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In Brief

Understanding Certainty: Smoking Kills and Global Warming Is Real

antarctica iceberg in the light
Mountainous terrain buried beneath Drake Passage, the waterway separating South America and Antarctica, may be responsible for much of the ocean mixing in the region. (Image credit: Alan Homer and British Antarctic Survey)

Here's some vital perspective on the certainty of climate change: Scientists are as sure of global warming as they are that smoking cigarettes kills, the Associated Press reports.

Scientists are 95 percent certain that climate change is underway and humans are to blame, the Intergovernmental Panel on Climate Change (IPCC ), is expected to announce Friday (Sept. 27) in its latest report on the science of climate change. Because even 5 percent uncertainty can be quibbled with by skeptics, to help put that 95 percent number in context, the AP asked scientists for help.

Here are some examples: Gravity is one of the few things more certain than climate change. Drop a rock and it will fall down. But scientists are reluctant to say they're 100 percent certain the sun will rise tomorrow. And 95 percent is equivalent to the current certainty that the universe is 13.8 billion years old and that smoking cigarettes is linked to cancer.

Read more: FAQ: IPCC Upcoming Climate Change Report Explained

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Becky Oskin
Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.