A closer look at new data on the weather across the U.S. in 2013 — and how that fits in with long-term global climate trends.
With fingers and toes still numb from record low temperatures across much (not all) of the U.S. in the month just ended, it may be a bit of a challenge to think back to where we were just over a year ago.
We then were remembering 2012 for its extraordinary weather extremes: record-setting heat, wildfires, punishing drought, a record number of billion-dollar-plus natural disasters, and of course the “superstorm” that swamped the Northeast, killing 125 people.
In contrast, the weather in 2013 across most of the U.S. seemed to many to be much calmer and milder, a perception supported by the National Oceanic and Atmospheric Administration’s newly released annual “State of the Climate” report.
But don’t get used to it, experts caution. Climate projections suggest that in the long run, we’ll be seeing more years like 2012 — or even more extreme — than like 2013. And a closer look at the 2013 data shows that even last year wasn’t all that calm or cool.
2013 A Cooler Year In U.S., but with Plenty Of Heat
What we saw in 2013
2013 was warmer than the 20th-century average, and it was the 37th-warmest year on record in the contiguous United States, according to the NOAA report.
Last year may have brought cool relief compared to 2012, but that’s the case in part because 2012 was the hottest year in the United States since record-keeping began.
And although it was a not-quite-so-hot year for the U.S., 2013 was among the 10 hottest years on record for the Earth as a whole, according to a pair of reports released by NOAA and NASA in January (see related story).
Over the long term, scientists say there is strong evidence that the globe as a whole will keep heating up. The Intergovernmental Panel on Climate Change, which provides scientific assessments of climate change, says continued rising global temperatures are “virtually certain.”
Scientists say the United States, too, will see a warm-up in coming decades. “U.S. temperatures will continue to rise, with the next few decades projected to see another 2 degrees F to 4 degrees F of warming in most areas,” wrote the authors of the 2013 draft National Climate Assessment.
More Record Colds Than Record Hots in U.S. in 2013
What we saw in 2013
Last year’s weather was notable in part because, for the first time in 20 years, the U.S. broke more cold weather records than hot ones. Specifically, there were 28,800 cool weather records broken or tied and 26,100 warm records broken or tied, according to the NOAA report.
Which is not to say that is the case across the whole globe: Australia in 2013 experienced its hottest year on record, with an average temperature more than 2 degrees F higher than the 1961-1990 average, NOAA reported.
Scientists predict that in the U.S. and across the globe, record-breaking high temperatures will resume, again outpacing the number of record-breaking low temperatures.
As Climate Central climate writer Andrew Freedman — soon headed to a new climate beat with mashable.com — has explained, in the past decade, record-breaking local heat records have been falling far more often than record colds. Ordinarily, one would expect cold records to occur about as frequently as hot records. But between 2000 and 2009, new hot records across the U.S. were about twice as common as cold records.
So does the fact that the U.S. set quite a few cold records in 2013 disprove the apparent warming trend?
Not to the scientists who spend their lives studying climate and weather issues. As Penn State University climate scientist and National Academy of Sciences member Richard Alley put it in a recent Yale Forum webinar, “Climate doesn’t make weather go away.”
“We’ve only warmed the world one degree so far, and one degree — sometimes a record is set by two or three, so it has not even totally made record lows go away,” he said. “We still have many more record highs than record lows, but they haven’t completely gone.”
2013 Rains in the U.S. for Me … But not for Thee
What we saw in 2013
In 2013, the U.S. wasn’t as hot as in recent years, but in many places across the country, it was unusually damp.
Average precipitation for the country as a whole exceeded the 20th-century average by two inches, according to NOAA. Michigan and North Dakota experienced record precipitation, and four states — New York, South Carolina, Georgia, and Florida — each had their wettest summers in history.
In contrast, some parts of the West were much drier than normal, continuing a persistent drought that remains a major concern today. For Oregon, 2013 goes down as the fourth-driest year, and for Idaho the 12th-driest. California, which received 15 inches less precipitation than average, had its driest year on record, and also its third-largest wildfire ever, NOAA reported. And the proverbial “Golden State’s” early start to the 2014 wildfire season is offering little comfort for those looking for a wetter near-term future.
Across the globe, some regions saw unusual drought or flooding. Botswana and Namibia had what NOAA calls “their worst droughts in 30 years.” But in northwest India, thousands of people died in floods after twice as much rain as normal fell during June.
It comes as no surprise to hear that warm air holds more moisture than cool air, and it’s part of the reason that scientists predict that as temperatures rise, periods of heavy rainfall will increase in some places.
As IPCC put it in 2007, “It is very likely that hot extremes, heat waves and heavy precipitation events will continue to become more frequent.”
Scientists also project that by the end of this century, it’s likely that droughts will grow longer or more intense in some areas around the globe.
“It is considered very likely that the southwestern United States will experience a net decrease in precipitation,” according to a 2011 report by the National Resource Council.
A Wintry Mix
What we saw in 2013
NOAA reports that the U.S. winter of 2012-2013 was warmer than average, mostly because December 2012 was unusually toasty.
Last winter, Americans got snow — a lot of it. According to satellite data, the snow cover extent for the season was 1.3 million square miles, the 15th-largest snow cover extent since record-keeping began in 1966.
But paradoxically, there wasn’t much snow left by spring in some places. NOAA reports that “many locations across the Sierra Nevada Mountains, Great Basin, and Southern Rockies had snow pack totals less than 50 percent of normal as of April 1st.”
As meteorologist Brett Anderson has noted, last winter’s large snow cover extent falls in line with recent trends. In fact, the Northern Hemisphere’s snow cover has been on the upswing in recent years — but only if you focus on the winter months.
In contrast, snow cover extents have been falling dramatically for summer months. You can see the difference in these charts from the Rutgers University Global Snow Lab.
“Temperatures in June are just getting too warm to support snow cover in some areas that were normally still covered with snow over the past 40 years,” Anderson explains on the AccuWeather Climate Change blog.
On this point, IPCC reported in 2013 that scientists suspect that spring snow cover extents will decrease by the end of this century.
So after 2012′s year of intense heat and drought and 2013′s cooler temperatures and extreme precipitation, what’s next? As changes to the climate system continue to unfold, it seems the only guarantee is that we’re in store for more wacky weather in 2014 — and beyond. It’s likely to keep the public interested, but sometimes confused…and meteorologists and climatologists plenty busy figuring it all out and explaining it to the public and their policymakers.