"We have reached the critical moment of decision on climate change. There are few, if any, genuine doubters left," Blair told G20 energy and environment ministers in Chiba, near Toyko.
"If the average person in the United States is say, to emit per capita, one tenth of what they do today and those in Britain or Japan one fifth, we're not talking of adjustment, we're talking about a revolution."
The average American emits the equivalent of about 24 tonnes of carbon dioxide a year. In China the figure is about four tonnes.
The talks in Chiba are billed as a dialogue, not a negotiation, and ministers are meeting to discuss ways to curb carbon emissions, technology transfer, funding schemes for developing nations to pay for clean energy as well as adaptation.
"We have reached the critical moment of decision on climate change. There are few, if any, genuine doubters left"
Tony Blair, former British prime minister
Ministers at the talks were being ferried around in fuel-cell powered cars, and supporting staff were served traditional "bento" lunches with reusable boxes and chopsticks, instead of the more common throw-away versions.
At the end of the first session on technology, one delegate said South Africa, Indonesia, India and Brazil rejected the label of being major emitters, as defined by a separate forum created by the administration of George Bush, the US administration.
"They said 'we may be major economies but we are not major emitters if you look at per-capita figures'," said the delegate, adding there was also division between developing nations and Japan's push for sectoral emissions targets for industry.
Near the talks venue, a small group of protesters staged a mock play criticising Japan's focus on sectoral targets, saying the G20 should not accept Tokyo's proposal to curb emissions from polluting industries, such as steelmakers.
Britain said on Friday that sectoral targets were no solution because they were hard to monitor and it was unclear if they would be mandatory or voluntary.
"There is a growing rough consensus that this is an effective approach," Akira Amari, Japanese trade minister, told reporters. "But there were opinions that some aspects were not clear."
Blair said UN-led talks launched in Bali last December were the right forum to work on a replacement for the Kyoto Protocol by the end of 2009 that binds all nations to cut greenhouse gas emissions.