Jeremy Littell

Warmer spring temperatures since 1980 have reduced snow cover throughout the Rocky Mountains of western North America, according to research from the U.S. Geological Survey.

By Denise Chow
LiveScience

Snow cover across the entire Rocky Mountain range has been shrinking due to warmer spring temperatures over the past 30 years, a new study finds.

Researchers at the U.S. Geological Survey (USGS) studied historic snowpack variations in the Rocky Mountains and found that warmer spring temperatures since 1980 are triggering an estimated 20 percent decline in snow cover throughout the range, which runs for more than 3,000 miles (4,800 kilometers) in western North America.

The scientists used monthly temperature and precipitation data from 1895 to 2011 to build models of snow cover in the Rocky Mountains. This enabled them to see long-term trends, including how fluctuations in winter temperatures, spring temperatures and precipitation are influencing the region's snowpack. [8 Ways Global Warming Is Already Changing the World]

"Each year, we looked at temperature and precipitation variations and the amount of water contained within the snowpacks as of April," Greg Pederson, an ecologist at the USGS Northern Rocky Mountain Science Center in Bozeman, Mont., and lead author of the new study, said in a statement.

Snow decline
After poring through the historical data, the researchers observed a shift beginning in 1980.

"Snow deficits were consistent throughout the Rockies due to the lack of precipitation during the cool seasons during the 1930s — coinciding with the Dust Bowl era," Pederson said. "From 1980 on, warmer spring temperatures melted snowpack throughout the Rockies early, regardless of winter precipitation. The model in turn shows temperature as the major driving factor in snowpack declines over the past 30 years."

While snowpack accumulation is known to be highly sensitive to fluctuations in temperature and precipitation, pinpointing the factors that trigger these changes remains challenging. This is because the region's climate is influenced by the complex mountain topography coupled with dynamic ocean-atmosphere phenomena, such as La Niña and El Niño, which affect precipitation differently in the northern, southern and central Rockies, and due to a lack of detailed snow records, the researchers said.

The meltwater that flows from the Rocky Mountain winter snowpack as it melts accounts for up to 80 percent of the annual water supply for more than 70 million people in the western United States, according to the researchers. This runoff is affected by the water content in the snowpack and the timing of the snowmelt, which has important implications for the region's water supply.

Water issues
Snowmelt that occurs faster and earlier in the year changes when water is available for irrigating crops and producing energy at hydroelectric dams, the researchers said. The timing of the snowmelt also affects the risk of floods and wildfires in the region, and the natural health of the water cycle in western watersheds.

The new study expands upon previous USGS research that found unusually rapid declines in the snowpack in the northern Rocky Mountains since the 1980s.

And while the extent to which either natural temperature variations or the man-made effects of global warming are contributing to this decline remains unclear, the potential repercussions need to be addressed, study co-author Julio Betancourt, also a USGS researcher, said in a statement.

"Both natural variability in temperature and anthropogenic warming have contributed to the recent snowpack decline, though disentangling their influences exactly remains elusive," Betancourt said. "Regardless of the ultimate causes, continuation of present snowpack trends in the Rocky Mountains will pose difficult challenges for watershed management and conventional water planning in the American West."

The study's findings were published online May 12 in the journal Geophysical Research Letters, a publication of the American Geophysical Union.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

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Public domain

President Obama's proposed 2014 budget promises to maintain or expand research funding in many areas.

By Tanya Lewis
LiveScience

The proposed 2014 budget released by the White House Wednesday brings good news for science: Under the budget, civilian research spending would swell by 9 percent from 2012 levels.

President Barack Obama's budget provides a total of $143 billion for research and development (R&D), which includes investments in energy, space exploration, basic research and STEM (science, technology, engineering and mathematics)education, cybersecurity and climate monitoring.

"The state of the R&D budget is quite strong," said John Holdren, assistant to the president for Science and Technology and director of the Office of Science and Technology Policy, during a briefing of the White House Office of Management and Budget (OMB) earlier Thursday.

Although the budget does include funding cuts, these are much more strategic than the sledgehammer approach of the sequester, the across-the-board cuts that took effect March 1. Here are five areas of research that will take center stage under the proposed budget.

