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The CEO of energy giant Royal Dutch Shell has said that the carbon dioxide released by burning fossil fuels must be captured and stored in the ground if the world is going to avoid potentially catastrophic levels of global warming.

"We cannot burn all the hydrocarbon resources we have on the planet in an unmitigated way and not expect to have a CO2 loading in the atmosphere that is often being linked to the 2C scenario," Ben van Beurden, Shell's chief executive, told the Guardian.

International diplomats have agreed to limit global temperature rise to 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels.

Van Buerden said that he was "absolutely convinced" that without finding a way "on a large scale" to capture the carbon produced by burning fossil fuels, "we are not going to be able to stay within that CO2 emission budget."

Global temperatures have already risen by 0.8 C (1.4 F) above pre-industrial levels, according to the UN Intergovernmental Panel on Climate Change, the leading international body on the topic. The agency predicts that between 2016 and 2035 global temperatures will "likely" rise by 0.3-0.7 C (0.5-1.3 F) compared to average temperatures between 1986 and 2005. By the end of the century, global temperature rise could reach a sweltering 4.8 C (8.5 F), the agency projects.

As for Shell's controversial energy exploration in the Arctic Ocean, van Beurden said that it's something he and others had reflected on. "I had to go through a personal journey on that," he told the Guardian.

Meanwhile, in the port of Bellingham, Washington, a young woman named Chiara D'Angelo went through a personal journey of her own after strapping herself to the anchor chain of the Arctic Challenger, a ship leased by Shell.

Her action was the latest in an ongoing round of protests in the Pacific Northwest aimed at halting Shell's Arctic drilling plans.

D'Angelo, who had been on the chain since Friday evening, came down this morning at about 9:30 Pacific Time after showing signs of hypothermia, Petty Officer 1st Class George Degener of the US Coast Guard told VICE News. She was brought to the Coast Guard Station in Bellingham, evaluated by medics, and issued a summons by the Bellingham Police.

Before she came off the chain, Degener said that the Coast Guard was "transporting food and water and just checking on her well-being, to make sure that if anything, she does need to get off the chain, we're there to help her."

D'Angelo had been joined for a short time by another activist, Matt Fuller. According to the Coast Guard, Fuller asked to come down around 4:30 am Sunday, Pacific Time. After being brought to the same Coast Guard station, he was greeted by the police.

"They spoke with him, but he was not arrested, and he was released in good condition," Degener told VICE News.

Shell did not return a request for comment on van Beurden's remarks to The Guardian nor on the ship being occupied in Washington.