690 replies to this topic

[Weather Ship]

Observed decreases in the Canadian outdoor skating season due to recent winter warming


Global warming has the potential to negatively affect one of Canada's primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada.

http://iopscience.io..._7_1_014028.pdf

[Weather Ship]

Greenland ice sheet may melt completely with 1.6 degrees global warming

The Greenland ice sheet is likely to be more vulnerable to global warming than previously thought. The temperature threshold for melting the ice sheet completely is in the range of 0.8 to 3.2 degrees Celsius global warming, with a best estimate of 1.6 degrees above pre-industrial levels, shows a new study by scientists from the Potsdam Institute for Climate Impact Research (PIK) and the Universidad Complutense de Madrid. Today, already 0.8 degrees global warming has been observed. Substantial melting of land ice could contribute to long-term sea-level rise of several meters and therefore it potentially affects the lives of many millions of people.

http://www.eurekaler...c-gis030912.php

[songster]

Interesting, but frankly tangential to the real issue, which is the speed of change. If (say) the Greenland ice cap is doomed, and destined to melt fully away over the next 50,000 years... should we really care? Even with 8 degrees C warming, their model says it still takes 2000 years to melt the Greenland ice cap - i.e. a sea level rise of ~0.8m / century, and noticeably less than that for the first few centuries. Perhaps perversely, I find this reassuring.

However, I understand that the rate-of-melt question - despite being the most important - is the one that's most poorly characterised. At this point I'm not sure we need more models of equilibrium climate change: we need much better understanding of the non-equilibrium dynamics of ice cap melt.

[Weather Ship]

Iron is key to reversing global warming, Concordia and McGill research shows

Montreal, March 14, 2012 - Canada defines itself as a nation that stretches from coast to coast to coast. But can we keep those coasts healthy in the face of climate change? Yves Gélinas, associate professor in Concordia’s Department of Chemistry and Biochemistry, has found the solution in a surprising element: iron.

http://www.concordia...mate-change.php

[loafer]

(PhysOrg.com) -- The ability of plants to absorb carbon dioxide emissions from human activity appears to be surprisingly robust as the climate warms, according to groundbreaking research.

http://www.physorg.c...conditions.html

[Weather Ship]

A new proxy.

Scientists use rare mineral to correlate past climate events in Europe, Antarctica

New study published in April issue of Earth and Planetary Science Letters

The first day of spring brought record high temperatures across the northern part of the United States, while much of the Southwest was digging out from a record-breaking spring snowstorm. The weather, it seems, has gone topsy-turvy. Are the phenomena related? Are climate changes in one part of the world felt half a world away?
To understand the present, scientists look for ways to unlock information about past climate hidden in the fossil record. A team of scientists led by Syracuse University geochemist Zunli Lu has found a new key in the form of ikaite, a rare mineral that forms in cold waters. Composed of calcium carbonate and water, ikaite crystals can be found off the coasts of Antarctica and Greenland.
"Ikaite is an icy version of limestone," say Lu, assistant professor of earth sciences in SU's College of Arts and Sciences. "The crystals are only stable under cold conditions and actually melt at room temperature."
It turns out the water that holds the crystal structure together (called the hydration water) traps information about temperatures present when the crystals formed. This finding by Lu's research team establishes, for the first time, ikaite as a reliable proxy for studying past climate conditions. The research was recently published online in the journal Earth and Planetary Science Letters and will appear in print on April 1. Lu conducted most of the experimental work for the study while a post-doctoral researcher at Oxford University. Data interpretation was done after he arrived at SU.
The scientists studied ikaite crystals from sediment cores drilled off the coast of Antarctica. The sediment layers were deposited over 2,000 years. The scientists were particularly interested in crystals found in layers deposited during the "Little Ice Age," approximately 300 to 500 years ago, and during the "Medieval Warm Period," approximately 500 to 1,000 years ago. Both climate events have been documented in Northern Europe, but studies have been inconclusive as to whether the conditions in Northern Europe extended to Antarctica.
Ikaite crystals incorporate ocean bottom water into their structure as they form. During cooling periods, when ice sheets are expanding, ocean bottom water accumulates heavy oxygen isotopes (oxygen 18). When glaciers melt, fresh water, enriched in light oxygen isotopes (oxygen 16), mixes with the bottom water. The scientists analyzed the ratio of the oxygen isotopes in the hydration water and in the calcium carbonate. They compared the results with climate conditions established in Northern Europe across a 2,000-year time frame. They found a direct correlation between the rise and fall of oxygen 18 in the crystals and the documented warming and cooling periods.
"We showed that the Northern European climate events influenced climate conditions in Antarctica," Lu says. "More importantly, we are extremely happy to figure out how to get a climate signal out of this peculiar mineral. A new proxy is always welcome when studying past climate changes."

