Image via NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Last year, to celebrate the 42nd Earth Day, we took a look at 10 of the most surprising, disheartening, and exciting things we’d learned about our home planet in the previous year—a list that included discoveries about the role pesticides play in bee colony collapses, the various environmental stresses faced by the world’s oceans and the millions of unknown species are still out in the environment, waiting to be found.

This year, in time for Earth Day on Monday, we’ve done it again, putting together another list of 10 notable discoveries made by scientists since Earth Day 2012—a list that ranges from specific topics (a species of plant, a group of catfish) to broad (the core of planet Earth), and from the alarming (the consequences of climate change) to the awe-inspiring (Earth’s place in the universe).

Even the supposedly pristine Antarctic landscape is marred by trash heaps. Image via Germany Federal Environment Agency Report (PDF)

1. Trash is accumulating everywhere, even in Antarctica. As we’ve explored the most remote stretches of the planet, we’ve consistently left behind a trail of one supply in particular: garbage. Even in Antarctica, a February study found (PDF), abandoned field huts and piles of trash are mounting. Meanwhile, in the fall, a new research expedition went to study the Great Pacific Garbage Patch, counting nearly 70,000 pieces of garbage over the course of a month at sea.

2. Climate change could erode the ozone layer. Until recently, atmospheric scientists viewed climate change and the disintegration of the ozone layer as entirely distinct problems. Then, in July, Harvard researcher Jim Anderson (who won a Smithsonian Ingenuity Award for his work) led a team that published the troubling finding that the two might be linked. Some warm summer storms, they discovered, can pull moisture up into the stratosphere, an atmospheric layer 6 miles up. Through a chain of chemical reactions, this moisture can lead to the disintegration of ozone, which is crucial for protecting us from ultraviolet (UV) radiation. Climate change, unfortunately,  is projected to cause more of these sorts of storms.

3. This flower lives on exactly two cliffs in Spain. In September, Spanish scientists told us about one of the most astounding survival stories in the plant kingdom: Borderea chouardii, an extremely rare flowering plant that is found on only two adjacent cliffs in the Pyrenees. The species is believed to be a relic of the Tertiary Period, which ended more than 2 million years ago, and relies on several different local ant species to spread pollen between its two local populations.

4. Some catfish have learned to kill pigeons. In December, a group of French scientists revealed a phenomenon they’d carefully been observing over the previous year: a group of catfish in Southwestern France had learned how to leap onto shore, briefly strand themselves, and swim back into the water to consume their prey. With more than 2,000,000 Youtube views so far, this is clearly one of the year’s most widely enjoyed scientific discoveries.

5. Fracking for natural gas can trigger moderate earthquakes. Scientists have known for a while that whenever oil and gas are extracted from the ground at a large scale, seismic activity can be induced. Over the past few years, evidence has mounted that injecting water, sand and chemicals into bedrock to cause gas and oil to flow upward—a practice commonly known as fracking—can cause earthquakes by lubricating pre-existing faults in the ground. Initially, scientists found correlations between fracking sites and the number of small earthquakes in particular areas. Then, in March, other researchers found evidence that a medium-sized 2011 earthquake in Oklahoma(which registered a 5.7 on the moment magnitude scale) was likely caused by injecting wastewater into wells to extract oil.

6. Our planet’s inner core is more complicated than we thought. Despite decades of research, new data on the iron and nickel ball 3,100 miles beneath our feet continue to upset our assumptions about just how the earth’s core operates. A paper published last May showed that iron in the outer parts of the inner core is losing heat much more quickly than previously estimated, suggesting that it might hold more radioactive energy than we’d assumed, or that novel and unknown chemical interactions are occurring. Ideas for directly probing the core are widely regarded as pipe dreams, so our only options remains studying it from afar, largely by monitoring seismic waves.

The berries of Pollia condensata were found to produce the most intense color in the natural world. Image via PNAS

7. The world’s most intense natural color comes from an African fruit. When a team of researchers looked closely at the blue berries of Pollia condensata, a wild plant that grows in East Africa, they found something unexpected: it uses an uncommon structural coloration method to produce the most intense natural color ever measured. Instead of pigments, the fruit’s brilliant blue results from nanoscale-size cellulose strands layered in twisting shapes, which which interact with each other to scatter light in all directions.

8. Climate change will let ships cruise across the North Pole. Climate change is sure to create countless problems for many people around the world, but one specific group is likely to see a significant benefit from it: international shipping companies. A study published last month found that rising temperatures make it probable that during summertime, reinforced ice-breaking ships will be able to sail directly across the North Pole—an area currently covered by up to 65 feet of ice—by the year 2040. This dramatic shift will shorten shipping routes from North America and Europe to Asia.

9. One bacteria species conducts electricity. In October, a group of Danish researchers revealed that the seafloor mud of Aarhus’ harbor was coursing with electricity due to an unlikely source: mutlicellular bacteria that behave like tiny electrical cables. The organisms, the team found, built structures that traveled several centimeters down into the sediment and conduct measurable levels of electricity. The researchers speculate that this seemingly strange behavior is a byproduct of the way of the bacteria harvests energy from the nutrients buried in the soil.

