Tiempo Climate Newswatch

Urban plants make a significant contribution to limiting climate change as they remove carbon from the atmosphere, according to a survey of the amount of vegetation in the British city of Leicester. In the United Kingdom, land classified as urban is assumed to have a zero biological carbon density. The new study shows this assumption is incorrect. "There is a substantial pool of carbon locked away in the vegetation within a city," Zoe Davies from the University of Kent reported.

"Large trees are particularly important carbon stores," Davies said. "Most of the publicly owned land across Leicester is grassland. If just 10 per cent of this was planted with trees, the existing carbon pool across the city could be increased by 12 per cent." The British government aims to cut carbon emissions by at least 80 per cent below 1990 levels by the year 2050. "Although it is not a panacea for emissions reduction, our results demonstrate the potential benefits of accounting for, mapping and appropriately managing above-ground vegetation carbon stores, even within a typical densely urbanized European city," Davies commented. The survey is part of a larger assessment of the urban carbon footprint.

Over the year 2010, renewable energy supplied an estimated 16 per cent of global final energy consumption and nearly 20 per cent of global electricity generation, reports the Renewable Energy Policy Network for the 21st Century (REN21). Global solar power generation doubled in 2010 over 2009 due to incentive programmes and the falling price of photovoltaic panels.

The REN21 report concludes that renewable energy policies continue to be the main driver behind renewable energy growth. By early 2011, at least 119 countries had some type of policy target or support policy, with more than half of these countries in the developing world. Of all the policies used by governments to support renewable power generation, feed-in tariffs remain the most common. "The global performance of renewable energy despite headwinds has been a positive constant in turbulent times," said Mohamed el-Ashry, who chairs the REN21 steering committee.

The Earth's soils and oceans are becoming less effective in buffering global warming as the climate system alters, report scientists from Europe and the United States. On land, the increasing amount of carbon in the air is accelerating the release of methane and nitrous oxide from the soil as microscopic organisms thrive, offsetting gains due to the removal of carbon dioxide from the atmosphere. "This feedback to our changing atmosphere means that nature is not as efficient in slowing global warming as we previously thought," said Kees Jan van Groenigen of Trinity College Dublin, who reviewed 49 studies of the process.

In a second study, thirty years' data for the North Atlantic Ocean suggest that rising air and water temperatures are slowing oceanic absorption of carbon over the tropics. Warmer water cannot hold as much carbon dioxide as colder water. The researchers found that the ocean uptake was highly dependent on the area and period analysed. "Because the ocean is so variable, we need at least 25 years' worth of data to really see the effect of carbon accumulation in the atmosphere," said University of Wisconsin-Madison assistant professor Galen McKinley. "This is a big issue in many branches of climate science – what is natural variability, and what is climate change?"