Predicting where, how and how quickly Greenland's ice will melt is difficult. Projections by the best models are cloudy, and new research suggests clouds are doing the clouding.

Currently, models of Greenland's melting ice sheet put the greatest emphasis on the impacts of greenhouse gas emissions. But new research, published this week in the journal Nature Climate Change, suggests the microphysics of clouds are equally important.

Under high emission scenarios, the uncertainties of Greenland ice sheet models are caused almost entirely by the uncertainties of cloud dynamics.

Cloud cover dictates the ice sheet's longwave radiation exposure. When clouds over Greenland are thicker, they operate like an insulating blanket, encouraging longwave radiation and surface-level melting.

Thinner clouds are associated with reduced melt rates, researchers determined.

The uncertainty caused by clouds translates to a difference of nearly five inches of global sea level rise by the end of the century.

The accelerated melting of Greenland's ice sheet could threaten many coastal communities across the globe. To better project this threat, authors of the new paper suggest scientists work to figure out how climate change will impact cloud dynamics in the Arctic.

"Observations of cloud properties in the Arctic are expensive and can be challenging," lead author Stefan Hofer, PhD student at the University of Bristol, said in a news release. "There are only a handful of long-term observations of cloud properties in the Arctic which makes it very challenging to constrain cloud properties in our climate models."

"The logical next step would be to increase the amount of long-term observations of cloud properties in the Arctic, which then can be used to improve our climate models and predictions of future sea level rise," Hofer said.

Dutchman swims epic ice-skating course threatened by climate change
The Hague (AFP) June 24, 2019 –

A Dutchman on Monday completed a marathon swim along the route of the country's most famed ice skating race — which has not been held for two decades as climate change bites.

Instead of skating the daunting "Elfstedentocht" (Eleven cities race), Olympic gold marathon swimmer Maarten van der Weijden ploughed his way through all 195 kilometres (121 miles) of its murky canals.

Van der Weijden embarked on the epic journey across northern Friesland province on Friday afternoon and finally finished it on Monday evening, as the Netherlands basked in a heatwave.

"It took a long time but it was also very special and very beautiful," the 38-year-old was quoted as saying by broadcaster NOS.

Van der Weijden is a cancer survivor who overcame leukaemia to win a gold medal in the 2008 Summer Olympics in Beijing in the 10-kilometre open water race.

His feat of endurance raised 3.9 million euros for cancer research.

It is Van der Weijden's second bid to complete the route after failing last year.

This time he said he had slept and eaten more, and worn a warmer wetsuit, Dutch news agency ANP reported.

"I love swimming, helping others and setting goals for myself," he told the Christian-based broadcaster EO in a recent interview.

– Sorry, no medal –

The swimmer followed the same route as the Elfstedentocht, one of the Netherlands' most beloved traditions which is now enduring a record-equalling drought.

The previous edition was in 1997, the last time the ice was thick enough to support both skaters and the hundreds of thousands of spectators that the event normally attracts.

With meteorologists predicting ever-warmer weather due to global warming, it is uncertain when another Elfstedentocht will be held again on ice.

In the meantime, Van der Weijden's alternative marathon along the course has captured the country's imagination, with supporters cheering him on along his route.

Dutch Prime Minister Mark Rutte hailed the swimmer's "incredible performance", saying on Twitter: "The whole of the Netherlands is swimming with you!".

Completing the skating race is seen as a major achievement and so important that soldiers are allowed to wear its medal, called the "Elfstedenkruisje" (Eleven cities cross), on their military uniforms.

Participants qualify for the medal after collecting stamps on a card from all the 11 cities around Friesland with the start and end in the city of Leeuwarden.

Unfortunately for Van der Weijden, the famously rule-abiding Dutch say he will not receive an Elfstedenkruisje at the end of his epic swim.

"Perhaps he deserves a cross, but he won't get one," Immie Jonkman, chairwoman of the Eleven cities marathon, told Frisian regional radio.

"Our cross is only for people who have skated the marathon. Although we applaud him, we cannot make an exception."