The UK and Germany lead a list of the EU’s most polluting coal-fired power stations compiled by environmental campaigners, who say coal emissions are undermining efforts to combat climate change. Both countries have nine of the so-called “dirty 30” and the campaigners say coal burning is increasing due to the relatively low price of the fuel compared to gas.

David Cameron is warned today by Graça Machel, widow of the late South African statesman Nelson Mandela, that unless world leaders made 2015 a year for development, the consequence would not just bepoverty but also growing military conflicts from which the rich would be unable to protect themselves for decades to come.

It is Machel's first global political act since the death of her husband last year.

The letter to Cameron has also been signed by Archbishop Desmond Tutu, the rock star Bono, the Nobel peace prize winner Muhammad Yunus, the billionaire entrepreneur Mo Ibrahim and the 17-year-old Pakistani activist Malala Yousafzai.

UAE Vice President, Prime Minister and Ruler of Dubai His Highness Sheikh Mohammed bin Rashid Al Maktoum announced the launch of an international prize of $1 million for finding sustainable solutions to water shortage all over the world through the use of solar energy to desalinate and purify water. His Highness also announced the establishment of UAE Water Aid Foundation with the aim of conducting research and studies to support the production of clean water using solar energy so as to provide new, cheap and innovative solutions for millions around the world who suffer from scarcity of water and polluted drinking water.

Aid group Oxfam has called on other rich nations to follow the example of Germany, which has promised €750m ($1bn) for the UN's fledgling Green Climate Fund.

"This announcement ends the deafening silence we've had so far around the empty Green Climate Fund that is supposed to support poor countries in the battle against climate change. Now others must follow suit," Oxfam Germany's Jan Kowalzig said.