Ozone-eating chemicals (remember fluorocarbons?) are warming the Arctic.

Nature reports on an old environmental menace. Climate simulations, they say, show that the mass emission of chlorofluorocarbons (CFCs) beginning in the 1950s could be responsible for up to half of the effects of climate change observed in the Arctic from 1955 to 2005:

The Arctic is warming at more than twice the average rate of the rest of the globe — a phenomenon known as Arctic amplification — and it is losing sea ice at a staggering pace.

Ozone-depleting substances, including chlorofluorocarbons (CFCs), are known to warm the atmosphere thousands of times more efficiently than carbon dioxide. But most of the research on these chemicals has focused on their effects on the planet’s protective ozone layer — especially over the Southern Hemisphere, where they are responsible for the formation of the Antarctic ozone hole, says Mark England, a climate scientist at Scripps Institution of Oceanography in La Jolla, California.

England and his colleagues compared climate simulations both with and without the mass emission of CFCs that began in the 1950s. Without CFCs, the simulations showed an average Arctic warming of 0.82 °C. When the presence of ozone-depleting compounds was factored in, that number jumped to 1.59 °C. The researchers saw similarly dramatic changes in sea-ice coverage between the two sets of model simulations. By running the models with fixed CFC concentrations while varying the thickness of the ozone layer, the team was able to attribute the warming directly to the chemicals — rather than changes these substances caused in the ozone layer.

Global CFC concentrations have been on the decline since the turn of the millennium, following the 1989 adoption of the Montreal Protocol, which called for a phase-out of the substances. Although many other factors contribute to Arctic amplification, the result suggests that Arctic warming and sea-ice melt might be tempered in the future….