This hadn’t been a bad tornado year until Monday. In fact, it had been remarkably quiet, with 274 tornadoes reported around the United States as of Monday, much lower than the average, which would be 491 through May 20.

It had been a welcome break from a string of years in which violent thunderstorms — spawning tornadoes, hail and powerful straight-line winds, and possibly ramped up by climate change — caused record amounts of insurance losses in addition to large losses of life.

In 2011, massive, long-track tornadoes struck Tuscaloosa, Ala., and Joplin, Mo., and insurance companies paid a highest-ever $26 billion in claims. The years 2008, 2009, 2010 and 2012 were also far above the norm in insured losses. In fact, the last five years are the five years in U.S. history with the highest insured losses from thunderstorms and their effects, said Robert Hartwig, president of the Insurance Information Institute, a trade association for the insurance industry.

“From our perspective, when we look at long-term trends, it does appear that the weather is getting worse,” Hartwig said.

Is that from anthropogenic global warming?

Hartwig said it’s not the job of his industry to answer that.

“We do see an increase in variability, volatility and the cost associated with natural disaster events, not only in the United States but around the globe,” he said. “It’s not for the insurance industry to determine whether climate change is the cause of any weather event. Insurers have a responsibility to measure this risk and assess this risk and be financially prepared and logistically prepared to respond. Whether it’s global warming, per se, that’s going to be left to the scientific community to ascertain.”

Hartwig said that insurance adjusters are only now getting to Moore, and it’s too soon to know how much damage the huge twister caused. But he said the 1999 tornado that hit Moore cost a billion dollars, and this could be comparable.

“It’s going to be hundreds of millions of dollars, no question. Could it surpass the billion-dollar threshold? Yes, it could. It’s not uncommon for these events to occur in this day and age.”

Peter Hoeppe, director of geophysical risks for Munich RE, the huge reinsurance company, said Monday’s tornado outbreak wasn’t terribly unusual in scale. What’s relatively uncommon, and expensive, he said, is when a violent tornado makes a direct strike on a densely populated area.

“That’s bad luck. It’s relatively rare because the states within the Tornado Alley are not densely populated,” Hoeppe said. “Tornadoes are not attracted by settlements, nor driven away by settlements. They make their track according to the atmospheric conditions.”

The key for tornado-prone communities is to ensure that people have a safe room, ideally an underground shelter, within easy reach, Hoeppe said. A typical house cannot be built to withstand the most powerful tornadoes, he said.

“If you have a tornado with a power of E4 or E5, there is no structure that can withstand them, at least not a structure that is economically sensible to build,” Hoeppe said.