Thursday, March 29, 2012

Most sea level rise due to melting polar ice, study confirms

From: EarthSky

Image Credit: 	  Sean O'Flaherty on Wikimedia Commons

Image Credit: Sean O'Flaherty on Wikimedia Commons

Researchers report that Earth’s polar regions are losing 502 billion tons of water annually out of the total amount 536 billion tons lost annually worldwide.

Scientists published results in a February 2012 issue of Nature that reveal a detailed picture of how Earth’s glacier regions have changed over the last eight years. In previous publications, GRACE satellite data confirmed that Earth’s polar regions are the major contributors to rising sea levels. The recent publication focuses on the high mountain areas, such as the Himalayas and Andes, and shows that these ecosystems are remarkably robust: they are not losing nearly as much water to the ocean as the polar regions.

Earth’s ocean levels are rising at a rate of 1.48 millimeters – about .06 inches – annually. This might sound like a small number, but actually equates to approximately 500 billion tons of water added to our oceans every year! GRACE scientists wanted to know for certain where this water is coming from. One of the central mandates of the GRACE satellite project – which has been making detailed measurements of Earth’s gravity since its launch in March 2002 – is to ascertain the source of the water being added to Earth’s oceans.

Map showing the September ice extent in the Arctic in 1980, 2007, 2008, 2009, 2010, and 2011. The magenta line indicates the median September ice extent for the period 1979-2000. Image Credit: National Snow and Ice Data Center Sea Ice Index:

From simple visual evidence, if nothing else, it is clear that our polar glacier regions are depleting due to melting ice.

Arctic report card for 2011

Meanwhile, exactly how much water is being lost by glaciers in high-mountain regions, including the Alps, Andes, the Himalayas among others? In the February 2012 Nature article, GRACE researchers report that the polar regions are losing 502 billion tons of water annually out of the total amount 536 billion tons lost annually worldwide.

Glaciers in the Alps and other high mountain areas are not the greatest contributors to sea level rise, according to data from the two GRACE satellites. Courtesy of J. Balog, Extreme ICE Survey

How does GRACE track ice loss to the oceans? The GRACE project measures minute discrepancies in the Earth’s gravitational field in order to track changes in mass (the amount of matter) through different regions of our planet. Earth possesses an approximately spherically symmetric shape. If it were exactly so, it would produce a spherically symmetric gravitational field. That would mean that, regardless of one’s latitude or longitude, Earth’s gravitational field would pull on us with the same force.

Of course, this isn’t exactly the case. Earth is not exactly spherically symmetric. Instead, Earth is bulged along its equator as a result of its rotation. Mountainous regions also cause the planet to be slightly loop-sided. These deviations from perfect spherical symmetry cause slight alterations in the orbits of satellites around our planet. It is by experiencing these discrepancies in the orbits of satellites that GRACE is able to track minute variations in mass from place to place within our planet.

The GRACE project actually consists of two satellites, one following the other in orbit around Earth.

The GRACE project actually consists of two satellites, one following the other in orbit around Earth. The distance between them is measured by a radio frequency laser bouncing between the two satellites. This method of distance measurement, known as interferometry, utilizes the wavelength of the laser as its measuring stick and is capable of resolving a distance of a few micrometers over hundreds of kilometers. If the Earth were perfectly spherically symmetric, the distance between the satellites would remain constant. This is not the case however, and to complicate the picture even more, the mass distribution of our planet changes with time. It is exactly these time dependent processes that GRACE wishes to track.

The GRACE satellites are still transmitting data more than 10 years after the start of their mission. What’s more the mission has been multifaceted. For example, GRACE’s precise measurement of Earth’s gravitational field anomalies provide images of places where our planet’s tectonic plates – the great blocks of Earth’s crust that slide around slowly over very long timescales to create ocean basins and mountain ranges – are overlapping. In addition to providing data on mass loss to the oceans, the project – through its ability to track heat – has provided us with never before seen details of our ocean’s currents.

GRACE stands for Gravity Recovery and Climate Experiment. The project is headed by Dr. Bryon Tapley at the University of Texas.

Bottom line: A publication in Nature in February 2012 presents the results of an analysis of GRACE satellite data, showing that high mountain areas, such as the Himalayas and Andes, are not losing nearly as much water to the ocean as Earth’s polar regions.

Wednesday, March 28, 2012

Insight: how will sea-level rise affect economic growth?

