Sir David Attenborough and Archbishop Desmond Tutu have called on world leaders to do more to protect the poor from the devastating effects of climate change, which hits them the hardest.
The two were among 19 signatories of a letter to The Times urging Western countries to "lead the way" at the United Nations climate change summit in Poznan, Poland.
With disease, droughts and uncertainty over crops being blamed on global warming, they said it was essential that agreements were reached.
Signatories included campaigners such as Sheila Watt-Cloutier, a Canadian Inuit activist, and Janina Ochojska, president of the Polish Humanitarian Organisation, alongside musicians, authors and actors, including Scarlett Johansson, Annie Lennox, Ian McEwan and Colin Firth.
They said it was "desperately unfair that the poor should again feel the brunt, despite being least responsible".
The letter, organised by Oxfam, was sent as the conference entered its second week and hopes of making progress on agreeing funds to help poorer nations to adapt to climate change began to fade.
The economic downturn has raised doubts among delegates that measures to bring down emissions are financially viable.