Tweets from around the world, plotted by location as part of a new study. Click to enlarge. Image via First Monday/Leetaru et. al.

It’s hard to appreciate just how quickly and thoroughly Twitter has taken over the world. Just seven years ago, in 2006, it was an idea sketched out on a pad of paper. Now, the service is used by an estimated 554 million users—a number that amounts to nearly 8 percent of the all humans on the planet—and an estimated 170 billion tweets have been sent, with that number climbing by roughly 58 million every single day.

All these tweets provide an invaluable source of news, entertainment, conversation and connection between people. But for scientists, they’re also valuable as something rather different: raw data.

Because Twitter features an open API (which allows for tweets to be downloaded as raw, analyzable data) and many tweets are geotagged, researchers can use billions of these tweets and analyze them by location to learn more about the geography of humans across the planet. Last fall, as part of the Global Twitter Heartbeat, a University of Illinois team analyzed the language and location of over a billion tweets from across the U.S. to create sophisticated maps of things like positive and negative emotions expressed during Hurricane Sandy, or support for Barack Obama or Mitt Romney during the Presidential election.

As Joshua Keating noted on Foreign Policy‘s War of Ideas blog, members of the same group, led by Kalev Leetaru, have recently gone one step further. As published in a new study earlier this week in the online journal First Monday, they analyzed the locations and languages of 46,672,798 tweets posted between October 23 and November 30 of last year to create a stunning portrait of human activity around the planet, shown at the top of the post. They made use of the Twitter decahose, a data stream that  captures a random 10 percent of all tweets worldwide at any given time (which totaled 1,535,929,521 for the time period), and simply focused on the tweets with associated geographic data.

As the researchers note, the geographic density of tweets in many regions—especially in the Western world, where computers, mobile devices, and Twitter are all used at peak levels—closely matches rates of electrification and lighting use. As a result, the maps of tweets (such as the detail view of the continental U.S., below) end up looking a lot like satellite images of artificial light at night.

Click to enlarge. Image via First Monday/Leetaru et. al.

As a test to see how well tweets matched artificial light use, they created the composite map below, in which tweets are shown as red dots and nighttime lighting is shown as blue. Areas where they correspond in frequency (and effectively cancel each other out) are shown as white, and areas where one outweighs the other remain red or blue. Many areas end up looking pretty white, with some key exceptions: Iran and China, where Twitter is banned, are noticeably blue, while many countries with relatively low electrification rates (but where Twitter is still popular) appear as red.

Click to enlarge. Image via First Monday/Leetaru et. al.

The project got even more interesting when the researchers used an automated system to break down tweets by language. The most common language in Twitter is English, which is represented in 38.25 percent of all Tweets. After that came Japanese (11.84 percent), Spanish (11.37 percent), Indonesian (8.84 percent), Norwegian (7.74 percent) and Portugese (5.58 percent).

The team constructed a map of all tweets written in the 26 most popular languages, with each represented by a different color, below:

Click to enlarge. Image via First Monday/Leetaru et. al.

While most countries’ tweets are dominated by their official languages, many are revealed to include tweets in a variety of other languages. Look closely enough, and you’ll see a rainbow of colors subtly popping out from the grey dots (English tweets) that blanket the U.S.:

Click to enlarge. Image via First Monday/Leetaru et. al.

Among other analyses, the research team even looked at the geography of retweeting and referencing—the average distance between a user and someone he or she retweets, as well as the average distance between that user and someone he or she simply references in a tweet. On average, the distance for a retweet was 1,115 miles and 1,118 for a reference. But, counterintuitively, there was a positive relationship between the number of times a given user retweeted or referenced another user and their distance: Pairs of users with just a handful of interactions, on the whole, were more likely to be closer together (500-600 miles apart) than those with dozens of retweets and references between them.

This indicates that users who live far apart are more likely to use Twitter to interact on a regular basis. One explanation might be that the entities with the most followers—and thus the most references and retweets—are often celebrities, organizations or corporations, users that people are familiar with but don’t actually have a personal relationship with. A global map of retweets between users is below:

Click to enlarge. Image via First Monday/Leetaru et. al.

The paper went into even more detail on other data associated with tweets: the ratio between mainstream news coverage and number of tweets in a country (Europe and the U.S. get disproportionate media coverage, while Latin America and Indonesia are overlooked), the places Twitter has added the most users recently (the Middle East and Spain) and the places where users have, on average, the most followers (South America and the West Coast).

