But the prime minister's speech was delivered against a backdrop of criticism of Labour's environmental record and accusations that the timing showed it was a pre-election ploy - the speech was only his second over the last four years to address the issue.
Anti-road campaigners were also in evidence for Mr Blair's arrival at the conference organised by the World Wildlife Fund.
'Pre-election stunt'
Mr Blair used his speech to highlight his concern over the sometimes damaging effects of economic growth, saying sustainable development would be the "key issue" of the century ahead.
"There will always be dilemmas in the politics of the environment, there is no point in any practising politician saying anything else is the case," he said.
Mr Blair said that although long term there would be benefits from pursuing sustainable economic growth, he acknowledged that "short term, there is often pain involved and hard and difficult decisions".
The Conservatives accused the prime minister of launching a "a pre-election stunt to win votes", while the Liberal Democrats said Labour had "failed miserably" on the environment.
World crisis
One of the issues that Mr Blair addressed was the world population crisis - up to 9bn people by 2050 from 5.9bn in 1998 - and a crisis of flood and drought.
About two-thirds of the world's population will be affected by "water stress" by 2050, Mr Blair said.
He also accepted that by the year 2100, the concentration of carbon dioxide in the atmosphere, the key greenhouse gas leading to global warming, could be between 90% and 250% higher than 350 years previously.
He said that the government was moving to achieve a 23% reduction in the gases by 2010.
But Mr Blair warned: "We can only succeed if we make tackling climate change a commercial opportunity."
A government Performance and Innovation Unit report later this year will identify which types of wind, wave and solar power should benefit from the £100m fund.
"Countries that invest in these technologies now will reap a long-term reward," Mr Blair said.
He also argued that the renewable energy industry as a "huge long-term commercial opportunity".
Friends of the Earth welcomed the money announced by the prime minister, but said it was not enough.
Hostile reception
Demonstrators who greeted Mr Blair as he arrives at the World Wildlife Fund event in Chatham House included veterans of the Twyford Down and Newbury protests.
And Conservative environment spokesman Damien Green described Mr Blair's speech as "yet another pre-election stunt".
"The prime minister has already proved he is profoundly uninterested in the environment and is fooling no one with this sudden burst of fake concern.
"Four years of failure on green issues cannot be repaired by one speech."
Liberal Democrat leader Charles Kennedy suggested Labour had no "gut instinct" on green issues.
"I think the prime minister and the government generally have failed miserably where the environment is concerned," he said.
Any attempt by Chancellor Gordon Brown to present a "jolly green giant" budget on Wednesday would be met by public cynicism, Mr Kennedy predicted.