When it comes to lake water, some McGill University geographers are in deep.

They spent the past three years calculating the most precise estimates yet for the amount of water contained in the world’s 1.42 million lakes.

And ecologists, climate-change experts and other scientists are about to reap the benefits of their research, published Thursday in the journal Nature Communications.

Most lakes have been mapped but “one thing that was completely missing was the volume of lake water,” said senior author Bernhard Lehner, an associate professor in McGill’s geography department.

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ROME (Thomson Reuters Foundation) - Countries most dependent on agriculture are also at high risk of experiencing changes in climate over the next 30 years and face the biggest costs in dealing with the effects of extreme weather, according to a global climate index published on Monday.

Sub-Saharan Africa is home to 17 of the 20 countries most economically reliant on agriculture in the world.

Of the 17, all but two are at "high" or "extreme" risk of experiencing changes in temperature and rainfall, and extremes such as drought and floods, according to the Climate Change Exposure Index.

These are typically countries whose governments lack the financial or technical resources to plan 20 or 30 years in advance, said Richard Hewston, principal environmental analyst at Verisk Maplecroft, a UK-based risk management company which compiled the index.

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Chronicle Urban Design Critic John King explores the challenges posed by sea level rise in the Bay Area, from the perils facing San Francisco's crumbling Embarcadero to the struggles to revive marshes and the creation of a small city on Treasure Island.

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By studying growth rings in the shells of quahog clams, scientists have pieced together the history of the North Atlantic Ocean over the past 1,000 years. The method is similar to how tree rings can serve as climate proxies by revealing clues about past weather and climate changes, including droughts.

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By studying the clams' shells, scientists from Cardiff University and Bangor University in Wales found that the ocean's relationship with the atmosphere drastically changed over the centuries. That is likely due to the influence of greenhouse gases such as carbon dioxide and methane that have been pumped into the atmosphere from humanity's burning of fossil fuels, beginning with the Industrial Revolution.

Although clams have been used as climate proxies through the field called sclerochronology since the 1970s, the new study is the first time researchers have been able to obtain a 1,000-year record of the ocean with absolute dating precision, according to lead author David Reynolds of Cardiff University.

In the pre-industrial era, roughly before 1800, the climate was driven by natural factors such as volcanic eruptions and solar activity, he said. At that time, the ocean influenced the atmosphere. But since then, it's been the other way around: The atmosphere, with its increasing levels of carbon dioxide and other greenhouse gases, has driven major shifts underwater.

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President-elect Donald Trump has described global warming as a hoax, and Republicans in Congress who reject science showing that greenhouse gases have warmed the planet have blocked funding to help the Pentagon assess the damage and plan for the future.

The House voted in June to bar the Defense Department from spending money to evaluate how climate change would affect military training, combat, weapons purchases and other needs.

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But the debate is settled at the Pentagon. Rising sea levels and temperatures have forced it to rebuild or move roads, housing, airfields and other vulnerable facilities damaged by mudslides in Hawaii, floods in Virginia, drought in California and thawing permafrost in Alaska.

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The Pentagon doesn’t say that climate change alone will cause wars. But the 2014 Quadrennial Defense Review, the Defense Department’s major planning plan for the next four years, calls it an “accelerant of instability” and a “threat multiplier.”

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In 1721, missionary Hans Egede sailed a ship called The Hope from Norway to Greenland, seeking Norse farmers whom Europeans hadn't heard from in 200 years in order to convert them to Protestantism. He explored iceberg-dotted fjords that gave way to gentle valleys, and silver lakes that shimmered below the massive ice cap. But when he asked the Inuit hunters he met about the Norse, they showed him crumbling stone church walls: the only remnants of 500 years of occupation. "What has been the fate of so many human beings, so long cut off from all intercourse with the more civilized world?" Egede wrote in an account of the journey. "Were they destroyed by an invasion of the natives … [or] perished by the inclemency of the climate, and the sterility of the soil?"

Archaeologists still wonder today. No chapter of Arctic history is more mysterious than the disappearance of these Norse settlements sometime in the 15th century. Theories for the colony's failure have included everything from sinister Basque pirates to the Black Plague. But historians have usually pinned most responsibility on the Norse themselves, arguing that they failed to adapt to a changing climate. The Norse settled Greenland from Iceland during a warm period around 1000 C.E. But even as a chilly era called the Little Ice Age set in, the story goes, they clung to raising livestock and church-building while squandering natural resources like soil and timber. Meanwhile, the seal-hunting, whale-eating Inuit survived in the very same environment.