1. Energy gets a turbo boost
The proposed 2014 budget provides $5 billion for the Department of Energy's Office of Science — a 5.7 percent increase over 2012 levels (all numbers refer to 2012 funding, because the complete appropriations bills for 2013 were not enacted when the budget was drafted).

The funding will go toward supporting clean energy and advanced manufacturing, promoting energy independence, dealing with climate change and modernizing nuclear weapons systems. [The 10 Best Alternative Energy Bets]

"No area holds more promise than our investments in American energy," Obama wrote in his budget message to Congress.

2. NASA heads for asteroids and Mars
Despite trying economic times, space exploration remains a priority for the president. NASA would receive $17.7 billion in discretionary funding under the proposed budget. Whereas the total funding is 0.3 percent, or about $50 million, less than 2012 amounts, it heals deep cuts to the agency under sequestration.

NASA Administrator Charles Bolden is optimistic. "The president's budget ensures that the United States will remain the world's leader in space exploration and scientific discovery for years to come while making critical advances in aeronautics to benefit the American public," Bolden said in the OMB briefing.

With this funding, NASA plans to renew its space exploration efforts, supporting crew transportation to the International Space Station as well as manned missions to an asteroid in 2025 and robotic and manned missions to Mars. Under the new budget, NASA is also on track to launch the James Webb Space Telescope, the successor to the Hubble Space Telescope, in 2018.

3. Push for STEM education and brain research
Basic research and education in STEM fields will see their funding continue at current levels or increase under the proposed budget.

The National Science Foundation (NSF), which funds basic research and education in all fields of science and engineering, would receive $7.6 billion, an 8 percent increase from 2012 levels. The National Institutes of Health (NIH), the world's largest supporter of biomedical research, would receive $31 billion in funding, an increase of 1.6 percent over 2012 levels.

Among other things, the funding will support research efforts in massive, complex datasets known as "big data," funding for STEM education (especially for minority students) and the new brain-mapping initiative announced by Obama last week. Visionaries of BRAIN, which stands for Brain Research through Advancing Innovative Neurotechnologies and was initially called the Brain Activity Map (BAM) project, outlined their final goals in the journal Science in March. They called for an extended effort to develop tools for monitoring up to a million neurons at a time. The end goal is to understand how brain networks function. [Inside the Brain: A Photo Journey Through Time]

4. Better cybersecurity
Given an increasing reliance on digital data and communication, it's not surprising that the new budget highlights cybersecurity.

The budget proposal calls for $830 million in funding for unclassified cybersecurity research across all networking and IT R&D groups, up $150 million from 2012.

"These increases reflect the high priority cybersecurity has in (the Obama) administration," Patricia Falcone, the associate director of National Security and International Affairs at the White House Office of Science and Technology Policy, said in Thursday's briefing.

These funds will support efforts to address current cybersecurity threats to the nation, businesses and individuals.

5. Weather and climate research heats up
The proposed federal budget would continue to support important efforts in climate monitoring and modeling.

The National Oceanic and Atmospheric Administration (NOAA) is requesting $5.4 billion, which would include a total R&D budget of $733 million — $160 million more than the 2012 allotment.

Extreme weather events such as Hurricane Sandy demonstrate a need for accurate weather tracking and forecasting, and NOAA funding would go toward supporting satellite systems designed to enable this work.

NOAA also plans to expand its climate research and ocean observation programs. Holdren said these efforts were good news, "because we do plan to continue to be well-informed stewards of planet Earth."

Follow Tanya Lewis on Twitter and Google+. Follow us @livescience, Facebook and Google+. Original article on LiveScience.com.

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Eric Kayne / Getty Images

In this file photo, construction worker Chester Gibson wipes sweat from his face on a hot day in Houston, Tex.

Hot and muggy weather over the past few decades has led to about a 10 percent drop in the physiological capacity of people to do their work safely and those drops will be even greater as the climate continues to warm, a new study finds.

People may continue to work in the hot and muggy conditions, "but their misery will increase while they are productive," John Dunne, a research oceanographer with the National Oceanic and Atmospheric Administration in Princeton, N.J., told NBC News.

Dunne is the lead author of the study, which addresses the impact of rising humidity associated with global warming on the capacity of people to safely do their jobs — from toiling in agricultural fields to crunching numbers at a desk.

The federal government maintains industrial and military guidelines that call for laborers to take breaks when conditions on a widely-used heat-stress index cross certain thresholds. 

