Those who think man-made climate change is fiction, consider this -- the ozone layer over the Arctic has thinned by a record 40% this winter. The United Nation's World Meteorological Organization said that's 10% more thinning compared to the previous season.
"The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities," the U.N. weather agency's secretary-general Michel Jarraud said.
The ozone layer is crucial because of keeps ultraviolet radiation from the sun from reaching earth. The thinner the layer, the more rays that get through. Chemicals in air pollutants can eat away at the ozone. The U.N. said very cold weather also contributed to the record thinning.
"This is pretty sudden and unusual," said Bryan Johnson, an atmospheric chemist who works in the U.S. National Oceanic and Atmospheric Administration's Earth System Laboratory in Boulder, Colorado.
Johnson said even though this is limited to the Arctic right now, there's the concern that "if this were to happen every year — even though the ozone naturally regenerates itself — you might see a trending downward of the atmospheric ozone layer."
Warnings about the ozone layer were first raised in the early 1970s, leading to a 1987 treaty called the Montreal Protocol to cut back on chemicals known as CFCs used in air conditioning, aerosol sprays, foam packaging and other products.
But CFCs have long atmospheric lifetimes, so it will take decades for them to disappear. The ozone layer isn't expected to recover to pre-1980 levels until sometime between 2030 and 2040.
However, some scientists say if the treaty hadn't been adopted, two-thirds of the world's ozone layer would be gone about a half-century from now, and our climate would already be several degrees warmer.