Kepler 62f, discovered yesterday, is the most promising exoplanet candidate yet in terms of its potential to harbor life. Image via NASA/Ames/JPL-Caltech

10. Our Earth isn’t alone. Okay, this one might not technically be a discovery about Earth, but over the past year we have learned a tremendous amount about what our Earth isn’t: the only habitable planet in the visible universe. The pace of exoplanet detection has accelerated rapidly, with a total of 866 planets in other solar systems discovered so far. As our methods have become more refined, we’ve been able to detect smaller and smaller planets, and just yesterday, scientists finally discovered a pair of distant planets in the habitable zone of their stars that are relatively close in size to Earth, making it more likely than ever that we might have spied an alien planet that actually supports life.

New research finds that the superstorm’s massive ocean waves produced seismic activity as far away as Seattle. Image via NASA

If you weren’t on the East Coast during Hurricane Sandy, you likely experienced the disaster through electronic means: TV, radio, the internet or phone calls. As people across the country tracked the storm by listening to information broadcast through electromagnetic waves, a different kind of wave, produced by the storm itself, was traveling beneath their feet.

Keith Koper and Oner Sufri, a pair of geologists at the University of Utah, recently determined that the crashing of massive waves against Long Island, New York and New Jersey—as well as waves hitting each other offshore—generated measurable seismic waves across much of the U.S., as far away as Seattle. As Sufri will explain in presenting the team’s preliminary findings today during the Seismological Society of America‘s annual meeting, they analyzed data from a nationwide network of seismometers to track microseisms, faint tremors that spread through the earth as a result of the storm waves’ force.

The team constructed a video (below) of the readings coming from 428 seismometers over the course of a few days before and after the storm hit. Initially, as it traveled up roughly parallel to the East Coast , readings remained relatively stable. Then, “as the storm turned west-northwest,” Sufri said in a press statement, “the seismometers lit up.” Skip to about 40 seconds into the video to see the most dramatic seismic shift as the storm hooks toward shore:

The microseisms shown in the video differ from the waves generated by earthquakes. The latter arrive suddenly, in distinct waves, while the microseisms that resulted from Sandy arrived continuously over time, more like a subtle background vibration. That makes converting these waves to the moment magnitude scale used to measure earthquakes somewhat complicated, but Koper says that if the energy from these microseisms was compressed into a single wave, it would register as a 2 or 3 on the scale, comparable to a minor earthquake that can be felt by a few people but causes no damage to buildings.

The seismic activity peaked when Sandy changed direction, the researchers say, triggering a sudden increase in the number of waves running into each other offshore. These created massive standing waves, which sent significant amounts of pressure into the seafloor bottom, shaking the ground.

It’s not uncommon for events other than earthquakes to generate seismic waves—Hurricane Katrina produced shaking that was felt in California, landslides are known to have distinct seismic signatures and the meteor that crashed in Russia in February produced waves as well. One of the reasons the readings from Sandy scientifically interesting, though, is the potential that this type of analysis could someday be used to track a storm in real-time, as a supplement to satellite data.

That possibility is enabled by the fact that a seismometer detects seismic motion in three directions: vertical (up-and-down shaking) as well as North-South and East-West movement. So, for example, if most of the shaking detected by a seismometer in one location is oriented North-South, it indicates that the source of the seismic energy (in this case, a storm) is located either North or South of the device, rather than East or West.

A nationwide network of seismometers—such as Earthscope, the system that was used for this research and is currently still being expanded—could eventually provide the capacity to pinpoint the center of a storm. “If you have enough seismometers, you can get enough data to get arrows to point at the source,” Koper said.

Satellites, of course, can already locate a hurricane’s eye and limbs. But locating the energetic center of the storm and combining it with satellite observations of the storm’s extent could eventually enable scientists to measure the energy being released by a hurricane in real-time, as the storm evolves. Currently, the Saffir-Simpson scale is used to quantify hurricanes, but there are several criticisms of it—it’s solely based on wind speed, so it overlooks the overall size of a storm and the amount of precipitation in produces. Including the raw seismic energy released by a storm could be a way of improving future hurricane classification schemes.

The prospect of seismometers (instruments typically used to detect earthquakes) being employed to supplement satellites in tracking storms is also interesting because of a recent trend in the exact opposite direction. Last month, a satellite data was used for the first time to detect an earthquake by picking up extremely low pitched sound waves that traveled from the epicenter through outer space. The fields of meteorology and geology, it seems, are quickly coming together, reflecting the real-world interaction between the Earth and the atmosphere that surrounds it.

Humid air causes hydrogen bonds to form between the proteins in your hair, triggering curls and frizz. Image via Flickr user Simon Gotz

If you have long hair, you probably don’t need to look up a weather report to get an idea of how much humidity’s in the air: You can simply grab a fistful of hair and see how it feels. Human hair is extremely sensitive to humidity—so much that some hygrometers (devices that indicate humidity) use a hair as the measuring mechanism, because it changes in length based on the amount of moisture in the air.

