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

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

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

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

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

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

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

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

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

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

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

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

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

Wild bees, such as this Andrena bee visiting highbush blueberry flowers, provide crucial pollination services to crops across the globe. Photo by Daniel Cariveau

Insect pollination is crucial for the healthy development of our favorite foods, from apples and avocados to cucumbers and onions. Of the 100 crop species that provide 90 percent of the global population’s food, nearly three-quarters rely on pollination by bees. The rest need beetles, flies, butterflies, birds and bats to act as pollinators. It’s a mutually beneficial system—the flowers of most crops require pollen from another plant of the same crop to produce seeds or fruits, and bees and other critters transfer pollen from one plant to the next as they drink a flower’s nectar.

The agriculture industry relies on both wild pollinators and human-managed ones like honeybees, kept and cared for in hives across the country. Concern over the latter’s gradual decline has grown in recent times, but new research shows it might be the wild pollinators we should be worrying about.

In a study of 600 fields of 41 major crops (fruits, grains and nuts) on six continents, published today in the journal Science, researchers found that wild insects pollinate these crops more effectively than honeybees that are in the care of humans. In fact, compared to bees living in apiaries, wild pollinators lead to twice as much of what’s called “fruit set”—the amount of flowers that develop into mature fruits or seeds.

Pollination is essential for the production of fruits like cherries, cranberries and blueberries. Blueberries, along with tomatoes, especially depend on buzz pollination, a process by which bees vibrate their flight muscles rapidly to unleash a visible cloud of pollen into a flower. Honeybees aren’t capable of this kind of pollination, says lead study author Lucas Garibaldi, a professor at the National University of Río Negro in Argentina. Of all pollinator-dependent crops, approximately 8 percent require buzz pollination, he says.

Pollination, then, is central to ensuring our both our food staples and our varied diet.“These ecosystem services are free, but they’re important for our survival,” Garibaldi adds. “They need to be promoted and maintained if we want to continue living on this planet.”

Another new study found that wild bee population, as well as the number of different species of the insects, has plummeted over the last 120 years. Researchers used observations of interactions between plants and their pollinators in Illinois collected at three points in time: in the late 1800s, the 1970s and the first decade of this century. Of the 109 bee species seen visiting 26 woodland plants in the 19th century, only 54 remained by 2010. Rising temperatures caused mismatches in peak bee activity, measured by visits to different plants, and flowering times, a break in the delicate balance of insect-plant relationship.

Less diversity in the wild bee population meant fewer interactions between flowers, a change that in the agricultural world could result in smaller crop yields, says lead author Laura Burkle, an ecology professor at Montana State University. This throws off global agriculture production and speeds up land conversion to compensate for the loss.

“Things have changed for the worst,” Burkle says. “There’s an incredible amount of robustness within these interaction networks of species that allow them to persist in the face of really strong environmental changes, both in temperature and land-use change.” Unfortunately, these pollinators are “getting punched from a variety of sides,” she adds.

Can honeybees substitute for our disappearing wild pollinators? Garibaldi and colleagues found that these insects couldn’t fully replace the contributions of diverse populations of pollinators for a wide range of crops on farmlands on every continent. Flooding farmland with human-managed honeybees only supplemented pollination by wild insects, even for crops such as almonds, whose orchards are stocked routinely with bees.

Human-managed hives stocked with bees, ready to aid in pollination at an almond grove. Photo by Daniel Cariveau

Several culprits are behind the continuing decline of these wild pollinators. The insects usually live in forests and grasslands, and continuing conversion of such natural habitats into farmland results in shrinking numbers and types of wild pollinators, meaning fewer flowers receive the pollen necessary for reproduction. 

Last year, many plants in the eastern U.S. flowered a month earlier than any other time in the last 161 years, a result of such unusually warm weather. Burkle says bee development doesn’t always catch up to changing flowering times in plants, which leads to more mismatches in interaction and decreased pollination services. Another study in the same year found that elevated levels of carbon dioxide, combined with the use of nitrogen-infused fertilizer, altered some plants’ lifetime development. The toxic pairing led them to produce flowers with nectar more attractive to bumblebees than usual, but caused the plants to die sooner.

The waning insect population has already taken a measurable toll on crop production, including on one very near and dear to our hearts: coffee. A 2004 study of coffee pollination in Costa Rica found that when numbers of human-introduced honeybees shrunk in a given forest area, diverse pollinators native to the area, such as stingless bees known as meliponines native to the area, helped compensate for the loss. But these insects couldn’t survive at the edges of the forest like honeybees could, so the production of coffee, a crop highly dependent on pollination, eventually plummeted.