There are a few caveats to all this data. For one, though the tweets analyzed number in the tens of millions, they are still just 0.3 percent of all tweets sent, so they might not adequately represent all Twitter patterns, especially if users who enable geotagging behave differently than others. Additionally, in the fast-changing world of Twitter, some trends might have already changed significantly since last fall. But as Twitter continues to grow and as more data become available, it stands to reason that this sort of analysis will only become more popular for demographers, computer scientists and other researchers.

New isotopic analysis of Apollo-era Moon rocks shows that the water locked inside them likely came from our planet . Image via Wikimedia Commons/Gregory H. Revera

In September 2009, after decades of speculation, evidence of water on the surface of the Moon was discovered for the first time. Chandrayaan-1, a lunar probe launched by India’s space agency, had created a detailed map of the minerals that make up the Moon’s surface and analysts determined that, in several places, the characteristics of lunar rocks indicated that they bore as much 600 million metric tonnes of water.

In the years since, we’ve seen further evidence of water both on the surface and within the interior of the Moon, locked within the pore space of rocks and perhaps even frozen in ice sheets. All this has gotten space exploration enthusiasts pretty excited, as the presence of frozen water could someday make permanent human habitation of the Moon much more feasible.

For planetary scientists, though, it’s raised a knotty question: How did water arrive on the Moon in the first place?

A new paper published today in Science suggests that, unlikely as it may seem, the Moon’s water originated from the same source as the water that comes out of the faucet when you open a tap. Just as many scientists believe the Earth’s entire supply of water was initially delivered via water-bearing meteorites that traveled from the asteroid belt billions of years ago, a new analysis of lunar volcanic rocks brought back during the Apollo missions indicates the Moon’s water has its roots in these same meteorites. But there’s a twist: Before reaching the Moon, this lunar water was first on Earth.

A closeup of a melt inclusion inside lunar rocks. These inclusions reveal clues about the water content trapped within the Moon. Image via John Armstrong, Geophysical Laboratory, Carnegie Institution of Washington

The research team, led by Alberto Saal of Brown University, analyzed the isotopic composition of hydrogen found in water within tiny bubbles of volcanic glass (supercooled lava) as well as melt inclusions (blobs of melted material trapped in slowly cooling magma that later solidified) in the Apollo-era rocks, as shown in the image above. Specifically, they looked at the ratio of deuterium isotopes (“heavy” hydrogen atoms that contain an added neutron) to normal hydrogen atoms.

Previously, scientists have found that in water, this ratio changes depending on where in the solar system the water molecules initially formed, as water that originated closer to the Sun has less deuterium than water formed further away. The water locked in the lunar glass and melt inclusions was found to have deuterium levels similar to that found in a class of meteorites called carbonaceous chondrites, which scientists believe to be the most unaltered remnants of the nebula from which the solar system formed. Carbonaceous chondrites that fall to Earth originate in the asteroid belt between Mars and Jupiter.

Higher deuterium levels would have suggested that water was first brought on to the Moon by comets—as many scientists have hypothesized—because comets largely come from the Kuiper belt and Oort Cloud, remote regions far beyond Neptune where deuterium is more plentiful. But if the water in these samples represents lunar water as a whole, the findings indicate that the water came from a much closer source—in fact, the same source as the water on Earth.

The simplest explanation for this similarity would be a scenario in which, when a massive collision between a young Earth and a Mars-sized proto-planet formed the Moon some 4.5 billion years ago, some of the liquid water on our planet was somehow preserved from vaporization and transferred along with the solid material that would become the Moon.

Our current understanding of massive impacts, though, doesn’t allow for this possibility: The heat we believe would be generated by such an enormous collision would theoretically vaporize all lunar water and send it off into space in a gaseous form. But there are a few other scenarios that might explain how water was transferred from our proto-Earth to the Moon in other forms.

One possibility, the researchers speculate, is that the early Moon borrowed a bit of Earth’s high-temperature atmosphere the instant it formed, so any water that had been locked in the chemical composition of Earth rocks pre-impact would have vaporized along with the rock into this shared atmosphere after impact; this vapor would have then coalesced into a solid lunar blob, binding the water into the chemical composition of lunar material. Another possibility is that the rocky chunk of Earth was kicked off to form the Moon retained the water molecules locked inside its chemical composition, and later on, these were released as a result of radioactive heating inside the Moon’s interior.

