“We’ve added, in the last eight years, $4 trillion of debt to the nation’s obligations.”

We know the public debt has grown dramatically during the past eight years.

Rahm Emanuel, Barack Obama’s White House chief of staff, pegged the increase at $4 trillion recently.

Emanuel appeared on Meet the Press the Sunday before Obama took office and was asked about Obama’s spending plans and whether he was concerned about adding even more to the national debt.

Emanuel began by pointing out that the national debt increased significantly during the Bush administration, then he defended the need for a stimulus bill to help the economy.

“Actually, there was a surplus at one time, and now we’ve added, in the last eight years, $4 trillion of debt to the nation’s obligations,” Emanuel said.

Emanuel was actually using two different ways of talking about the budget. We’ll explain.

The federal government creates a budget every year. When it spends more money than it takes in, it runs a deficit. When tax revenues run higher than expenses, that’s a budget surplus. At the end of the Clinton administration, there were several years of budget surpluses.

But those surpluses were not enough to compensate for the previous deficit years. So the government still carried what’s called the national debt.

(For more detail on these concepts, check out this “Frequently Asked Questions about the Public Debt” Web page put together by the Treasury Department.)

Here, we wanted to look at Emanuel’s claim that during the past eight years we’ve added $4 trillion to the national debt. Is it that much?

Turns out, it’s even more than that.

Emanuel didn’t mention the Bush administration specifically, but that’s what most people think of when they think of the last eight years. So we decided to check the national debt from when Bush took office to when he left.

When Bush took office, the national debt was $5.73 trillion. When he left, it was $10.7 trillion. That’s a difference of $4.97 trillion, almost $1 trillion more than what Emanuel said.

But the debt has shot up significantly during the past few months, mostly due to the economic meltdown of 2008 and the government’s efforts to shore up the federal banking system.

As recently as Sept. 18, 2008, Emanuel would have been correct with the $4 trillion number.

You can check out all these numbers for yourself via the Treasury Department’s debt history search application .

So what does the Truth-O-Meter say when someone is off by $1 trillion? As we’ve said with our policy on statistical claims , “to assess the truth for a numbers claim, the biggest factor is the underlying message.” So even though he is off by about 20 percent, the fact that the number has been surging lately supports his point that the debt increased greatly under Bush. So we rate his statement Mostly True.