“This study supports the theoretical prediction that having many different species, which each respond to the environment in slightly different ways, is like having a stock portfolio from many different companies, rather than investing all your money in a single company’s stock,” explains Jason Tylianakis, a terrestrial ecology professor at the University of Canterbury in New Zealand. Tylianakis discussed the implications of Science’s two new studies in a paper also published today. “We should expect this kind of ‘insurance effect’ to become less common as more native pollinators go extinct.”

Given the mounting evidence, Tylianakis writes in an email that concerns about a global pollination crisis are not overstated. A changing climate, the rapid spread of farmland and a reliance on pesticides means diverse, wild pollinators will continue to face challenges as this century unfolds. If pollinators are dying out worldwide—and if pace of this die out continues with the variety of species getting cut in half each century, leaving behind less effective substitutes—food production as we know it could start to crumble.

“The bottom line is that we need biodiversity for our survival, and we can’t simply replace the services provided by nature with a few hand-picked species like the honeybee,” he says.

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.

Ice melt in Greenland will significantly affect water levels throughout the world, most of all the equatorial Pacific and South Africa. Photo by Christine Zenino

If you live on the coast, watch out–the shoreline close to home is moving. The planet’s two largest ice sheets, in Antarctica and Greenland, have been melting at an unprecedented pace for the past decade, and ice melt is the biggest contributor to rising sea levels. But not all coasts will draw closer inland. Scientists have determined (PDF) that water levels will rise in some parts of the world and dip in others.

Now, new research published in the journal Geophysical Research Letters and coordinated by the European organization Ice2sea shows in specific detail the effect of ice melt on sea levels by the year 2100.

Looking at Antarctica’s 15 major drainage basins and three glaciers in Greenland, the researchers relied on two ice-loss scenarios–one a mid-range melt and the other a more significant deterioration of glacial ice–and used sophisticated computer modeling to examine where and how severe the alterations in sea level would be. They keyed in on three main factors: Changes in water distribution due to the warming of the oceans; alterations in the Earth’s mass distribution that continue to occur as the crust rebounds after the last ice age, 10,000 years ago; and the fact that as glaciers melt, the Earth’s gravitational pull in the surrounding areas decreases, sending water away from the glaciers and redistributing it to other parts of the world.

What the modeling showed is that water will rush away from some polar regions and toward the equator, making the low-elevation coastal zones of the equatorial Pacific, particularly those with gently dipping shorelines, most vulnerable to rising sea levels. At the same time, water levels in some polar regions will actually drop. The total rise in the worst affected parts of the equatorial oceans could start at two feet and spike to more than three feet. This is in comparison to the six-inch sea-level rise that occurred globally in the 20th century.

In the United States, Hawaii will be hit hard. Both the moderate and more extreme ice-melt scenarios place Honolulu in the crosshairs of rising sea levels. “Honolulu is located in the broad area in the Pacific Ocean where the sea-level fingerprint is expected is expected to attain its largest… amplitude,” the authors wrote. Trouble will be brewing well before 2100, the research shows. In the latter half of the 21st century, sea levels could rise 0.32 inches per year in Hawaii, according to the more severe scenario studied.

Honolulu lies in the region that will be most affected by sea-level rise. Photo by Wally Gobetz

Other parts of the U.S. will also be affected, including the Gulf of Mexico and the East Coast, from Miami to New York City. Europe, however, will be relatively unscathed. Its close proximity to the melting ice will slow down sea-level rise. But that’s not entirely good news because it will be at the expense of greater sea-level rise in other parts.

One ramification to these rises is obvious: Coastal flooding. It’s likely that hurricanes, high seasonal waves and tsunamis will send water further inland. Also, new wetlands will be created–which sounds like a theoretical boon, but will alter surface drainage and therefore result in flooding at high tides and during heavy rainfall. In addition, coastal erosion will occur, as will the salinification of coastal groundwater aquifers, creating problems for countries like water-strapped India.

A concern the scientists have is that planners building sea walls and taking other precautionary measures are relying on outdated information. “The most reliable ‘old data’ at our disposal are those saying that sea level HAS BEEN effectively rising, on the average, by 15 to 20 cm [about six inches] during the 20th century,” the study’s lead author, Giorgio Spada of Italy’s University of Urbino, told Surprising Science in an email. “A wall of [two feet] could be enough… but we have evidence that the sea level rise is accelerating and it is ‘very likely’ that it will rise by more than 20 cm globally during the 21st century.”

Moving forward, the researchers believe that even more detailed modeling is necessary. “We need to get to a higher geographic resolution before we will really be giving planners and policy-makers what they need,” David Vaughan, program coordinator of Ice2Sea told Surprising Science. “There will be some variations in how sea-level rise changes risk between one seaside town and another 100 km [32 feet] down the coast. But we’re not in a position to advise at this level of detail.”

