Theresa May has used her speech at the United Nations assembly to send a veiled warning to Donald Trump, saying that his plan to exit the Paris Accord ranks alongside North Korea’s nuclear tests as a threat to global security. The prime minister did not name Trump directly but made clear that she believed global cooperation through the Paris Agreement was the only way to tackle climate change. “As the global system struggles to adapt, we are confronted by states deliberately flouting – for their own gain – the rules and standards that have secured our collective prosperity and security,” she said. The prime minister also said that climate change was “depleting and degrading the planet we leave to our children”, the Financial Times reports. May’s speech also indicated that Britain’s departure from the EU does not represent a retreat from its commitment to international co-operation. “I believe that the only way for us to respond to this vast array of challenges is to come together and defend the international order that we have worked so hard to create — and the values by which we stand,” she said. The Telegraph reports that May’s comments came moments before she met with the President at a summit on the margins of the UN assembly. The Independent, the Daily Mirror and the Wall Street Journalalso have this story.

Nicaragua has announced it will sign the Paris Accord, which leaves the US and Syria as the only two countries indicating that they will not participate in the agreement to tackle climate change. Newspaper El Nuevo Diario reported that, on September 18, Nicaragua’s President Daniel Ortega said: “We will soon adhere, we will sign the Paris Agreement. We have already had meetings addressing the issue and we have already programmed the accession.” The president had originally opposed signing the accord because he believed its goals did not require enough sacrifice from wealthy nations, Bloomberg reports. The move means that Syria, which is in the midst of civil war, as the only country not involved in the Paris agreement. But President Trump has called the agreement a “bad deal” for the US and outlined his intentions to withdraw from the accord within the next four years, suggesting that US may soon stand alone with Syria. The Hill reports that Trump is also the only world leader not to acknowledge the scientific consensus of climate change, according to a recent Sierra Club survey. Mashable also has the story.

Energy industry trade group Energy UK will “seriously question” Prof Dieter Helm’s government-commissioned review of the cost of energy if it attempts to rule out low-cost renewable power, reports Utility Week. The warning, saying bills will increase if the cheapest renewables [onshore wind and solar] are excluded, is part of a 15 September, 10-point letter from Energy UK chief executive Laurence Slade, published earlier this week. Carbon Brief took an in-depth look at the challenges facing Prof Helm’s cost of energy review when it was announced in August.

California cities San Francisco and Oakland have filed separate lawsuits against five oil companies seeking billions of dollars to protect against rising sea levels caused by climate change. The lawsuits, filed in state courts in San Francisco and Alameda Counties asked for funds to finance infrastructure from Chevron Corp, ConocoPhillips, Exxon Mobil Corp, BP Plc, and Royal Dutch Shell Plc. “These fossil fuel companies profited handsomely for decades while knowing they were putting the fate of our cities at risk,” San Francisco City Attorney Dennis Herrera said in a statement, the Hill reports. “Instead of owning up to it, they copied a page from the Big Tobacco playbook. They launched a multi-million dollar disinformation campaign to deny and discredit what was clear even to their own scientists: global warming is real, and their product is a huge part of the problem.” The lawsuits do not specify a compensation amount, but updating San Francisco’s seawall alone to prepare for sea level could cost up to $5bn, Buzzfeedreports. These so-called nuisance lawsuits are the latest in a string of climate lawsuits being filed across the world. “We’ve seen other suits like this and I think we’re going to see a lot more,” Sabrina McCormick of George Washington University’s Milken Institute School of Public Health told BuzzFeed News. Carbon Brief recently published a guest posting on using the science of extreme weather attribution in the courtroom.

Australia’s Bureau of Meteorology has been left “debilitated” by attacks from climate deniers, the former head of the bureau has said. Rob Vertessy, who retired as director of the BoM in April 2016, said the agency is now unable to fulfil its role of predicting climate risks because of attacks from deniers. In the Guardian’s Planet Oz blog, Vertessy said: ““From my perspective, people like this, running interference on the national weather agency, are unproductive and it’s actually dangerous. Every minute a BoM executive spends on this nonsense is a minute lost to managing risk and protecting the community. It is a real problem.” He claimed that the bureau is under constant attack from writers of the Australian, a Rupert Murdoch-owned broadsheet newspaper. “I think the Australian play on very dangerous ground here,” he said, adding that some staff at the newspaper could be guilty of “perpetuating nonsense”.

Earth could face a sixth mass extinction event by the end of the century because of climate change, new research suggests. A new study finds that the human-driven release of CO2 into the atmosphere could cause waves of species extinction by 2100 by disrupting the natural carbon cycle. Professor Daniel Rothman, co-director of the Massachusetts Institute of Technology’s Lorenz Centre, looked back through the geological records and found that found four out of the five previous mass extinctions on Earth took place when carbon cycle disruption crossed a “threshold of catastrophic change”. However, several factors are known to contribute to the risk of mass extinction event, such as mass volcanic eruptions, ocean anoxia and methane release. The Sun also has this story.

In the months following Donald Trump’s declaration that the US would withdraw from the Paris climate deal, 15 states have vowed to continue upholding the agreement and its aims. The alliance currently includes California, Colorado, Connecticut, Delaware, Hawaii, Massachusetts, Minnesota, New York, North Carolina, Oregon, Rhode Island, Vermont, Virginia and Washington; plus Puerto Rico. All but two states are led by Democratic governors. Brad Plumer explores what these states “can and can’t do” to tackle climate change. “In theory, state governments have plenty of ways to cut emissions without federal help. They can require electric utilities to use more renewable power, modify building codes and impose tougher efficiency standards on appliances,” he writes. ” The real test, analysts say, will come as states try to juggle ever-greater shares of intermittent renewable power and tackle other, harder-to-decarbonize sectors like transportation and industry.”

“We’ve known for decades that the Earth is warming, but a key question is, how fast?” asks Prof John Abraham in The Guardian. In his recent research, he attempted to answer this question by measuring the extra heat that is being trapped in the climate as a result of human activity. “The key to measuring the extra heat is by comparing the incoming and outgoing energy – just like you watch your bank account, keeping track of income and expenses to tell whether your bank balance will increase or not,” he says. The researchers chose to measure changes in heat in the the world’s oceans because they are less prone to annual fluctuations in temperature than the air. The results show that scientists need less than four years of ocean heat measurements to detect a clear climate change signal. “We believe, and argue, that ocean heat content is the key to quantifying how fast the climate is changing, and it has important implications for regional patterns of climate,” he concludes.

Driftwood deposition can be used to estimate ocean surface currents and ice sheet locations thousands of years in the past. A new estimate uses 913 driftwood samples from across the western Arctic to produce of a high-resolution reconstruction of Holocene Arctic Ocean surface current and sea ice dynamics. Sparse driftwood in the early Holocene, more than 8,000 years in the past, was followed by increased driftwood deposition in the warmer mid-Holocene (8,000 to 4,000 before present). Late Holocene cooling (less than 4,000 years before present) is also found. In recent millennia (< 2,000 years before present), a more variable driftwood record makes firm conclusions difficult.

A new study looks at a number of different approaches to attribution of the 2015 summer drought in Europe. They present contradicting conclusions on the relevance of human influence, depending on the chosen data source and methodology. They find an overall enhanced drought risk in Europe compared to preindustrial times when using all available models, other evaluations show contradictory evidence. This highlights the need for a multi-model and multi-method framework in event attribution research, especially for events with a low signal-to-noise ratio and high model dependency such as regional droughts.