These forms of direct action have secured the publicity that clearly has focused people's minds, not just on the threat of climate change but importunately on the solutions available to us.
John McDonnell has praised the efforts of Extinction Rebellion protesters who paralysed parts of London.
The shadow chancellor said the "relatively minor disturbance" caused by the activists and the school student strikes movement had "definitely been worth it".
More than 1,000 arrests were made by police during Extinction Rebellion protests in London over 10 days in April.
In a speech in London, Mr McDonnell said: "The relatively minor disturbance to everyday life caused by the demonstrations by Extinction Rebellion and the school student strikes has definitely been worth it.
"These forms of direct action have secured the publicity that clearly has focused people's minds, not just on the threat of climate change but importunately on the solutions available to us."
He said a national effort similar to that under Clement Attlee's government to rebuild Britain following the Second World War was needed to tackle climate change.
Mr McDonnell launched an inquiry into the "shadow banking" sector as part of the effort to shift finance away from polluting industries.
It would examine what state intervention may be required to increase "transparency and accountability" of institutions which do not have the same regulatory scrutiny as banks.
"I am setting up a review group to overview the financial system as it currently relates to the climate emergency, in terms of both: where and how it is causing or exacerbating the problem of climate change; and where and how it could be providing solutions to problems," he said.
"The review will cover commercial banks, investment banks, pension funds, hedge funds, private equity, asset managers, derivatives and securities traders and exchanges, and any other aspect of the finance sector of relevance."
Mr McDonnell said he had also put forward a plan to legislate so that any company listed on the London Stock Exchange would be "required to contribute to tackling the climate change crisis" - with de-listing as a sanction.
"When we de-list companies that fail to meet environmental criteria from the London Stock Exchange, investors can be confident that their money is not going on making the world uninhabitable for their children," he said.
Mr McDonnell promised that as chancellor he would use the "full might of the Treasury" to address the problem of climate change.
Stephen Jones, chief executive of industry body UK Finance, said: "The shadow chancellor has today posed the question of whether the financial sector is up for rising to the challenge of climate change.
"Achieving net zero carbon by 2050 is a difficult but critical target that we must all work together to address and as an industry we stand ready to respond."
David Hughes is the Press Association's political editor.