The historic Egyptian city of Alexandria is crumbling due to rising sea levels, scientists have found.

Over the past decade, the rate at which buildings have collapsed along the ancient city's seafront has increased from around one per year to as many as 40 per year, according to a study published Feb. 12 in the journal Earth's Future.

In the past 20 years, 280 buildings in this 2,300-year-old port city — known for being the birthplace of Cleopatra and the ancient home of the famed Library of Alexandria — have collapsed due to coastal erosion, and 7,000 more are at risk of collapsing in the future, according to the paper. Between 2014 and 2020 alone, 86 buildings completely crumbled, and 201 partially collapsed across the city, resulting in 85 deaths.

"The true cost of this loss extends far beyond bricks and mortar," study co-author Essam Heggy, a water scientist at the University of Southern California's Viterbi School of Engineering, said in a statement. "We are witnessing the gradual disappearance of historic coastal cities, with Alexandria sounding the alarm. What once seemed like distant climate risks are now a present reality."

The crumbling of coastal buildings results from sea level rise and the subsequent intrusion of seawater into the ground under the city. As saltwater creeps farther inland due to rising sea levels, it increases groundwater levels beneath buildings and other infrastructure and erodes the soil. This can lead the ground to sink, which makes buildings unstable and at risk of collapse. Additionally, saltwater corrodes the steel reinforcements of building foundations, further weakening the structures.

Average global sea levels have risen by between 8 and 9 inches (20 to 23 centimeters) since 1880, with a 4-inch (10 cm) rise since 1993 alone, according to the National Oceanic and Atmospheric Administration (NOAA). If nothing is done to curb climate change, U.S. sea levels could rise by as much as 7.2 feet (2.2 meters) by 2100 compared with the levels seen in 2000.

Low-lying cites face the highest risk of erosion and flooding due to sea level rise, especially those along the U.S. East Coast, West Coast and Gulf Coast, according to NASA.

"Our study challenges the common misconception that we'll only need to worry when sea levels rise by a meter," Heggy said. "However, what we're showing here is that coastlines globally, especially Mediterranean coastlines similar to California's, are already changing and causing building collapses at an unprecedented rate."

In the study, the researchers mapped collapsed buildings around Alexandria between 2001 and 2021, and compared satellite images from between 1974 and 2021 with maps of the city from 1887, 1959 and 2001 to determine sea level rise. Using this data, they determined that Alexandria has seen its coastline move inland by tens of meters over the past few decades, with some regions experiencing up to 79 to 118 feet (24 to 36 m) of soil erosion per year.

The researchers also analyzed chemical isotopes in the soils to determine the degree of soil erosion.

"Our isotope analysis revealed that buildings are collapsing from the bottom up, as seawater intrusion erodes foundations and weakens the soil," study co-author Ibrahim Saleh, a soil radiation scientist at Alexandria University, said in the statement. "It isn't the buildings themselves, but the ground underneath them that's being affected."

The researchers suggest several ways that Alexandria could prepare for the oncoming onslaught of seawater. These steps include building sand dunes and other barriers along the coast, elevating buildings, and relocating people who live in the highest-risk areas.

"Historic cities like Alexandria, which represent the cradle of cultural exchange, innovation and history, are crucial for safeguarding our shared human heritage," Heggy said. "As climate change accelerates sea level rise and coastal erosion, protecting them isn't just about saving buildings; it's about preserving who we are."

Hurricane Irma's winds are among the highest ever seen for an Atlantic hurricane, and those winds bring the threat of significant storm surge and high waves. But experts say the extent of that threat depends on where the hurricane goes, and the local characteristics of the coast and seafloor.

Everyone from the Florida Panhandle to South Carolina should be on alert to "see some really serious storm surge depending on this track," said Hal Needham, a storm-surge specialist and founder of Marine Weather and Climate, a private company that helps communities improve resiliency against coastal hazards.

Right now, that track is uncertain, but for any one spot, "a little change in the track can really change your surge potential," he told Live Science. [Hurricane Irma Photos: Images of a Monster Storm]

Rising waters

Storm surge is the rise in sea level that happens along a coast as the howling winds of a hurricane create a buildup of water. Intense storms like Irma — which is packing winds of 185 mph (298 km/h) at its core and is among the strongest hurricanes ever measured in the Atlantic — generate more surge than weaker storms do, as surge increases exponentially with winds. Storm surge accounts for nearly half of all hurricane-related deaths, according to the National Oceanic and Atmospheric Administration.

Storm size also plays a role, with bigger storms both amplifying surge levels and bringing the potential for storm surge to a wider area. Irma is relatively big for a Category 5 storm — the highest ranking on the Saffir-Simpson scale of hurricane strength — so it poses a significant threat, Needham said.

But how big storm surge is in a given area also depends on local characteristics, he said. Storm surge is higher in areas with shallow coastal waters and where the coastline is concave, which focuses the incoming water.

Conversely, the waves that a hurricane's winds whip up tend to be highest where there are deep coastal waters, he said.

