A warmer world evidently is also a wilder and weirder one.

That's a reasonable conclusion based on the utterly unreasonable behavior of the atmosphere in 2011, a year characterized by the improbable mixed with the unbelievable.

Philadelphia smashed precipitation records that will not easily be matched. Since Jan. 1, more than five feet of rain and melted snow and ice have fallen atop the official measuring station.

As early as the end of February, the region had had about twice its normal snowfall. The summer of 2011 was Philadelphia's hottest ever.

Nationally, the year has been almost unimaginably tragic and costly.

It has set a record for river flooding and tornadoes. A mega-tornado in Joplin, Mo., killed more than 140 and was the single deadliest tornado in 64 years.

The season moved Russ Schneider, the low-key director of the government's Severe Storm Center, in Norman, Okla., to declare it historic. And, he added, "we really don't throw around historic loosely."

In all, the National Weather Service blamed the atmosphere for more than 1,000 deaths. And for the first time, 12 separate billion-dollar disasters occurred, including the devastation wrought here and elsewhere by the remnants of Hurricane Irene.

The damage total for 2011 has topped $50 billion.

In short, Jeff Masters, meteorologist at the Weather Underground website, said of 2011: "It was extremely amazing."

What's going on?

Inarguably, the world has warmed substantially over the last three decades, be it from greenhouse gases or earlier starts to the presidential campaign season.

In a report this month, NASA scientists John Christy and Roy Spencer said that, based on satellite data, the Earth's temperature had risen about 0.8 of a degree Fahrenheit since 1979.

The increase in the Arctic region - 3-plus degrees - was more dramatic. At a level unprecedented in the period of observation, liberated Arctic waters have been interacting with the overlying atmosphere.

Masters and Rutgers University sea-ice expert Jennifer Francis are certain the interaction is affecting the global atmosphere.

It may have had something to do with creating a pattern in the North Atlantic Ocean that in the last two winters drove cold and snow into the Philadelphia region, which had a total accumulation of close to 10 feet of the white stuff.

A warmer world also appears to affect precipitation patterns. Intuitively, it would make sense that a warmer atmosphere would be capable of holding more water vapor.

Quantifying the effects of worldwide warming on day-to-day weather can be a maddening exercise, however. Climate specialists are quick to caution against attributing any one event to global warming.

In Asheville, N.C., the National Climatic Data Center is trying to keep score, publishing a monthly U.S. Climate Extremes Index, which takes into account temperature, precipitation, and drought anomalies.

Overall, it shows a general increase in extreme weather in the United States in the last two decades.

Wherever the course of climate events leads, if the atmosphere had a Hall of Fame, 2011 would be a first-ballot selection.

Contact staff writer Anthony R. Wood at 610-761-8423 or twood@phillynews.com.