The US has regained top spot from China as the biggest investor in clean energy in 2011, according to global rankings.

The table, published in a report by the Pew Charitable Trusts, showed that US invested more than $48bn (£30bn) in the sector, up from $34bn in 2010.

China slipped to second place, the authors reported, with investment only increasing by $0.5bn to $45.5bn.

Globally, overall financial backing in clean energy technologies hit a record $263bn, up 6.5% from 2010 levels.

Energy demands in South Asia are growing at rate of over 6.0 per cent a year - a pace that is far in excess of the region's capacity to meet. The fact that a sizeable section of the population does not have access to electricity makes energy security a daunting challenge for the countries of this region.

 “PM2.5” seems an odd and wonky term for the blogosphere to take up, but that is precisely what has happened in China in recent weeks. It refers to the smallest solid particles in the atmosphere—those less than 2.5 microns across. Such dust can get deep into people’s lungs; far deeper than that rated as PM10. Yet until recently China’s authorities have revealed measurements only for PM10. When people realised this, an online revolt broke out. Such was the public pressure that authorities caved in, and PM2.5 data are now being published for Beijing and a handful of other cities.

India’s forest cover decreased by 367 square kilometers between 2007 and 2009, and it was primarily tribal and hilly regions that were to blame, according to the biennial forest survey released last week by the Ministry of Environment and Forest.