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RE: Greenhouse Gases
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The world cannot afford to wait before tackling climate change, the UK prime minister has warned.
A report by economist Sir Nicholas Stern suggests that global warming could shrink the global economy by 20%.
But taking action now would cost just 1% of global gross domestic product, the 700-page study says.
Tony Blair said the Stern Review showed that scientific evidence of global warming was "overwhelming" and its consequences "disastrous".

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Of late, the enormous glaciers that flow down to the sea from the interior of Greenland have been picking up speed. In the last few years, enough ice has come off the northern landmass to sustain the average flow of the Colorado River for six years or fill Lake Mead three times over or cover the state of Maryland in 10 feet of water, assuming it were perfectly flat. And whether it is the glaciers' weight, speed or volume that is measured, a quickening of the their movement can be detected. In fact, the latest gravity-based measurements show that the glaciers lost roughly 101 gigatons of ice annually between 2003 and 2005, according to a paper published online in Science.

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Greenland ice loss
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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.

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Climate change
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The world is the warmest it has been in the last 12,000 years as a result of rapid warming over the past 30 years, a study has suggested.

Nasa climatologists said the Earth had warmed by about 0.2C in each of the last three decades.
Pollution from human activity was pushing the world towards dangerous levels of climate change, they warned.

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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.

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Global Warming
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As temperatures rise with global warming, an increased risk of forest fires, droughts and flooding is predicted for the next 200 years by climate scientists from the University of Bristol, UK.

Despite the commitment we have already to global warming, even if we stopped emitting greenhouse gases now the researchers predict that Eurasia, eastern China, Canada, Central America, and Amazonia are at risk of forest loss (up to 30% probability for a global warming of less then 2°C and increasing to more than 60% for a warming of more than 3°C), while the far north, Amazonia and many semi-arid regions will become more susceptible to wildfires.
Less freshwater availability, and with it more intense droughts, are likely to occur in West Africa, Central America, southern Europe and the eastern USA. Other regions, particularly areas north of 50˚N, tropical Africa and northwest South America, will be at significant risk of excessive runoff as trees are lost, increasing the chances of flooding as temperatures rise.
The researchers also found that if the temperature increase is more than 3°C, land carbon sinks could release their stored carbon, starting a positive feedback loop that would increase atmospheric carbon dioxide.

"Most importantly we show the steeply increasing risks, and increasingly large areas affected, associated with higher warming levels. This analysis represents a considerable step forward for discussions about ‘dangerous’ climate change and its avoidance" - Marko Scholze, lead author on the paper published in PNAS this week.

The team from QUEST (Quantifying and Understanding the Earth System, a project funded by the Natural Environment Research Council and based at Bristol University), with a colleague from the University of Southampton, quantified the risks of climate-induced changes in key ecosystem processes, using novel methods. They gathered results from more than 50 climate model simulations to calculate these risks and then grouped the results according to varying amounts of global warming: less than 2°C, 2-3°C, and more than 3°C.
For each of the temperature groups they show the probability of shifts in forest cover and the areas which exceed the natural variability in wildfire frequency or freshwater supply for the coming 200 years.

Source University of Bristol, UK

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RE: Greenhouse Gases
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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

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Ancient Climatic Events
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For the second time in as many months, the IODP Arctic Coring Expedition (ACEX) is making news with new analysis of ocean-floor sediments. In the Aug. 10 issue of Nature, an article authored by several of the expedition scientists summarizes their findings: more evidence that the Arctic was extremely warm, unusually wet, and ice-free up to the time the last massive amounts of greenhouse gases were released into the Earth's atmosphere – a period calculated to have occurred 55 million years ago, and known as the Palaeocene/Eocene thermal maximum, or PETM.

Researchers have long recognised that a massive release of greenhouse gases, probably carbon dioxide or methane, occurred during the PETM. Surface temperatures also rose in many places by as much as 15 degrees Fahrenheit in the (relative) geological instant of about 100,000 years.
Arctic sediment samples were largely unavailable until 2004, when ACEX scientists recovered the first deep-ocean sediment samples from beneath the ice-laden waters near the North Pole. ACEX, only the second scientific expedition to be conducted by the Integrated Ocean Drilling Program (established in late 2003), recovered 339 meters of subseafloor sediment samples.

"Building a picture of ancient climatic events is a lot like putting together a jigsaw puzzle, and what ACEX allowed us to do was fill in a blank section of the PETM picture. The ACEX cores clearly show that the Arctic got very warm and wet during the PETM. Even tropical marine plants thrived in the balmy conditions" - Gerald Dickens, a Rice University geochemist and co-author, who conducted the initial, shipboard chemical analyses of all the ACEX core samples.

In today's oceans, certain species of microscopic plants are known to rapidly multiply and create algal blooms. Dickens said that fossils of these plants – known only to originate in the tropics before the PETM – are commonly seen in the ACEX cores. Furthermore, the chemistry of the organic carbon in the ACEX cores may rule out some earlier theories about what caused the PETM. The diminution of these alternate explanations strongly suggests that an enormous amount of carbon entered the atmosphere at the beginning of the PETM, either from volcanic eruptions or the melting of oceanic gas hydrates – mixtures of methane and ice on the seafloor.
ACEX co-authors include Mark Pagani and Nikolai Pedentchouk of Yale University, Matthew Huber of Purdue University, Appy Sluijs and Henk Brinkhuis of Utrecht University (Netherlands), and Stefan Schouten and Jaap Sinninghe Damsté of the Royal Netherlands Institute for Sea Research.
The ACEX 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.

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Methane hydrate
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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.

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Hockey Stick Graph.
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The Earth was hotter in the late 20th Century than it had been in the last 400 or possibly 1,000 years, a report requested by the US Congress concludes.

It backs some of the key findings of the original study that gave rise to the iconic "hockey stick" graph.
The new report, carried out by a panel of the US-based National Research Council (NRC), largely vindicates the researchers' work, first published in 1998.
The review looked at large-scale surface temperature reconstructions from different research groups, together with instrumental records, to try to establish the Earth's surface temperature over the last 2,000 years.
Because thermometer records extend no further back than 150 years ago, scientists have to rely on "proxy data" to glean information about Earth's climate prior to that time.
Tree rings, corals, ocean and lake sediments, cave deposits, ice cores, bore holes, and glaciers are all used to infer the climate of the distant past.

The NRC report concludes: "Based on the analyses presented in the original papers by Mann et al and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th Century than during any comparable period over the preceding millennium."

The report says it has very high confidence that the last few decades of the 20th Century were warmer than any comparable period in the last 400 years.
However, it added that climate estimates between the years AD 900 and AD 1600 were less reliable, and less still before AD 900. It called for more research to gain better proxy data for these periods.

Source BBC

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