Evidence from recent lunar missions suggests that lunar rocks—not just craters at the poles—indeed contain substantial amounts of water, and this new analysis suggests that water originally came from Earth. So the findings will force scientists to rethink models of how the Moon could have formed, given that it clearly didn’t dry out completely.

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.

The rare coealacanth’s genome is slowly evolving—and contrary to prior speculation, it probably isn’t the common ancestor of all land animals. Image via Wikimedia Commons/Amelia Guo

On December 23, 1938, South African Hendrick Goosen, the captain of the fishing trawler Nerine, found an unusual fish in his net after a day of fishing in the Indian Ocean off of East London. He showed the creature to  local museum curator Marjorie Courtenay-Latimer, who rinsed off a layer of slime and described it as “the most beautiful fish I had ever seen…five foot long, a pale mauvy blue with faint flecks of whitish spots; it had an iridescent silver-blue-green sheen all over. It was covered in hard scales, and it had four limb-like fins and a strange puppy dog tail.”

The duo, it turned out, had made one of the most significant biological discoveries of the 20th century. The fish was a coelacanth, a creature previously known only from fossilized specimens and believed to have gone extinct about 80 million years earlier. Moreover, its prehistoric appearance and unusual leg-like lobed fins immediately suggested to biologists that it could be an ancient ancestor of all land animals—one of the pivotal sea creatures that first crawled onto solid ground and eventually evolved into amphibians, reptiles, birds and mammals.

Now, though, the coelacanth’s full genome has been sequenced for the first time, and the results, published by an international team of researchers today in Nature, suggest otherwise. Genetic analysis suggests that the coelacanth doesn’t appear to be the most recent shared ancestor between sea and land animals—so its lobed fins didn’t make that first fateful step onto land after all.

When the researchers used what they found out about the coelacanth’s genome to build an evolutionary tree of marine and terrestrial animals (below), they found it’s more likely that ancestors of closely-related class of fish called lungfish played this crucial role. The ancestors of coelacanths and lungfish split off from each other before the latter group first colonized any land areas.

The genetic sequencing showed that terrestrial animals share a more recent common ancestor with lungfish, rather than coelacanths. Image via Nature/Amemiya et. al.

Additionally, the coelacanth’s prehistoric appearance has led to it commonly being considered a “living fossil”: a rare, unchanging biological time capsule of a bygone prehistoric era. But the genomic sequencing indicated that the fish species is actually still evolving—just very, very slowly—supporting the recent argument that it’s time to stop calling the fish and other seemingly prehistoric creatures “living fossils.”

“We found that the genes overall are evolving significantly slower than in every other fish and land vertebrate that we looked at,” Jessica Alföldi, a scientist at MIT and Harvard’s Broad Institute and a co-author, said in a press statement. Small segments of the fish’s DNA had previously been sequenced, but now, she said, “This is the first time that we’ve had a big enough gene set to really see that.”

The fact that the fish is evolving isn’t surprising—like all organisms, it lives in a changing world, with continuously fluctuating selection pressures that drive evolution. What’s surprising (though reflected by its seemingly-prehistoric appearance) is that it’s evolving so slowly, compared to a random sampling of other animals. According to the scientists’ analysis of 251 genes in the fish’s genome, it evolved with an average rate of 0.89 base-pair substitutions for any given site, compared to 1.09 for a chicken and 1.21 for a variety of mammals (base-pair substitution refers to the frequency with with DNA base-pairs—the building blocks of genes—are altered over time).

The research team speculates that the coelacanth’s extremely stable deep Indian Ocean environment and relative lack of predators might explain why it has undergone such slow evolutionary changes. Without new evolutionary pressures that might result from either of these factors, the coelacanth’s genome and outward appearance have only changed slightly in the roughly 400 million years since it first appeared on the planet.

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.

As the Arctic warms, more of it will be covered by shrubs (like the Arctic National Wildlife Refuge, above) and even by forest. Image via ANWR

You probably think of the Arctic as a cold, frozen tundra—home to lichen, polar bears and scattered herds of reindeer. In many places, this view would be accurate, but in a few relatively southern areas in Canada, Alaska and Russia, warming temperatures over the past few decades have allowed new types of plants, such as shrubs, to take root.