The difference has to do with how water of different depths reacts to the energy of a hurricane. In deeper waters, the energy the storm generates doesn't break until it reaches land, "so it forms these monster waves" that can reach 50 feet (15 meters) or higher, Needham said. In contrast, in shallow water, the energy breaks many times before it reaches shore, so waves aren't as high, and surge dominates. [Hurricane Irma: Everything You Need to Know About This Monster Storm]

In Irma's crosshairs

The waters off the Leeward Islands and other islands in the Caribbean region are relatively deep, so although surge was expected to be significant there, it won't be as high as it might be along a shallower coastline. The National Hurricane Center forecast storm surge of 7 to 11 feet (2 to 3 m) for the northern Leeward Islands and the British and U.S. Virgin Islands, and 15 to 20 feet (4.5 to 6 m) for Turks and Caicos and the southeastern Bahamas.

"These super intense storms are pushing a tremendous amount of storm surge, so even areas without shallow bathymetry [depth] can observe locally high surges," Needham said in an email.

Large waves will act on top of that surge, the NHC warned. Such waves can also push water far inland, Needham said, and waves can pile on top of one another, with one wave breaking before the water from a previous one has washed back to sea.

Waves and surge can also outrun a storm, as happened when Hurricane Ike hit Texas and Louisiana in 2008, Needham said. Many people were waiting to evacuate before the worst winds hit but were caught when waves inundated the area and cut off evacuation routes.

For Hurricane Irma, the main question mark for storm surge is Florida, as it's uncertain what track the storm will take as it approaches the mainland U.S.

"All eyes are on Florida, where we could see a substantial surge," Needham said.

Forecast for Florida

Right now, the Florida Keys look to be the most likely part of the state to see some impact. But, as with the Leeward Islands, the relatively deep waters around the Florida Keys would mean lower storm-surge levels, Needham said, though it doesn't take much surge to overrun the low-lying roads there and cut off evacuation routes. [A History of Destruction: 8 Great Hurricanes]

If Irma makes its expected northward turn earlier along its path, it could rake along the east coast of Florida. This would likely lead to the worst-case storm-surge scenario, Needham said, because the counterclockwise circulation of the storm would keep winds pushing water onshore for an extended period of time. By contrast, if the storm were to parallel Florida's west coast, that same circulation would mean winds along the coast would move offshore, pushing water away.

The coast south of Palm Beach has deeper waters, but there are some areas, such as Biscayne Bay, where the shape of the coastline concentrates the surge, Needham said. That area saw the highest storm surge when Hurricane Andrew came ashore in 1992, the last Category 5 storm to make landfall in the U.S.

North of Palm Beach, the water is shallower; this area likely will have the biggest storm-surge threat if Irma moves up that way, Needham said. Of particular concern are the coasts of Georgia and South Carolina, where the coastline, like in Biscayne Bay, tends to amplify the surge.

It is also possible that Irma could make landfall in South Florida and move up through the middle of the state, which would put the biggest storm-surge threat at the state’s southern tip.

Experts are also concerned because the population of Florida has grown substantially in the past decade, and the state's coasts are considerably more built up than during the highest surges many spots have previously seen.

In Palm Beach, for example, the highest surge on record was 11 feet (3 m), in 1947. If Irma takes a worst-case path, the storm could easily produce a surge of 17 feet (5 m) there, Needham said.

In nearby Miami, the highest surge on record was 15 feet (4.5 m), in 1926. Needham cited a picture of that flooding that shows what such a surge can do.

"You just see the tops of palm trees sticking out," he said.

Original article on Live Science.

SAN FRANCISCO — About one-quarter of the world's population lives in coastal areas that will be unlivable by the year 2100 because of rising sea levels, researchers say.

In a special issue of the journal Earth's Future, coastal scientists and engineers detailed projections for sea-level rise for the year 2100, and described their model Monday (Dec. 12) here at the annual meeting of the American Geophysical Union.

Sea-level rise is a global phenomenon, with more than 130 cities with populations of 1 million people or more along vulnerable coasts, said Robert Nicholls, a professor of coastal engineering at the University of Southampton in the U.K. [Images of Melt: Earth's Vanishing Ice]

"To really understand how this might be impacted by sea-level rise, or other kinds of change, we need to understand all of the different scales and how they interact," Nicholls said. "That's what we've been doing in this big project."

The Earth's Future research project focused on creating a new model for sea-level rise that takes a more holistic approach in considering factors that will impact coastal communities, the scientists said. The traditional "bathtub model" — which simply raises water a certain height based on estimated ice melt — takes into account only rising water levels. In their new study, researchers built a model that considers not only rising water levels, but also incorporates the impacts of tides, storm surges, coastal infrastructure and defense frameworks (such as dikes).

What they found was a much more dynamic picture of how coastal communities will be affected by rising seas. Predictions typically look 50 to 100 years into the future, when the coastal systems will have changed dramatically, said Scott Hagen, director of the Louisiana State University Center for Coastal Resiliency.

For instance, models show that if sea levels rose 6.6 feet (2 meters) — the general estimation by scientists for sea-level rise if if carbon dioxide emissions continue — for a salt marsh along the coast of Louisiana, much of the marsh area would become open water by 2100.

"When that marsh is converted to open water, then what we can consider is that a hurricane storm surge can move more freely, farther into that coastal land," Hagen said. "Knowing what's happening at these salt marsh regions is really important for us to understand the ecosystem impacts of sea-level rise in general, and climate change as a whole."