"Black flag" conditions in military parlance, for example, correspond to a reading of greater than 90 degrees on the wet bulb global temperature index. Under those conditions, all non-mission critical physical training and strenuous exercise is suspended.

Dunne and colleagues combined historical analysis of the heat-stress index and model projections of future climate with the worker safety guidelines. 

They found that environmental heat stress has reduced worker capacity over the past few decades to 90 percent during the hottest months of the year and project a further reduction to 80 percent in peak months by 2050 and less than 40 percent by 2200.

The highest plausible warming scenario modeled will expose “mid-latitude regions such as the US east of the Rockies to environmental heat stress experienced only by the most extremely hot regions of the present day” such as parts of India, Dunne and colleagues write in a paper published today in Nature Climate Change. 

Dunne noted the findings come with several caveats. For example, uncertainty remains over how much the climate will warm in coming decades and how people will adapt their lifestyles to accommodate warmer conditions. It’s possible that agricultural work will shift to higher latitudes, for example, and afternoon siestas could be routine in mid-latitudes.

"The thing I like about this metric," noted Dunne, "is it is something that people have adapted their life to across the globe in the present day."

John Roach is a contributing writer for NBC News. To learn more about him, check out his website. 

NCAR

Bacteria living in storm clouds could seed the ice crystals that form rain, new research suggests.

By Tia Ghose, LiveScience

The storm clouds in Earth's atmosphere are filled with microbial life, according to a new study.

The research, published Jan. 23 in the journal PLoS One, revealed that hailstones drawn from storm clouds harbor several species of bacteria that tend to reside on plants, as well as thousands of organic compounds normally found in soil. Some of the bacterial species can seed the tiny ice crystals that lead to rain, suggesting they play a role in causing rain.

"Those storm clouds are quite violent phenomena," said study co-author Tina Santl Temkiv, an environmental chemist at Aarhus University in Denmark. "They are sucking huge amounts of air from under the clouds, and that's how the bacteria probably got into the cloud."

Living on a cloud
In the past, researchers have found bacterial life in clouds that drift over mountaintops. Bacteria have been found as far up as 24.8 miles and may even survive as spores into space, Temkiv said. [ Holey Clouds: Gallery of Formations Cut By Airplanes ]

Temkiv and her colleagues wanted to see if bacteria lived in the violent storm clouds that hover above the Earth's surface. To find out, they studied 42 hailstones that had formed in a thunderstorm over Ljubljana, Slovenia, in May 2009.

After carefully removing the outer layer and sterilizing the hailstone, they analyzed its chemical composition.

The team found thousands of organic, or carbon-containing, compounds — nearly as many as found in a typical river, Temkiv said. In addition, they found several species of bacteria that normally live on plants. Some of the bacteria make a pinkish pigment that allows them to withstand the punishing ultraviolet rays in the atmosphere.

Some of bacteria found are ice-nucleators, meaning they can act as seeds for ice crystals to attach to in the clouds above Earth. When these same ice crystals get large enough, they fall as rain or snow, depending on the air temperature.

The findings suggest that bacteria could influence weather patterns, possibly making rain, Temkiv said.

"They may be growing in clouds, increasing in number and then modifying the chemistry in the cloud but also in the atmosphere indirectly," she told LiveScience.

The researchers think the bacteria come from the air hovering just above Earth that gets swept into the storm clouds through updrafts. That would suggest the atmosphere is a thread that can connect distant ecosystems, and that certain bacteria may be better at colonizing faraway environments, Pierre Amato, a researcher at France's Blaise Pascal University who was not involved in the study, wrote in an email.

"Clouds can be thought of as transient ecosystems selecting for certain [types of bacteria] that are better fitted than others, and that can thus quickly disperse over the globe," Amato said. "Understanding how microbes disperse is relevant, of course, for epidemiology, and also for microbial ecology."

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NASA/Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center

Hurricane Felicia, seen as a Category 1 hurricane by NASA's Terra satellite on Aug. 8, 2009. The storm had weakened from its peak strength as a Category 4 storm.

By Charles Choi, contributor, OurAmazingPlanet

Hurricanes generate sound waves detectable through the air thousands of miles away, which could be a good way to measure the wave conditions near these storms, a new study suggests.

Such findings could help improve models to predict and prepare for dangerous storms, the scientists behind the study said.