And by 2050—if current warming trends continue—we’ll see a dramatically different ecosystem across the Arctic, starting with something that’s largely unknown in the area currently: trees. According to research published today in Nature Climate Change, tree cover in the Arctic could increase by more than 50 percent over the next few decades.

The research team, which included scientists from a number of universities and was led by Richard Pearson of the American Museum of Natural History, made the calculation based off of current projections of how the Arctic’s climate will change by 2050. So far, temperatures in the region have risen about twice as fast as those for the planet as a whole.

They created a model that predicts which class of plants (various grasses, mosses, shrubs or trees) will grow given a particular temperature and precipitation range expected for the future; for each spot on a map of the Arctic, they fed in the 2050 projections. Doing this kind of vegetative modeling for the Arctic, they say, is relatively straightforward compared to doing it for somewhere like the tropics, because there are hard limits on the temperature and growing season length that given plant types can tolerate.

They found that tree cover will expand drastically, covering up to 52 percent more land area than currently, rising far north of the current tree line in Alaska and Canada. This new tree cover will mostly come at the expense of areas currently covered by shrubs, but shrubs will take over places now dominated by tundra plants (lichens and mosses), and some areas presently under ice will convert into tundra.

In effect, the area’s warming climate and lengthening growing season will shift all current vegetation zones to more northerly and colder regions. Already, these vegetation zones have shifted an average of five degrees of latitude over the past 30 years–in other words, the vegetation in one spot resembles how a location five degrees south looked 30 years ago.

But by 2050, this shift will be even more dramatic—perhaps equaling 20 degrees of latitude—and a projected 48 to 69 percent of the Arctic’s vegetated areas will switch to a different class of plants. Some rare plant species could be at risk of extinction if they’re not able to migrate as quickly as the vegetation zones move.

Presently (left), vegetated areas of Alaska are mostly covered by small shrubs and tundra mosses (represented by the pea green color). By 2050 (right), much of this area will be dominated forests (bright green). Image via Nature Climate Change/Pearson et. al.

In Canada, areas currently covered by tundra shrubs (purple at left) will be taken over by forest (bright green at right). Image via Nature Climate Change/Pearson et. al.

Because plants are the base of any food chain, this conversion will have wide-ranging effects, both locally and elsewhere. “These impacts would extend far beyond the Arctic region,” Pearson said in a press statement. “For example, some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground-nesting.” Their migrations patterns would presumably be altered by the growth of forests on what had been open tundra.

Most troubling, the conversion of white, snow-covered land to dark vegetation will further affect the warming of the planet. Because darker colors absorb more radiation than the white of ice and snow, shifting large masses of land to a darker color is projected to further accelerate warming, creating a positive feedback loop: more warming leads to a greener Arctic, which leads to more warming.

Given all the other problems that the area is rapidly encountering as the climate changes—melting glaciers, increasing oil exploration and hybridizing bear species—it’s clear that the Arctic will be one of the most environmentally fragile regions of the planet over the coming century.

Rapidly melting sea ice will open up shipping lanes across the Arctic, potentially making the Northwest Passage (left) and North Pole (center) navigable during the summer. Image via PNAS/Smith and Stephenson

Rapidly melting ice has already remade shipping possibilities in the Arctic. Over the past decade, commercial use of the Northern Sea Route (the blue shipping lane along the northern coast of Russia in the map above) during late summer has become commonplace, dramatically shortening the journey from Europe to the Far East.

If present trends continue, though, the options for shipping goods across the Arctic will expand even more. According to a paper published today in the Proceedings of the National Academy of Sciences, by 2040, the legendary Northwest Passage (the shipping lane on the left side of the map, along the cost of Canada and Alaska) could be accessible during some summers to normal oceangoing ships without specially reinforced ice-breaking hulls. Most surprisingly, at times, reinforced polar icebreakers might even be able to plow straight across the North Pole, making the shortest possible journey across the Arctic.

All this is due to the fact that, over the past two decades, temperatures have risen even faster in the Arctic than the planet as a whole. Although the polar ice pack grows each winter and shrinks each summer, the overall trend has been a decrease in total ice cover, as seen in the video below. In the future, this will open up a window for reinforced ships to break through weaker ice, and for normal ships to cruise through ice-free corridors.