http://www.eurekaler...u-sur032112.php

[Weather Ship]

CO2 was hidden in the ocean during the Ice Age

Bremerhaven/Bern, 29 March 2012. Why did the atmosphere contain so little carbon dioxide (CO2) during the last Ice Age 20,000 years ago? Why did it rise when the Earth's climate became warmer? Processes in the ocean are responsible for this, says a new study based on newly developed isotope measurements. This study has now been published in the scientific journal "Science" by scientists from the Universities of Bern and Grenoble and the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.
Around 20,000 years ago, the atmospheric CO2 concentration during the last Ice Age was distinctly lower than in the following warm period. Measurements from Antarctic ice cores showed this already two decades ago. An international team of glaciologists thereafter looked even further back in time. The climate researchers found that this close connection between carbon dioxide and temperature has existed over the past 800,000 years: with low CO2 concentrations during the Ice Ages and higher CO2 values during warm periods. Now they tried to answer also the question as to where the carbon dioxide was hidden during the Ice Ages and how it got back into the atmosphere at their ends.
"We have now been able to identify processes in the ocean which are connected to the observed rise in CO2", says Dr. Jochen Schmitt, lead author of the recently published study and researcher at the Oeschger Centre for Climate Change Research at the University of Bern. According to Schmitt, during the Ice Age more and more carbon dioxide accumulated in the deep ocean, causing the concentration of atmospheric CO2 to drop. Only at the end of the Ice Age was this stored CO2 transported back to the sea surface through changing ocean circulation and thus emitted back into the atmosphere, write the scientists in the scientific journal "Science".
A new method for isotope measurements has now made it possible for the first time "to reliably decode the fingerprint of the CO2 preserved in the ice", explains Schmitt. He and his colleague Prof. Hubertus Fischer initially developed these new isotope measurement methods for ice cores at the Alfred Wegener Institute for Polar and Marine Research and further refined them in many years of research work after moving to Bern. Using the new method the glaciologists extract the air trapped in the ice core completely and the CO2 contained in the air is thoroughly cleaned. The different isotopes of the CO2 are analysed in a mass spectrometer and from this data the origin of the carbon dioxide can be derived.
Researchers suggested back in the eighties that this puzzle could be solved using an isotopic "CO2 fingerprint". However, it had so far not been possible to make a precise analysis of the carbon dioxide trapped in the Antarctic ice due to the technical hurdles. The glaciologists and the climate researchers at the Universities of Bern and Grenoble and of the Alfred Wegener Institute for Polar and Marine Research have now managed a breakthrough with their study.
Development of Future Scenarios
"The new data have already enabled us to revise and improve a few theories about the possible reasons for CO2 fluctuations. Measurement data from the past enable us to gain a clearer idea about how the climate must have looked at the end of the Ice Age", says Jochen Schmitt. And now the data must be compared with the results from climate models to verify and further develop the models. "In addition to the scientific curiosity about how our Earth functioned in the past, the main question to be asked is how the Earth will develop under the influence of man", explains Jochen Schmitt. These are important scenarios for the future because the CO2 content in the atmosphere has never been anywhere near as high over the past 800,000 years as today, says the climate researcher.
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http://www.eurekaler...g-cwh032912.php

[Weather Ship]

UNH Research Brings New Understanding to Past Global Warming Events

DURHAM, N.H. – A series of global warming events called hyperthermals that occurred more than 50 million years ago had a similar origin to a much larger hyperthermal of the period, the Pelaeocene-Eocene Thermal Maximum (PETM), new research has found. The findings, published in Nature Geoscience online on April 1, 2012, represent a breakthrough in understanding the major “burp” of carbon, equivalent to burning the entire reservoir of fossil fuels on Earth, that occurred during the PETM.
“As geologists, it unnerves us that we don’t know where this huge amount of carbon released in the PETM comes from,” says Will Clyde, associate professor of Earth sciences at the University of New Hampshire and a co-author on the paper. “This is the first breakthrough we’ve had in a long time. It gives us a new understanding of the PETM.” The work confirms that the PETM was not a unique event – the result, perhaps, of a meteorite strike – but a natural part of the Earth’s carbon cycle.
http://www.unh.edu/n...bp02warming.cfm

[Weather Ship]

Confirming carbon's climate effects

Researcher helps paint the fullest picture yet of how increases in CO2 helped end the ice age

