The speed and size of the Extinction Rebellion (XR) protests over the past year add weight to the idea that people in this decade were in revolt before they had any clear idea what form a revolution might take. Politically it has long looked like a whole generation was up for grabs. In the beginning of the decade this anger veered leftwards with movements like Occupy, but at the end it has moved greenwards, under XR. The question is how much of the country will go with it.

Extinction Rebellion succeeded in putting the climate crisis on the political agenda. This is a welcome pivot to an existential issue for a society that has become gummed up by enervating fights over Brexit. There is an urgent need to decouple economic activity from carbon emissions and ecological destruction. For all the fine words global emissions of carbon dioxide are higher than they have ever been, almost three decades after the first global conference aimed at reducing them. The situation is becoming dangerous for human life. The latest figures show there is little more than a decade to save ourselves and the other creatures with whom we share the planet.

To meet this challenge it is heartening that XR has adopted non-violent resistance, in which unarmed people engage in a coordinated set of strikes, rallies and boycotts to confront the authorities over environmental inaction. When the group shut down major parts of central London with a carnival of protest making business as usual impossible in April, the demonstrators ended up meeting with London’s mayor and cabinet ministers before securing their aim of getting parliament to declare a “climate emergency”. Extinction Rebellion’s policy and language have become mainstream in a remarkably short space of time. By comparison it might appear that this latest set of “uprisings” has seen XR go backwards rather than forward. There were no meetings with high-profile politicians. The targetting of London’s public transport network at rush hour would have lost the group significant goodwill among parts of the population. Yet XR has gone global, with 60 cities experiencing protests.

XR has become more inventive as the protests against the National Portrait Gallery’s links with BP attest. In Britain the use of arrest as a tactic to draw more support has been particularly effective, with 1,700 peaceful protesters so far hauled away by the police as a record number of people took part in acts of resistance. The police in London will also have helped build opposition by taking measures which amount to an assault on the right to protest. If the authorities adopt a harder line they will boost the power of non-violence, by attracting people to demonstrations because of heavy-handed tactics.

Disobedience is at the heart of non-violent struggle. As Martin Luther King Jr wrote: “We know through painful experience that freedom is never given by the oppressor; it must be demanded by the oppressed.” XR’s strategy is influenced by the work of Harvard’s Erica Chenoweth, whose studies revealed that campaigns of non-violent resistance were twice as effective as ones which used violence in achieving their goals, and campaigns that involved more than 3.5% of the population – in the UK that is 2.3m people – invariably succeeded. But numbers alone will not create change; crowds are necessary but not sufficient. There’s also a danger that people show up but nothing changes – that mass action doesn’t work. This is the wrong conclusion to draw. However, people being in the streets isn’t effective without a strategy, and XR needs a clearer one for what could be years of struggle. There is an open question whether tactics that toppled dictators work in a liberal democracy.

This perhaps explains XR’s reluctance to spell out whether it wishes to achieve a revolution to overturn a political order or to create pressure to persuade governments to act. Reform or revolution – XR will have to make this call as it reflects on its own success.