The new study, by Laurence Smith and Scott Stephenson of UCLA, uses existing climate models to examine how this trend will change Arctic shipping for the years 2040 to 2059. They looked at theoretical ice conditions under a pair of climate scenarios from the UN’s Intergovernmental Panel on Climate Change’s most recent report, one that assumed a medium-low level of greenhouse gas emissions going forward, and another that assumed a high level. They also explored the navigational possibilities for two different types of ships: Polar Class 6 ice-breaking ships and normal oceangoing vessels.

Their analysis found that in both scenarios, the Northern Sea Route—already navigable for reinforced vessels in late summer most years—will become wider, opening up for a greater number of months each summer and allowing for a greater geographical diversity in routes. The wider lane will enable ships to take routes further away from the Russian coast and closer to the North Pole, shortening the journey over the top of our planet, and will allow unreinforced ships to travel through without an ice-breaking escort.

Currently, the Northwest Passage is inaccessible for normal vessels, and has only been transited a handful of times by reinforced ice-breaking ships. Under both of the scenarios in the model, though, it becomes navigable to Polar Class 6 ships every summer. At times, it could even be open to unreinforced vessels as well—the study shows that, when multiple simulations were run in both medium-low and high levels of greenhouse gas emissions, open sailing was possible for 50 to 60 percent of the years studied.

Finally, the straight shot over the North Pole—a route that would currently take would-be captains through a sheet of ice as much as 65 feet thick in areas—could also become possible for Polar Class 6 ships in both scenarios, at least in warmer years. “Nobody’s ever talked about shipping over the top of the North Pole,” Smith said in a press statement. “This is an entirely unexpected possibility.”

The most striking part of the study might be that these dramatic changes occurred in simulations assuming both medium-low and high levels of emissions, and that the time period studied isn’t all that far away, beginning just 27 years from the present. “No matter which carbon emission scenario is considered, by mid-century we will have passed a crucial tipping point—sufficiently thin sea ice—enabling moderately capable icebreakers to go where they please,” Smith said.

The unprecedented levels of fine particulates that pollute Beijing’s air can cause lung cancer, heart attacks and other health problems. Image via Flickr user jaaron

Beijing’s terrible air quality is currently in the news, and for good reason: The level of pollution present in the air there is unprecedented for a heavily populated area, and several times worse than what any U.S. resident has likely ever experienced.

The New York Times recently reported on the air quality problems of Salt Lake City, Utah, and how the area’s geographical features and weather systems occasionally trap pollution in the city’s bowl-shaped basin. But the highest reading on the EPA’s Air Quality Index (AQI) scale ever recorded in Salt Lake City was 69 micrograms of soot and other particles per cubic meter.

In Beijing, that number frequently rises above 300—sometimes going much higher. Yesterday, a sandstorm blew into the city, mixing sand and dust with smog and pushing the AQI to 516. The scale was only designed to go up to 500, but on January 12, a measurement from the U.S. Embassy in Beijing read 755. For reference, the EPA recommends that for any number above 200, ”People with heart or lung disease, older adults, and children should avoid all physical activity outdoors. Everyone else should avoid prolonged or heavy exertion.”

Beijing’s air pollution is literally off the charts, at least according to the EPA’s Air Quality Index. Image via EPA

What exactly makes physical activity in this sort of environment so dangerous? First, it’s important to understand exactly what AQI measures in the chart above: the weight of solid particles smaller than 2.5 micrometers wide (commonly known as fine particulates) that are suspended in an average cubic meter of air. In a heavily populated place like Beijing, most of the fine particulates are a result of industrial activity, the burning of diesel and gasoline for transport, or the burning of coal for energy or heat.

When we breathe in larger particles than those measured by the AQI (those typically bigger than 10 micrometers in size), they’re typically filtered out by cilia or mucus in our nose and throat. But those smaller than 10 micrometers can slide past these protections and settle in our bronchi and lungs. And the fine particulates commonly measured by the AQI can penetrate even further—entering the tiny air sacs known as alveoli where our bodies exchange carbon dioxide for oxygen—where they can cause some serious damage over time.

Researchers have linked many health problems to high levels of these tiny particulates in the air, but the most obvious effect has been lung cancer. One study spanning 16 years found that, over the course of an individual’s lifetime, an average increase of 10 on the AQI was associated with a 8 percent higher chance of developing the disease. When multiplied out over a broad area with a large population, the effect can be massive. A World Health Organization report estimated that fine particulates are responsible for 5% of the deaths resulting from lung cancer worldwide—800,000 deaths annually.

