As the past decade slips away, it is easy to remember it economically as one which began with the dotcom boom and ended with the "Great Implosion" that left Britain, the US and other industrialised nations struggling with the most painful recession in the postwar period.

But a deeper shift has been going on – the rise and rise of China and other key economies grouped under the banner of "emerging". Indeed, the growing political and economic muscle of China was highlighted by its recent intransigence at the Copenhagen climate talks, where it refused to be forced into any binding agreement to reduce its emissions.

While many economists have grown used to the idea that the US economy – still the world's biggest – is the locomotive of the global economy, it is China, helped by a huge fiscal stimulus from Beijing last year, which is roaring ahead and helping to drag the rest of Asia and countries such as Germany, which exports a lot of machine tools to China, out of recession too. China is one of the key reasons the world did not experience an even worse 2009 than it actually did.

China is not alone; other Asian countries that are booming include Thailand, South Korea, Malaysia and Taiwan. But in terms of sheer size and importance, key emerging economies now include Brazil, Russia and India. Together with China, these are known as the Brics, a term coined by Jim O'Neill at Goldman Sachs early in the Noughties to denote their growing economic importance.

Their rising power stands in sharp contrast to struggling European economies such as Portugal, Ireland, Greece and Spain, known collectively, if unkindly, as the Pigs. (The list is often extended to include Italy, but PIIGS makes for an untidy acronym.)

The Brics now account for 15% of the global economy, more than half of the size of the US. As O'Neill points out, China has overtaken Germany to become the world's third-largest economy and is likely to move into second place, ahead of Japan, over the next year or so. By 2030 it is likely to have eclipsed the US as the world's top economy. Brazil will overtake France and Britain to become the world's fifth-largest economy by 2025 at the latest. Along with India and Russia, it has overtaken or is about to overtake Canada, a member of the G7 leading economies. No wonder the G20, which includes the Brics, has been recognised as the primary forum for global economic discussions.

All the Brics are set to grow strongly.Goldman also lays to rest the myth that Americans are the world's "consumers of last resort", forecasting that the Brics, rather than simply being huge exporters, are likely to account for almost half of global consumption growth in 2010.

"We expect income per capita to continue to rise in the Brics and spending power to shift from the richest countries towards a growing middle-income bloc, comprising emerging markets in general and the Brics in particular," it says.

But while most of the impact of emerging economies is benign, that cannot be said for China. Some economists say its emergence on to the world stage brought with it a key reason for the global economic meltdown between 2007 and 2009. For similar reasons, its successful integration into the global economy will likely define the success of the new decade.

Holding down its exchange rate to make its exports cheaper meant China built up huge current account surpluses, which it reinvested in the government bonds of countries such as the US, helping to push down long-term interest rates and pump up the American economy, sucking in even more Chinese imports.

The flip side of its surpluses were current account deficits in many western countries, in particular Britain and the US. Cheap Chinese goods kept western shoppers buying and inflation low, letting central banks such as the US Federal Reserve and Bank of England hold interest rates low, thus pumping up the prices of assets such as shares and housing. This cheap, plentiful credit is blamed by many for ultimately leading to the peddling by banks of sub-prime mortgages and derivatives based on them, all of which collapsed with devastating results.

In his recently-published book The Trouble with Markets, veteran economist Roger Bootle argues that a rebalancing of the global economy, with countries such as Britain and the US reducing their current account deficits and China shrinking its surplus, will be key to a successful next decade. The alternative – protectionism and trade wars – could be disastrous.

"China is sitting on a time bomb," he said. "Choosing to run a huge surplus means other countries have to run huge deficits. Unless China acts to boost consumption and reduce its reliance on a large trade surplus, the west will achieve the latter for China by imposing protectionist measures, and the Chinese will be left trying to achieve the former in an atmosphere of deep economic and political crisis."

Chinese leaders have been browbeaten about the value of their currency for several years and in 2005 decided to let it rise in value. Results so far have been mixed, at best. Over the past 10 months, for example, it has fallen by 14% against the euro. Its trade-weighted value is now back to its 2002 level. The value of the yuan will be arguably the most important thing to watch over the next decade.