Banks around the world must refinance more than $5 trillion of debts in the coming three years, a massive rollover that poses threats to financial stability and growth.

The need to replace these debts, which are medium and long term, will place pressure on bank profit spreads and in turn may either prompt deleveraging, where banks sell assets that they can no longer economically finance, or simply lead to a bout of credit rationing, where borrowers must pay more to borrow, thus crimping investment and economic growth.

For banks in the UK, according to the Bank of England Financial Stability Report, the refinancings amount to about $1.2 trillion by the end of 2012.

If banks in Britain raise funds at the same pace they have been this year, they will only collect half of their needs in time. This is even before the fact that the banks need desperately to turn some of their riskier short-term funding into more reliable funding with a longer maturity.

“If funding costs increase dramatically, which is perfectly possible in what could be pretty febrile market conditions, that will hit profitability (and the banks ability to raise capital organically) until they are able to re-price loans and facilities,” according to Richard Barwell, an economist at the Royal Bank of Scotland in London.

“And to the extent that banks are unwilling or unable to roll over funds that would trigger forced deleveraging. Both outcomes imply a sharp contraction in credit conditions for those within and outside financial markets, putting considerable downward pressure on activity and asset prices.”

Banks outside of Britain are perhaps doing marginally better in meeting their needs, but still face an uphill struggle.

U.S. banks have issued $230 billion of debts in the first five months of the year, about 60 percent of the rate they need to achieve over the three year period. Euro zone banks have issued $133 billion, or about 70 percent of their needed run rate.

One easy to see consequence is that, all things being equal, the cost for banks to issue debt should rise, as should competition among banks for consumer deposits. It is possible that a global desire to save more helps to blunt this effect, but even so the macroeconomic effect and the effect on asset prices will both be strongly downward.

BANKS WILL HAVE THEIR FUNDS

The track record of the past three years tells us one thing is likely: the banks will get their money, courtesy of government support if needed.

Unless there is a profound sovereign debt crisis, we can count on governments taking the needed steps to see that the banking system does not fall over for lack of funding. So, if liquidity or support schemes need to be extended or invented anew, they will be.

But a banking system that has not fallen over, while a precondition for strong economic growth, is not in and of it self sufficient to cause strong economic growth. Expensive funding and a rising term premium will stunt growth and they will impose a haircut on risk asset prices.

Viewed another way, however, higher funding costs for banks is really nothing other than the market demanding a different capital structure from banks.

It is not simply that a lot of money needs raising all at the same time, but rather that the people who have in the past supplied the money have a new appreciation of the risks in lending to banks, or should that simply be of the risks of lending.

The Financial Stability Report also looks at the costs and benefits of higher amounts of capital in banking. The benefits are straightforward: a reduced chance of systemic crises. Costs are thornier, but also quite high. The BOE used an assumption that for every 7 basis points of additional lending spread charged by banks should create a 0.1 percent permanent reduction of GDP. On their estimates upping capital in banking by one percent then equates to present value cost of about 4.0 percent of UK GDP.

This puts into perspective not just how challenging it will be to create growth going forward, but just how artificially growth during the boom was goosed by very loose and easy lending.

For the UK and for Europe, this will be happening at the same time that fiscal austerity programmes will be dampening growth.

Something has to give, and it will probably be monetary policy. Look for extraordinarily low rates for a very long time, and for new and bigger quantitative easing programmes.