Straight hair goes wavy. If you have curly hair, humidity turns it frizzy or even curlier. Taming the frizz has become a mega industry, with different hair smoothing serums promising to “transform” and nourish hair “without weighing hair down.” But just why does humidity have this strange effect on human hair?

Bundles of keratin proteins (the middle layer of black dots above) are susceptible to changing shape on a humid day. Image from Gray’s Anatomy

Hair’s chemical structure, it turns out, makes it unusually susceptible to changes in the amount of hydrogen present in the air, which is directly linked to humidity. Most of a hair’s bulk is made up of bundles of long keratin proteins, represented as the middle layer of black dots tightly packed together in the cross-section at right.

These keratin proteins can be chemically bonded together in two different ways. Molecules on neighboring keratin strands can form a disulfide bond, in which two sulfur atoms are covalently bonded together. This type of bond is permanent—it’s responsible for the hair’s strength—and isn’t affected by the level of humidity in the air.

But the other type of connection that can form between adjacent keratin proteins, a hydrogen bond, is much weaker and temporary, with hydrogen bonds breaking and new ones forming each time your hair gets wet and dries again. (This is the reason why, if your hair dries in one shape, it tends to remain in roughly that same shape over time.)

Hydrogen bonds occur when molecules on neighboring keratin strands each form a weak attraction with the same water molecule, thereby indirectly bonding the two keratin proteins together. Because humid air has much higher numbers of water molecules than dry air, a given strand of hair can form much higher numbers of hydrogen bonds on a humid day. When many such bonds are formed between the keratin proteins in a strand of hair, it causes the hair to fold back on itself at the molecular level at a greater rate.

On the macro level, this means that naturally curly hair as a whole becomes curlier or frizzier due to humidity. As an analogy, imagine the metal coil of a spring. If you straighten and dry your hair, it’ll be like the metal spring, completely straightened out into a rod. But if it’s a humid day, and your hair is prone to curling, water molecules will steadily be absorbed and incorporated into hydrogen bonds, inevitably pulling the metal rod back into a coiled shape.

A mixture of plant oils, bacterial spores and ozone is responsible for the powerful scent of fresh rain. Image via Wikimedia Commons/Juni

Step outside after the first storm after a dry spell and it invariably hits you: the sweet, fresh, powerfully evocative smell of fresh rain.

If you’ve ever noticed this mysterious scent and wondered what’s responsible for it, you’re not alone.

Back in 1964, a pair of Australian scientists (Isabel Joy Bear and R. G. Thomas) began the scientific study of rain’s aroma in earnest with an article in Nature titled “Nature of Agrillaceous Odor.” In it, they coined the term petrichor to help explain the phenomenon, combining a pair of Greek roots: petra (stone) and ichor (the blood of gods in ancient myth).

In that study and subsequent research, they determined that one of the main causes of this distinctive smell is a blend of oils secreted by some plants during arid periods. When a rainstorm comes after a drought, compounds from the oils—which accumulate over time in dry rocks and soil—are mixed and released into the air. The duo also observed that the oils inhibit seed germination, and speculated that plants produce them to limit competition for scarce water supplies during dry times.

These airborne oils combine with other compounds to produce the smell. In moist, forested areas in particular, a common substance is geosmin, a chemical produced by a soil-dwelling bacteria known as actinomycetes. The bacteria secrete the compound when they produce spores, then the force of rain landing on the ground sends these spores up into the air, and the moist air conveys the chemical into our noses.

“It’s a very pleasant aroma, sort of a musky smell,” soil specialist Bill Ypsilantis told NPR during an interview on the topic. “You’ll also smell that when you are in your garden and you’re turning over your soil.”

Because these bacteria thrive in wet conditions and produce spores during dry spells, the smell of geosmin is often most pronounced when it rains for the first time in a while, because the largest supply of spores has collected in the soil. Studies have revealed that the human nose is extremely sensitive to geosmin in particular—some people can detect it at concentrations as low as 5 parts per trillion. (Coincidentally, it’s also responsible for the distinctively earthy taste in beets.)

Ozone—O_3, the molecule made up of three oxygen atoms bonded together—also plays a role in the smell, especially after thunderstorms. A lightning bolt’s electrical charge can split oxygen and nitrogen molecules in the atmosphere, and they often recombine into nitric oxide (NO), which then interacts with other chemicals in the atmosphere to produce ozone. Sometimes, you can even smell ozone in the air (it has a sharp scent reminiscent of chlorine) before a storm arrives because it can be carried over long distances from high altitudes.

But apart from the specific chemicals responsible, there’s also the deeper question of why we find the smell of rain pleasant in the first place. Some scientists have speculated that it’s a product of evolution.

Anthropologist Diana Young of the University of Queensland in Australia, for example, who studied the culture of Western Australia’s Pitjantjatjara people, has observed that they associate the smell of rain with the color green, hinting at the deep-seated link between a season’s first rain and the expectation of growth and associated game animals, both crucial for their diet. She calls this “cultural synesthesia”—the blending of different sensory experiences on a society-wide scale due to evolutionary history.

It’s not a major leap to imagine how other cultures might similarly have positive associations of rain embedded in their collective consciousness—humans around the world, after all, require either plants or animals to eat, and both are more plentiful in rainy times than during drought. If this hypothesis is correct, then the next time you relish the scent of fresh rain, think of it as a cultural imprint, derived from your ancestors.

