Tag Archives: flooding

Environs

Sea Levels Just Keep Rising, Really

house-on-holland-island

The rise in the global sea level is not a disputable fact, as some would still have you believe. The sea level is rising and it is rising faster. It is a fact backed by evidence. Period. This fact has been established through continuous, independent and corroborated scientific studies in many nations across all continents by thousands of scientists.

And, as the oceans rise communities that touch the water face increasing threats. A growing number of areas now have to plan and prepare for more frequent and more prolonged tidal erosion and storm surges. Worse still, some communities, in increasing numbers, have to confront the prospect of complete resettlement caused by the real danger of prolonged and irreversible flooding. Today it may be some of the low lying areas of Norfolk, Virginia or a remote Pacific Island; tomorrow it may be all of downtown Miami and much of the Eastern Seaboard of the US.

From the New York Times:

The little white shack at the water’s edge in Lower Manhattan is unobtrusive — so much so that the tourists strolling the promenade at Battery Park the other day did not give it a second glance.

Up close, though, the roof of the shed behind a Coast Guard building bristled with antennas and other gear. Though not much bigger than a closet, this facility is helping scientists confront one of the great environmental mysteries of the age.

The equipment inside is linked to probes in the water that keep track of the ebb and flow of the tides in New York Harbor, its readings beamed up to a satellite every six minutes.

While the gear today is of the latest type, some kind of tide gauge has been operating at the Battery since the 1850s, by a government office originally founded by Thomas Jefferson. That long data record has become invaluable to scientists grappling with this question: How much has the ocean already risen, and how much more will it go up?

Scientists have spent decades examining all the factors that can influence the rise of the seas, and their research is finally leading to answers. And the more the scientists learn, the more they perceive an enormous risk for the United States.

Much of the population and economy of the country is concentrated on the East Coast., which the accumulating scientific evidence suggests will be a global hot spot for a rising sea level over the coming century.

The detective work has required scientists to grapple with the influence of ancient ice sheets, the meaning of islands that are sinking in Chesapeake Bay, and even the effect of a giant meteor that slammed into the earth.

The work starts with the tides. Because of their importance to navigation, they have been measured for the better part of two centuries. While the record is not perfect, scientists say it leaves no doubt that the world’s oceans are rising. The best calculation suggests that from 1880 to 2009, the global average sea level rose a little over eight inches.

That may not sound like much, but scientists say even the smallest increase causes the seawater to eat away more aggressively at the shoreline in calm weather, and leads to higher tidal surges during storms. The sea-level rise of decades past thus explains why coastal towns nearly everywhere are having to spend billions of dollars fighting erosion.

The evidence suggests that the sea-level rise has probably accelerated, to about a foot a century, and scientists think it will accelerate still more with the continued emission of large amounts of greenhouse gases into the air. The gases heat the planet and cause land ice to melt into the sea.

The official stance of the world’s climate scientists is that the global sea level could rise as much as three feet by the end of this century, if emissions continue at a rapid pace. But some scientific evidence supports even higher numbers, five feet and beyond in the worst case.

Scientists say the East Coast will be hit harder for many reasons, but among the most important is that even as the seawater rises, the land in this part of the world is sinking. And that goes back to the last ice age, which peaked some 20,000 years ago.

As a massive ice sheet, more than a mile thick, grew over what are now Canada and the northern reaches of the United States, the weight of it depressed the crust of the earth. Areas away from the ice sheet bulged upward in response, as though somebody had stepped on one edge of a balloon, causing the other side to pop up. Now that the ice sheet has melted, the ground that was directly beneath it is rising, and the peripheral bulge is falling.

Some degree of sinking is going on all the way from southern Maine to northern Florida, and it manifests itself as an apparent rising of the sea.

The sinking is fastest in the Chesapeake Bay region. Whole island communities that contained hundreds of residents in the 19th century have already disappeared. Holland Island, where the population peaked at nearly 400 people around 1910, had stores, a school, a baseball team and scores of homes. But as the water rose and the island eroded, the community had to be abandoned.

Eventually just a single, sturdy Victorian house, built in 1888, stood on a remaining spit of land, seeming at high tide to rise from the waters of the bay itself. A few years ago, a Washington Post reporter, David A. Fahrenthold, chronicled its collapse.

