Are Humans the Primary Cause of Recent Global Warming?

Are humans the primary cause of recent global warming?

Check out this answer from Consensus:

The scientific consensus is clear and robust: human activities, especially the burning of fossil fuels, are the primary cause of recent global warming. This conclusion is supported by extensive research and is reflected in the overwhelming agreement among climate scientists. While public perception may lag behind scientific understanding, efforts to communicate the human causes of global warming can help bridge this gap and foster greater support for necessary climate policies.

The question of whether humans are the primary cause of recent global warming has been extensively studied and debated within the scientific community. Numerous research papers have investigated the extent of human influence on climate change, providing a robust body of evidence on this topic.

Key Insights

• High Consensus Among Climate Scientists:
  • A significant majority of climate scientists (90-100%) agree that humans are causing recent global warming1 6 10.
  • The consensus is supported by multiple studies, including a survey of 11,944 abstracts and 2,412 authors, which found a 97% agreement on human-caused global warming1.
• Human Activities as Primary Drivers:
  • Human activities, particularly the burning of fossil fuels, have significantly increased greenhouse gases like carbon dioxide and methane, leading to global warming3 4 7.
  • Climate model simulations show that anthropogenic forcings have caused 0.9 to 1.3°C of warming in global mean near-surface air temperature from 1850-2019, with natural forcings contributing negligibly5.
• Impact on Climate and Environment:
  • Human-induced climate change is not only causing global warming but also influencing extreme weather events such as heavy rainfalls, droughts, and storms, which have substantial societal and environmental costs2.
  • The increase in atmospheric carbon dioxide and alterations in the nitrogen cycle due to human activities have profound effects on ecosystems and biodiversity4.
• Public Perception and Policy Support:
  • Despite the overwhelming scientific consensus, public understanding of human-caused global warming varies, with only about 60% of the US population recognizing human activities as the primary cause8.
  • Providing information about the human causes of global warming can increase public understanding, concern, and support for climate policies8.

Are humans the primary cause of recent global warming?

Michael Wehner has answered Near Certain

An expert from Lawrence Berkeley National Laboratory in Climatology

Volume 1 of the recent 4th US National Climate Assessment report concluded “It is extremely likely that more than half of the global mean temperature increase since 1951 was caused by human influence on climate (high confidence).” In fact, this is the most conservative statement that could be made about the human influence on the observed climate. The phrase “extremely likely” is taken from the calibrated language of the Intergovernmental Panel on Climate change and has special meaning. In this statement, it specifically refers to the result that the lower bound on a 5-95% statistical confidence interval of the human contribution to the observed increase in global mean surface air temperature is estimated to be greater than one half. The specifics of the confidence interval are based on climate model simulations. However, this statement is consistent with other techniques that don’t use models to estimate the human increase in the surface energy budget. Some of these techniques date to the 19th century.

The report goes on further to make a statement not just about the lower bound of the human influence on the climate system but to make a best estimate of this influence. Also from Key Finding #1 of chapter 3: “The likely range of the human contribution to the global mean temperature increase over the period 1951–2010 is 1.1° to 1.4°F…” Again, the word “likely” is taken from the IPCC calibrated language meaning that there is a two-thirds chance that the true influence lies in this range. The observed warming over this period is 1.2°F. Hence, the key finding goes on to state that there is “a likely human contribution of 93%–123% of the observed 1951–2010 change.” 

 Because the best estimate lies near the center of this range, it is appropriate to state that this report defends the statement “that human activities have caused all of the observed warming since 1951 in the context of this quantified uncertainty.”

These two statements in the report about the lower bound and best estimate of the human influence on climate are supported by a vast body of peer reviewed scientific literature spanning several decades. The lower bound is particularly constrained by our understanding of the climate system. However, the report does not make a statement about the less well constrained upper bound. This worst case scenario is important in a risk assessment context.

Are humans the primary cause of recent global warming?

Alexander Cheesman has answered Near Certain

An expert from James Cook University in Climatology, Biology, Plant Ecology

When considering human activities we need to consider not only the direct injection of CO2 into the atmosphere by the burning of fossil fuels, but also the alteration of natural systems through landcleairng, changing albedo, and alteration of nutrient cycling that impacts atmospheric processes. Together there has been a net impact of human activity in elevating the earths surface temperatures. Natural cycles and patterns (i.e. solar progression, volcanic activity) can, and do, impact the earths surface temperature however our understanding of these processes suggests that in the absence of human activity current global temperatures should be declining. The fact that global mean surface temperatures are continuing to increase means that it is actually despite these natural systems that humans are having an impact on recent global warming.

Are humans the primary cause of recent global warming?

Ben McNeil has answered Near Certain

An expert from UNSW Sydney in Oceanography, Climatology, Marine Science

Yes, it’s highly likely. Why? Natural causes like solar activity or volcanic eruptions since 1980 would point to a cooling of the climate.However the increase in greenhouse gas concentrations via human activity has lead to a strong warming that extends well beyond the scope of natural causes. The attached figure shows the real climate warming from one reliable global data-set, while the blue line shows the expected temperature if only caused by natural variations in the climate.

Are humans the primary cause of recent global warming?

Mark Jacobson has answered Near Certain

An expert from Stanford University in Energy Systems, Renewable Energy, Atmospheric Science, Climatology

Yes, humans are by far the major cause of global warming. Not only do the data at

https://web.stanford.edu/group/efmh/jacobson/Articles/I/TempModVsNASA.png

show the Earth has warmed by over 1.1 degree Celsius (Kelvin) during the past century, but model simulations of the physics of the impacts of human-emitted greenhouse gases and dark particles show, in the same link, by cause and effect, that such warming is caused by humans.

Further, whereas, Earth’s temperature has been higher than today in the past (e.g., 100 million years ago, the Earth was ice free, and soon after Earth’s formation 4.5 billion years ago, the Earth was molten), the rate of increase of temperature is greater today than any time since the most rapid period of deglaciation during the past ice age – Slide 45 of

https://web.stanford.edu/group/efmh/jacobson/POLbook2/APGWCh12Figs.pptx

suggesting natural variation cannot practically cause the warming over the past century.

Finally, the fact that the stratosphere is cooling while the troposphere is warming – Slide 48 of

https://web.stanford.edu/group/efmh/jacobson/POLbook2/APGWCh12Figs.pptx

is further evidence that the global warming seen today is due to the buildup of human-emitted greenhouse gases in the troposphere. Such greenhouse gases absorb a portion of the thermal-infrared radiation emitted by the Earth’s surface. The absorption in the troposphere prevents such radiation from getting to the stratosphere, where it would otherwise be absorbed by background ozone and carbon dioxide in the stratosphere, heating the stratosphere. Since that radiation does not reach the stratosphere, the stratosphere cools. The observed stratospheric cooling coupled with tropospheric warming can be explained only by the buildup of greenhouse gases in the troposphere. Sunspots cannot explain it because sunspots would warm the stratosphere since ozone in the stratosphere would absorb the additional solar radiation from a sunspot.

Are humans the primary cause of recent global warming?

Katsumi Matsumoto has answered Near Certain

An expert from University of Minnesota in Oceanography, Palaeoclimatology, Geochemistry

Yes, global warming has been detected and attributed to human activities with very high probability.

Are humans the primary cause of recent global warming?

Dennis Hartmann has answered Near Certain

An expert from University of Washington in Climatology

Science has established the human impact on warming with virtual certainty in about 2000, although the basic physics have been known for much longer than that. Every passing year makes the scientific evidence stronger, so that the human impact on warming is generally considered a scientific fact by the vast majority (> 97%) of credible scientists.