Scientists have identified a link between global warming and extreme weather events such as heat waves. Photo by Flickr user perfectsnap

During the month of July 2011, the United States was seized by a heat wave so severe that roughly 9,000 temperature records were set, 64 people were killed and a total of 200 million Americans were left very sweaty. Temperatures hit 117 degrees Fahrenheit in Shamrock, Texas, and residents of Dallas spent 34 consecutive days stewing in 100-plus-degree weather.

For the past couple of years, we’ve heard that extreme weather like this is tied to climate change, but until now, scientists weren’t sure exactly how the two were related. A new study published yesterday in the journal Proceedings of the National Academy of Sciences reveals the mechanism behind events such as the 2011 heat wave.

What it comes down to, according to scientists at Potsdam Institute for Climate Impact Research (PIK), is that higher temperatures caused by global warming are disrupting the flow of planetary waves that oscillate between Arctic and tropical regions, redistributing the warm and cold air that usually help regulate the Earth’s climate. “When they swing up, these waves suck warm air from the tropics to Europe, Russia, or the US, and when they swing down, they do the same thing with cold air from the Arctic,” lead author Vladimir Petoukhov of PIK explained in a statement.

Under pre-global-warming conditions, the waves might have initiated a short, two-day burst of warm air followed by a rush of cooler air in Northern Europe, for example. But these days, with global temperatures having climbed 1.5 degrees Fahrenheit in the past century and escalating particularly sharply since the 1970s, the waves increasingly stall out, resulting in 20- to 30-day heat waves. 

The way it occurs is this: The greater the temperature difference between regions like the Arctic and Northern Europe, the more air circulates between the areas–warm air rises over Europe, cools over the Arctic, and rushes back down to Europe, keeping it chilly. But with global warming heating up the Arctic, the temperature gap between the regions is closing, stanching the flow of air. In addition, land masses warm and cool more easily than oceans. ”These two factors are crucial for the mechanism we detected,” Petoukhov said. “They result in an unnatural pattern of the mid-latitude air flow, so that for extended periods the… waves get trapped.”

The scientists developed models of this phenomenon and then entered daily weather data for the middle latitudes of the Northern Hemisphere during the summers from 1980 to 2012. They found that during several major heat waves and episodes of prolonged rain–which led to floods–the planetary waves had indeed been trapped and amplified.

Researchers examined the July 2011 heat wave in the U.S. for new clues on global warming and extreme weather. (Reds represent above-average temperatures and blues are lower-than-average temps.) Image via NASA Earth Observatory

“Our dynamical analysis helps to explain the increasing number of novel weather extremes,” said Hans Joachim Schellnhuber, director of PIK and co-author of the study. “It complements previous research that already linked such phenomena to climate change, but did not yet identify a mechanism behind it.”

The research joins another recent study (PDF) by scientists at Harvard that highlights how changes to air circulation patterns are spreading drought. As warm tropical air rises, it triggers rains before migrating to higher latitudes. The dry air then descends, heats up and eventually travels again, landing in regions characterized by desert. These dry regions used to be confined to narrow bands spanning the globe. But now, these bands are expanding by several degrees in latitude.

“That’s a big deal, because if you shift where deserts are by just a few degrees, you’re talking about moving the southwestern desert into the grain-producing region of the country, or moving the Sahara into southern Europe,” study author Michael McElroy said in a statement. In this way, climate change threatens national security because drought, heat and other extreme weather events can jeopardize food stocks, destroy roads and bridges, and ultimately lead to political instability, the authors note.

The connection between climate change and extreme weather will be highlighted this summer, if current trends continue. The summer of 2012 was even hotter in the U.S. than that of 2011, and according to the PIK scientists, it was also marked by prolonged, amplified waves in the mid-latitudes of the Northern Hemisphere.

Unfortunately, the frequency of these atmospheric patterns is only expected to increase. When the researchers compared the period from 1980 to 1990 with that from 2002 to 2012, they saw that the incidence of trapped waves had doubled. Bottom line: Heat waves are not only here to stay, they’ll become more frequent and will linger for longer.

Dust lofted up from the Sahara can be blown across the Pacific and seed clouds over California. NASA image courtesy MODIS Rapid Response Team, Goddard Space Flight Center

The fascinating idea that a butterfly flapping its wings in Asia can change the path of a hurricane over the Pacific is, alas, probably not accurate. But slight changes in one part of the atmosphere can indeed have disproportionate effects elsewhere, a concept known as the butterfly effect.

Just how slight one of these factors can be—and how incredibly far away their effects can reach—is vividly illustrated by a new finding by an international team of atmospheric scientists and chemists from the U.S. and Israel. As they document in a study published today in Science, dust blown from as far away as the Sahara desert of Africa can seed rain and snow clouds in the Sierra Nevada mountains of California.

The research team, led by Kimberly Prather of the University of California, San Diego, came to the finding after using aircraft to collect atmospheric data over the Sierra Nevada mountains, as well as analyzing precipitation that fell at the Sugar Pine Dam in Northern California. They also retroactively tracked storm masses backward across the Pacific and Asia to pinpoint the origin of the dust they found in the clouds.

