Guangan, China: A worker rides past coal-fuelled cooling towers at a power plant. The carbon ‘debt’ in 2008 was equivalent to the joint emissions of the US and China. Photograph: Frederic J Brown/AFP

The world is rapidly depleting its “carbon budget” for the first half of this century and must slash the carbon intensity of the global economy, a new report said today.

Economists and climate change experts at PricewaterhouseCoopers (PwC) said their new research highlights the need for an ambitious carbon reduction agreement at the Copenhagen climate conference, which starts next week.

The report’s authors calculated the global carbon budget between 2000 and 2050 required to limit temperature rises to 2C, the climate threshold defined as “dangerous” by the EU.

Nasa graphic showing the extent of the ozone hole over Antarctica

The hole in the Earth’s ozone layer has shielded Antarctica from the worst effects of global warming until now, according to the most comprehensive review to date of the state of the Antarctic climate. But scientists warned that as the hole closes up in the next few decades, temperatures on the continent could rise by around 3C on average, with melting ice contributing to a global sea-level increases of up to 1.4m.

The western Antarctic peninsula has seen rapid ice loss as the world has warmed, but other parts of the continent have paradoxically been cooling, with a 10% increase in ice in the seas around the region in recent decades. Many climate change sceptics have used the Antarctic cooling as evidence against global warming.

Shukdev Das, who lost his home on Ghoramara island, India, when sea levels rose. Photograph: Peter Caton/Greenpeace

Nicholas Stern

The two defining challenges of our century are managing climate change and overcoming poverty. And if we fail on one we will fail on the other. So the world faces a stark choice at the United Nations climate change conference in Copenhagen.

Do we collaborate and act to reach a strong political agreement that both decisively cuts the devastating risks posed by climate change, and rapidly opens up the opportunities offered by low-carbon economic growth? Do we in that way set ourselves to overcome poverty and promote prosperity? Or, do we give way to narrow, short-term interests, quarrelling, lack of ambition and delay, thus allowing the risks to the climate to grow to dangerous levels which will derail development in both rich and poor countries?

The speed in which the market for carbon trading grows will depend on whether the Copenhagen summit gives a go-ahead to a low-carbon economy, say traders. Photograph: Stringer /Reuters

The carbon market could become double the size of the vast oil market, according to the new breed of City players who trade greenhouse gas emissions through the EU’s emissions trading scheme.

Rajendra Pachauri accepts the Nobel prize on behalf of the IPCC in 2007. Photograph: AFP/Getty Images

Hotel guests should have their electricity monitored; hefty aviation taxes should be introduced to deter people from flying; and iced water in restaurants should be curtailed, the world’s leading climate scientist has told the Observer.

Rajendra Pachauri, the chair of the Intergovernmental Panel on Climate Change (IPCC), warned that western society must undergo a radical value shift if the worst effects of climate change were to be avoided. A new value system of “sustainable consumption” was now urgently required, he said.