If this week is anything to go by, 2021 will be the “Year of Green”.

On Tuesday, BlackRock said it will demand that all companies demonstrate plans to reach carbon zero by 2050. That same day, attendees at the virtual World Economic Forum issued pious climate pledges.

On Wednesday, Mark Carney, former Bank of England governor, and Bill Winters, head of Standard Chartered bank, pledged to turbocharge the carbon offsets market. US president Joe Biden also suspended the issue of new oil and gas drilling permits on federal land.

Meanwhile, ExxonMobil, America’s largest oil major, is considering further cuts to fossil fuel investments and more spending on sustainable technologies. This shift, which comes as the company is under pressure from activists, is arguably the most startling of all. Exxon has hitherto been so defiantly wedded to fossil fuel that it has been a top target of environmentalists.

As the green bandwagon accelerates, though, it is time to consider a linguistic rethink. When teenage activist Greta Thunberg burst on to TV screens a couple of years ago, she demanded an immediate shift from carbon-emitting activities, like fossil fuels, to sustainable ones.

This “brown” versus “green” framing was admirably clear. Ms Thunberg also has a knack for irritating middle-aged executives, and thus deserves credit for shifting the debate. That is especially so as she also promoted understanding of a crucial concept: our globe has a measurable carbon “budget” which limits the emissions the planet can tolerate before irreparable environmental damage is done.

However, the issue now is not to divide the world into binary buckets of “green” and “brown”, as activists still demand and the European Commission’s new taxonomy attempts to do. Rather, it is to make currently brown activities less damaging and as fast as possible; in effect, create a blend of greenish-brown.

Thus it might be better to call 2021 the “Year of Olive”. What then really matters now is how quickly “olive” companies turn their activities a lighter shade of green and that they do so in a way that can be measured credibly.

Take the activist battle at Exxon, which looks like a tale of green David versus brown Goliath. The oil group was one of America’s largest and most respected companies. The activist, Engine No. 1, was created last month and owns just $40m in Exxon shares.

However, its “Reenergize Exxon” campaign has won backing from Calstrs, the huge California teachers retirement plan. DE Shaw wants spending cuts and BlackRock may back the activists. That is because Engine No. 1 understands olive. It is not demanding an immediate cessation of drilling but a credible plan that Exxon become net zero, fairly fast.

Exxon officials, of course, say they are already working on this. Their corporate website trumpets investments in carbon capture technology and other strategies to offset emissions. In that respect, it is not alone. Numerous other companies talk about carbon offsets too, which often involve planting forests. That is partly because trees are telegenic, but also because groups such as Salesforce have launched an eye-catching “trillion-tree” campaign.

Offsets can be a useful complement to decarbonisation plans. But there has been some lamentably poor reporting and greenwashing in this market. So Messrs Carney and Winters are now trying to put it on a more credible path. Let us hope they succeed.

Meanwhile, the “Reenergize Exxon” group rightly wants more. Offsets cannot be more than a small part of any solution. It is equally if not more important to fund new technologies, as Bill Gates did last week. Offsets such as planting trees also cannot become a distraction from the key task: making proper cuts to emission laden activities.

What Engine No. 1 wants Exxon to do is: show precisely how it will become a greener shade of olive quickly, by cutting oil and gas activities and embracing renewables.

This approach will not satisfy purists, who want “green now” and oppose funding anything short of that. But it is more likely to work. These days, investors increasingly award a share price premium to companies that are moving faster along the olive spectrum than their rivals. Financiers are also developing instruments that cut the cost of capital for greener groups.

Call this, if you like, an emerging olive yield curve. As such, it is welcome — with two caveats. First, it is not good enough for companies to tiptoe along this yield curve; the maths of the carbon budget means they need to move fast. Second, investors need a credible system for placing companies on an olive yield curve and measuring their progress.

In that respect, it is disappointing that BlackRock was vague this week about how it will measure the credibility of companies’ plans to get to carbon zero. It is also unnerving that the European Commission’s green taxonomy seems focused on a rigid, binary framework and that it is taking so long to harmonise sustainable accounting standards.

If we are going to make real progress on fighting climate change, it is vital to recognise the need to embrace an olive framework, track a company’s movement along an olive yield curve and speed its transformation. That will demand far more than planting trees, no matter how telegenic they are.