Recent economic gains have been primarily illusory, driven by weather-related factors that are not sustainable, economist David Rosenberg told CNBC.

“Is it growing? How could it not be growing,” Rosenberg said. “We’ve got four years of trillion-dollar-plus deficits, we have a Fed balance sheet that’s tripled in size, zero policy rates for three years. Of course you’re going to get some growth.”

“If you want to take a big-picture perspective, this goes down as the weakest economic recovery ever, despite all the ramp up in government stimulus, and that really tells you something,” he said.

“Employment data were affected by the seasonal adjustments,” he said. “It felt like March in February, and if you apply the March seasonal factors to February, employment would have actually declined.”

“As you look at the US economy over the next two years, is the US economy going to improve more or less than other economies around the world?” said Richard Bernstein, head of Richard Bernstein Advisors and a former colleague of Rosenberg’s at Merrill Lynch. “We are in the early stages of a long-term period of US asset outperformance.”