Hurricanes can generate winds of more than 160 mph (250 kph), whipping up the sea surface to waves up to 70 feet (20 meters) high. When one such ocean wave slams into an equally tall wave traveling in the opposite direction, the collision results in low-frequency sound waves in the atmosphere that scientific instruments can hear thousands of miles away. These infrasound signals are known as microbaroms.

"Signals of ocean waves were first observed in seismic records in the early 1900s and were considered noise to their earthquake signals," said researcher Kwok Fai Cheung, an ocean engineer at the University of Hawaii at Manoa. "In the 1940s, articles were published in scientific journals tracing the signals recorded in the middle of North America to marine storms. This is reinforced by a paper published by Russian scientists in the 1990s that traced the origin of infrasound signals recorded in Siberia to the hurricanes in the Pacific."

As hurricanes move, past studies revealed, waves they generated earlier in time will interact with ones they generate later. This produces a strong microbarom signal in the storm's wake. Indeed, it is possible "to hear storms making waves halfway across the globe," said researcher Justin Stopa, an ocean engineer also at the University of Hawaii at Manoa.

Storms signals
In principle, listening to microbaroms can help researchers continuously monitor ocean wave activity and track marine storms. "The strongest infrasound signals come from the storm center, which is the most dangerous portion of the hurricane," Stopa told OurAmazingPlanet.

However, regular surface ocean behavior generates microbaroms as well, including ocean swell, surface waves and other kinds of storms. To see if they could tell the difference between microbaroms from different sources, researchers used an International Monitoring System infrasound sensor array in Hawaii to monitor signals generated during the passage of Hurricanes Neki and Felicia in 2009. Neki peaked as a Category 3 tropical cyclone with maximum sustained wind speeds of 120 mph (194 kph), while Felicia peaked as a Category 4 tropical cyclone with maximum sustained wind speeds of 129 mph (208 kph). (Tropical cyclone is the generic term for hurricanes, tropical storms and typhoons.)

Using modeled wind speed data, the investigators simulated wave conditions during the hurricanes. These estimates served as the basis of an acoustic model to calculate microbarom activity.

The research team's predictions matched the microbarom signals the Hawaii sensor array detected. In fact, the scientists note the microbaroms from the hurricanes drowned out the much weaker signals from other phenomena.

Understanding hurricane behavior
The researchers are now extending their study to storms across the globe with the aid of French colleagues and are also investigating whether they can analyze extratropical storms and large-scale weather patterns in addition to hurricanes. (Extratropical storms are powered by the temperatures differences across a frontal system, whereas tropical storms are fueled by convection and warm tropical waters.)

"This combination of observations and simulated data will enable better understanding of marine storms, including hurricane behavior and our climate," Stopa said. "This will enable better models that have the ability to predict and mitigate hazards harmful to humankind." [ In Photos: Notorious Retired Hurricane Names ]

The models need further refinement, however, the researchers noted.

"There is much more work that needs to be done before infrasound measurements can be used as a forecasting tool," Cheung told OurAmazingPlanet. The atmosphere is a difficult environment to model how sound travels due to rapidly changing conditions there, which affect the density of air and thus the speed of sound through it. These new findings "represent a first step of this long process," Cheung said.

Stopa, Cheung and their colleagues Milton Garcés and Nickles Badger detailed their findings in the December issue of the Journal of Geophysical Research-Oceans.

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NASA Goddard Institute for Space Studies

This map represents global temperature anomalies averaged from 2008 through 2012. NASA ranked 2012 as the ninth warmest on record in a new analysis released Tuesday.

By John Roach, NBC News

Government scientists said Tuesday that 2012 was among the top ten warmest on record globally and continues a trend of rising temperatures due to increasing emissions of the greenhouse gas carbon dioxide.

“The 'climate dice' are now sufficiently loaded,” James Hansen, director of NASA’s Goddard Institute for Space Studies, wrote in a note explaining the findings. 

Loaded dice mean that temperature extremes such as the heat and drought in the central Rockies and Great Plains in 2012; and Oklahoma, Texas and Northern Mexico in 2011 are becoming more common than they were several decades ago.

"The observant person who is willing to look at the past over several seasons and several years, should notice that the frequency of unusual warm anomalies has increased and the extreme anomalies," Hansen said in telephone conference with reporters. 