In a developed area, such as Bangladesh (one of the most vulnerable areas to sea-level rise, according to Nicholls), the new model included such systems as pollution and land use, and even poverty and health, to determine risk.

Nicholls said such considerations as the deterioration of dikes will drastically change the sea-level rise prediction. A side-by-side comparison with the traditional model showed that the new systematic model determined there could be much wider, and more devastating flooding.

"You can see that it's a rather different picture from the bathtub model, the area could easily be flooded so much more," Nicholls said. "This is just one realization of what might happen, there are a lot of different pathways. But the point is that you're getting a much richer, more detailed picture of what might happen."

Original article on Live Science.

Winter storm Jonas brought with it record-breaking amounts of snow and blustering winds when it plowed through the northeastern and mid-Atlantic United States in late January. Now, scientists at NASA have created a new map showing the direction and speeds of the massive storm's wind gusts.

The map, released by NASA's Earth Observatory on Jan. 29, shows especially strong winds along the coasts of Maryland, Delaware and southern New Jersey.

Winds during winter storm Jonas wreaked havoc in coastal areas, with some gusts reaching 90 mph (145 km/h) — strong enough to be considered hurricane-force winds, according to NASA. The arrows on the map represent wind direction, and the shades of blue indicate wind speeds increasing from dark to light blue. [Winter Storm Photos: Watch Jonas Wallop the Eastern US]

But the new map does not use direct measures of wind speed and direction. Instead, it is based on data from RapidScat, a sensor mounted on the International Space Station.

RapidScat measured microwave pulses that were reflected off the ocean surface back toward the sensor. Waters that were disturbed more by the wind returned a strong signal, while calmer waters returned a weak signal, allowing scientists to infer wind speed and direction based on the position and roughness of the waves, NASA officials said. RapidScat is an important tool for meteorologists, because maximum sustained winds are not always equally distributed in a storm, agency officials added.

As the storm worsened on Jan. 23, the formidable winds caused a storm surge, or an abnormal rise of the water level, leading to significant coastal flooding. Along the New York Harbor area, the storm surge added around 3 feet (0.9 meters) to the normal tides, said Patrick Maloit, a meteorologist at the National Weather Service.

The massive storm caused historic coastal flooding and widespread power outages in New Jersey. The town of Cape May, New Jersey, experienced its highest coastal flood on record, beating the levels that resulted from Hurricane Sandy in 2012, according to Gary Szatkowski, another meteorologist for the National Weather Service.

Hurricane Sandy was pivotal in highlighting the problem of expanding coastal cities in the Northeast without adequate infrastructure to deal with extreme weather. With sea levels rising at a faster rate than ever before, according to climatologists at NASA, storms like Sandy and Jonas have the potential to cause even more devastation to both infrastructure and natural resources.

In Delaware, beaches in Rehoboth and Bethany lost sand dunes due to winter storm Jonas, according to news reports. And in Virginia, aerial photographer Patrick Hendrickson captured an image (above) of several new breaches in a beach on Assateague Island.

Sea-level rise and the resulting beach erosion hit especially close to home for NASA because half to two-thirds of NASA's assets stand within 16 feet (5 m) of sea level. In fact, the beach on Assateague Island helps protect launch infrastructure on Wallops Island, where several commercial and government rockets are launched each year — and it's increasingly threatened by rising sea levels.

Follow Knvul Sheikh on Twitter @KnvulS. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Melting ice triggered by global warming may make Earth whirl faster than before and could shift the axis on which the planet spins, researchers say.

This could also affect sunset times, as the length of Earth's day depends on the speed at which the planet rotates on its axis. Prior research found the rate at which Earth spins has changed over time.

For instance, ancient Babylonian, Chinese, Arab and Greek astronomers often recorded when eclipses occurred and where these phenomena were seen. This knowledge, in combination with astronomical models that calculate what the positions of the Earth, sun and moon were on any given date and time, can help reveal how fast Earth must have been spinning. To do so, researchers calculate the speed necessary for the planet to face the sun and moon in ways that allowed those astronomers to observe the eclipses. [50 Amazing Facts About Earth]

In general, the gravitational pull of the moon and sun on Earth is relentlessly slowing the planet's rate of spin. However, in the short term, a variety of different factors can also speed up and slow down how fast Earth whirls.

Previous research has found that melting glaciers triggered by global warming helped cause a significant amount of global sea-level rise in the 20th century. In theory, rising sea levels — once estimated to be climbing at a rate of about 0.06 to 0.08 inches (1.5 to 2 millimeters) per year — should also have slightly shifted Earth's axis and increased the rate at which the planet spins.

When polar ice caps melt, they remove weight off underlying rock, which then rebounds upward. This makes the poles less flat and the planet more round overall. This should in turn cause Earth to tilt a bit and spin more quickly.

However, previous research mysteriously could not find evidence that melting glaciers were triggering a shift in either Earth's rotation or axis that was as great as predicted. This problem is known as "Munk's enigma," after oceanographer Walter Munk at the Scripps Institution of Oceanography in La Jolla, California, who first noted the mystery, in 2002.

Now, in a new study, researchers may have solved this enigma and shown that rising sea levels are indeed affecting Earth's spin and axis.

