Investors became uncertain once again when we got an abnormal large U.S. March trade deficit of $51.4 billion, which was the largest since October 2008.

But, and this is important, the number didn’t give the full picture.

As an investor I wouldn’t overlook imports surged $17.1 billion in March mainly as a result of the unwinding of the West Coast ports strike and I’d prefer to wait for the April deficit number before taking conclusions.

No doubt, the deficit number caused pressure on the dollar. Everything will be on the table with the employment situation numbers on Friday, which are expected to be good, and if so, could take pressure away from the dollar and Treasury yields to rise.

In the meantime and what could be more important is since April 21 we’ve seen government bond yields in Europe and to a lesser extend in the U.S., but also in the UK have gone up in a rather remarkable way, especially the German 10-year Bund after Bill Gross tweeted: “German 10yr Bunds = The short of a lifetime. Better than the pound in 1993. Only question is Timing / ECB QE.”

Question now has become if this moment in time could become the start of a profound change in the extraordinarily low and negative levels of yields seen, especially in the European sovereign bond markets in recent weeks.

When we take a look at the yield of the 10-year German bund, it has risen a mindboggling 550 percent in only 15 days from 0.08 percent to 0.52 percent or 44 basis points while the yield of the 10-year U.S. Treasury has risen 14 percent from 1.92 percent to 2.19 percent or 27 basis points and the yield on the 10-year UK Gilt is up 25 percent from 1.57 percent to 1.97 percent or 40 basis points.

Please pay attention that percentages are not equal to “percentage points,” which are arithmetic units between two percentage numbers.

No, these are not “normal” moves over such a short time span, which could be a warning signal the end of the era of markets that have been fueled too long by Fed money.

It’s now close to 30 years when Alan Greenspan, in response to the stock market crash in October 1987, before markets opened on Monday, October 19 issued that historical statement, which reads: “The Federal Reserve, consistent with its responsibilities as the Nation's central bank, affirmed today its readiness to serve as a source of liquidity to support the economic and financial system.”

Since then we’ve seen what we now could call, with hindsight, the era of the 30-year Greenspan-Bernanke-Yellen put, or Fed put, where investors have become convinced the Fed would always be there in bad times to minimize the losses with ever easier monetary policy settings.

And investors have been right so far as we have seen each bust in 1998, 2000 and 2008, all have been met with more extreme monetary policy responses that, in turn, provided even easier funding for those using leverage. It has been a “carry trade” paradise thanks to artificially and extremely low interest rates and a weak dollar, at least, since 1985

Now, the probability is rising that era could be closing in to its end if, and that’s a big if, European sovereign bond yields continue to rise to more normal levels, as European bonds could come back on the shopping lists of the bond buyers.

If that would be the case, this could well be the first real sign of the bond bubble bursting.

Of course, we’ll have to wait and see.

One thing is for sure: “Nothing is forever.”