The US dollar and oil prices are breaking from their historical trade link. An economist explains why this signals a 'double whammy' for global markets.

Historically, a strong US dollar puts downward pressure on oil prices as contracts for the commodity are priced in the US currency. That hasn't happened recently.

As the Federal Reserve winds down the easy money era and tightens policy, the dollar has strengthened to a 20-year high against the world's other major currencies.

As Russian supplies disappear from the market, global stockpiles shrink, and demand ramps up, the price of crude has gone up by over $60 per barrel.

It's a double blow for everyone outside the US, according to an economist at Boston College. The rising dollar and rising oil prices have other countries paying more for crude. The US is dealing with the price increases.

The dollar had plummeted to a record-low against major US trading partners as the Fed was cutting interest rates during the financial crisis. The dollar's weakness helped cushion the price of oil in other countries.

The dollar's strength makes crude barrels more expensive in local currency. The price of a barrel of oil is equivalent to $150, according to analysts at Goldman.

The premium over 2008 levels is even more steep in some currencies. The price of oil in the Indian rupee is more than the price in the South African rand.

Saudi Arabia entered talks with China to price an oil deal using the Chinese currency. A deal in a currency other than dollars between the world's top oil exporter and the world's biggest oil importer would mark a dramatic shift away from the past.

The strength of the dollar in the US is less important than it is in other countries. Other countries are paying more for crude because their currencies are not strong enough.

Tomic said that the dollar's strength made it more difficult for people outside the US. We won't see relief on it quickly.