"The rise of sea level and the melting of glaciers during the 20th century is confirmed not only by some of the most dramatic changes in the Earth system — for example, catastrophic flooding events, droughts [and] heat waves — but also in some of the most subtle — incredibly small changes in Earth's rotation rate," said study lead author Jerry X. Mitrovica, a geophysicist at Harvard University in Cambridge, Massachusetts.

First, the scientists noted that recent studies suggested 20th-century glacial melting was about 30 percent less severe than Munk assumed. This should significantly reduce the predicted amount of shift in Earth's spin and axis.

Moreover, the research team's mathematical calculations and computer simulations found that prior research relied on erroneous models of Earth's internal structure. This meant previous studies did not correctly account for how much glaciers would deform underlying rock and influence Earth's spin.

Furthermore, interactions between Earth's rocky mantle and the planet's molten metal outer core should have helped slow the planet's spin more than was previously thought.

Altogether, these adjustments helped the scientists find that ongoing glacial melting and the resulting sea-level rise are affecting the Earth in ways that match theoretical predictions, astronomical observations, and geodetic or land-survey data.

"What we believe in regard to melting of glaciers in the 20th century is completely consistent with changes in Earth's rotation [as] measured by satellites and astronomical methods," Mitrovica told Live Science. "This consistency was elusive for a few years, but now the enigma is resolved.

"Human-induced climate change is of such pressing importance to society that the responsibility on scientists to get things right is enormous," Mitrovica said. "By resolving Munk's enigma, we further strengthen the already-strong argument that we are impacting climate."

The scientists detailed their findings online today (Dec. 11) in the journal Science Advances.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Rising sea level is among the most potentially catastrophic effects of human-caused climate change. Increases in sea level strengthen the destructive power of storms, and threaten to swamp major coastal cities, as well as small-island and low-lying nations. In the United States alone, more than 8 million people live in areas at risk of coastal flooding.

During the 20th century, global sea levels crept up by about 6.7 inches (17 centimeters), and the rate of increase appears to have accelerated since the 19th century.

This century, scientists expect to see sea levels continuing to rise as more warming causes water to expand and melts ice that flows into the ocean. But just how high sea levels will go in the next 87 years is a wide open question. A soon-to-be released report won't have definitive answers, but it is expected to offer a range of projections drawn from current research.

On Friday, Sept. 27, the Intergovernmental Panel on Climate Change (IPCC) is scheduled to release a summary of the physical sciences section of its Assessment Report 5. The numbers in the IPCC’s assessment reports serve as a reference point for decision makers and for the general understanding of climate change.

Mysterious ice sheets

Six years ago, an earlier version of the IPCC's report estimated average sea levels could rise by somewhere between 7 inches (18 centimeters) and 1.9 feet (0.59 meters) by 2100. But scientists lacked key information when they put this report together, and work done since indicates that end-of-the-century sea levels could be higher. 

"The key point about those projections is they included only part of the story,” Chris Little, an associate research scholar at Princeton University, said of the sea level projections in 2007. Namely, the authors could not fully consider potential contributions from ice sheets covering Greenland and Antarctica.

Scientists know that these ice sheets could give a large boost to sea levels because of the sheer amount of water locked up in them. These massive layers of ice take up water from the oceans through snowfall (water evaporates from the oceans and turns to precipitation in the atmosphere) and return it through melt, but scientists didn’t understand aspects of this process well enough to fully account for how climate change might affect it.

In recent years, understanding of ice sheets’ potential contribution has improved, to some degree.

"I think we understand it much more," said David Vaughan, coordinator of the European Union-funded Ice2sea program. Though he added, "We don't understand it to my satisfaction "

Work by Ice2sea has pushed projections higher than those contained in the IPCC's 2007 report, with the highest plausible projection at a little over 1 meter (3.3 feet), Vaughan said. [8 Ways Global Warming is Already Changing the World]

"It is truly an ongoing process," Little said. "The information is going to continue to get better over time."

Controversy at the high end

The IPCC projectionshave relied on scientists' understanding of physical processes that contribute to sea level change. Another type of model has yielded higher future sea level projections, topping out at 2 m (6.6 feet). These semi-empirical models rely heavily on the historical relationship between changes in temperatureand sea level to look into the future.

"The big argument in the scientific community is, 'How much is this going to look like past events?" because this really is different," said Josh Willis, a climate scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. "We are dumping carbon dioxide into the atmosphere faster than anything done in millions of years, and the temperature is changing really rapidly."

What’s more, after the peak of the last ice age, much more ice was available to melt and raise sea levels than at present, he said.

But the other alternative, physics-based models, still don't account for all of the processes that can influence changing sea levels, potentially underestimating the impact. "So we are stuck between a rock and a hard place," Willis said.

"The 2 meters by 2100 is cited a lot, but if you ask scientists what they think of that number, they say it is probably a little high, maybe 1.5 meters [4.9 feet] is more like an upper bound," Willis said.

Follow us @livescience, Facebook & Google+. Original article on LiveScience.

Special instruments installed in Greenland and Antarctica to measure melting ice may help scientists more accurately predict the rate of rising sea levels in the future.

