The National Grid has been forced to take on £18m in costs for its plans to avoid blackouts this winter. The Grid asked Ofgem to cover the £113m it spend on contracts with closed coal power plants at Drax and SSE’s Fiddler’s Ferry for “Black Start” services, meaning that they would be able to restart themselves independently in the case of a power outage. However, Ofgem said refused to cover 30% of the cost of the Drax contracts, saying that the National Grid should have foreseen that Drax might mothball some of its coal capacity. The Times also has the story.

California’s lawmakers have approved a bill to extent the state’s emissions reductions efforts. It would require a cut of 40% by 2030, based on 1990 levels. California’s current legislation only extends to 2020. The bill passed 42-29, with one more vote than required, and is expected to easily pass the Senate. However, Reuters reports that the state posted disappointing results from an auction of carbon permits that is key to the plan minutes after the bill was passed. Climate Centralalso covers the news.

Scientists have gained some important insights about how melting glaciers in Antarctica are affecting the oceans — and they couldn’t have done it without some “special helpers”, it says. The scientists fitted elephant seals with special scientific instruments to help them to figure out what’s going on below the surface of the ocean, to better understand how melting ice could disrupt ocean currents. The Mail Online and the Times also cover the story, as did Carbon Brief.

Climate change could be to blame for one of the world’s largest document ice avalanches, which is flummoxing researchers. Around 100 million cubic metres of ice and rocks gushed down a narrow valley in Tibet on 17 July, killing nine herders and hundreds of sheep and yaks. The avalanche was unusual because it started from a flat point, rather than in steep terrain. Researchers think that it would have been caused by lubrication of the ice from rain or glacial melt, with increasing precipitation in recent years to blame.

Investors managing more than $13 trillion of assets have urged leaders of the G20 group to ratify the UN Paris Agreement on climate change and to step up efforts to move away from fossil fuels. In a letter to the G20, 130 investors called on them to double global investment in clean energy, develop carbon pricing and phase out fossil fuel subsidies. The 20 biggest economies are meeting for a summit in China on 4-5 September. The Financial Times also covers the story.

In one of a series looking at President Obama’s science legacy as he prepares to leave office, Nature assesses what he achieved on climate change. His biggest push was around the UN climate deal, but he also undertook other piecemeal bits of action, including more funding for clean energy research. But Obama’s work could be undone by domestic legal action, it warns, and some environmentalists argue that he should have pushed harder for a comprehensive climate bill.

Ed Hawkins, a climate scientist at the University of Reading, looks at recent comments by Cambridge scientist Peter Wadhams, suggesting that this year will see a record low in Arctic sea ice and that it could disappear completely in the next few years. But Wadhams has not made his methodology public, and has made such claims before, which turned out never to materialise, says Hawkins. “Such dramatic sea ice forecasts make headlines,” he says. “They are shared widely around the world. But, our credibility as climate scientists depends on communicating forecasts based on our best physical understanding.”

The US can expect more natural disasters in an age of climate change, and the government needs to do more to prepare for them, says an editorial in the New York Times. It points to rules proposed by the Federal Emergency Management Agency on Monday that would see some people having to build at higher elevations, but argues that these do not go far enough.

A new study suggests sponges may not be ‘winners’ in response to ocean warning and acidification, as has been suggested in the past. The study of four abundant Great Barrier Reef species exposed to conditions predicted for 2100 under a high emissions scenario found a drop in the survival rates of all species, an increases in levels of tissue necrosis and bleaching. The interactive effects of warming and acidification varied across species and the latter alone had little adverse effect, say the authors.

Using a single using a single value for the commonly-used El Niño index isn’t enough to capture the full strength of an event, or to compare the magnitude of different events, according to new research. The paper argues for incorporating uncertainties associated with sea surface temperature observations. Doing so makes the strongest three events on record indistinguishable in terms of strength – the most recent 2015-16 El Niño ties with 1997-98 and 1982-83. The three strongest La Niña events occurred in 1955-56, 1973-74, and 1975-76.

A new study looking at how projected sea ice loss might increase opportunities for Arctic-transit shipping finds that routes across the central Arctic become more available by mid-century, with the navigable periods doubling in frequency. The models also show that European routes to Asia typically become 10 days faster by mid-century, and 13 days faster by late-century, while North American routes become 4 days faster.