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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