Earlier this year, David Holland, a professor of mathematics at the Center for Atmosphere Ocean Science at New York University, spent two months installing devices on the Greenland Ice Sheet and the West Antarctic Ice Sheet.

These instruments, which are all roughly the size of a large suitcase and weigh about 100 pounds (45 kilograms), will study the atmosphere by collecting information on wind, air temperature and humidity. Other water-based devices will gather data on ocean temperatures, enabling the researchers to track the movement of warm ocean currents that melt portions of the ice sheets.

"Right now, there seems to be more melting going on than before," Holland told LiveScience. "By measuring the melting glaciers, we can see how much water is going into the ocean and raising sea levels." [Photos of Melt: Glaciers Before and After]

When ice melts, the water flows down slopes and eventually empties into the ocean, causing sea levels to rise. But, understanding why these changes are happening — and how much sea levels are rising — remains challenging, Holland said.

This is partly because researchers do not have enough data on melting ice in Greenland and Antarctica. Currently, most of the changes in the ice sheets have been observed by satellites in space.

"We can see that the ice is getting lower, and the oceans are rising higher," Holland said. "But, there is only so much we can see from space. We cannot see into the ocean, or below the ice surface, so that's why we go to these locations and put instruments into the ocean."

With more precise measurements, scientists may be able to determine the extent that human activities are contributing to the dwindling ice sheets, he added.

"Right now, we don't have enough data to really distinguish if what's going on is completely natural, or related to human activity in a changing climate," Holland said. "We need sustained measurements for several years in order to separate natural changes from possible anthropogenic changes."

As more and more information is collected, researchers will be able to feed data into complex mathematical formulas to develop computer models of rising global sea levels, Holland explained. He intends to use these instruments indefinitely to track long-term changes in the polar ice sheets.

"You can't build a model until you have observations of what you're trying to build," Holland said. "Polar regions, particularly Antarctica, are very difficult to access, which is why we hope this will really benefit our researchers and, really, the entire international community."

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

A set of 80-year-old photographs discovered in a basement archive reveals the remarkable sensitivity of Greenland's glaciers to climate change, according to a new study that one scientist called "glaciological research with a splash of Indiana Jones."

The research, published online May 27 in the journal Nature Geoscience, reveals a pattern of stop-and-go melting along Greenland's southeastern coast. Aerial photographs dating back to 1931 show a period of glacier retreat between 1933 and 1943, followed by a cool period of advancing ice until 1972. More recently, most of those gains have been lost as temperatures creep upward.

"From these images, we see that the midcentury cooling stabilized the glaciers," said Jason Box, a geographer at the Byrd Polar Research Center at Ohio State University. "That suggests that if we want to stabilize today's accelerating ice loss, we need to see a little cooling of our own." [Images: Greenland's Gorgeous Ice]

Early retreat

The long-lost photographs were taken during an expedition led by Danish explorer Knud Rasmussen and include aerial photos of land, sea and ice in southeastern Greenland. After expedition researchers created a map from the photographs, the glass-plate images were tucked away at the National Survey and Cadastre of Denmark and forgotten.

National Survey researchers were cleaning out the basement of their archives when they ran across the glass plates. They contacted Anders A. Bjørk, a doctoral fellow at the Natural History Museum of Denmark. For Bjørk, the find was a gold mine. Satellites have kept an orbiting eye on Greenland's ice since the 1970s, but measurements from before then are rare. That makes it tough to determine the ice's sensitivity to temperatures.

Bjørk, Box and their colleagues digitized the photographs and used software to compare them with images taken by the U.S. military in the World War II era and to modern satellite and aerial photographs. They found the 1933-43 ice retreat followed an unusually warm period in Arctic history. From about 1919 to 1932, temperatures in the region rose by about 3.6 degrees Fahrenheit (2 degrees Celsius) per decade — about a half-degree Celsius cooler than today's Arctic temperature, but still a useful parallel.

Between 1933 and 1943, glaciers retreated by about 33 to 164 feet (10-50 meters) per year, the photos revealed. Glaciers that terminated on land retreated just as fast as glaciers that fed the sea. In the current period of ice loss that began in the 2000s, ocean-abutting glaciers are melting much more quickly than land-bound glaciers. It could be that the 1930s ice loss pushed glaciers back to higher elevations and stripped them of surface area, making them less vulnerable to warming temperatures.

Today, average ice loss in southeastern Greenland is 164 feet (50 meters) of retreat each year, higher than the 1930s rates. Several fast-melting glaciers, including one losing 2,910 feet (887 meters) of ice each year, are driving up the average.

A cool period

Between these periods of melt, things were looking up for Greenland's glaciers. During the 1943-72 cooling period, 60 percent of southeastern Greenland's glaciers advanced, and 12 percent stayed stationary.

The cooling was likely due in part to natural atmospheric cycles and in part to sulfur dioxide pollution. Sulfur dioxide, an industrial pollutant that is a main cause of acid rain, wrecks havoc on human health, but it also reflects sunlight away from the Earth. Atmospheric sulfur dioxide levels decreased following the Clean Air Act of 1963.

The glaciers' response to heat and cold was faster than previous studies had suggested, the researchers found, suggesting a high degree of sensitivity to air and ocean temperatures.

