If you look at the images of destruction from Colorado, it's not hard to see why officials have called the Waldo Canyon Fire the most destructive in state history. Last week, it was like a monster roaring down a mountainside, swallowing houses whole.

And that's not even the biggest blaze at the moment. A fire in Montana's Custer National Forest is raging over 186,800 acres.

As many as 13 new large fires were reported Sunday, the National Interagency Fire Center said. In all, 14 states, mostly in the West, are dealing with active fires.

Does it seem like wildfires in the United States are getting bigger and badder?

It's a question fire expert Max Moritz has been hearing a lot lately.

That's because the University of California, Berkeley professor published a report on global fire risks on June 12, just before the massive fires in Colorado ignited.

"In the long run, we found what most fear -- increasing fire activity across large parts of the planet," he said.

Moritz's study concluded that some areas of the world, including the western United States, "should brace themselves for more fire."

Nationally, wildfires have scorched about 2.2 million acres this year. That's less than half the number in July of last year.

But the gap has been closing rapidly over the last few days, said Ken Frederick, spokesman for the National Interagency Fire Center. He said the United States was on pace to match or go beyond last year's acreage.