From: Environmental Research Web

Sea-level rise is seen as one of the most threatening impacts of climate change. But most analyses have focused only on the direct impact of a change in sea level, such as the number of people at risk from coastal floods, and there's been little study of other, more indirect, consequences.

Looking only at direct impacts may, however, give a biased view of the real consequences of sea-level rise. When coastal regions are affected by a disaster   such as a hurricane   it is more important to know whether and how the region can bounce back rather than simply assess the number of damaged houses, crucial though this is. In the same way, and over longer timescales, assessing the direct impact of sea-level rise is necessary but is clearly not sufficient. It appears more important to know how sea-level rise can impair development, especially in the poorest regions of the world. To do so, the direct impacts of sea-level rise should be understood as one additional burden on the shoulders of societies and economies that are undergoing constant evolution and that are subject to many other factors.

This is a highly complex problem, and it is difficult to compare studies based on different assumptions. To clarify the situation, we have proposed a framework for investigating the impact of sea-level rise on economic growth via five identified channels through which sea level can affect the growth potential of coastal regions. These are: loss of coastal land, loss of infrastructure and physical capital, loss of social capital, additional costs incurred from extreme events and coastal floods, and increased funds needed to protect coasts.

The study shows how little we know about these channels, and how important it is to know more. In particular, it highlights the need for more research on each channel to be able to answer questions that are really policy-relevant. Who cares how many houses are threatened by sea-level rise if we do not know whether this process represents a significant threat to alleviating poverty and economic development in coastal regions?

About the author

Stéphane Hallegatte is an economist and lead climate-change specialist with the World Bank and Méteo-France. His research deals with climate change and natural-disaster management, and with the public policies needed for green economic growth.

Tuesday, March 27, 2012

Climate change could cause frequent flooding

From: Houma Today  By Nikki Buskey

Sea-level rise from global climate change could increase flooding problems for already vulnerable residents of Terrebonne and Lafourche parishes, according to a new report.

Terrebonne and Lafourche ranked as the most-populated parishes in Louisiana facing the highest risk from sea-level rise.

They came in behind Jefferson and Orleans parishes. Houma and Bayou Cane are also ranked among the most-populated and exposed cities.

The report, “Surging Seas,” is the first to analyze how sea-level rise caused by global warming is increasing risk from storm surges for communities throughout the coastal U.S. It is also the first to generate local and national estimates of what land, housing and population is in vulnerable low-lying areas and how sea-level rise will affect these communities over time.

Tidal records show that the sea rose 8 inches over the last century, and projections point to a steep acceleration.

Coastal Louisiana residents are already accustomed to dealing with regular floods. Lower Terrebonne residents have faced a flood every few years over the past decade.

But could we flood even more often? Even small amounts of sea-level rise make floods more common by adding to tides and storm surge, scientists say.

By 2030, many communities will see storm surges combine with sea-level rise to raise waters at least 4 feet above the local high-tide line.

About 35 percent of Terrebonne residents and 53 percent of Lafourche residents live below this level. About 15,000 homes in Terrebonne and 20,000 homes in Lafourche would be threatened by flooding with 4 feet of sea-level rise.

Louisiana is projected to face 19 inches of sea-level rise by 2050, according to the report. That would put a population of 1.4 million people at risk, including 634,000 people and 4.7 million acres of land.

About 113 cities along the coast will have at least half their populations at risk of serious flooding problems, the report says.

Currently, Louisiana residents face a 17 percent chance of suffering a flood so severe it might happen once in a century. With sea-level rise, that goes up to 20 percent.

“Sea-level rise is not some distant problem that we can just let our children deal with. The risks are imminent and serious,” lead author Ben Strauss said. “Just a small amount of sea-level rise, including what we may well see within the next 20 years, can turn yesterday’s manageable flood into tomorrow’s potential disaster. Global warming is already making coastal floods more common and damaging,” he said.

Nationwide, nearly 5 million U.S. residents live in 2.6 million homes on land below this level. More than 6 million people live on land below 5 feet; by 2050, the study projects that widespread areas will experience coastal floods exceeding this higher level.

In Terrebonne and Lafourche parishes, it’s not just major floods from storm surge that might become more frequent, said Denise Reed, a researcher with the University of New Orleans and a Montegut resident. But smaller floods, too.

“This really underscores the need to provide some kind of protection, for our area in particular,” Reed said. “It’s not just because we’re low-lying. There’s literally nothing between us and the Gulf of Mexico.”

Low-lying roads and yards in bayou communities go underwater once or twice a year now during tropical storms or during strong southeasterly winds.