The ice losses of the last decade or so largely has wiped out the gains of the midcentury cool period. The current loss of ocean-terminating glaciers is a problem because it is the major contributor to sea-level rise, according to Benjamin Smith, a University of Washington researcher. Smith, who was not involved in the study, wrote an accompanying editorial in Nature Geoscience. He compares the study launched by the long-lost photos to an Indiana Jones quest.

Although recent melting has outpaced the 1930s melting, the patterns of melt are similar, Smith says.

"This indicates that the retreat in the 2000s was a typical response of the ice sheet to warmer air and ocean temperatures, and that future warming events can be expected to have similar consequences," he wrote.

Recent images reveal that Greenland's glaciers are moving 30 percent faster than they were a decade ago.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

You've probably heard about the effects of global warming: rising temperatures, melting ice caps and rising sea levels in the near future. But Earth's changing climate is already wreaking havoc in some very weird ways. So gird yourself for such strange effects as savage wildfires, 25-mile long icebergs, disappearing lakes, freak allergies, and the threat of long-gone diseases re-emerging.

Forest Fire Frenzy

While it's melting glaciers and creating more intense hurricanes, global warming also seems to be heating up forest fires in the United States. In western states over the past few decades, more wildfires have blazed across the countryside, burning more area for longer periods of time. Scientists have correlated the rampant blazes with warmer temperatures and earlier snowmelt. When spring arrives early and triggers an earlier snowmelt, forest areas become drier and stay so for longer, increasing the chance that they might ignite.

Ruined Ruins

All over the globe, temples, ancient settlements and other artifacts stand as monuments to civilizations past, which until now have withstood the tests of time. But the immediate effects of global warming may finally do them in. Rising seas and more extreme weather have the potential to damage irreplaceable sites. Floods attributed to global warming have already damaged a 600-year-old site, Sukhothai, which was once the capital of a Thai kingdom.

Rebounding Mountains

Though the average hiker wouldn't notice, the Alps and other mountain ranges have experienced a gradual growth spurt over the past century or so thanks to the melting of the glaciers atop them. For thousands of years, the weight of these glaciers has pushed against the Earth's surface, causing it to depress. As the glaciers melt, this weight is lifting, and the surface slowly is springing back. Because global warming speeds up the melting of these glaciers, the mountains are rebounding faster.

Speedier Satellites

A primary cause of a warmer planet's carbon dioxide emissions is having effects that reach into space with a bizarre twist. Air in the atmosphere's outermost layer is very thin, but air molecules still create drag that slows down satellites, requiring engineers to periodically boost them back into their proper orbits. But the amount of carbon dioxide up there is increasing. And while carbon dioxide molecules in the lower atmosphere release energy as heat when they collide, thereby warming the air, the sparser molecules in the upper atmosphere collide less frequently and tend to radiate their energy away, cooling the air around them. With more carbon dioxide up there, more cooling occurs, causing the air to settle. So the atmosphere is less dense and creates less drag.

Survival of the Fittest

As global warming brings an earlier start to spring, the early bird might not just get the worm. It might also get its genes passed on to the next generation. Because plants bloom earlier in the year, animals that wait until their usual time to migrate might miss out on all the food. Those who can reset their internal clocks and set out earlier stand a better chance at having offspring that survive and thus pass on their genetic information, thereby ultimately changing the genetic profile of their entire population.

The Big Thaw

Not only is the planet's rising temperature melting massive glaciers, but it also seems to be thawing out the layer of permanently frozen soil below the ground's surface. This thawing causes the ground to shrink and occurs unevenly, so it could lead to sinkholes and damage to structures such as railroad tracks, highways and houses. The destabilizing effects of melting permafrost at high altitudes, for example on mountains, could even cause rockslides and mudslides. Recent discoveries reveal the possibility of long-dormant diseases like smallpox could re-emerge as the ancient dead, their corpses thawing along with the tundra, get discovered by modern man.

Pulling the Plug

A whopping 125 lakes in the Arctic have disappeared in the past few decades, backing up the idea that global warming is working fiendishly fast nearest Earth's poles. Research into the whereabouts of the missing water points to the probability that permafrost underneath the lakes thawed out. When this normally permanently-frozen ground thaws, the water in the lakes can seep through the soil, draining the lake, one researcher likened it to pulling the plug out of the bathtub. When the lakes disappear, the ecosystems they support also lose their home.

Arctic in Bloom

While melting ice in the Arctic might cause problems for plants and animals at lower latitudes, it's creating a downright sunny situation for Arctic biota. Arctic plants usually remain trapped in ice for most of the year. Nowadays, when the ice melts earlier in the spring, the plants seem to be eager to start growing. Research has found higher levels a certain type of the pigment chlorophyll (telltale sign of photosynthesis) in modern soils than in ancient soils, showing a biological boom in the Arctic in recent decades. [Arctic Phytoplankton Blooms Earlier]

Heading for the Hills

Starting in the early 1900s, we've all had to look to slightly higher ground to spot our favorite chipmunks, mice and squirrels. Researchers have found that many of these animals have moved to greater elevations, possibly due to changes in their habitat caused by global warming. Similar changes to habitats are also threatening Arctic species like polar bears, as the sea ice they dwell on gradually melts away. [See images of swimming polar bears]

Aggravated Allergies

Have those sneeze attacks and itchy eyes that plague you every spring worsened in recent years? If so, global warming may be partly to blame. Over the past few decades, more and more Americans have started suffering from seasonal allergies and asthma. Though lifestyle changes and pollution ultimately leave people more vulnerable to the airborne allergens they breathe in, research has shown that the higher carbon dioxide levels and warmer temperatures associated with global warming are also playing a role by prodding plants to bloom earlier and produce more pollen. With more allergens produced earlier, allergy season can last longer. Get those tissues ready.