The average temperature in 2012 was about 58.3 degrees Fahrenheit (14.6 Celsius), which is 1.0 F (0.6 C) warmer than the mid-20th century baseline, NASA reported.

The average global temperature has risen about 1.4 degrees F (0.8 C) since 1880, according to the new analysis.

Ranking the warmth
NASA ranked 2012 as the ninth warmest since record keeping began in 1880. A separate analysis from NOAA said 2012 was the 10th warmest since that time and the warmest La Nina year on record. 

La Nina is the cold phase of El Nino phenomenon characterized by cooler than average temperatures in the eastern Pacific.

The difference between the two reports hinges on the different methods the agencies use to collect and interpret data. One biggie is that NASA extrapolates observational data into regions without meteorological stations, including the polar regions, whereas NOAA does not.

Some of the fastest warming is occurring in the Arctic, which hit a new low for summer sea ice extent in 2012. 

NASA noted that with the exception of 1998, which had an exceptionally strong el Nino and thus warm temperatures, the nine warmest years in its 132 year record have all occurred since 2000, with 2010 and 2005 ranking as the hottest on record. 

NOAA reported that 2012 marks the 36th consecutive year with a global temperature above the 20th century average. The last below average year was 1976.

Warming flatlines
The mean pace of warming over the past five years has been flat, Hansen noted, a phenomenon he explained as likely due to several recently strong la Nina years, which lead to a cooling in the tropical eastern Pacific Ocean, and the effect of aerosols, or airborne particles that reflect sunlight.

"We are very suspicious that global aerosols have increased," Hansen said. "We know from anecdotal evidence that China and some developing countries their air pollution has gotten worse."

What’s more, the sun’s irradiance has decreased over the last solar cycle, which has a slight effect on temperatures as well.

Nevertheless, Hansen noted, the long term trend is warming. 

"Each decade has been significantly warmer than the prior decade since the mid 1970s and that warming trend has been conclusively linked to the effect of increasing greenhouse gases, particularly carbon dioxide," he said.

Hot in the US
The new reports on global temperatures fall on the heels of a NOAA report released earlier this month that found 2012 was the warmest ever on record in the US and a draft assessment from the federal government that found global warming is already impacting American life. 

A new report from the Natural Resources Defense Council released Tuesday found that said 2012 saw 3,527 monthly weather records broken for heat, rain, and snow in the US.

"The evidence is undeniable: extreme weather events are pounding our communities and if we don't curb climate change, many will grow more severe," Frances Beinecke, the environmental group's president, wrote in a blog post about the new report.

The record warmth in the continental U.S. was offset by notably cooler than average temperatures in Alaska, far western Canada, central Asia, parts of the eastern and equatorial Pacific and parts of the Southern Ocean.

In addition to the warmth in the US, above average temperatures were felt in South America, most of Europe and Africa, and western, southern, and far northeastern Asia, the NOAA report said.

Temperatures this "past year, unlike the US temperature, were not a record globally, but they certainly were warm," Thomas Karl, director of NOAA’s National Climatic Data Center, said in the call with reporters. 

"In fact it marks a consistent above average global temperature. Every year has been above average since 1976." 

John Roach is a contributing writer for NBC News. To learn more about him, check out his website.

J. Zavaleta / NASA

This is a NASA Global Hawk being loaded with monitoring equipment for the ATTREX mission.

By Becky Oskin
Our Amazing Planet

Water may play a critical role in controlling the ozone gas high up in Earth's atmosphere that can act as a greenhouse gas or protect living things on the surface below from the sun's harmful ultraviolet rays, depending on where in the atmosphere it is found.

To better understand how water vapor and ozone interact, NASA plans to send a remote-controlled plane laden with monitoring equipment into the stratosphere — the layer of the atmosphere where protective ozone is found — above the tropics.

The drone will crisscross the tropopause, the boundary between the troposphere (the layer of the atmosphere we breathe and where most weather occurs), and the stratosphere. The boundary is a fluid layer whose thickness can change and depends on the latitude it is located over but that is generally found about 8 to 11 miles (5 to 7 kilometers) above Earth's surface.

In the middle reaches of the troposphere, ozone is a greenhouse gas, trapping heat and contributing to smog. But high in the troposphere and the stratosphere, the familiar ozone layer protects the planet from harmful UV radiation.

