As workers across the European Union went on protest strike today, it was hard to disagree with the trade union leader who told the BBC that austerity economics isn't working. "It's increasing inequalities. It's increasing the social instability in society. And it's not resolving the economic crisis," she said.

All of that is true and serious. Addressing those things is fundamental. But we are going to have to get used to austerity. Because relative scarcity, and the need to do more with less, are not going to go away in a hurry. Austerity is remaking our world. The point is to make the best of it. Welcome to 21st-century Europe.

Today's quarterly inflation review by the Bank of England is merely the latest in a series of indicators that remind governments and peoples across Europe and beyond that the old days are simply over, done, finished. Recovery would be sustained but slow, said the Bank. The economy was sluggish. The environment unfavourable. Things might be weaker for longer.

The message is hard to miss. Times have changed. The only thing that is certain is further uncertainty. We may have come out of recession again, but the idea that Britain, let alone the countries of the eurozone, can expect to see any resumption of the kind of growth rates to which we have all been accustomed since the second world war, is increasingly fanciful. We are living through not a downturn but an epochal change, and we need to make a more consistent effort to understand what this implies.

The most interesting news story of the last week – which was nothing to do with the BBC and made few of the newspapers – illustrates what is at stake. During the next 50 years, according to a newly published OECD growth report, the world economy is expected to grow at about 3% a year. Most of that growth, however, will be in Asia and the developing nations. Growth in Europe, including the UK, will be much less robust – and will often actually decline.

Got that? Growth in Britain will often decline over the coming half-century. It will not resume. We can talk all we like about stimulus and investment, as Labour did today in its latest denunciation of George Osborne, quite rightly in its way. But, during the next 50 years, growth is going to be halting and uneven and will sometimes be negative. Just like now, in fact.

The OECD said something else, too. As the world economy grows, it reported, our European share of it will decline. Economic power is shifting to China, whose economy will outstrip that of the eurozone next year and of the United States before Barack Obama leaves the White House in 2016, as well as to India. Without wishing to fall into mercantilist heresy, this means that while the world will have more, we will have less of it – and maybe less in real terms, too. We are confronting scarcity of a sort we have forgotten.

It is tempting to read a report like the OECD's and say, yeah yeah, we all know all that stuff about the rise of Asia and the decline of the west. And maybe we all do. But probably only at a rather theoretical level. For most of us, relative decline is something we read about but don't think about until it hits us on the head. Most of us have barely started to grasp what it may mean for our living standards and our politics.

And not just in 50 years' time, either. These large shifts are already under way. Their impact is now, as well as later. Just look around the world this week.

In China, a nation where annual growth in the last 20 years has never been less than twice that of Europe, even when Europe was thriving, a new leadership is seamlessly introduced for another 10-year span.

In Europe, by contrast, a series of weak leaders, vulnerable to democratic rejection of a sort with which Xi Jinping will not need to concern himself, struggle to assert some degree of control over a floundering currency and unification project. Meanwhile in the US, a re-elected but domestically weak president faces a series of defining political battles over spending and taxes, with only limited chance of achieving radical outcomes, even if that is what he wants.

Smart leaders should recognise that austerity in some form is the context for most of the foreseeable political options in countries like Britain. As a timely American book on this theme this year by Thomas Byrne Edsall argues, scarcity will remake US politics as rising expectations meet diminishing resources on a global scale. The same is true in a different context in Europe. That does not mean there is no alternative to relentless fiscal consolidation, or that all austerity strategies are the same as all other austerity strategies. The opposite is true. But it does mean that political parties in economically developed countries no longer have the same breadth of spending options as they did.

This is not a defeatist but a realistic assessment. It is not necessarily all bad news for the centre left, either. Although the 20th-century social democratic project may have stalled amid economic decline, the financial crisis has undoubtedly opened up a fresh opportunity to redefine the terms on which the rich and poor can coexist without social unrest in times of greater scarcity.

Ed Miliband appears to believe this. So – in an interesting break with the past that illustrates the new options – does a new pamphlet this week from the Blairite group Policy Network. But the hope is likely to prove optimistic if the left simply shouts the old mantras.

Clearly, though, the right is more comfortable in such times. But there is a huge difference between the slash-and-burn right in America and the more collectivist right in Europe in the way they respond. It was significant that George Osborne was so quick this week to align himself with Barack Obama's re-election victory. Obama's win, said the chancellor, is proof that incumbent governments can win re-election in economically weak times.

He is right about that. Osborne's touch may have deserted him recently, but he has the huge advantage of being alive to the context and politics of these new times in ways that the left across Europe is still struggling to match.