Since 1900, global sea levels have crept upward about seven inches. Rising temperatures are melting glaciers and ice sheets, as well as warming the oceans directly, which causes them to expand. Various researchers have attributed only a portion of the rise in water level to carbon dioxide (CO₂) released by human actions—and blamed the rest on natural factors such as solar activity. The latest study goes much further, faulting people for more than three-quarters of the sea-level change during the past century.

Records of tide height have been kept for centuries at several seaports (Amsterdam since 1700, Liverpool since 1768, Stockholm since 1774, and many other places since 1850). Such long records have enabled Svetlana Jevrejeva, of the British government’s Proudman Oceanographic Laboratory in Liverpool, and two colleagues to statistically model the influence of various factors on sea level during the past three centuries, and to extrapolate the findings over the past millennium.

The team found that up until about 1800, sea levels actually fell owing to volcanic eruptions that periodically injected ash into the atmosphere, veiling the Sun and cooling the Earth. But as the waters rose after 1850, the biggest contributing factor was increasing atmospheric CO2.

Significantly, Jevrejeva’s team calculated that without the ongoing, mitigating effects of volcanic activity since 1880, sea levels would now be about three inches higher than they are. 

This research was published in the journal Geophysical Research Letters.

Our planet and its inhabitants - including we humans - are in a precarious position as we approach Earth Day, April 22.

While global warming is widely accepted as a reality by scientists and many governments and industrial leaders, progress to curb greenhouse gases and other forms of pollution remains limited. The current economic climate will likely make pollution control efforts more difficult, analysts say.

Recent studies, as well as the 2007 report by the Intergovernmental Panel on Climate Change (IPCC) have pointed to some of the likely effects of uncurbed greenhouse gas emissions: rising global temperatures, rising sea levels, Arctic sea ice melt, the disappear of glaciers, epic floods in some areas and intense drought in others.

These effects are intensified when combined with other forms of pollution the world's rising population.

Humans will face widespread water shortages. Famine and disease will increase. Earth’s landscape will transform radically, with a quarter of plants and animals at risk of extinction.

While putting specific dates on these traumatic potential events is challenging, this timeline paints the big picture and details Earth's future based on several recent studies and the longer scientific version of the IPCC report. This timeline is an updated version of one first published by LiveScience in 2007.

2008

Arctic sea ice hits its second lowest summer ice extent on record (the lowest extent was in 2007). A massive chunk of ice breaks away from Greenland's Petermann Glacier. Several breakups of ice shelves in Antarctica are observed. (NSIDC; Jason Box, Ohio State University; ESA, NSIDC)

Global oil production peaks sometime between 2008 and 2018, according to a model by a Swedish physicist. Others say this turning point, known as "Hubbert’s Peak," won’t occur until after 2020. Once Hubbert’s Peak is reached, global oil production will begin an irreversible decline, possibly triggering a global recession, food shortages and conflict between nations over dwindling oil supplies. (Doctoral dissertation of Frederik Robelius, University of Uppsala, Sweden; report by Robert Hirsch of the Science Applications International Corporation)

The Bush Administration enacts changes to the Endangered Species Act that affect reviews of government projects.

Polar bears and beluga whales are placed on the Endangered Species List. Gray wolves are delisted in certain areas.

2009

The U.S. Environmental Protection Agency declares carbon dioxide and other heat-trapping gases to be pollutants under the Clean Air Act.

An ice bridge connected to the Wilkins Ice Sheet of Antarctica breaks apart.

Many of the world's major rivers are found to be losing water. (Aiguo Dai, NCAR, Journal of Climate)

2012

The first phase of the Kyoto Protocol, an international environmental treaty created to limit the production of greenhouse gases, expires. Nations will have to draw up and enact a succesor treaty to further limit emissions, should they choose to do so.

2020

Flash floods will very likely increase across all parts of Europe. (IPCC)

Less rainfall could reduce agriculture yields by up to 50 percent in some parts of the world. (IPCC)

World population will reach 7.6 billion people. (U.S. Census Bureau)

2030

Diarrhea-related diseases will likely increase by up to 5 percent in low-income parts of the world. (IPCC)

Up to 18 percent of the world’s coral reefs will likely be lost as a result of climate change and other environmental stresses. In Asian coastal waters, the coral loss could reach 30 percent. (IPCC)

World population will reach 8.3 billion people. (U.S. Census Bureau)

Warming temperatures will cause temperate glaciers on equatorial mountains in Africa to disappear. (Richard Taylor, University College London, Geophysical Research Letters:)

In developing countries, the urban population will more than double to about 4 billion people, packing more people onto a given city's land area. The urban populations of developed countries may also increase by as much as 20 percent. (World Bank: The Dynamics of Global Urban Expansion)

The Arctic Sea could be ice-free in the summer. (James Overland, NOAA, Muyin Wang, University of Washington, Geophysical Research Letters)

2050

The Group of Eight top industrial nations has endorsed cutting greenhouse gas emission in half by this year.