Cloud formation depends upon tiny particles such as dust that serve as cloud condensation nuclei or ice nuclei—flecks that act as a surface on which water can condense. Previous studies have found that dust from as far away as the Taklimakan desert in China can be blown around the globe. But temperate deserts such as the Taklimakan and the Gobi are frozen much of the year, while the Sahara never freezes, the researchers noted. Could the Sahara and deserts in the Middle East serve as a significant source of year-round dust which, when lofted high into the atmosphere, seeded storms across the planet?

The answer is yes. Of the six storms the researchers sampled, all showed at least some trace of dust. Then, working backward to determine the origin of each of these air masses and using existing data from previous studies on wind currents across the Pacific, they found strong evidence that the majority of the dust had originated in Africa, the Middle East or Asia and traveled around the globe. Additionally, the observed height of various drafts of dust (as collected by a U.S. Navy program) on the days when the air masses would have moved past the African and Asian regions matched the altitude necessary for the particles to get lifted up into the air currents.

The dust particles carried across the Pacific from Africa, the Middle East and China are laregly responsible for cloud formation in the Western U.S. Image via Science/Creamean et. al.

Satellite analysis of the storm masses as they moved across the Pacific also confirmed that they carried dust all the way. As shown in the map above, most came from Northeast China or the Taklimakan, but a sizable amount came from as far as the Middle East or even the Sahara.

Although the butterfly’s role in all this seems to be nonexistent, the study did find that one type of living creature does play a part in cloud formation: bacteria. In recent years, scientists have discovered that bacteria, along with dust, can be lofted up high in the atmosphere and serve as nuclei for cloud formation.  In this study, the researchers found that small amounts of bacteria were mixed in with the dust, and likely originated in Asia and Africa as well.

So if you live on the West Coast, the next time you get caught in a rainstorm think of this: Each drop that hits you might contain dust and bacteria that’s traveled halfway around the planet. A close look at something as mundane as our daily weather, it turns out, can open a new window to the complex interconnectedness of our world.

High temperatures and high levels of humidity reduce the human body’s ability to do work. Image via Flickr user zoonabar

If you feel sluggish and have difficulty getting physical work done on very hot, humid days, it’s not your imagination. Our bodies are equipped with an adaptation to handle high temperatures—perspiration—but sweating becomes ineffective at cooling us down when the air around us is extremely humid.

Add in the fact that climate change is projected to increase the average humidity of Earth as well as its temperature, and you could have a recipe for a rather unexpected consequence of greenhouse gas emissions: a reduced overall ability to get work done. According to a study published yesterday in Nature Climate Change, increased heat and humidity has already reduced our species’ work capacity by 10% in the warmest months, and that figure could rise to 20% by 2050 and 60% by the year 2200, given current projections.

The Princeton research team behind the study, led by John Dunne, came to the finding by combining the latest data on global temperature and humidity over the past few decades with American military and industrial guidelines for how much work a person can safely do under environmental heat stress. For their projections, they used two sets of climate regimes: a pessimistic scenario, in which greenhouse gas emissions rise unchecked through 2200, and an optimistic one, in which they begin to stabilize after 2060.

The team also considered a range of possible activities we might consider work: heavy labor (such as heavy lifting or digging) that burns 350-500 Calories per hour, moderate labor (such as continuous walking) that burns 200-350 Calories per hour and light labor (such as standing in place) that burns less than 200. For each of these levels of activity, there is a cut-off point of temperature and humidity past which the human body cannot safely work at full capacity.

Much of the reduced work capacity, the researchers say, will occur in tropical latitudes. In the map from the study below, shaded areas correspond to places where, over the course of a year, there are more than 30 days during which heat and humidity stresses reduce work capacity. Purple and blue cover areas for which this is only true for mostly heavy labor, while green and yellow indicate regions where even moderate labor is impacted:

Image via Nature Climate Change/Dunne et. al.

Under the pessimistic emissions scenario, in 2100, the area of the globe for which humidity curtails work will expand dramatically, covering much of the U.S., and reducing total human work capacity by 37% overall worldwide during the hottest months. Red covers areas for which capacity for even light labor is reduced due to climate for more than 30 days per year:

Image via Nature Climate Change/Dunne et. al.

The effect, they note, is that “heat stress in Washington DC becomes higher than present-day New Orleans, and New Orleans exceeds present-day Bahrain.” This doesn’t include other types of dynamics which could accelerate the consequences of climate change in highly populated areas, such as the urban heat island effect—it’s just a basic calculation given what we project will happen to the climate and what we know about how the human body works.

Looking at the map and thinking about how the study defines “work” can lead to a troubling conclusion: in 2100, throughout much of the U.S., simply taking an extended walk outdoors might not be possible for many people. The economic impacts—in terms of construction and other fields that rely upon heavy manual labor—are another issue entirely. Climate change is certain to bring a wide range of unpleasantconsequences, butthe effect of humidity on a person’s ability to work could be the one that impacts daily life the most.

