Climate Change

Many giant shelves of ice hanging off Antarctica into the Southern Ocean are now melting rapidly. But up to now, it has been a mystery why much of the resulting fresh water ends up in the depths instead of floating above saltier, denser ocean waters. Scientists working along one major ice shelf believe they have found the answer: earth’s rotation is pushing meltwater sideways as it bleed off the ice, preventing it from reaching the surface. The finding has implications for how ocean circulation may affect the planet’s future climate. The research was published this week in the journal Nature.

In the far north, climate is warming two to three times faster than the global average. As a result, both tundra and boreal forests are undergoing massive physical and biological shifts. Columbia University’s Lamont-Doherty Earth Observatory and other institutions are engaged in a long-term project to sort out what allows trees to survive or not in this borderline environment.

A new study says that human-induced climate change has doubled the area affected by forest fires in the U.S. West over the last 30 years. According to the study, since 1984 heightened temperatures and resulting aridity have caused fires to spread across an additional 16,000 square miles than they otherwise would have—an area larger than the states of Massachusetts and Connecticut combined. The authors warn that further warming will increase fire exponentially in coming decades.

Powerful tropical cyclones like the super typhoon that lashed Taiwan with 150-mile-per-hour winds last week and then flooded parts of China are expected to become even stronger as the planet warms. That trend hasn’t become evident yet, but it will, scientists say.

In much of France and Switzerland, the best wine years are traditionally those with abundant spring rains followed by an exceptionally hot summer and late-season drought. This drives vines to put forth robust, fast-maturing fruit, and brings an early harvest. Now, a new study shows that warming climate has largely removed the drought factor from the centuries-old early-harvest equation. It is only the latest symptom that global warming is affecting biological systems and agriculture.

Humans have been burning fossil fuels for only about 150 years, yet that has started a cascade of profound changes that at their current pace will still be felt 10,000 years from now, a new study shows. Coastal areas, in particular, will experience the long-term effects as rising seas slowly redraw the world map as we know it and continue to rise long after emissions are brought down. Even in a scenario in which global temperatures warm to only about 2° Celsius above pre-industrial times, the analysis shows that several of the world’s coastal megacities will eventually be submerged.

The Indonesian peat fires that have been choking cities across Southeast Asia with a yellow haze are creating more than a local menace—the burning peat releases immense stores of CO2, contributing to global warming, writes Jonathan Nichols.

A new study in Science questions the provocative idea that climate change may shape the texture of the sea floor. Lamont's Jean-Arthur Olive and his co-authors argue that the fabric of the sea floor is better explained by faults that form, offsetting the crust as the plates pull apart. Their paper is the first to explain the characteristic spacing of abyssal hills quantitatively as a function of seafloor spreading rate within a single theoretical framework.

Since the late 1990s, global warming has stabilized, even as greenhouse gases have risen. That defies simple models that say the temperature should keep going up. Many scientists think the so-called “hiatus” is taking place in part because much of the heat trapped in the atmosphere by greenhouse gases is being soaked up and stored by the oceans–at least for now. The Pacific is believed to play an especially powerful role, with winds in its eastern regions sweeping heat into its depths, like dirt getting swept under the rug. The problem is, scientists checking under the rug by measuring subsurface temperatures have not necessarily found the predicted increases in heat. This has come to be known as the riddle of the “missing heat.” A team of oceanographers now says they know where it went: It has been exported from the Pacific to the Indian Ocean. Their study, out this week in the journal Nature Geoscience, finds that this movement may account for more than 70 percent of all heat absorbed by the entire upper world ocean in the past decade.

Increasing heat is expected to extend dry conditions to far more farmland and cities by the end of the century than changes in rainfall alone, says a new study. Much of the concern about future drought under global warming has focused on rainfall projections, but higher evaporation rates may also play an important role as warmer temperatures wring more moisture from the soil, even in some places where rainfall is forecasted to increase, say the researchers.

The global treaty that headed off destruction of earth’s protective ozone layer has also prevented major disruption of global rainfall patterns, even though that was not a motivation for the treaty, according to a new study in the Journal of Climate.

Some 40 million people depend on the Colorado River Basin for water but warmer weather from rising greenhouse gas levels and a growing population may signal water shortages ahead. In a new study in Nature Climate Change, climate modelers at Columbia University’s Lamont-Doherty Earth Observatory predict a 10 percent drop in the Colorado River’s flow in the next few decades, enough to disrupt longtime water-sharing agreements between farms and cities across the American Southwest.

For the first time, scientists have identified tropical and subtropical species of marine protozoa living in the Arctic Ocean. Apparently, they traveled thousands of miles on Atlantic currents and ended up above Norway with an unusual—but naturally cyclic—pulse of warm water, not as a direct result of overall warming climate, say the researchers. On the other hand: arctic waters are warming rapidly, and such pulses are predicted to grow as global climate change causes shifts in long-distance currents. Thus, colleagues wonder if the exotic creatures offers a preview of climate-induced changes already overtaking the oceans and land, causing redistributions of species and shifts in ecology. The study, by a team from the United States, Norway and Russia, was just published in the British Journal of Micropalaeontology.

