A watermelon vendor looks at yuan banknotes at a market in Changzhi, Shanxi province June 21, 2010. China's yuan soared on Monday to close at its highest level against the dollar since its July 2005 revaluation, as the central bank stepped aside and tolerated broad gains on the first trading day after it ditched the currency's two-year peg to the dollar. REUTERS/Stringer China is printing a lot of money.

In January, M2 growth — or cash in circulation, essentially — reached 14%, a 19-month high, exceeding analyst expectations of about 12%.

The money was injected into the economy in the form of renminbi loans.

In a note to clients, Deutsche Bank argued that this growth in cash was unsustainable and threatened financial stability.

According to data from Deutsche Bank and Macquarie:

New loans surged to 2.5 trillion renminbi, compared with 1.5 trillion in the prior year. The expectation was for only 1.9 trillion.

New loans set a record, more than quadruple the December total of 598 billion.

a In January, the ratio of debt to gross domestic product increased by about 5 percentage points, "the fastest pace since Jan 2010," according to Macquarie.

Here's a chart showing cash growth running ahead of economic growth, at left, and the total amount of newly issued loans leaping upward in January:

Those new loans caught our eye because China is becoming increasingly indebted as its economy slows.

Debt gets harder to pay back as your economic growth declines.

Something, then, has got to change: China needs to grow faster than its debts, push those debts off into the future, or go through a period of defaults that force a restructuring of its economy. The restructuring option could be disastrous for the global economy.

People used to worry about cash growth a lot. Print too much money, and you end up with spiralling price inflation, as happened in the Weimar Republic and Zimbabwe, where people had to carry around bank notes with "billion" written on them.

In the West, however, economists don't worry much about M2 anymore. The US Federal Reserve, the Bank of England, and the European Central Bank have been pumping new money into their economies for years, and there hasn't been any consumer-price inflation to speak of (though there has been asset-price inflation, exemplified by the private tech company valuations in the US and urban property prices in Europe).

So the question for China is whether its M2 growth will look more like that of Zimbabwe or that of the US. The folks at Deutsche Bank are slightly scared:

We believe the current strong credit growth is unsustainable. The gap between the M2 growth and nominal GDP growth will likely widen further in H1, and cause concerns in the policy circle about financial stability.

The Macquarie team is more sanguine:

Although China is already highly leveraged with the debt-to-GDP ratio at around 250%, in a state capitalism like China, it doesn't mean an imminent debt crisis or any inability by policy makers to add any more leverage. In our view, judging from recent speeches by top leaders and Jan's credit growth, this year policy makers seem to be determined to make the economy grow above their bottom line of 6.5%. That said, we don't think policy makers have any appetite to over-stimulate. As such, we see 2016 as another year of a muddle-through ...