Fine particulates have also been linked with many other sorts of health issues, both long- and short-term. There’s evidence that, in individuals already predisposed to heart problems, they can trigger heart attacks. They can also exacerbate asthma, cause coughing or difficulty breathing in healthy people, and reduce the lungs’ ability to take in oxygen for people with COPD (chronic obstructive pulmonary disease).

Additionally, there are risks associated with even smaller particulates, known as nanoparticles, that are smaller than 100 nanometers in size. Only preliminary research on nanoparticles’ effect on the human body has been completed, but scientists believe that nanoparticles may be capable of penetrating even further into an organism, burrowing through cell membranes and potentially causing a range of problems, including damage to the lungs and circulatory system.

There has been limited research so far on the direct health impacts of air pollution in China, but one study found that, when air pollution was curtailed due to restrictions during the 2008 Olympics, several chemical biomarkers associated with cardiovascular disease in the blood of Beijing residents dropped off dramatically. Another study estimated that, if these same restrictions were extended permanently, lifetime risk of lung cancer for the city’s residents would be cut in half (a risk that has increased by 56 percent in the last 10 years, even as smoking has declined).

All told, there are very good reasons why many Beijing residents don’t venture out without a breathing mask—and why many Chinese are calling upon leaders to finally address the country’s air pollution problems in the coming political year, potentially by introducing rules that restrict industry and coal burning when air quality dips below acceptable levels.

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.

A rendering of Asteroid 2012 DA14, which will pass within 17,200 miles of Earth’s surface. Image via NASA/JPL

This Friday afternoon at approximately 2:26 Eastern time, an asteroid roughly half the size of a football field (147 feet) in diameter will pass extremely close to the Earth—just 17,200 miles from our planet’s surface. That said, there’s no need to worry, as NASA scientists confirmed with certainty nearly a year ago that the asteroid will not make an impact and poses absolutely no threat.

Nevertheless, the proximity of the asteroid’s path is noteworthy: it will come within a distance 2 times the Earth’s diameter, passing us by even closer than some geosynchronous satellites that broadcast TV, weather and radio signals. As Phil Plait writes in his comprehensive post on the asteroid over at Slate, “This near miss of an asteroid is simply cool. It’s a big Universe out there, and the Earth is a teeny tiny target.”

The asteroid will pass inside the ring of geosynchronous satellites that orbit earth. Image via NASA/JPL

The asteroid—likely made of rock and referred to as 2012 DA14 by scientists—was first spotted last February by astronomers at Spain’s Observatorio Astronómico de La Sagra. Asteroids, like planets, orbit the Sun, and this one passed us by on its last orbit as well, but at a much greater distance—it came within roughly 1.6 million miles last February 16. After this year’s near miss, the rock’s orbit will be altered significantly by the influence of Earth’s gravity, and scientists calculate that it won’t come near us again until the year 2046 at the soonest.

On Friday, though, it will pass by Earth between 18:00 and 21:00 UTC (1-4 p.m. Eastern time, or 10 a.m.-1 p.m. Pacific) and come closest at roughly 19:26 UTC (2:26 p.m. Eastern, 11:26 a.m. Pacific). That means that observers in Eastern Europe, Asia and Australia get to see its closest pass at nighttime, whereas those in North America, Western Europe and Africa will have to wait until after sunset, when the asteroid has already begun to move away.

For all observers, the asteroid will be too small to see with the naked eye, though it should be viewable with binoculars or a telescope. Universe Today has the technical details on where exactly to spot the asteroid in the sky. A number of observatories and organizations will also broadcast video streams of the asteroid live, including NASA.

A fly-by like the one on Friday isn’t particularly rare in terms of mere proximity. There are seven closer asteroid passes on record—in 2011, a tiny asteroid set the record for near misses by coming within 3300 miles of Earth, and in 2008, an even smaller one actually made contact with the atmosphere, burning up over Africa.

Both of those rocks, though, were less a meter across.What distinguishes this asteroid is that it’s passing close by and theoretically large enough to cause major damage if an impact were to occur. While an asteroid of this size passes this closely roughly every 40 years on average, a collision with an object this size only happens once every thousand years or so.