Small alpine glaciers will very likely disappear completely, and large glaciers will shrink by 30 to 70 percent. Austrian scientist Roland Psenner of the University of Innsbruck says this is a conservative estimate, and the small alpine glaciers could be gone as soon as 2037. (IPCC)

Ocean acidification could kill off most coral reefs. (Ken Caldeira, Carnegie Institution of Washington, Science)

At least 400 bird species could become endangered or extinct due to deforestation and climate change. (Walter Jetz, University of California, Davis, PLoS Biology)

In Australia, there will likely be an additional 3,200 to 5,200 heat-related deaths per year. The hardest hit will be people over the age of 65. An extra 500 to 1,000 people will die of heat-related deaths in New York City per year. In the United Kingdom, the opposite will occur, and cold-related deaths will outpace heat-related ones. (IPCC)

World population reaches 9.4 billion people. (U.S. Census Bureau)

Crop yields could increase by up to 20 percent in East and Southeast Asia, while decreasing by up to 30 percent in Central and South Asia. Similar shifts in crop yields could occur on other continents. (IPCC)

As biodiversity hotspots are more threatened, a quarter of the world’s plant and vertebrate animal species could face extinction. (Jay Malcolm, University of Toronto, Conservation Biology)

2070

As glaciers disappear and areas affected by drought increase, electricity production for the world’s existing hydropower stations will decrease. Hardest hit will be Europe, where hydropower potential is expected to decline on average by 6 percent; around the Mediterranean, the decrease could be up to 50 percent. (IPCC)

Warmer, drier conditions will lead to more frequent and longer droughts, as well as longer fire-seasons, increased fire risks, and more frequent heat waves, especially in Mediterranean regions. (IPCC)

2080

While some parts of the world dry out, others will be inundated. Scientists predict up to 20 percent of the world’s populations live in river basins likely to be affected by increased flood hazards. Up to 100 million people could experience coastal flooding each year. Most at risk are densely populated and low-lying areas that are less able to adapt to rising sea levels and areas which already face other challenges such as tropical storms. (IPCC)

Coastal population could balloon to 5 billion people, up from 1.2 billion in 1990. (IPCC)

Between 1.1 and 3.2 billion people will experience water shortages and up to 600 million will go hungry. (IPCC)

Sea levels could rise around New York City by more than three feet, potentially flooding the Rockaways, Coney Island, much of southern Brooklyn and Queens, portions of Long Island City, Astoria, Flushing Meadows-Corona Park, Queens, lower Manhattan and eastern Staten Island from Great Kills Harbor north to the Verrazano-Narrows Bridge. (NASA GISS)

2085

The risk of dengue fever from climate change is estimated to increase to 3.5 billion people. (IPCC)

2100

A combination of global warming and other factors will push many ecosystems to the limit, forcing them to exceed their natural ability to adapt to climate change. (IPCC)

Atmospheric carbon dioxide levels will be much higher than anytime during the past 650,000 years. (IPCC)

Ocean pH levels will very likely decrease by as much as 0.5 pH units, the lowest it’s been in the last 20 million years. The ability of marine organisms such as corals, crabs and oysters to form shells or exoskeletons could be impaired. (IPCC)

Thawing permafrost and other factors will make Earth’s land a net source of carbon emissions, meaning it will emit more carbon dioxide into the atmosphere than it absorbs. (IPCC)

Roughly 20 to 30 percent of species assessed as of 2007 could be extinct by 2100 if global mean temperatures exceed 2 to 3 degrees of pre-industrial levels. (IPCC)

New climate zones appear on up to 39 percent of the world’s land surface, radically transforming the planet. (Jack Williams, University of Wisconsin-Madison, Proceedings of the National Academy of Sciences)

A quarter of all species of plants and land animals—more than a million total—could be driven to extinction. The IPCC reports warn that current “conservation practices are generally ill-prepared for climate change and effective adaptation responses are likely to be costly to implement.” (IPCC)

Increased droughts could significantly reduce moisture levels in the American Southwest, northern Mexico and possibly parts of Europe, Africa and the Middle East, effectively recreating the “Dust Bowl” environments of the 1930s in the United States. (Richard Seager, Lamont Doherty Earth Observatory, Science)

2200

An Earth day will be 0.12 milliseconds shorter, as rising temperatures cause oceans to expand away from the equator and toward the poles, one model predicts. One reason water will be shifted toward the poles is most of the expansion will take place in the North Atlantic Ocean, near the North Pole. The poles are closer to the Earth’s axis of rotation, so having more mass there should speed up the planet’s rotation. (Felix Landerer, Max Planck Institute for Meteorology, Geophysical Research Letters)

{{ video="LS_090415-TakeAIM" title="Climate Change Gets a Music Video" caption="AIM = Adapt Innovate Mitigate. What happens at Earth's poles will rock your world." }}

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