys of climate experts put agreement that humans are causing recent warming at roughly 97% or higher, with some large-scale literature reviews reporting consensus estimates above 99%.

In summary, while Earth's climate has varied naturally in the past, the rapid warming observed since the mid-20th century is dominated by human emissions of greenhouse gases, with natural factors (solar variability and volcanoes) playing a minor and, in recent decades, slightly cooling role.

Citations (3)

1nasa.govGovernment
Causes - NASA Science
Backs: “The IPCC firmly states that human actors are the primary driver of global warming, and that "it is unequivocal and indisputable that humans are warming the" climate. The evidence for human responsibility includes: Dominant cause since mid-20th century: Scientists attribute the global warming trend observed since the…”
2carbonbrief.orgNews and mediaquality 0.85
Analysis: Why scientists think 100% of global warming is due to humans - Carbon Brief
Backs: “This increase happens because burning fossil fuels like coal and oil combines carbon with oxygen to make CO2, with clearing land for agriculture and other human activities also increasing concentrations. Quantification of human contribution: Humans emissions and activities have caused around 100% of the warming…”
3nasa.govGovernment
New U.N. report: Humans responsible for climate change - NASA Science
Backs: “In its 2013 fifth assessment report, the IPCC stated it is "extremely likely that more than half of the observed increase in global average surface temperature" from 1951 to 2010 was caused by human activity. By "extremely likely", it meant that there was between a 95% and 100% probability. A 2013 UN report summarized…”