Top 10 of 2012

(Climate Central) - Tomorrow NOAA is expected to announce that 2012 marked the warmest year in the contiguous U.S. since record keeping began more than a century ago.

But record heat was just one hallmark of the year we wrapped up last week. From unprecedented heat waves, to Hurricane Sandy, to never-before-seen levels of Arctic melt, 2012 was an extreme year for climate-related events.

Many of these events served to highlight the growing role that global warming is playing in tipping the odds in favor of high-impact weather events.

Here is our list of the top 10 extreme weather and climate events of 2012. Our ranking system takes into account each event's severity, societal impact, unusualness (was it a relatively routine occurrence or something that stands alone in recorded history), and the potential ramifications the event suggests for the climate system as a whole.

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No. 1 - Superstorm Sandy

The storm was the most destructive to hit the U.S. since Hurricane Katrina in 2005, and one of the worst storms in recorded history to strike New York and New Jersey. The storm claimed the lives of at least 125 people and caused an estimated $100 billion in damage.

No. 2 - Tenacious Drought

The drought that gripped most of the central U.S. since spring dried up ecosystems, devastated the agriculture industry, and caught forecasters entirely by surprise. The drought's severity and long life are linked to the above-average temperatures that have persisted since March.

No. 3 - Hottest Year on Record

2012 was the hottest year on record in the continental U.S., and while the number is not official yet, it likely smashed the previous record set in 1998 by more than 1°F.

No. 4 - Steamy Arctic

Snow cover across the Northern Hemisphere dropped to the lowest level ever seen. Ninety-seven percent of Greenland's ice cap experienced at least some surface melting. A glacier in Greenland shed an iceberg twice the size of Manhattan. In August, the sea ice covering the Arctic Ocean melted more than it has since satellite observations began in 1970, and then kept melting through mid-September.

No. 5 - Wildfires

Wildfires burned nearly 9.2 million acres of forest, brushland, and grassland in the U.S. this year. That is the second largest area burned since the National Interagency Fire Center began keeping records in 2000.

No. 6 - Record March Heat

An unprecedented March heat wave saw temperatures soar as high as 40 degrees above average in some locations, and set more than 7,000 daily record high temperatures.

No. 7 - Sizzling July

July 2012 topped July 1936 for warmest month since U.S. records began in 1895. In total, 4,420 daily high temperature records and 3,672 record-warm overnight low temperatures were set or tied.

No. 8 - Hurricane Isaac

Hurricane Isaac, a Category 1 storm, moved at a snail's pace after striking the Gulf Coast, and brought flooding, high winds and rain to the region for two days after making landfall.

No. 9 - Derecho

On June 29, an unusually powerful thunderstorm born of a heat wave roared across 12 states in as many hours and knocked out power to more than four million Americans from Indiana to Maryland, and led to at least 24 deaths.

No. 10 - 334 Straight Months of Warmer Temperatures

December is expected to have been the 334th consecutive month with global average surface temperatures above the 20th century average. Put another way, the world has not had a cooler-than-average month since 1985.