The exact causes behind the Permian-Triassic mass extinction have been much debated. Two separate pulses of CO2 into the atmosphere - a "one-two punch" - may have helped fuel the die-off, new research suggests. Changes to ocean acidity would have been one of the consequences, according to the study in Science journal. Computer models suggested that this CO2 may have been released by massive bouts of volcanism from the Siberian Traps, now represented as a large region of volcanic rock in northern Eurasia. The Permian-Triassic mass extinction, which took place 252 million years ago, wiped out more than 90% of marine species and more than two-thirds of the animals living on land. The event is thought to have played out over a 60,000-year period and acidification of the oceans lasted for about 10,000 years. The team led by Dr Matthew Clarkson from the University of Edinburgh analysed rocks unearthed in the United Arab Emirates - which were on the ocean floor at the time. The rocks preserve a detailed record of changing oceanic conditions at the time. They then developed a climate model to work out what drove the extinction. The researchers think the rapid rate of release of carbon was a crucial factor in driving the ocean acidification. The carbon was released at a similar rate to modern emissions. Dr Clarkson commented: "Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now.

The world is spending half a trillion dollars on fossil fuel subsidies every year, according to a new report. The Overseas Development Institute (ODI) says rich countries are spending seven times more supporting coal, oil and gas than they are on helping poorer nations fight climate change. Fuel subsidies to US farmers amounted to $1bn in 2011 says the ODI. Some countries including Egypt, Morocco and Pakistan, have subsidies bigger than the national fiscal deficit. The new report calls on the G20 to phase out the payments by 2020. While there is no globally agreed definition of what a fossil fuel subsidy actually is, the report draws on a range of sources from the International Monetary Fund to the International Energy Agency. It details the range of financial help given to oil, coal and gas producers and consumers from national governments and through international development. What emerges is a complicated web of different types of payments in different countries. In the United States, for example, the government in 2011 gave a $1bn fuel tax exemption to farmers, $1bn for the strategic petroleum reserve and $0.5bn for oil, coal and gas research and development. Germany gave financial assistance totalling 1.9bn euro to the hard coal sector in the same year. And the UK gave tax concessions worth £280m in 2011 for oil and gas production. Pakistan is a country with the second highest number of children out of school in the world. It has some of the worst nutrition, maternal mortality and child health indicators.

Current methods of measuring the full material cost of imported goods are highly inaccurate say researchers. In a new study, they found that three times as many raw materials are used to process and export traded goods than are used in their manufacture. Richer countries who believe they have succeeded in developing sustainably are mistaken say the authors. The research has been published in the Proceedings of the National Academy of Sciences. Many developed nations believe they are on a path to sustainable development, as their economic growth has risen over the past 20 years but the level of raw materials they are consuming has declined. But this new study indicates that these countries are not including the use of raw materials that never leave their country of origin. Heavy footprints The researchers used a new model that looked at metal ores, biomass, fossil fuels and construction materials to produce what they say is a more comprehensive picture of the "material footprint" of 186 countries over a 20 year period. In 2008, around 70bn tonnes of raw materials were extracted worldwide but just 10bn tonnes were physically traded. Over 40% were used to enable the processing and export of these materials. "By relying on current indicators, governments are not able to see the true extent of resource consumption," said Dr Tommy Wiedmann from the University of New South Wales.

Arctic Ocean 'acidifying rapidly' Photo1: Saunders Island and Wolstenholme Fjord with Kap Atholl in the background is shown in this picture taken during an Operation IceBridge survey flight in April 2013. Photo 2: arctic volcano. The Arctic seas are being made rapidly more acidic by carbon-dioxide emissions, according to a new report. Scientists from Norway's Center for International Climate and Environmental Research monitored widespread changes in ocean chemistry in the region. They say even if CO2 emissions stopped now, it would take tens of thousands of years for Arctic Ocean chemistry to revert to pre-industrial levels. Many creatures, including commercially valuable fish, could be affected. They forecast major changes in the marine ecosystem, but say there is huge uncertainty over what those changes will be. It is well know that CO2 warms the planet, but less well-known that it also makes the alkaline seas more acidic when its absorbed from the air.