After reviewing Alcoa's earnings released Monday, Jim Cramer came to the conclusion that the global economy is gaining momentum.

"I say the low interest rates at last might be working, and China and Europe might be joining the U.S. in some decent growth. That would be a gigantic, totally unexpected positive," the "Mad Money" host said.

Cramer always listens to Alcoa's conference call because it makes aluminum, which is influenced by several end markets around the world. He believes the call gives a better read on the economy than any brokerage house out there.

Alcoa painted a fantastic picture of the world in its second-quarter results, with CEO Klaus Kleinfeld confirming that aluminum has now become the go-to metal for automobiles, replacing steel. It is expected to grow at 20 percent annually until 2020.

Kleinfeld also affirmed strong auto production in Western Europe and China. China alone had a 5.2 percent increase in auto production year-over-year, an increase in sales by 9.3 percent, which included a 34 percent rise in crossover and SUV sales.

"Those are staggeringly good numbers, much better than anyone is talking about," Cramer said.

Cramer was even more impressed with the numbers for trucks, which are a sign of commercial activity. Western Europe had an 18.4 percent increase in truck registrations this year, and a 9.4 percent increase in production.

Chinese truck sales were up 25 percent year-over-year, with an increase of 14.1 percent in the past six months. Production is also up 25.8 percent for the year.

"That is eye-popping. I don't know a soul who is talking about that kind of growth," Cramer said.

Cramer monitors the Baltic Freight index as a gauge for Chinese growth. These numbers would explain why it has almost doubled in the past few months. They also explain why copper companies like Freeport-McMoRan and iron ore company Cliffs Natural Resources have been moving up.

The news surrounding aerospace was even better. While there is a lull in orders right now, Kleinfeld indicated that the lull should dissolve in the second half of 2016 and forecasted double-digit growth for 2017.

Oil and banks have also been showing signs of strength. Cramer noted that oil is no longer determining the direction of stocks.

Ever since the banks last reported, the price of oil has doubled. And every time oil nears $50, many oil companies sell crude in the futures market to raise cash.

This relieved many investor worries that oil companies won't be able to pay back the billions in dollars that banks have loaned to the oil patch.

"The fact is that Alcoa has started this earnings season mot with a whimper, but with a bang, and maybe that is what this big move in stocks is really signaling," Cramer said.

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