Humans: The primary cause of global climate change

Do most scientists agree that human activity is causing global climate change? Yes, they do, according to an extensive analysis of the abstracts or summaries of scientific papers published over the past 20 years, even though public perception tends to be that climate scientists disagree over the fundamental cause of climate change.

To help put a stop to the squabbling, two dozen scientists and citizen-scientists from Australia, Canada, the United Kingdom and the US-including Sarah Green, professor and chair of chemistry at Michigan Technological University in Houghton, Mich.- analyzed the abstracts of nearly 12,000 peer-reviewed scientific papers on climate change published between 1991 and 2011. They also surveyed the authors of those papers, to find out how well the analysis agreed with the authors' own views on how their papers presented the cause of climate change.

They found that more than 97 percent of the scientists who expressed any opinion in their papers about the primary cause of global climate change believed that human activity was the cause. Approximately the same percentage of authors who responded to the survey said that their papers endorsed anthropogenic (human-caused) climate change. Nine of the scientists, including Green, reported their findings today in the journal Environmental Research Letters, published by the Institute of Physics.

Green says she got involved because she was curious about the apparent disconnect between the general public's lack of concern about climate change and what she calls "the clear scientific evidence that humans are changing the planet's atmosphere." That led her to SkepticalScience.com, a web site that tracks and addresses common myths about climate change. She has since contributed several articles.

John Cook, who maintains the web site, is a climate communications fellow for the Global Change Institute at the University of Queensland in Australia. He found that one dominant myth about climate change is the idea that scientists disagree about the cause. To investigate how much disagreement there really is in the peer-reviewed scientific literature, Cook set up an on-line system that enabled a group of SkepticalScience.com authors to rate nearly 12,000 abstracts from the Web of Science database (1991-2011) on whether they report human activities as the main contributors to climate change.

"John cleverly set up the rating process so it felt like a game to me," says Green. "After I rated five abstracts, another five would quickly appear, and counters showed how many each person had done, making it like a contest."

The abstract raters were a combination of professional and citizen-scientists from Australia, Canada, the UK, Finland, the US and Germany. The group was organized through the skeptical science web site.

"I read and rated 4,146 abstracts for this study, over about 4 months in winter/spring 2012," Green explains. "This is the first time I've published a paper where all the research was accomplished sitting on my couch."

Green adds, "I found it fascinating to see the array of implications of climate change identified in the abstracts-beyond the usual ones we hear about. They examined everything from production of tea in Sri Lanka, the stripes on salamanders, child undernutrition, frequency of lightning strikes, distribution of prickly pear cactus (and pine trees, kelp beds, wild boars, penguins, arctic fishes, canine leishmaniasis, and many, many others), mitochondrial electron transport activity in clams, copper uptake by minnows, lake effect snowfall, the rotational speed of the Earth and the prevalence of naked foxes in Iceland."

Green also found a large number of papers addressing mitigation of climate change through alternative energy and other ways to limit carbon emissions.

"It is critical to raise public awareness of the scientific consensus on climate change, so the public can make policy decisions based on factual evidence," she says. "Typically, the general public thinks that only around 50 percent of climate scientists agree that humans are causing global warming. This research has shown that the reality is 97 percent."