In an effort to understand how plants around the world will act in a warming climate, researchers have relied increasingly on experiments that measure how they respond to artificial warming. But a new study says that such experiments are underestimating potential advances in the timing of flowering and leafing four to eightfold, when compared with natural observations. As a result, species could change far more quickly than the experiments suggest, with major implications for water supplies, pollination of crops and ecosystems. The comparison, done by an interdisciplinary team from some 20 institutions in North America and Europe, appears this week in the leading journal Nature.

As human ancestors rose on two feet in Africa and began their migrations across the world, the climate around them got warmer, and colder, wetter and drier. The plants and animals they competed with and relied upon for food changed. Did the shifting climate play a direct role in human evolution?

Climate scientists at a meeting of the American Association for the Advancement of Science this week were elated to hear that the United States and five other countries had agreed to work toward cutting pollutants other than carbon dioxide thought to cause about a third of current human-influenced global warming. After all, many of them had done the work that led directly to the pact, by showing the effects of such substances, and how emissions might be reduced.

A major new international prize for public communication on climate-change issues has been awarded to Gavin Schmidt of the Earth Institute-affiliated NASA Goddard Institute for Space Studies.

A team led by Kevin Anchukaitis of the Lamont-Doherty Earth Observatory Tree Ring Lab is currently in Alaska’s Arctic National Wildlife Refuge, studying the effects of changing climate on trees. Ferried in by a bush pilot who landed on the tundra to drop them off, they are practically at treeline–the place where it is too far north for trees to grow. But there are still some spindly white spruces here, and they are taking cores from these, which can be used to measure weather of the past.

El Niño and La Niña, the periodic shifts in Pacific Ocean temperatures, affect weather around the globe, and many scientists have speculated that a warming planet will make those fluctuations more volatile, bringing more intense drought or extreme rainfall to various regions.

The recent earthquake in Japan shifted the earth’s axis by half a foot. You may be wondering if that’s enough to change earth’s weather. No, not really, says Jerry McManus, a climate scientist at Columbia’s Lamont-Doherty Earth Observatory.

As the last ice age was ending, about 13,000 years ago, a final blast of cold hit Europe, and for a thousand years or more, it felt like the ice age had returned. But oddly, despite bitter cold winters in the north, Antarctica was heating up. For the two decades since ice core records revealed that Europe was cooling at the same time Antarctica was warming over this thousand-year period, scientists have looked for an explanation.

New results from a drilling expedition off Antarctica may help scientists learn more about a dramatic turn in climate 34 million years ago, when the planet cooled from a “greenhouse” to an “icehouse” state. In just 400,000 years – a blink of an eye in geologic time – carbon dioxide levels dropped, temperatures plunged and ice sheets formed over what was then the lush continent of Antarctica.

The seasonal monsoon rains in Asia feed nearly half the world’s population, and when the rains fail to come, people can go hungry, or worse. A new study of tree rings provides the most detailed record yet of at least four epic droughts that have shaken Asia over the last thousand years..

Scientists broadly agree that global warming may threaten the survival of many plant and animal species; but global warming did not kill the Monteverde golden toad, an often cited example of climate-triggered extinction, says a new study.

Scientists aboard the research ship the JOIDES Resolution recently drilled two kilometers into Earth’s crust, setting a new record for the deepest hole drilled through the seafloor on a single expedition.

Each person on the planet produced 1.3 tons of carbon last year—an all-time high--despite a global recession that slowed the growth of fossil fuel emissions for the first time this decade, according to a report published this week in the journal Nature Geoscience. Emissions grew 2 percent last year, to total 8.7 billion tons of carbon dioxide.

A new study adds evidence that climate swings in Europe and North America during the last ice age were closely linked to changes in the tropics. The study, published this week in the journal Science, suggests that a prolonged cold spell...

But Global Warming May Have Helped Override Some Recent Eruptions

Climate researchers have shown that big volcanic eruptions over the past 450 years have temporarily cooled weather in the tropics—but suggest that such effects may have been masked in the 20^th century by rising global temperatures

 Task Force, Advised by Columbia Scientists, Will Draw Plans to Battle Rising Seas, Strains on Water and Electricity

Much of New York City’s waterfront is projected to be vulnerable to flooding in coming decades.

 A study released on May 11, 2007 provides some of the first solid evidence that warming-induced changes in ocean circulation at the end of the last Ice Age caused vast quantities of ancient carbon dioxide to belch from the deep sea into the atmosphere. Scientists believe the carbon dioxide (CO2) releases helped propel the world into further warming.

Scientists from the Lamont Doherty Earth Observatory (LDEO) have provided new evidence that ocean circulation changes lagged behind, and were not the cause of, major climate changes at the beginning and end of the last ice age (short intervals known as glacial boundaries), according to a study published in the March 2005 issue of Science magazine.

For years, researchers have examined climate records indicating that millennial-scale climate cycles have linked the high latitudes of the Northern hemisphere and the subtropics of the North Pacific Ocean. What forces this linkage, however, has been a topic of considerable debate. Did the connection originate in the North Pacific with the sinking of oxygen-rich waters into the interior of the ocean during cool climate intervals, or did it originate in the subtropical Pacific with the transfer of heat between the ocean and the atmosphere?