Harvard scientists are helping to paint the fullest picture yet of how a handful of factors, particularly world-wide increases in atmospheric carbon dioxide, combined to end the last ice age approximately 20,000 to 10,000 years ago.
As described in a paper published April 5 in Nature, researchers compiled ice and sedimentary core samples collected from dozens of locations around the world, and found evidence that while changes in Earth's orbit may have touched off a warming trend, increases in CO₂ played a far more important role in pushing the planet out of the ice age.
"Orbital changes are the pacemaker. They're the trigger, but they don't get you too far," lead author Jeremy Shakun, a visiting postdoctoral fellow in Earth and Planetary Science Shakun, said. "Our study shows that CO₂ was a much more important factor, and was really driving worldwide warming during the last deglaciation."
Though scientists have known for many years, based on studies of Antarctic ice cores, that deglaciations over the last million years and spikes in CO₂ were connected, establishing a clear cause-and-effect relationship between CO₂ and global warming from the geologic record has remained difficult, Shakun said. In fact, when studied closely, the ice-core data indicate that CO₂ levels rose after temperatures were already on the increase, a finding that has often been used by global warming skeptics to bolster claims that greenhouse gases do not contribute to climate change.
Many climate scientists have addressed the criticism and shown that the lag between temperature and CO₂ increases means that greenhouse gases were an amplifier, rather than trigger, of past climate change, but Shakun and his colleagues saw a larger problem – while CO₂ measurements taken from air bubbles in the ice cores reflect levels throughout the global atmosphere, temperatures recorded in the ice only reflect local Antarctic conditions.
To get a more accurate picture of the relationship between global temperature and CO₂, they synthesized dozens of core samples – 80 in all – collected from around the world.
"We have ice cores from Greenland, people have cored the sea floor all around the world, they've cored lakes on the continents, and they have worked out temperature histories for all these sites," Shakun said. "Putting all of these records together into a reconstruction of global temperature shows a beautiful correlation with rising CO₂ at the end of the ice age. Even more interesting, while CO₂ trails Antarctic warming, it actually precedes global temperature change, which is what you would expect if CO₂ is causing the warming.
"The previous science clearly said that CO₂ had something to do with warming," Shakun added. "It has gone up and down in tandem with the ice ages, so it is clearly involved. If it was an amplifier, the question was how big of an amplifier? Does it explain a lot of climate change, or was it a small piece, and other factors were more important? I think this research really points a strong finger at the idea that CO₂ was a major player."
Armed with that evidence, Shakun and colleagues were able to sketch out how a series of factors aligned that eventually led to a worldwide warming trend and the end of the ice age.
Most scientists now believe, Shakun said, that the first domino wasn't an increase in greenhouse gases, but a gradual change in Earth's orbit. That orbital change resulted in more sunlight hitting the northern hemisphere. As the ice sheets over North America and Europe melted, millions of gallons of fresh water flooded into the North Atlantic and disruped the cyclical flow of ocean currents.
"Ocean circulation works like a global conveyor belt," Shakun said. "The reason it's important for climate is because it's moving heat around. If you look at it today, the northern hemisphere is on average, a couple degrees warmer than the south, and that's partly because the ocean is pulling heat northward as it flows across the equator in the Atlantic.
"But if you turn the conveyor belt off, it's going to warm the south because you're no longer stealing that heat away. Warming the southern hemisphere, in turn, shifts the winds and melts back sea ice that had formed a cap, trapping carbon in the deep ocean."
As more and more CO₂ enters the atmosphere, Shakun said, the global warming trend continues, "and pretty soon you're headed out of an ice age."
While the research strengthens the link between CO₂ and the Ice Ages, Shakun believes it also reinforces the importance of addressing CO₂-driven climate change in our own time.
"I don't think this tells us anything fundamentally new about global warming," Shakun said. "Most scientists are not in doubt about the human-enhanced greenhouse effect – there are nearly a dozen strong pieces of evidence that it is affecting global climate. This is just one more log on the fire that confirms it."

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Shakun's research was supported by a National Oceanic and Atmospheric Administration Climate and Global Change Fellowship and by the National Science Foundation, and conducted using resources at the Oak Ridge National Laboratory.

http://www.eurekaler...u-ccc040312.php

[Gray-Wolf]

http://www.arcus.org...thesis_2011.pdf

Latest on Arctic Ice loss.

[Weather Ship]

Pollution teams with thunderclouds to warm atmosphere

New simulation study shows that atmosphere warms when pollution intensifies storms


RICHLAND, Wash. -- Pollution is warming the atmosphere through summer thunderstorm clouds, according to a computational study published May 10 in Geophysical Research Letters. How much the warming effect of these clouds offsets the cooling that other clouds provide is not yet clear. To find out, researchers need to incorporate this new-found warming into global climate models.
Pollution strengthens thunderstorm clouds, causing their anvil-shaped tops to spread out high in the atmosphere and capture heat -- especially at night, said lead author and climate researcher Jiwen Fan of the Department of Energy's Pacific Northwest National Laboratory.

http://www.eurekaler...l-ptw051812.php