In the meantime, the Intergovernmental Panel on Climate Change (IPCC) is working on its fifth assessment report, a comprehensive analysis of the potential effects of climate change and suggestions for mitigating the risks. Scheduled for publication next year, it will incorporate new research–perhaps even these findings–conducted since the last report, published in 2007.

The Tigris River basin is chief among the regions in the Middle East that have suffered massive groundwater depletion in recent years. Photo by Charles Fred

Climate change, believed to have contributed to the decline of the Ottoman Empire (PDF) when drought forced villagers into a nomadic life in the late 16th century, is once again having an adverse affect on the Middle East. Precipitation has dropped off and temperatures have climbed for the past 40 years, with conditions growing especially severe in the last decade. A 2012 Yale study (PDF) showed that a drought from 2007 to 2010 so seriously stunted agriculture in the Tigris and Euphrates river basins that hundreds of thousands of people fled Iran, eastern Syria and northern Iraq.

A new study published today in the journal Water Resources Research puts an even finer point to the climate change fall-out in the Middle East: The Tigris and Euphrates river basins lost 117 million acre-feet of their stored freshwater from 2003 to 2010, an amount almost equivalent to the entire volume of water in the Dead Sea. The research, conducted by scientists at UC Irvine, NASA’s Goddard Space Flight Center and the National Center for Atmospheric Research, is one of the first large-scale hydrological analyses of the region, encompassing parts of Turkey, Syria, Iraq and Iran.

Drought typically sends water-users underground in search of aquifers, and in the midst of the 2007 water crisis, the Iraqi government, for one, did just that, drilling 1,000 wells. Such pumping has been the primary cause of recent groundwater depletion, according to the new study. Sixty percent of the lost water was removed from underground reservoirs, while dried-up soil, dwindling snowpack and losses in surface water from reservoirs and lakes exacerbated the situation. “The [groundwater storage loss] rate was especially striking after the 2007 drought,” hydrologist Jay Famiglietti, principle investigator of the study and a professor at UC Irvine, noted in a statement. Overall, the area has experienced “an alarming rate of decrease in total water storage,” he added.

Since gathering information on the ground in a region marked by such political instability isn’t very practical–or in some cases, even possible at all–the scientists instead utilized data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites. These satellites measure a region’s gravitational pull; over time, small changes observed in the strength of this pull are influenced by factors such as rising or falling water reserves. From this, the scientists uncovered variations in water storage over much of the last decade.

The video below is a visualization of groundwater fluctuations in the Tigris and Euphrates basins using GRACE satellite imagery; blues represent wet conditions and reds are indicative of dry conditions. The drought that began in 2007 is clearly reflected.

“The Middle East just does not have that much water to begin with, and it’s a part of the world that will be experiencing less rainfall with climate change,” said Famiglietti. “Those dry areas are getting dryer.” In fact, the region is experiencing the second-fastest rate of groundwater storage loss on the planet, surpassed only by India.

Yet, demand for freshwater continues to rise worldwide, including in the U.S., where aquifer depletion is also a growing problem. Groundwater supplies in the Southwest and western Great Plains have been stressed for many years, according to the United States Geological Survey (USGS). The area surrounding Tucson and Phoenix in south-central Arizona has seen the highest drop in groundwater levels–300 to 500 feet–but other regions have also suffered. Long Island and other parts of the Atlantic coast, west-central Florida and the Gulf Coast region–notably Baton Rouge–are out of balance. And perhaps most surprisingly, the Pacific Northwest is experiencing groundwater depletion as a result of irrigation, industrial water use and public consumption.

According to study co-author Matt Rodell of NASA, such depletion is unsustainable. “Groundwater is like your savings account,” Rodell said. “It’s okay to draw it down when you need it, but if it’s not replenished, eventually it will be gone.”

What’s to be done? More research, according to the authors of the new Middle East study. “The opportunity to construct the most accurate and holistic picture of freshwater availability, for a particular region or across the globe, is now on us,” they wrote. “Such science-informed studies are essential for more effective, sustainable, and in transboundary regions, collaborative water management.” Building on that last point, they called for international water-use treaties and more consistent international water laws.

They will also spread word of their findings by traveling to the Middle East. Famiglietti and three of his UC Irvine colleagues, including the study’s lead author, Katalyn Voss, are heading to Israel, Palestine and Jordan tomorrow to share their data with water authorities, scientists, water managers and NGOs; verify the GRACE measurements with locally obtained data; and begin collaborating with local groups on hydrology and groundwater-availability research.

They hope to educate themselves on the region’s best practices for water efficiency, with the goal of introducing those techniques to other water-strapped areas, including California. “Ideally, this trip will set the foundation for future research collaborations in the region, with universities and government agencies, as well as provide an opportunity for cross-regional learning between California and the Middle East,” Voss told Surprising Science.