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.

Brazil says Amazon deforestation rose 28% in a year

Brazil says the rate of deforestation in the Amazon increased by 28% between August 2012 and last July, after years of decline. The government is working to reverse this "crime", Environment Minister Izabella Teixeira said. Activists have blamed the increase in destruction on a controversial reform to Brazil's forest protection law. Last year Brazil reported the lowest rate of deforestation in the Amazon since monitoring began. The provisional statistics from August 2012 to last July suggest that the area suffering deforestation was 5,843 sq km (2,255 sq miles), compared to 4,571 sq km (1,765 sq miles) in the previous 12 months. The 28% rise interrupts a period of declining deforestation which began in 2009. However, it still remains the second lowest annual figure for forest loss in absolute terms. The worst year on record was 2004, when 27,000 sq km of forest was destroyed. Monthly data from several scientific institutions had suggested the deforestation rate might be on the rise.

The WMO says that fossil fuel activities such as oil refining are driving atmospheric levels of CO2 to record highs. The levels of gases in the atmosphere that drive global warming increased to a record high in 2012. According to the World Meteorological Organization (WMO), atmospheric CO2 grew more rapidly last year than its average rise over the past decade. Concentrations of methane and nitrous oxide also broke previous records. Thanks to carbon dioxide and these other gases, the WMO says the warming effect on our climate has increased by almost a third since 1990. The WMO's annual greenhouse gas bulletin measures concentrations in the atmosphere, not emissions on the ground. Carbon dioxide is the most important of the gases that they track, but only about half of the CO2 that's emitted by human activities remains in the atmosphere, with the rest being absorbed by the plants, trees, the land and the oceans. Since the start of the industrial era in 1750, global average levels of CO2 in the atmosphere have increased by 141%. According to the WMO there were 393.1 parts per million (ppm) of carbon dioxide in the atmosphere in 2012, an increase of 2.2ppm over 2011. This was above the yearly average of 2.02ppm over the past decade. "The observations highlight yet again how heat-trapping gases from human activities have upset the natural balance of our atmosphere and are a major contribution to climate change," said WMO Secretary-General Michel Jarraud.

Carbon dioxide passes symbolic mark - Noaa atmospheric lab - The measurements are made at a station on the Mauna Loa volcano The level of carbon dioxide in the atmosphere has risen above 400 parts per million for the first time in human history, US researchers say. The "Keeling Lab" in Hawaii has the longest continuous measurement of the greenhouse gas, which is a key driver of climate change. Thursday's measurement, made atop the Mauna Loa volcano, registered 400.03. The last time CO2 was regularly above 400ppm was about 3-5 million years ago - before modern humans existed. The climate back then was also considerably warmer than it is today, according to scientists. The usual trend seen at the volcano is for the CO2 concentration to rise in winter months and then to fall back as the northern hemisphere growing season kicks in and pulls some of the gas out of the atmosphere. This means the number can be expected to decline by a few ppm in the coming weeks. But the long-term trend is upwards. When the late Charles Keeling began recording CO2 concentrations at the volcano in 1958, they were around 315 ppm (parts per million by volume - that is 315 molecules of CO2 for every one million molecules in the air). Every year since then, the curve has squiggled resolutely higher.