What kind of damage would that impact wreak? For a comparison, many are noting the Tunguska event, an explosion over a remote area Russia in 1908 that was likely caused by an asteroid of similar size burning up in the atmosphere. The explosion knocked down more than 80 million trees covering an area of some 830 square miles; scientists estimate it released more than 1,000 times as much energy as the nuclear bomb dropped on Hiroshima and triggered shock waves that would have registered a 5.0 on the Richter scale.

Of course, unlike in 1908, we now have the power to observe approaching asteroids well ahead of time—and might have the ability to prevent potential collisions. Bill Nye is among those who argue that this event should serve as a wake-up call for the importance of investing in asteroid-detecting infrastructure, such as observatories and orbiting telescopes. The B612 Foundation supports this mission, and advocates for the development of technologies that could slightly alter the path or speed of an approaching object to avoid an impact.

This time, at least, we’re lucky. But Ed Lu, a former astronaut and head of B612, says this event should not be taken lightly. ”It’s a warning shot across our bow,” he told NPR. “We are flying around the solar system in a shooting gallery.”

Sockeye salmon rely on a magnetic map to navigate home after years spent at sea. Credit: Putman et al., Current Biology

Scientists have long known that various marine animals use the earth’s magnetic forces to navigate waters during their life cycles. Such inherent navigational skills allow animals return to the same geographic area where they were born, with some migrating thousands of miles, to produce the next generation of their species.

As hatchlings, sea turtles scuttle from their sandy birthplace to the open sea as if following an invisible map, and, as adults, the females return to that spot to lay their own eggs. Bluefin tuna home in on their natal beaches after years at sea to spawn. Similarly, mature sockeye salmon leave open water after gorging on zooplankton and krill to swim back to the freshwater streams and rivers in which they were born.

But the mechanisms underlying this behavior are not well understood for most species, including the silver-bellied salmon. Previous studies suggest that tiny variations in earth’s magnetic field might have something to do with it, but research has been mostly limited to laboratory experiments—until now.

Using fisheries data spanning 56 years, researchers examined sockeye salmon’s mysterious sense of direction in their natural habitat. The findings, reported online today in Current Biology, show that sockeye salmon “remember” magnetic values of geographic locations. They imprint their birth location on this map when they leave their freshwater home for the sea, and use it as a compass during their journey back several years later, successfully returning home to spawn.

The salmon in this study originate in British Columbia’s Fraser River. They typically spend two to four years at sea, distributed widely throughout the Gulf of Alaska. As ruby-colored adult salmon, they begin their trek home. But on their way, they encounter a roadblock: Vancouver Island, the top of a submerged mountain range that stretches for 285 miles from the Juan de Fuca Strait in the south to Queen Charlotte Straight in the north. To get back to the Fraser River, the fish have to choose—the northern inlet or the southern inlet?

If the fish did possess some internal GPS that uses earth’s magnetic field as a map, researchers expected to see the salmon’s choice of inlet change in predictable ways over the years. This is because the planet’s magnetic field doesn’t remain constant; the field’s intensity and small-scale patterns change gradually over time through a process called geomagnetic field drift, caused mainly by movement in the Earth’s fluid core.

And that’s exactly what researchers observed: salmon showed a greater preference in a given year for the inlet that most closely resembled the magnetic signature of the Fraser River when they swam from it two years earlier. Their homeward route reflected how closely the field at each entryway, at the time of their return, resembled the field that the salmon experienced two years before, when they left the river to forage at sea.

Sockeye Salmon from Fraser River in British Columbia typically spend two to four years at sea, feeding on zooplankton. Credit: Current Biology, Putman et al.

Specifically, as the difference in the magnetic field’s strength between the Fraser River and Queen Charlotte Strait decreased, a higher proportion of salmon migrated through the northern inlet. Likewise, when the difference in magnetic intensity between the river and the Strait of Juan de Fuca decreased, a higher proportion of salmon migrated through the southern inlet.

For salmon, this ability is important, and in some cases, a matter of life and death. Efficiently navigating from foraging grounds to coastal breeding areas means more time spent feeding in open water, which translates into more energy for the journey home, researchers say. The imprinting capacity also ensures salmon reach their spawning sites at the right time.

Understanding this capacity may have implications for both wild and farmed salmon, a commercially important fish. For the last decade, salmon has been the third most consumed type of seafood in the United States, behind canned tuna and shrimp, with the average American citizen chowing down on two pounds of the fish per year.

