Fact check: Scientific consensus says humans are dominant cause of climate change

Rick Rouan, USA TODAY
·5 min read

The claim: Human-caused climate change is a hoax

President Joe Biden pledged during a virtual climate summit, held on Earth Day, to cut U.S. greenhouse gas pollution to help mitigate a global climate crisis.

The goal is to have 2030 emissions be half the level of 2005.

“The science is undeniable,” Biden said during the April 22 summit. “The cost of inaction keeps mounting.”

But some still deny.

Climate skeptics don’t believe climate change is caused by humans, despite overwhelming scientific evidence to support the conclusion. Some don’t acknowledge global warming is happening at all.

One Facebook user posted on April 19 claiming, among other things, that "man-made climate change (is a) scam."

"Don't you dare question it though or you will be branded a 'Climate change denier' and you shall be canceled for it," the user wrote.

The Facebook account that posted the claim did not respond to a request for comment.

Earth Day: Biden promises 50% reduction in US greenhouse emissions

What is global warming?

While natural forces can contribute to global temperature changes, scientific data show warming has accelerated since the mid-20th century.

The “hockey stick” graph introduced in 1998 in the journal Nature shows relatively flat temperature fluctuations over hundreds of years before a sharp incline, particularly over the past 50 years.

The graph has been controversial among climate skeptics but was endorsed in 2006 by the National Academy of Sciences.

Most scientists say the sharp incline is related to human-made emissions in the post-industrial period. That is a result of the “greenhouse effect,” where the planet warms as gases that block heat from escaping build up in the atmosphere.

Carbon dioxide concentration in the atmosphere from human activities has increased by 47% since the start of the Industrial Revolution, according to NASA. Build-ups of water vapor, methane, nitrous oxide and chlorofluorocarbons also are contributing to the greenhouse effect.

As the planet has warmed, weather patterns have changed; melting glaciers and ice sheets have raised sea levels; and heat waves have become longer and more intense.

“On Earth, human activities are changing the natural greenhouse,” says a NASA website on the causes of climate change.

President Joe Biden shut down oil and gas lease sales from the nation's vast public lands and waters in his first days in office, citing worries about climate change. Now his administration has to figure out what do with the multi-billion dollar program without crushing a significant sector of the U.S. economy.
President Joe Biden shut down oil and gas lease sales from the nation's vast public lands and waters in his first days in office, citing worries about climate change. Now his administration has to figure out what do with the multi-billion dollar program without crushing a significant sector of the U.S. economy.

Scientific consensus

While climate deniers suggest the causes of climate change are uncertain, scientists have concluded with a high degree of certainty that the dominant cause of warming is human-produced greenhouse gases produced by humans becoming trapped in the atmosphere.

A synthesis of The Climate Science Special Report: Fourth National Climate Assessment says it is “extremely likely” – meaning at least 95% – that unprecedented concentrations of carbon dioxide, methane and nitrous oxide in the atmosphere driven by economic and population growth since the pre-industrial era are the dominant cause of warming.

In short, humans are causing climate change.

The Intergovernmental Panel on Climate Change, established by the United Nations in 1988, assembled the report. But other government research and scientific organizations have reached the same conclusion.

The National Oceanic and Atmospheric Administration, NASA, the National Science Foundation, the National Research Council and the Environmental Protection Agency all agree “Earth is warming mainly due to the increase in human-produced heat-trapping gases,” according to a post on NOAA’s Climate.gov website.

NOAA also points to a 2004 study in the journal Science, backed up in a 2016 review paper, that examined 928 peer-reviewed papers in scientific journals. None of the papers disagreed with the consensus.

The Backstory: How and why the USA TODAY Network fact checks issues, people and statements in the news

A 2018 Congressional Research Service report summarizing the “evolving assessments” of the causes of climate change since the early 19th century said this: “Current climate scientific assessment states high confidence (extremely likely) that human influence is the dominant cause of the observed warming over the past half-century.”

The report said the conclusion is relatively recent, in part because of better science. That includes better measurement technologies, the development of better simulation models and longer series of observations.

“We have independent evidence that says when you put in greenhouse gases, you get the changes that we see,” Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, said in a Columbia Climate School State of the Planet blog from 2017. “If you don’t put in greenhouse gases, you don’t. And if you put in all the other things people think about — the changes in the earth’s orbit, the ocean circulation changes, El Niño, land use changes, air pollution, smog, ozone depletion — all of those things, none of them actually produce the changes that we see in multiple data sets across multiple areas of the system, all of which have been independently replicated.”

President Biden signed executive actions tied to combating climate change, including elevating climate change as a national security concern.
President Biden signed executive actions tied to combating climate change, including elevating climate change as a national security concern.

Our rating: False

The claim that human-caused climate change is a hoax is FALSE, based on our research. The scientific consensus is that climate change is a product of human-produced gases that trap heat on Earth. Both government organizations and papers in scientific journals have concluded with a high degree of certainty that climate change is human-made.

Our fact-check sources:

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper replica here.

Our fact check work is supported in part by a grant from Facebook.

This article originally appeared on USA TODAY: Fact check: Scientific consensus humans main cause of climate change