When storms punch water vapor through the tropopause, into the stratosphere, scientists suspect chemical reactions between water and free radicals such as chlorine may zap and destroy the protective ozone. The NASA experiment will sample this layer near the equator off the coast of Central America where tall thunderstorms often occur.

The flights, which start this month, are the first of a multiyear campaign to study how changes in water vapor in the stratosphere can affect global climate. The Airborne Tropical Tropopause Experiment (ATTREX) relies on a Global Hawk drone, which can cruise for 30 hours from its home at Edwards Air Force Base in California. The aircraft are also used by the U.S. Air Force and Navy.

Predictions of stratospheric humidity changes are uncertain because of gaps in the understanding of the physical processes occurring in the tropical tropopause layer, NASA said in a statement.

"The ATTREX payload will provide unprecedented measurements of the tropical tropopause," Eric Jensen, ATTREX principal investigator, said in a statement. "This is our first opportunity to sample the tropopause region during winter in the Northern Hemisphere when it is coldest and extremely dry air enters the stratosphere."

Reach Becky Oskin at boskin@techmedianetwork.com. Follow her on Twitter @beckyoskin. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

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By Tia Ghose
LiveScience

A 1,500-year drought in Australia may have led to the demise of an ancient aboriginal culture, a new study suggests.

The results, published Nov. 28 in the journal Geophysical Research Letters, show that geological traces of a mega-drought in the northwest Kimberley region of Western Australia coincide with a gap and transition in the region's rock art style. The finding suggests that the people who lived prior to the drought, called the Gwion, either left the region or dramatically altered their culture as a result of the drought, and a new culture called the Wanjinda eventually took its place.

"There is this significant gap in rock art. A possible reason for that is that the climate at that time changed so markedly that the artists who produced the Gwion art moved on from the Kimberley region," said study co-author Hamish McGowan, a climatologist at the University of Queensland in Australia.

But not everyone agrees with that interpretation. While the evidence for a drought is very convincing, archaeological sites show continuous occupation during that time, said Peter Veth, an archaeologist at the University of Western Australia who is an expert in the Kimberley's rock art and was not involved in the study.

"They reconfigure themselves on the land and often do portray things quite differently, but I don't see it as a different people," Veth told LiveScience.

Ancient inhabitants
Aboriginal cultures have inhabited Northwest Australia for the past roughly 45,000 years, McGowan said. But at least 17,000 years ago during the Pleistocene Era, a culture called the Gwion began depicting aspects of their life on the rocks in the region. The Gwion art depicted some extinct animals (such as a marsupial lion that went extinct during the last ice age) but also groups of slim figures in what look like ancient celebrations. [ Image Gallery: Europe's Oldest Rock Art ]

But between 5,000 and 7,000 years ago, traces of the Gwion rock art disappeared, and it wasn't until around 4,000 years ago when a new style of rock-art painting called the Wandjina, which depicts round faces with big eyes, emerged. It is still practiced today.

Pollen record
To understand why the rock art changed, McGowan and his colleagues analyzed sediments drilled from Black Springs, Australia. They found that around 6,300 years ago, the type of pollen started to change, suggesting a transition from a lush environment to one characterized by scrubby forests and open grasslands. The sediments also show an increase in dust, suggesting much drier conditions.

The results painted a picture of an ancient mega-drought that roughly coincided with the disappearance of Gwion art, McGowan said.

"The northwest of Australia can undergo very substantive natural changes in climate, which in the past have severely impacted aboriginal society," he told LiveScience, adding the climate change and disappearance of Gwion art suggest these people left the region.

But while it's likely that the drought radically altered the local societies, the rock art from the area isn't dated well enough to make conclusions about the complete disappearance of the culture, Veth said.

What's more, archaeological evidence suggests the area was continuously occupied, he told LiveScience. For instance, archaeologists find very similar stone tools throughout the drought, Veth said.

"They have identified a very interesting climate episode and it does seem to correlate with this switch — and that's the word I would use — a switch in the way people are portraying art," he said.

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If you found yourself bundling up in scarves, hats, and long underwear less than usual last year, you weren't alone: 2012 was the warmest year on record in the contiguous United States, according to scientists with The National Oceanic and Atmospheric Administration.