Aside from this general sinking of land up and down the East Coast, some places sit on soft sediments that tend to compress over time, so the localized land subsidence can be even worse than the regional trend. Much of the New Jersey coast is like that. The sea-level record from the Battery has been particularly valuable in sorting out this factor, because the tide gauge there is attached to bedrock and the record is thus immune to sediment compression.

Read the entire article here.

Image: The last house on Holland Island in Chesapeake Bay, which once had a population of almost 400, finally toppled in October 2010. Courtesy of Astrid Riecken for The Washington Post.

Environs

Only Three Feet

Three feet. Three feet is nothing you say. Three feet is less than the difference between the shallow and deep ends of most swimming pools. Well, when the three feet is the mean ocean level rise it becomes a little more significant. And, when that three feet is the rise predicted to happen within the next 87 years, by 2100, it’s, well, how do you say, catastrophic.

A rise like that and you can kiss goodbye to your retirement home in Miami, and for that matter, kiss goodbye to much of southern Florida, and many coastal communities around the world.

From the New York Times:

An international team of scientists has found with near certainty that human activity is the cause of most of the temperature increases of recent decades, and warns that sea levels could rise by more than three feet by the end of the century if emissions continue at a runaway pace.

The scientists, whose findings are reported in a summary of the next big United Nations climate report, largely dismiss a recent slowdown in the pace of warming, which is often cited by climate change contrarians, as probably related to short-term factors. The report emphasizes that the basic facts giving rise to global alarm about future climate change are more established than ever, and it reiterates that the consequences of runaway emissions are likely to be profound.

“It is extremely likely that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010,” the draft report says. “There is high confidence that this has warmed the ocean, melted snow and ice, raised global mean sea level, and changed some climate extremes in the second half of the 20th century.”

The “extremely likely” language is stronger than in the last major United Nations report, published in 2007, and it means the authors of the draft document are now 95 percent to 100 percent confident that human activity is the primary influence on planetary warming. In the 2007 report, they said they were 90 percent to 100 percent certain on that issue.

On another closely watched issue, however, the authors retreated slightly from their 2007 position.

On the question of how much the planet could warm if carbon dioxide levels in the atmosphere doubled, the previous report had largely ruled out any number below 3.6 degrees Fahrenheit. The new draft says the rise could be as low as 2.7 degrees, essentially restoring a scientific consensus that prevailed from 1979 to 2007.

Most scientists see only an outside chance that the warming will be as low as either of those numbers, with the published evidence suggesting that an increase above 5 degrees Fahrenheit is likely if carbon dioxide doubles.

The new document is not final and will not become so until an intensive, closed-door negotiating session among scientists and government leaders in Stockholm in late September. But if the past is any guide, most of the core findings of the document will survive that final review.

The document was leaked over the weekend after it was sent to a large group of people who had signed up to review it. It was first reported on in detail by the Reuters news agency, and The New York Times obtained a copy independently to verify its contents.

It was prepared by the Intergovernmental Panel on Climate Change, a large, international group of scientists appointed by the United Nations. The group does no original research, but instead periodically assesses and summarizes the published scientific literature on climate change.

“The text is likely to change in response to comments from governments received in recent weeks and will also be considered by governments and scientists at a four-day approval session at the end of September,” the panel’s spokesman, Jonathan Lynn, said in a statement Monday. “It is therefore premature and could be misleading to attempt to draw conclusions from it.”

The intergovernmental panel won the Nobel Peace Prize along with Al Gore in 2007 for seeking to educate the world’s citizens about the risks of global warming. But it has also become a political target for climate contrarians, who helped identify several minor errors in the last big report from 2007. This time, the group adopted rigorous procedures in hopes of preventing such mistakes.

On sea level, one of the biggest single worries about climate change, the new report goes well beyond the one from 2007, which largely sidestepped the question of how much the ocean could rise this century.

The new report lays out several scenarios. In the most optimistic, the world’s governments would prove far more successful at getting emissions under control than they have been in the recent past, helping to limit the total warming.

In that circumstance, sea level could be expected to rise as little as 10 inches by the end of the century, the report found. That is a bit more than the eight-inch rise in the 20th century, which proved manageable even though it caused severe erosion along the world’s shorelines.

Read the entire article here.

Image courtesy of the Telegraph.