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Scientists have reached an overwhelming consensus on human-caused climate change

Despite outsized media and political attention to climate change deniers, climate scientists long ago reached a consensus that not only is climate change occurring, but it’s largely due to human actions. A new study in Environmental Research Letters further strengthens this consensus: looking at 4,000 peer-reviewed papers researchers found that 97 percent of them supported anthropogenic (i.e. human caused) global warming. Climate change denialists, many of them linked to fossil fuel industries, have tried for years—and often successfully—to undercut action on mitigating climate change through carefully crafted misinformation campaigns.

“Our findings prove that there is a strong scientific agreement about the cause of climate change, despite public perceptions to the contrary,” lead author John Cook with the University of Queensland said. “There is a gaping chasm between the actual consensus and the public perception. It’s staggering given the evidence for consensus that less than half of the general public think scientists agree that humans are causing global warming.”

Focusing on peer-reviewed papers covering climate science, the researchers tackled a massive sampling of research, wading through 11,994 papers by nearly 30,000 scientists over the last 20 years. Around one third (4,000) of these staked out a position on anthropogenic global warming. Of those that stated a position, 97.1 percent favored human caused climate change, while only 2 percent (87 papers) actually disputed human-caused climate change.

In addressing the fact that two thirds of papers expressed no opinion, the study’s authors write, “Of note is the large proportion of abstracts that state no position on anthropogenic global warming. This result is expected in consensus situations where scientists ‘. . . generally focus their discussions on questions that are still disputed or unanswered rather than on matters about which everyone agrees’ (Oreskes 2007, p 72).”

This is similar to the fact that most biology papers don’t stake out a stance on evolution, but take it as a given.

The climate study isn’t surprising, as past research has come away with similar findings: a study in 2010 questioned nearly 1,000 scientists and found that 97.5 percent agreed that climate change is being caused by human activities. Although the two studies used hugely different methodologies, it’s notable that their findings came away with almost exactly the same percentages that accept human-caused climate change.

Global climate change has risen temperatures by approximately 0.8 degrees Celsius (1.4 degrees Fahrenheit) since the beginning of the Industrial Revolution due to greenhouse gas emissions. Hotter temperatures have led to rising sea levels, melting glaciers, vanishing Arctic sea ice, wildlife migrations, and more extreme weather among other impacts. In fact, greenhouse gas emissions have also led to ocean acidification which is imperiling many marine species, including the world’s coral reefs. Recent research has also found that climate change may be shifting the jet stream, leading to extreme weather and unseasonable temperatures (both warm and cold) in the northern hemisphere.

Despite the science, nations have been slow to react and greenhouse gas emissions continue to rise year-after-year. Scientists say we will have to keep temperatures from rising above 2 degrees Celsius (3.6 degrees Fahrenheit) in order to stave off catastrophic global warming, but time is running out. This month, it was announced that carbon concentrations in the atmosphere have hit 400 parts per million (ppm), the first time this threshold has been crossed for several million years. In fact, human beings have never lived in a world where carbon concentrations were so high until now.

“When people understand that scientists agree on global warming, they’re more likely to support policies that take action on it,” Cook says.

High Park wildfire in Colorado in 2012. The evidence is increasing that climate changes is leading to more extreme weather events, such as droughts and floods. Droughts, and higher temperatures, have played a role in worsening wildfires in the U.S. and elsewhere. Last year, Colorado saw a number of massive and devastating wildfires. Photo by: U.S. Department of Agriculture.
High Park wildfire in Colorado in 2012. The evidence is increasing that climate changes is leading to more extreme weather events, such as droughts and floods. Droughts, and higher temperatures, have played a role in worsening wildfires in the U.S. and elsewhere. Last year, Colorado saw a number of massive and devastating wildfires. Photo by: U.S. Department of Agriculture.

CITATION: John Cook, Dana Nuccitelli, Sarah A Green, Mark Richardson, Bärbel Winkler, Rob Painting, Robert Way, Peter Jacobs, Andrew Skuce. Quantifying the consensus on anthropogenic global warming in the scientific literature. Environmental Research Letters, 2013; 8 (2): 024024 DOI: 10.1088/1748-9326/8/2/024024

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