Smithsonian.com

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.”