“The Earth’s magnetic field is quite weak compared to the magnetic fields that humans can produce,” said study author Nathan Putman, a professor in the fisheries and wildlife department at Oregon State University, in a statement. “If, for instance, hatchery fish are incubated in conditions with lots of electrical wires and iron pipes around that distort the magnetic field, then it is conceivable that they might be worse at navigating than their wild counterparts.”

Using new technology, scientists can study how infestations by insects like the western spruce budworm play a role in climate change. Photo by Paul Williams

It’s become a destructive cycle in the western U.S.: Warmer temperatures and drought conditions prolong the life cycle of mountain pine beetles, allowing them to prey on the pine, spruce and fir trees that blanket the mountains. The trees turn reddish-brown before dying off–a phenomenon the National Park Service deemed “an epidemic stretching from Canada to Mexico.” There’s widespread concern that such tree mortality creates an excellent fuel source for wildfires.

Until recently, scientists were left to survey the damage from the ground, with little ability to understand the causes and processes. But now new technology is enabling them to use satellite imagery to identify the sources of small, ecosystem-altering events–some of which, for example beetle outbreaks, are related to climate change drivers. A computer program called LandTrendr, developed by Boston University Earth and Environment professor Robert Kennedy, allows scientists to combine data they collect on the ground with satellite imagery from the U.S. Geological Survey (USGS) and NASA to get a better understanding of environmental disturbances.

Since 1972, NASA and the USGS have deployed satellites that snap specialized digital photographs of Earth’s landscapes. They’re able to capture details that exist in wavelengths invisible to the human eye, including those slightly longer than visible light called the near infrared. Healthy plants reflect energy in the near infrared, and by scanning the imagery, scientists can detect disruptions in Earth’s landscapes.

In the past, these images were prohibitively expensive, limiting scientists’ access. “We’d look at an image from 2000 and one from 2005 and ask, ‘What’s changed?’” Kennedy explained. “If you’re only looking at two images, it’s very difficult to track slowly evolving changes. You can tell something’s changed, but you don’t know how long it’s taken.”

When the USGS began providing these images for free in 2008, it was a turning point for Earth scientists. They now had access to thousands of shots of any given geographic region–images that Kennedy’s LandTrendr tool utilizes. “By looking at all the images, you can watch [changes] unfold. You have more confidence that you’re actually seeing trends,” he said. This is particularly useful for understanding climate change and land use change, which are “all about process,” according to Kennedy.

Kennedy is currently using LandTrendr technology to look at the net carbon exchange of forests; among other things, his work analyzes the amount of carbon lost in forests due to fire, clear cuts, partial cuts and urbanization. Studies of climate change in the Arctic and in transition zones between ecosystems are also utilizing LandTrendr. But in the Pacific Northwest, Garrett Meigs, a forestry PhD candidate at Oregon State University, is using LandTrendr to study the intersection of wildfire and insects.

Specifically, Meigs is examining the large wildfires that have ravaged Washington and Oregon since 1985, and how outbreaks of the mountain pine beetle and western spruce budworm affect subsequent fire activity. “When there’s drought, stress, a higher susceptibility to infestation, we can see the dieback of forest,” he said.

The LandTrendr algorithm incorporates satellite images of the regions affected by fire and bugs with Meigs’ own fieldwork and historical aerial data from the U.S. Forest Service, which has long used airplanes to survey insect infestations. “There were things we couldn’t detect or see before, but now we’re able to,” Meigs said.

Below is a video showing a LandTrendr visualization of the Pacific Northwest. Kennedy explains how it works: Stable evergreen forests are represented by the blue areas; when a mountain pine beetle infestation erupts, in this case in the Three Sisters area of Oregon, the imagery glows red. And when a slow-moving western spruce budworm moves into an area–there, the southern foothills of Mount Hood–it morphs yellow.

Could LandTrendr help predict climate change? Possibly. “We can’t see the future, we can only document with the satellites what has happened. But the whole game with science is to develop understandings that allow for prediction,” Kennedy says. “My hope is that by creating these maps and capturing these processes in ways we haven’t been able to see them before, we can test [climate change] hypotheses” by documenting where, when and if predicted effects occur, he said.

While Meigs’ study of insects and wildfire is largely retrospective, it has the potential to aid in future forecasting efforts. “We have a baseline to measure future change,” he says. “By seeing the conditions leading up to big insect outbreaks or wildfires, we may be able to recognize them as they emerge in the future.”

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.”