The average temperature for 2012 was 55.3 degrees Fahrenheit, 3.2 degrees above normal and a full degree higher than the previous warmest year recorded -- 1998 -- NOAA said in its report Tuesday. All 48 states in the contiguous U.S. had above-average annual temperatures last year, including 19 that broke annual records, from Connecticut through Utah.

“We’re taking quite a large step,” said Jake Crouch, a climate scientist from the NOAA National Climatic Data Center, which has recorded temperatures in the contiguous U.S. for the past 118 years.

It was also a historic year for "extreme" weather, scientists with the federal agency said. With 11 disasters that surpassed $1 billion in losses, including Superstorm Sandy, Hurricane Isaac, and tornadoes across the Great Plains, Texas, and the Southeast and Ohio Valley, NOAA said 2012 was second only to 1998 in the agency's "extreme" weather index.

A long-term warming trend for the U.S., combined with drought and a northerly jet stream, led to the record heat, explained Crouch. 

"During the winter season, the jet stream tended to stay further north of the U.S.-Canadian border, so that limited colder outbreaks in the country. It also limited precipitation. So that led to a warm and dry winter season, and that persisted through the spring," he said. 

Matt Rourke / AP file

People play in water from an open fire hydrant during the afternoon heat on July 18, 2012, in Philadelphia. July was the hottest month ever on record in the contiguous U.S.

"That warm and dry spring and winter laid the groundwork for the drought we had this summer... . When we have drought, it tends to drive daytime temperatures upward."

The unprecedented warm weather wasn't contained to the United States.

A corresponding rise in global temperatures prompted the World Meteorological Organization to call the rate at which the Arctic sea ice was melting "alarming" in its Nov. 28, 2012, report.

“The extent of Arctic sea ice reached a new record low. The alarming rate of its melt this year highlighted the far-reaching changes taking place on Earth’s oceans and biosphere. Climate change is taking place before our eyes and will continue to do so as a result of the concentrations of greenhouse gases in the atmosphere, which have risen constantly and again reached new records,” World Meteorological Organization Secretary-General Michel Jarraud said.

Each year since 2001 has been among the warmest on record worldwide, with 2012 likely to "be no exception despite the cooling influence of La Niña early in the year," the report added.

'Horrible' sea level rise of more than 3 feet plausible by 2100, experts say 

Watch NBC's special coverage of the 2012 drought 

'Wake-up call': Chicago set to break 73-year-old snowless record

NOAA expects to have global data for 2012 sometime in the coming weeks, but Crouch said scientists already know with certainty "it's going to be in the top ten" warmest years ever.

Adding to the extremes: 2012 was the driest year on record for the U.S., with 26.57 inches of average precipitation -- 2.57 inches below average. Those dry conditions created an ideal environment for wildfires in the West, which charred 9.2 million acres -- the third highest amount ever recorded, NOAA said Tuesday.

Other notable climate activity from 2012:

• Snowpack totals across the Central and Southern Rockies were less than half normal.
• July was the hottest month ever on record in the contiguous U.S.
• Tornado activity was concentrated toward the beginning of the season, with large outbreaks in March and April in the Ohio Valley and Central Plains, but the final 2012 tornado count will likely be less than 1,000 -- the least since 2002. "The factors behind that are kind of related to what was going on with the drought. We didn't have these large storm systems moving through the country, so that limited precipitation, and that also limited severe weather outbreaks," Crouch said. What made this year so high on the extreme weather index were cyclones, hurricanes, and the heat, he said.
• Alaska was cooler and slightly wetter than average, and had a record-cold January. "Their January temperatures were 14 degrees below average. Many locations in Alaska had temperatures 30 degrees below zero," Crouch said, adding that Anchorage, Alaska, set a new snow record.
• Hawaii experienced growing drought conditions, with 47.4 percent of the state experiencing moderate-to-exceptional drought at the beginning of 2012 and 63.3 percent at the end of the year. Alaska and Hawaii were not included in the bulk of NOAA's 2012 report because of terrain issues, and because scientists don't have records dating back as far as states in the contiguous U.S.

While NOAA made no meteorological forecasts for 2013, Crouch said the drought was going to continue to be an issue.

"The drought got a lot of attention this summer when it was having impacts on agriculture. More than 60 percent of the country is still in drought," he said. "And if things don't change, the drought is going to continue to be a big story in 2013."

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