The audience was told to expect "biting satire" and "menacing bohemian wit" from Friday's performance by members of the Berliner Philharmoniker of cabaret songs from the Weimar era. But the crowd at the Queen Elizabeth Hall in London looked nonplussed when a choir of climate activists climbed to the stage in the foyer during the interval to launch Shell Out Sounds, a new campaign against the oil giant's sponsorship.

Global warming may have caused extreme events such as a 2011 drought in the United States and a 2003 heatwave in Europe by slowing vast, wave-like weather flows in the northern hemisphere, scientists said on Tuesday.

The study of meandering air systems that encircle the planet adds to understanding of extremes that have killed thousands of people and driven up food prices in the past decade.

2012 was among the 10 warmest years on record, rising above the long-term average for the 36th year in a row, according to data released on Tuesday.

Temperature records compiled separately by Nasa and the National Oceanic and Atmospheric Administration (NOAA) found global surface temperatures rose 1.03F above the long-term average last year, but did not match America's record-breaking heat. The average global temperature has risen about 1.4F since 1880.

Australia has started 2013 with a record-breaking heat wave that has lasted more than two weeks across many parts of the country. Temperatures have regularly gone above 48°C, with the highest recorded maximum of 49.6°C at Moomba in South Australia. The extreme conditions have been associated with a delayed onset of the Australian monsoon, and slow moving weather systems over the continent.

Australia has always experienced heat waves, and they are a normal part of most summers. However, the current event affecting much of inland Australia has definitely not been typical.