Over the last decade, however, new excavations across the North Atlantic have forced archaeologists to revise some of these long-held views. An international research collective called the North Atlantic Biocultural Organisation (NABO) has accumulated precise new data on ancient settlement patterns, diet, and landscape. The findings suggest that the Greenland Norse focused less on livestock and more on trade, especially in walrus ivory, and that for food they relied more on the sea than on their pastures. There's no doubt that climate stressed the colony, but the emerging narrative is not of an agricultural society short on food, but a hunting society short on labor and susceptible to catastrophes at sea and social unrest.

Historian Poul Holm of Trinity College in Dublin lauds the new picture, which reveals that the Greenland Norse were "not a civilization stuck in their ways." To NABO archaeologist George Hambrecht of the University of Maryland in College Park, "The new story is that they adapted but they failed anyway."

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The most scientifically capable weather satellite the United States has ever launched is slated to soar into orbit on 19 November. From its vantage point 35,800 kilometres up — nearly one-tenth of the way to the moon — the Geostationary Operational Environmental Satellite-R Series (GOES-R) will snap images of weather and atmospheric phenomena as they roll across the United States.

GOES-R can take pictures as often as every 30 seconds, much faster than the several-minute intervals of current GOES weather satellites. That rapid-fire imagery allows the satellite to track developing changes in thunderstorms, hurricanes and other severe storms. It also enables meteorologists to follow plumes of wildfire smoke or volcanic ash as they spread. And it helps emergency responders to better prepare for where to deploy resources as a storm advances, says Louis Uccellini, director of the National Weather Service.

The next-generation satellite can also take pictures with a sharper focus and in a broader range of wavelengths than the current GOES satellites. “It’s like going from black-and-white to a super-high-definition television,” says Stephen Volz, an assistant administrator with the National Oceanic and Atmospheric Administration (NOAA) in Silver Spring, Maryland.

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MISSOULA, Mont. — They are beautiful, glistening icons of the West, filled with life and history. But there is far more to mountain rivers, scientists are learning, than the water churning between their banks.

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“A river doesn’t just flow down the channel,” said F. Richard Hauer, a professor of stream ecology at the University of Montana and the lead author of the paper. “It flows over and through the entire flood plain system, from valley wall to valley wall, and supports an extraordinary diversity of life.”

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Melting snow and groundwater flow down the channel; this is what we think of as a “river.” But underground, far more water is moving slowly through a labyrinthine network of cobbles, gravel and sand that make up the entire valley bottom.

This deeply buried habitat is far more important and far more productive than thought. The matrix of gravel and sand cleans the water, filtering organic material and freeing up nitrogen and phosphorous embedded in the gravel.

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The medieval ship lay more than a half-mile down at the bottom of the Black Sea, its masts, timbers and planking undisturbed in the darkness for seven or eight centuries. Lack of oxygen in the icy depths had ruled out the usual riot of creatures that feast on sunken wood.

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Archaeologists date the discovery to the 13th or 14th century, opening a new window on forerunners of the 15th- and 16th-century sailing vessels that discovered the New World, including those of Columbus. This medieval ship probably served the Venetian empire, which had Black Sea outposts.

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Remarkably, the find is but one of more than 40 shipwrecks that the international team recently discovered and photographed off the Bulgarian coast in one of archaeology’s greatest coups.

In age, the vessels span a millennium, from the Byzantine to the Ottoman empires, from the ninth to the 19th centuries. Generally, the ships are in such good repair that the images reveal intact coils of rope, rudders and elaborately carved decorations.

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Firearm laws that strengthen background checks and require permits to purchase a gun are effective in reducing gun homicide rates, according to a study published by the Journal of the American Medicine Association Internal Medicine.

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The scientists found that overall, stronger guns laws did lower homicide rates. But what seemed to make the difference were robust background checks and permit-to-purchase requirements.

Laws designed ban assault weapons, improve child safety and interdict gun trafficking did not have any effect on homicide rates.

As for restrictions on concealed carry and carrying guns in public, the jury is still out. The evidence was mixed, according to the study.