Every year brings changes, but some years really are turning points: 1492, 1789, 1914, and 1989, for example. Does 2011 belong in the august company of such Really Important Years? Probably not, but it definitely qualifies for membership in the second tier of Quite Important Years.
Three big stories ran right through the year, any one of which would have qualified 2011 for membership status. The Arab Spring is an epochal event, even if democratic revolutions may fail in some countries in the end.
The euro crisis threatens the European Union with collapse, confirm-ing the shift of economic power from West to East. And the struggle to prevent disastrous climate change was abandoned for the rest of the decade.
The name, it should be noted, is the Arab Spring, not the Muslim Spring, because a majority of the world's Muslims already live in countries that are democratic: Turkey, Indonesia, Malaysia, Bangla-desh, Pakistan, and even Iran (in roughly descending order of how democratic they really are). But the Arab countries seemed remarkably impervious to democracy - until it suddenly became clear that they weren't.
The revolutions in Tunisia, Egypt and Libya were not just about elections. They were revolts against the arrogance and corruption of the ruling elites, against poverty, against the reign of fear that underpinned all of those regimes. But there was, and still is, a genuine democratic idealism at the heart of these revolutions, and despite all the disappointments and detours that will inevitably follow, something profound has changed in the Arab world.
Similar revolutions could well succeed to other Arab countries this coming year, but in some cases they may not be necessary. Formerly autocratic monarchies like Jordan and Morocco are in full retreat, hoping to safeguard their privileges by granting political freedoms to the people. And the long and increasingly bloody struggle in Syria could still end in a relatively peaceful transition to democracy, not civil war.
We should have learned not to underestimate people by now. The Arab Spring is the culmination of a wave of non-violent revolutions that started in Asia in the 1980s (Philippines, South Korea, Thailand, Indonesia, Bangladesh, plus failed attempts in China and Burma). They spread to Eastern Europe and the former Soviet Union in 1989-91, ended apartheid in South Africa in 1994, and brought down Slobodan Milosevic in Serbia in 2000.
Then there was a decade-long gap, but now they're back, and not just in the Arab world. The ruthless Burmese regime is retreating from power under relentless pressure from the pro-democracy movement led by Aung San Suu Kyi, and even Vladimir Putin in Moscow must suddenly feel vulnerable as he watches the crowds come out in Russia to demand their country back. Non-violence works. It will even work in China, eventually.
From the sublime to the ridiculous. The decade-old euro, which aspired to become the common currency of the European Union and even a rival to the US dollar, is in acute danger of collapse, and the efforts of European leaders to save it have been comically inept. Seventeen of the 27 countries in the EU, including all the big economies except Britain, use the euro, but that number may drop sharply in the next few years. It might even drop to zero.
The euro was a political project from the start, and it may also die of politics. The initial idea was that a common currency would bind the EU members closer together, but it never made any sense for low-productivity economies like Spain, Italy and Greece to use the same currency as high-performing economies like Germany.
The only way it could have worked was for the richer countries to subsidise the poorer countries forever (like the richer regions of France or Japan subsidise the poorer regions). Then, provided there was also a powerful central bank to stop the poorer countries borrowing too much (because they now had a strong currency, which let them borrow almost unlimited amounts of money at very low rates), the whole project might work.
The richer countries like Germany and France had no intention of subsidising the poorer ones, and they wouldn't allow a powerful central bank either, but the project went ahead anyway. The euro might have stumbled on, amid growing difficulties, for another decade - but the international financial crisis of 2008 put an end to that.
When the tide goes out, as legendary investor Warren Buffett put it, you find out who's been swimming naked. The European economies were as naked as jaybirds, and so the vultures began to circle (to mix a metaphor). Every month of this year has seen another "crisis summit" meeting of EU leaders, but they have produced no credible solution to the euro's problems because the richer countries are still unwilling to subsidise the poorer ones.
There are three possible outcomes to this mess. One is that the poorer countries simply bail out of the euro and revive their old separate currencies, which would cause some serious bank crashes in Europe and collateral damage elsewhere. The second is that the euro as a whole collapses, causing severe damage to all the Western economies including the United States. The third is that the European Union itself falls apart.
Option one is almost certain to happen. Option two is getting more likely by the month. Option three is still relatively unlikely - which is just as well, given what a disunited Europe used to be like. But the sheer vulnerability of what are still technically the world's most powerful economies is now plain for all to see.
