Atmospheric carbon dioxide levels pass 400ppm
Tue 21 May 2013
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Carbon dioxide levels in the Earth's atmosphere have exceeded 400 parts per million (ppm) for the first time according to measurements taken by a US government agency laboratory on Mauna Loa, Hawaii. Meanwhile, separate reports published in the last month predict a dramatic decline in biodiversity if CO2 emissions are not restrained and a higher than previously predicted sea level rise.
According to a report from the BBC, the last time CO2 was regularly above 400ppm was three to five million years ago - before modern humans existed. Scientists say the climate back then was also considerably warmer than it is today.
The usual trend seen at the Mauna Loa station, where measurements are regularly taken, is for the CO2 concentration to rise in winter months and then to fall back as the northern hemisphere growing season kicks in. Forests and other vegetation pull some of the gas out of the atmosphere. This means the number can be expected to decline by a few ppm below 400 in the coming weeks. But the long-term trend is upwards.
Dr James Butler, who is responsible for the Earth System Research Laboratory on Mauna Loa which belongs to the National Oceanic and Atmospheric Administration (Noaa) told BBC News: "Mauna Loa and the South Pole observatory are iconic sites as they have been taking CO2 measurements in real time since 1958. Last year, for the first time, all Arctic sites reached 400ppm.
"This is the first time the daily average has passed 400ppm at Mauna Loa."
Meanwhile, new research suggests that biodiversity around the globe will be significantly affected if temperatures rise more than 2C.
An international team of researchers has looked at the impacts of rising temperatures on nearly 50,000 common species of plants and animals of a projected global temperature in 2100 of four degrees Celsius above pre-industrial levels. In this model, some 34% of animal species and 57% of plants would lose more than half of their current habitat ranges.
According to Dr Rachel Warren from the University of East Anglia, this would have major impacts for everyone on the planet.
"Our research predicts that climate change will greatly reduce the diversity of even very common species found in most parts of the world. This loss of global-scale biodiversity would significantly impoverish the biosphere and the ecosystem services it provides," she said (quoted in The Independent).
"There will also be a knock-on effect for humans because these species are important for things like water and air purification, flood control, nutrient cycling, and eco-tourism."
The report - published as a paper in the journal, Nature Climate Change - projects that impacts on species will be felt more heavily in some parts of the world such as sub-Saharan Africa, Central America, the Amazon region and Australia.
However the researchers say that if global emissions of greenhouse gases are cut rapidly then the impact on biodiversity could be significantly curbed. If global emissions reach their peak in 2016 and temperature rises are held to 2C, then losses could be cut by 60%.
In a separate development, researchers have published their most advanced calculation for the likely impact of melting ice on global sea levels. The EU-funded team says the ice sheets and glaciers could add 36.8cm to the oceans by 2100.
Adding in other factors they say that sea levels could rise by up to 69cm, higher than previous predictions.
The report, called Ice2sea, was produced by EU-funded experts from 24 institutions in Europe and beyond. It makes what the scientists' term the "best estimate" yet of the impact of melting based on a mid-range level of carbon emissions that would increase global temperatures by 3.5C by the end of this century.
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