Lake-effect snow, which can blanket communities downwind of lakes, is influenced by upwind geographic features, a new study finds. Photo by Flickr user singloud12

People who live by large, inland bodies of water have a phrase in their lexicon that describes the blizzards that hit them throughout the winter: “lake-effect snow.”  When wintry winds blow over wide swaths of warmer lake water, they thirstily suck up water vapor that later freezes and drops as snow downwind, blanketing cities near lake shores. These storms are no joke: a severe one dumped nearly 11 feet of snow over the course of week in Montague, N.Y. before New Year’s Day, 2002; another week-long storm around Veteran’s Day in 1996 dropped around 70 inches of snow and left more than 160,000 residents of Cleveland without power.

Other lake-effect snowstorms, such as those that skim the surface of Utah’s Great Salt Lake, are more of a boon, bringing fresh, deep powder to ski slopes on the leeward side of nearby mountains. But new research shows that mountains don’t just force the moisture-laden winds to dump snow. Mountains upwind can actually help guide the cold air patterns over lakes, helping to produce severely intense snowstorms. Mountains far afield can also deflect cold wind away from water, reducing a lake’s ability to fuel large storms. If these forces work with smaller topographic features, they may help illuminate whether gently rolling hills near the Great Lakes contribute to the creation and intensity of lake-effect snow.

The research, published yesterday in the American Meteorology Society‘s journal, Monthly Weather Review, focused on wind patterns that swirl around the Great Salt Lake. “What we’re showing here is a situation where the terrain is complicated–there are multiple mountain barriers, not just one, and they affect the air flow in a way that influences the development of the lake-effect storm over the lake and lowlands,” said the study’s senior author Jim Steenburgh, in a statement.

Steenburgh, a professor of atmospheric sciences at the University of Utah, and lead author Trevor Alcott, a recent doctoral graduate from the university and now a researcher at the National Weather Service in Salt Lake City, became interested in studying Utah’s winter weather after they noticed that current weather forecast models struggle to anticipate the intensity of the dozen or so lake-effect storms that strike their state’s major cities each winter. These models don’t include the effects of topography, such as the Wasatch Range (which forms the eastern border of the valley that encloses the Great Salt Lake), the Oquirrh Mountains (which forms the western border of the valley) or the mountains along the north and northwest borders of Utah some 150 miles away from the population centers of Salt Lake City and Provo.

So Alcott and Steenburgh ran a computer simulation that incorporated mountains close to the lake as well as those closer to the Idaho and Nevada borders to mimic the creation of a moderate lake effect storm that occurred over the Great Salt Lake from Oct. 26-27, 2010, which brought up to 11 inches of snow to the Wasatch. After their first simulation–their “control”–was complete, they ran several more simulations that plucked out geographic features. Using this method, “We can see what happens if the upstream terrain wasn’t there, if the lake wasn’t there, if the Wasatch Range wasn’t there,” Steenburgh explained.

When they removed the lake and all mountains from their simulation, the model didn’t produce any snowfall. When they kept all the mountains but removed the lake, only 10% of the snow simulated the model of the real storm fell. Keeping the lake but flattening all the mountains resulted in only 6 percent of the snow falling. Resurrecting the Wasatch Range but removing the other mountains yielded 73 percent of the snow compared to the simulation of the real storm.

But the real surprise is what happened when both the Wasatch and Oquirrh ranges were retained, but the ranges in northern Utah at the Idaho and Nevada borders were removed. The result? 61 percent more snowfall than simulated in the real storm.  The Wasatch and Oquirrh ranges form a funnel, guiding wind over the lake and enhancing snowfall in the downwind cities of Salt Lake City and Provo. Further, without the barrier of the northern mountains, which range between 7,600 feet to 10,000 feet in peak elevation–considerably less than the Wasatch’s peak elevation of nearly 12,000 feet, waves of cold air can reach the Great Salt Lake without deflection.

In effect, Utah’s major cities are shielded by moderately sized mountains that together cast a long snow shadow!

A new study suggests that lightning alone—even without the other elements of a thunderstorm—might trigger migraines. Image via Wikimedia Commons

Migraine sufferers know that a variety of influences—everything from stress to hunger to a shift in the weather—can trigger a dreaded headache. A new study published yesterday in the journal Cephalalgia, though, suggests that another migraine trigger could be an unexpected atmospheric condition—a bolt of lightning.

As part of the study, Geoffrey Martin of the University of Cincinnati and colleagues from elsewhere asked 90 chronic migraine sufferers in Ohio and Missouri to keep detailed daily diaries documenting when they experienced headaches for three to six months. Afterward, they looked back over this period and analyzed how well the occurrence of headaches correlated with lightning strikes within 25 miles of the participants’ houses, along with other weather factors such as temperature and barometric pressure.

Their analysis found that there was a 28 precent increased chance of a migraine and a 31 precent chance of a non-migraine (i.e. less severe) headache on days when lightning struck nearby. Since lightning usually occurs during thunderstorms, which bring a host of other weather events—notable changes in barometric pressure—they used mathematical models to parse the related factors and found that even in the absence of other thunderstorm-related elements, lightning alone caused a 19 percent increased chance of headaches.

