* Astronomy

Greenland is currently losing about 100 billion tonnes of ice a year.
US space agency (Nasa) scientists have undertaken a new assessment of the rate of melting occurring on the great ice sheet that covers the region.
Their data comes from satellites that detect changes in mass by monitoring tiny fluctuations in the pull of gravity as they fly over the Earth.
Scott Luthcke, from the Goddard Space Flight Centre, and colleagues report their study in the journal Science.

Read more

A Europe-wide study has provided "conclusive proof" that climate change is responsible for spring arriving earlier each year, researchers say.

Scientists from 17 nations examined 125,000 studies involving 561 species.
The season was beginning on average six to eight days earlier than it did 30 years ago, researchers said.
In regions such as Spain, which saw the greatest increases in temperatures, the season began up to two weeks earlier.
The findings were based on what was described as the world's largest study of changes in recurring natural events, such as when plants flowered.
The team of researchers also found that the onset of autumn has been delayed by an average of three days over the same period.

Read more

Ancient plant life recovered in recent Arctic Ocean sampling cores shows that at the time of the last major global warming, humidity, precipitation levels and salinity of the ocean water altered drastically, along with the elevated temperatures and levels of greenhouse gases, according to a report in the August 10 issue of Nature.

The Arctic Ocean drilling expedition in 2004 allowed scientists to directly measure samples of biological and geological material from the beginning of the Palaeocene/Eocene thermal maximum (PETM), a period of rapid, extreme global warming about 55 million years ago. It has given researchers a direct resource of measurable information on global warming -- from a time when the overall global temperature was higher and more uniform from the subtropics to the arctic.

"Analysis of carbon and hydrogen isotopes in the recovered fossil plants told us a lot about the way water is transported in the atmosphere and its effect on the climate. The isotope traces we measured indicated that a large-scale alteration in the water cycle occurred and that future alterations may leave us poorly equipped to predict our water supply. Without being hysteric, it is important to realise that the impact of global warming is not just about searing hot summers -- it is about water as a resource. It is about when and where it rains and how much we have to drink. This is a red flag" - Mark Pagani, professor of geology and geophysics at Yale and principal author of the study.

Pagani and his collaborators show that water and atmospheric water vapour are a major indicator of the "greenhouse" changes. Rather than just looking at changes in ocean water -- that can be influenced by many factors -- the researchers measured carbon and hydrogen isotopes in the fossil plants and reconstructed the pattern of precipitation and characteristics of the ancient arctic water.

"We are all familiar with what happens when atmospheric fronts from the tropics meet cool northern fronts -- there is a "rainout" -- water leaves the atmosphere. When that happens, the water vapour isotope level becomes more negative. We were able to measure that as traces in the plant fossils. In the PETM, because there were no sharp warm and cold fronts meeting to triggering rainfall, massive amounts of water got transferred from the tropics and sub-tropics to the arctic. That drastically increased humidity and precipitation in the arctic. In turn, it led to increased river runoff that lowered the ocean salinity, changing its oxygen capacity and the plant life in the region. It also probably left the middle latitudes a lot dryer" - Mark Pagani.

Co author Matthew Huber, an assistant professor of earth and atmospheric sciences at Purdue University's College of Science compared data from the research expedition with complex climate-model simulations to study and predict the effects of greenhouse gases. Their measurements confirm that the carbon dioxide level increase in the PETM was at least twice as large as those previously proposed.

"We now have a pretty good correlation between records of past warmth and higher carbon dioxide concentrations. What it tells you is that it's not too difficult to push the climate system to a warm state. If you work out the numbers, it's almost identical to what we are expected to do over the next few hundred years" - Matthew Huber.

Co-authors of the work were Nikolai Pedentchouk at Yale; Appy Sluijs, Henk Brinkhuis and Gerald Dickens at Utrecht University; Stefan Schouten and Jaap Sinninghe Damste at the Royal Netherlands Institute for Sea Research, and "the Expedition 302 Scientists."
The expedition was an operation of the Integrated Ocean Drilling Program (IODP), an international marine research program primarily funded by the National Science Foundation, and Japan's Ministry of Education, Culture, Sports, Science and Technology. The Arctic Coring Expedition was led by the European Consortium on Ocean Research Drilling (ECORD), an IODP contributing member that represents 17 nations. ECORD is responsible for managing all IODP mission-specific operations, i.e. scientific expeditions conducted in unusual or demanding environments in which specific platform requirements must be used to meet specific science objectives. In all, 21 countries participate in IODP.