If the school bus can’t get down to those homes for a couple of days a year, it’s OK, Reed said. But if those roads start going under more frequently and for longer stretches, “it’s something that really starts to impact your day-to-day life. What’s now a minor inconvenience will become a much, much more frequent event.”

Locals, who have been dealing with flooding for years, have already begun to respond to the increasing flood threat by elevating homes and building levees. But Terrebonne’s current levee project, Morganza-to-the-Gulf, will only be built up to about 10 feet high. Levees will have to be taller and stronger if residents want to keep living in low-lying areas, because sea-level rise, combined with coastal erosion, will make flooding higher and more frequent.

“Right now, we know that’s not even going to protect us from extreme events,” Reed said. “And in the future, that might not even protect us from lesser floods.”

Visit the report’s website, surgingseas.org (http://sealevel.climatecentral.org/ ), to check out a searchable, interactive online map that can zoom down to neighborhood level to see your flood risk. The site features statistics for how 3,000 coastal towns, cities, counties and states will be affected by a sea-level rise of up to 10 feet.

Nikki Buskey can be reached at 857-2205 or nicole.buskey@houmatoday.com.

Monday, March 26, 2012

Damaging sea-level rise is on the way

From: Charlotte Observer By: Orrin H. Pilkey

New peer-reviewed research argues that both sea-level rise (SLR) and storm-surge elevations will be greater along much of the U.S. coastline than currently predicted. The impact for coastal communities could potentially be devastating.

This study, carried out by Climate Central, a nonprofit in Princeton, N.J., re-examined the impact of sea-level rise on storm surges by considering their elevation above the high-tide line. That’s a departure from current maps, which measure elevation from mid-tide levels.

The report predicts substantial increases “in the frequency of what are now considered extreme water levels within the next 50 years.”

If the world’s scientific community is to be believed, long-term global sea level rise is upon us and important changes are occurring on our coasts. A state-appointed SLR panel of N.C. scientists, like similar panels in other U.S. coastal states estimated a SLR on the order of 3 to 5 feet by the year 2100.

Northeastern North Carolina is in particular danger, especially around the Pamlico and Albemarle sounds. The slope of the mainland there is so gentle that a 1-foot rise in sea level will cause at least a 2-mile retreat of the shoreline.

The state’s lower coastal plain is home to more than a hundred small towns with populations ranging from a few hundred (Bath, 267) to more than a thousand (Manteo, 1,200) that are at low elevation already and at extreme risk from storm surges. A number of these communities are still recovering from storm-surge flooding caused by last year’s Hurricane Irene.

The people in these communities have real cause for concern and should be kept informed of the risks they and future generations face. For example, should one build or buy in one of the threatened towns? How much should communities commit to upgrading infrastructure? Are we going to abandon, move, raise or dike these communities?

Until recently the state, with federal funding, was making a study of the risk from a SLR of 39 inches, which would provide maps of future risk from both inundation and storm surges and provide a sound basis for long-term community planning.

Although the National Academy of Sciences, the Geological Society of America and the American Geophysical Union have all supported the strong possibility of a major SLR by the year 2100, deniers of SLR have proven strong and effective.

In North Carolina, NC 20 is such a group. It was formed by the state’s 20 coastal counties and is, according to its website, “dedicated to economic development of the member counties.” It has concluded that the sea level will rise 3 to 14 inches by 2100, a number dramatically at odds with global scientific opinion. Their efforts have led the state to back off its plans to map the impact of a SLR of 39 inches (the science consensus level) and instead map a SLR of 16 inches.

This isn’t the first time that government has tried to hide the unpleasantries of SLR. In 2008, the Bush administration refused to publish an EPA document by SLR guru Jim Titus (he eventually published it privately).

In 2011, The Texas Commission on Environmental Quality deleted references to SLR in a report on Galveston Bay written by Rice University geologist John Anderson. The paper was a synopsis of another peer-reviewed paper already published by the Geological Society of America.

The lesson here is that the denial of the scientific view of global climate change and in particular SLR has penetrated to a local level. It is an intrusion made all the more onerous in light of new studies that predict higher than previously predicted SLR and storm-surge levels in coming decades.

Preservation of the status quo (including real estate prices) may prevail along our coasts, but in a democratic society such as ours, the state has no right to shield citizens from unpleasant environmental realities.

Orrin H. Pilkey is James B. Duke Professor Emeritus of Geology at Duke University.

Read more here: http://www.charlotteobserver.com/2012/03/25/3124297/damaging-sea-level-rise-is-on.html