Despite these results, it’s probably a bit premature to argue that lightning is a definitive trigger of migraines. For one, a number of previous studies have explored the links between weather and migraine headaches, and the results have been unclear. Some have suggested that high pressure increases the risk of headaches, while others have indicated that low pressure increases the risk as well. Other previous studies, in fact, have failed to find a link between migraines and lightening, in particular.

This study’s results are still intriguing, though, for a few reasons. One key element of the study was that, instead of using instances of lightning as reported by individuals on the ground, the researchers relied upon a series of ground sensors that automatically detect lightning strikes in the areas studied with a 90 percent accuracy. The researchers say this level of precision improves upon previous research and makes their results more indicative of the actual weather outside.

The study also looked at the polarity of lightning strikes—the particular electrical charge, whether positive or negative, that a bolt of lightning carries as it surges from the clouds to the ground—and found that negatively charged lightning strikes had a particularly strong association with migraines.

The researchers don’t have a clear explanation yet for how lightning might play a role, but they mention a wide variety of possibilities. ”There are a number of ways in which lightning might trigger headaches,” Martin said. “Electromagnetic waves emitted from lightning could trigger headaches. In addition, lightning produces increases in air pollutants like ozone and can cause release of fungal spores that might lead to migraine.”

New Mexico’s 2012 Gila Wildfire was the largest in the state’s history. By Gila Forest

Earlier this week we learned that 2012 ranks as the hottest year on record, with an average temperature more than three degrees higher than the average for the 20th century. But a deeper look into the National Oceanic and Atmospheric Administration’s (NOAA) annual climate report shows that, in the United States, 2012 was also riddled with extreme weather events.

In fact, it was the second-most extreme year on record for weather, according to the U.S. Climate Extremes Index, which analyzes variations in precipitation, temperatures and land-falling tropical cyclones. There was a frenzy of events such as drought, heat waves, flooding, wildfires and tornadoes, many of which were more severe than in years past. And we also saw exotics like the derecho, a powerful thunderstorm cluster, and Sandy, dubbed a Frankenstorm in the press and a post-tropical cyclone by NOAA. Overall, the meterological spikes were almost twice the average. Several unusual occurrences stand out:

• Drought: Dry conditions were the norm from the get-go in 2012. The central and southern Rockies received less than half the usual amount of snow, and nationally the winter season had the third-smallest snow cover. To make matters worse, spring showers never made an appearance. Precipitation was 95 percent that of the spring-time average for the 20th century. As the year went on, more than 60 percent of the nation was plagued by a drought that peaked in intensity in July. The NOAA report noted that the conditions were “comparable to the drought episodes of the 1950s.”
• Blistering heat: The fourth-warmest winter on record was followed by the warmest March, the forth-warmest April and the second-warmest May. Overall, spring 2012 was two degrees hotter than any spring before it. These balmy conditions kickstarted an early growing season, which exacerbated the drought by depleting water from the soil earlier in the year than usual. July’s average temperature of 76.9 Fahrenheit made it the hottest month ever recorded for the contiguous U.S. and helped contribute to another record: the second-warmest summer. A third of Americans endured 100-degree-plus temperatures for 10 days or more. All told, every state had an above-average annual temperature and 356 all-time record high maximum temperatures were tied or broken in 2012.
• Mega wildfires: Dry conditions primed the nation for wildfires by creating fuel sources in dried-out vegetation. The heat then encouraged combustion. Some fires were sparked by natural phenomena (lightning), others had manmade sources (cigarettes, campfires, arson). Flames charred a total of 9.1 million acres nationwide, decimating an area the size of Massachusetts and Connecticut combined. New Mexico was torched by the biggest wildfire in its history and Colorado experienced its most costly wildfire. The most severe fire month nationally was August, when upward of 3.6 million acres went up in flames–more than any single month since 2000.
• Tropical cyclones: These storms suck heat from the ocean and then unleash that heat near the storm’s center. A total of 19 tropical cyclones touched down in the U.S. in 2012, making it the third-most-active tropical cyclone season on record. The most infamous were Isaac, which pummeled Louisiana with 106-mph gusts of wind, bringing Katrina flashbacks, and Sandy, which made landfall near Atlantic City, N.J.. Its 80-mph winds created record storm surges that resulted in 131 fatalities and left eight million people without power.
• Derecho: A band of thunderstorms packing tornado-force power, the derecho usually follows a straight path heading in one direction. To earn the National Weather Service’s derecho designation, the storms’ winds must reach at least 58 mph. Lower Michigan was whipped by a 130-mph derecho in 1998; the one that steamrolled the country from Indiana to Maryland in June was tamer, bringing winds of up to 80 mph. According to NOAA, derechos tend to occur on the heels of heat waves.
• Fewer, but severe, tornadoes: Although the number of tornadoes plummeted in 2012, reaching the lowest levels since 2002, the storms that did strike were fierce. A surge of 80 early-March tornadoes that swept through the Midwest caused 42 deaths. One that ravaged Indiana with winds between 166 and 200 mph ranked as a four on the Enhanced Fujita Scale of tornado strength, placing it in the top two percent of all tornadoes strength-wise.
• Storm flukes: Hawaii was struck by an anomalous tornado when a water spout churning off the coast of Oahua made landfall. True it was classified at zero on the Enhanced Fujita Scale, but its 60- to 70-mph winds reportedly destroyed several buildings and delivered another record: a grapefruit-sized hailstone, the biggest ever to hit the Hawaiian Islands.

