Businesses are being urged to become more environmentally friendly, after new figures showed they produce a third of London's total carbon emissions.
Businesses produce much of London's carbon emissions
A new "carbon map" of the UK shows London is the highest-polluting city, producing 9m tonnes of carbon a year.
About 34% is from firms and the public sector, the rest is from homes and transport, says the Carbon Trust.
Businesses can save money and help reduce global warming by becoming more energy efficient, says the trust.
It highlights the case of the Telegraph pub in Brixton, south London, which took out an interest-free loan from the trust to replace its roof.
The trust, which was set up by the government to help it meet climate change obligations, said the pub saved itself £9,000 a year.
Trust spokesman Garry Felgate said: "Local businesses account for more than a third of Greater London's emissions.
"If they act now, it will not only benefit the environment but also their bottom-line."
Mayor Ken Livingstone wants to introduce a low-emissions zone, in which old diesel lorries, buses and coaches would be charged to drive into Greater London, to help the UK meet its air quality targets.
The mayor, who wants to make London the world's most environmentally-friendly city, has already introduced a congestion charge and a Climate Change Agency for London.