The power shift from the old Atlantic world to the emerging economies of Asia was going to happen eventually in any case: the five centuries when the Europeans and their overseas kin were global top dogs are at an end. But the arrogant risk-taking, blind greed, and sheer ignorance that caused the crash of 2008 and its aftershocks are making the shift happen a lot faster.
And so to the really bad news. The Arctic sea ice is disappearing faster than even the pessimists feared, massive floods are devastating huge areas (Pakistan, Thailand, Australia), and the sea level is rising at twice the predicted speed, but nothing will be done about it for the next 10 years. That, effectively, was the decision - or rather, the non-decision - taken at the annual climate change summit in Durban in December.
It has been clear since the debacle at Copenhagen in 2009 that a global agreement to curb the warming was in grave trouble, but the deal in Durban may have been worse than no deal at all. The only existing agreement, the Kyoto Protocol of 15 years ago, has been extended for another five years, but it only limits the emissions of the developed countries, and even they will not be required to meet any stricter targets than those they accepted in 1997.
The emerging economies, whose emissions are growing very fast, still face no restrictions at all, although China is already the world's biggest emitter of greenhouse gases. The target date agreed for a new, more ambitious global agreement is now 2015, but they won't even start talking about that until 2013. And even if they do manage to make a new deal by 2015, which is far from certain, they have already agreed that it will not go into effect until 2020.
It's not the first time short-term self-interest has triumphed over the long-term common interest, but it may be the worst time. By 2020 it will probably be impossible to prevent the rise in average global temperature exceeding 2C, the generally agreed point of no return. After that, we will probably find ourselves in a new world of runaway warming. We know it, and yet we do nothing.
Compared to these huge changes in world politics, the global economy, and climate policy, everything else that happened in 2011 was very small potatoes, but some of it was very interesting.
Three bad men died, two of them violently: North Korea's Kim Jong-il, Libya's Muammar Gaddafi, and al-Qaeda's founder Osama bin Laden. Four Latin American countries - Argentina, Guatemala, Nicaragua and Peru - elected Presidents. Five African countries - Congo, Ethiopia, Nigeria, Zimbabwe and Zambia - achieved higher economic growth rates than Brazil (partly due to higher commodity prices, however).
An earthquake and tsunami devastated a large area of northern Japan, and the radioactive emissions from damaged nuclear reactors - about one-tenth of what came out of Chernobyl in 1986 - caused a global mini-panic. But in the end, the only country that announced a plan to shut down its reactors was Germany. (They'll burn coal instead. Oh, good.)
American troops finally left Iraq in December, still insisting they had accomplished their mission, whatever it was. Nato deployed its air power to help the rebels win in Libya, but it isn't going to Syria.
And the final shuttle flight from Cape Canaveral took off in July. Dr Mike Griffin, the former head of Nasa, said "the human spaceflight programme of the US will come to an end for the indefinite future" - but the Russians and Chinese are still sending people into space, and the Indians and Europeans are working on it.
The multi-national African "peacekeeping" force fighting in Somalia grew dramatically in size, although that's no guarantee of success. Sudan split into two countries. And Nigeria faced a growing terrorist threat from the Islamist "Boko Haram" sect.
The race to become the Republican presidential candidate in the United States started as farce and went straight downhill, with each "anybody but Mitt Romney" contender less plausible than the one before. It resembled the old film Those Magnificent Men in Their Flying Machines, about a 1910 air race from London to Paris, in which a collection of extremely weird pilots in ramshackle biplanes and triplanes took turns being briefly in the lead and then crashed and burned. So Barack Obama will probably be back in 2012.
There were widespread riots in England in August, and the "Occupy" movement spread across America like measles (and went away almost as quickly). They were both really about the growing gap between rich and poor, but they had as little visible impact on how governments do business as anti-corruption campaigner Anna Hazare's televised hunger strike in India.
India probably grew faster than China this year, though the final figures aren't in. And India's economy, unlike China's, isn't threatened by the biggest housing bubble in the history of the world. That race, if it is a race, may have an unexpected result, though we'll have to wait a couple of decades to know for sure.
Oh, and the world's population reached the seven billion mark in 2011. It passed through one billion around 1800, and was still only 2 billion in 1940. Enough said.