What does this all mean in terms of the impact of climate change on weather? Scientists don’t exactly agree. According to some, we shouldn’t read too much into the statistics. “Natural variability continues to dominate the occurrence of extreme weather events,” atmospheric scientist Judith A. Curry of the Georgia Institute of Technology told The Washington Post, adding that the global average temperature for 2012 will not top the charts, but rather will be the eighth-highest on record.

Gerald Meehl, a senior scientist at the National Center for Atmospheric Research, is in the opposing camp. “By adding just a little bit more carbon dioxide to the climate, it makes things a little bit warmer and shifts the odds toward these more extreme events,” Arndt told National Geographic. “What was once a rare event will become less rare.”

Coral from the Northern Line Islands reveals a link between climate change and El Niño. Photo by Forest Rohwe

El Niño, the climate pattern that increases Pacific Ocean surface temperatures every three to seven years, has long been known to pummel the Sierra Nevada with snow, limit Peruvian anchovy fishermen’s harvest and bless the Hawaiian Islands with dry, beach-friendly weather. The question of whether the effects of El Niño have become more extreme in recent decades, as climate change has intensified, hasn’t accrued a consensus among scientists. But now, new research released last week, sponsored by the National Science Foundation and published in Science, strengthens the link between El Niño activity and climate change.

During an El Niño season (the next one has been delayed, but is expected to begin later this year) the force of trade winds in the western and central Pacific diminishes or even reverses, causing a spike in surface water temperatures. As the slackened winds allow–or the reversed winds slowly push–the warmer water east across the ocean, rainfall follows it.

El Niño and its cold-water counterpart La Niña, which occurs between El Niño episodes when the regular trade winds intensify their westward push, have global ramifications. Wildfires in Australia and famines in India have been associated with the climate pattern. The cycle of El Niño and La Niña also appears to have intensified in recent years. Searching for reasons why, scientists debated a link with climate change as long ago as 1997, when researchers at the National Center for Atmospheric Research published a study titled “El Niño and Climate Change.” They couldn’t identify a clear connection, but they believed there was an unidentified force at work–one that required further investigation. “[A]t least part of what is happening… can not be accounted for solely by natural variability,” they wrote.

A year later, experts at the Nevada-based Western Regional Climate Center, which disseminates climate data and conducts research, also contemplated whether global warming was goosing El Niño. They were more overtly suspicious of a linkage, but again, lacked specific evidence. In a post on the center’s website, they noted:

It is plausible that a warmer earth would produce more and stronger El Niños. There is some evidence that the earth has warmed over the past two decades, and there is no doubt that El Niño has been much more frequent in that time. If the evidence of a warming earth is taken at face value (not universally accepted), there still remains a wide spectrum of opinions on whether we are seeing a manifestation of human modification of global climate, or whether the natural climate system would be exhibiting this behavior anyway.

In the new study, conducted by the Georgia Institute of Technology and the Scripps Institute of Oceanography, scientists traveled to the central tropical Pacific, where the variations in El Niño-driven temperature and precipitation patterns are most acute. Studying the region’s coral gave them a window into the historical effects of El Niño.

They extracted core samples from large coral rocks that had been pushed by storm activity onto Christmas (Kiritimati) and Fanning Islands, tiny spits of land within Kiribati’s Northern Line Islands. Using radioactive dating, they ascertained the ages of 17 samples, each of which spanned 20 to 80 years in time, allowing them to create a patchwork timeline covering 7,000 years.

Then they looked at the ratio of oxygen isotopes within the coral skeletons as a way of measuring variations in weather patterns. Since temperature and rainfall affect isotope ratios, they were able to glean the environmental conditions present during each phase of the corals’ lifespans. Dips and surges in rain and sea surface temperatures left an imprint in the coral samples, and in their analysis, scientists found significantly more intense and variable El Niño activity in the 20th century than most other periods represented.

“The level of [El Niño] variability we see in the 20th century is not unprecedented,” said the study’s lead author, Georgia Institute of Technology’s Kim Cobb in a statement, noting a similarly severe period in the 17th century. “But the 20th century does stand out, statistically, as being higher than the fossil coral baseline.”

The researchers reluctantly went a step further to connect the increase in El Niño activity to climate change: “We kind of answered the question, is El Niño changing with respect to recent natural variability?” said Cobb. “The answer is yes, tentatively so.” Yet despite the bounty of new data, researchers say they would need to go back even further in time to make a more definitive linkage between climate change and El Niño activity.

They were less ambiguous about the impact of the study on future climate change research. The new data will help other scientists investigate past climate change events in both paleoclimate records and model simulations, Cobb said. “Prior to this publication, we had a smattering of coral records from this period of interest,” she explained. “We now have tripled the amount of fossil coral data available to investigate these important questions.”