Source: Yale University

Gas escaping from the ocean floor may provide some answers to understanding historical global warming cycles and provide information on current climate changes, according to a team of scientists at the University of California, Santa Barbara. The findings are reported in the July 20 on-line version of the scientific journal, Global Biogeochemical Cycles.

Remarkable and unexpected support for this idea occurred when divers and scientists from UC Santa Barbara observed and videotaped a massive blowout of methane from the ocean floor. It happened in an area of gas and oil seepage coming out of small volcanoes in the ocean floor of the Santa Barbara channel -- called Shane Seep -- near an area known as the Coal Oil Point seep field. The blowout sounded like a freight train, according to the divers.
Atmospheric methane is at least 20 times more potent than carbon dioxide and is the most abundant organic compound in the atmosphere, according to the study's authors, all from UC Santa Barbara.

"Other people have reported this type of methane blowout, but no one has ever checked the numbers until now. Ours is the first set of numbers associated with a seep blowout" - Ira Leifer, lead author and an associate researcher with UCSB's Marine Science Institute. Leifer was in a research boat on the surface at the time of the blowouts.

Aside from underwater measurements, a nearby meteorological station measured the methane "cloud" that emerged as being approximately 5,000 cubic feet, or equal to the volume of the entire first floor of a two-bedroom house. The research team also had a small plane in place, flown by the California Department of Conservation, shooting video of the event from the air.
Leifer explained that when this type of blowout event occurs, virtually all the gas from the seeps escapes into the atmosphere, unlike the emission of small bubbles from the ocean floor, which partially, or mostly, dissolve in the ocean water. Transporting this methane to the atmosphere affects climate, according to the researchers. The methane blowout that the UCSB team witnessed reached the sea surface 60 feet above in just seven seconds. This was clear because the divers injected green food dye into the rising bubble plume.
Co-author Bruce Luyendyk, professor of marine geophysics and geological sciences, explained that, to understand the significance of this event (which occurred in 2002), the UCSB research team turned to a numerical, bubble-propagation model. With the model, they estimated methane loss to the ocean during the upward travel of the bubble plume.
The results showed that for this shallow seep, loss would have been approximately one percent. Virtually all the methane, 99 percent of it, was transported to the atmosphere from this shallow seep during the blowout. Next, the scientists used the model to estimate methane loss for a similar size blowout at much greater depth, 250 meters. Again, the model results showed that almost all the methane would be transported up to the atmosphere.
Over geologic time scales, global climate has cycled between warmer, interglacial periods and cooler, glacial periods. Many aspects of the forces underlying these dramatic changes remain unknown. Looking at past changes is highly relevant to understanding future climate changes, particularly given the large increase in atmospheric greenhouse gas concentrations in the atmosphere due to historically recent human activities such as burning fossil fuels.

One hypothesis, called the "Clathrate Gun" hypothesis, developed by James Kennett, professor of geological sciences at UCSB, proposes that past shifts from glacial to interglacial periods were caused by a massive decomposition of the marine methane hydrate deposits.
Methane hydrate is a form of water ice that contains a large amount of methane within its crystal structure, called a clathrate hydrate. According to Kennett's hypothesis, climatic destabilization would cause a sharp increase in atmospheric methane -- thereby initiating a feedback cycle of abrupt atmospheric warming. This process may threaten the current climate, according to the researchers. Warmer ocean temperatures from current global climate change is likely to release methane currently trapped in vast hydrate deposits on the continental shelves. However, consumption of methane by microbes in the deep sea prevents methane gas released from hydrates from reaching the ocean surface and affecting the atmosphere.
Bubbles provide a highly efficient mechanism for transporting methane and have been observed rising from many different hydrate deposits around the world. If these bubbles escape singly, most or all of their methane would dissolve into the deep-sea and never reach the atmosphere. If instead, they escape in a dense bubble plume, or in catastrophic blowout plumes, such as the one studied by UCSB researchers, then much of the methane could reach the atmosphere. Blowout seepage could explain how methane from hydrates could reach the atmosphere, abruptly triggering global warming.
Thus, these first-ever quantitative measurements of a seep blowout and the results from the numerical model demonstrate a mechanism by which methane released from hydrates can reach the atmosphere. Studies of seabed seep features suggest such events are common in the area of the Coal Oil Point seep field and very likely occur elsewhere.
The authors explain that these results show that an important piece of the global climate puzzle may be explained by understanding bubble-plume processes during blowout events. The next important step is to measure the frequency and magnitude of these events. The UCSB seep group is working toward this goal through the development of a long-term, seep observatory in active seep areas.

Read more