Sbsp affirmative- arl lab- ndi 2011
*** Positive Feedbacks *** AT: Forests
Download 1.74 Mb.
|
- Navigate this page:
- AT: Water Vapor
- AT: Clouds
- AT: Carbon Sinks
*** Positive Feedbacks ***AT: ForestsForest sinks are net positive – release comparatively worse microbesLauder 7/14 [Simon, 7/14/2011, ABC News Australia, “Study casts doubt on forest carbon capture plans,” http://www.abc.net.au/news/2011-07-14/tree-planting-carbon-offset/2794426, DS] US scientists have found that the more carbon dioxide goes into soil, the more the soil releases other, more potent, greenhouse gases. This means Australian companies planting trees to soak up CO2 in return for Carbon Credit Units under the carbon tax may not actually be counteracting their emissions. The study, published in the science journal Nature, found that plants taking up more carbon dioxide resulted in an accelerated production of nitrous oxide and methane. The study says the value of trees as carbon credits could be written down by a fifth. The value of the units is expected to be set in law if it is passed by the Senate next month. Forests and soil are often seen as carbon sink centres, with tree-planting the main method for offsetting carbon emissions. University of Florida researcher and co-author of the study Professor Craig Osenberg says Australia may need to rethink its emissions strategy. "Plants are taking up the carbon dioxide but in the process of that increased plant production and the carbon dioxide enrichment, the microbes are putting out nitrous oxide and methane," he said. But Professor Osenberg says the study still finds the method to be beneficial. Northern Arizona University and study co-author Professor Bruce Hungate says with all gases considered, planting trees is 20 per cent less effective than previously thought. "When you increase carbon dioxide in the atmosphere, you get a greater release of these potent greenhouse gases," he said. "One way to think about it is if carbon dioxide concentrations increase in the atmosphere we expect ecosystems to soak up more carbon. One of the things this effect does is it reduces the value of that increased carbon uptake, because by releasing these more potent greenhouse gases, you essentially get less of a cooling benefit of the ecosystem's natural response to rising carbon dioxide." Professor Hungate suggests Australia should go to the source of greenhouse emissions to reduce its carbon footprint. "The key thing is it's a lot more effective to reduce emissions by going to the source of increased greenhouse gases than it is to rely on natural systems to mop up on this for us," he said. AT: Water VaporWater vapor’s a positive feedback – global humidity measurements proveDessler et al, ‘8 - Professors of Atmospheric Sciences at Texas A&M [A.E., Z. Zhang, P. Yang; Geophysical Research Letters, “Water-vapor climate feedback inferred from climate fluctuations, 2003-2008,” http://www.agu.org/pubs/crossref/2008/2008GL035333.shtml, DS] Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations. Height-resolved measurements of specific humidity (q) and relative humidity (RH) are obtained from NASA's satellite-borne Atmospheric Infrared Sounder (AIRS). Over most of the troposphere, q [specific humidity] increased with increasing global-average surface temperature, although some regions showed the opposite response. RH [relative humidity] increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of λ q = 2.04 W/m2/K, similar to that simulated by climate models. The magnitude is similar to that obtained if the atmosphere maintained constant RH everywhere. AT: CloudsClouds are a positive feedback – best models and observations proveClement et al, ‘9 – Atmospheric Professors at U of Miami and Oceanography Prof at UC San Diego [Amy C. Clement (Miami), Robert Burgman (Miami), Joel R. Norris (UCSD), 7/24/2009, “Observational and Model Evidence for Positive Low-Level Cloud Feedback,” Science, http://www.sciencemag.org/content/325/5939/460.abstract?sid=5faf6442-a22f-489b-95a6-c3b80628e4e1, DS] Feedbacks involving low-level clouds remain a primary cause of uncertainty in global climate model projections. This issue was addressed by examining changes in low-level clouds over the Northeast Pacific in observations and climate models. Decadal fluctuations were identified in multiple, independent cloud data sets, and changes in cloud cover appeared to be linked to changes in both local temperature structure and large-scale circulation. This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales. The observed relationships between cloud cover and regional meteorological conditions provide a more complete way of testing the realism of the cloud simulation in current-generation climate models. The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback. AT: Carbon SinksCarbon sinks can’t stop warming – they’re a positive feedbackMcCarthy, ‘7 – Environment Editor at The Independent [Michael, 5/18/2007, The Independent, “Earth's natural defences against climate change 'beginning to fail',” http://www.independent.co.uk/environment/climate-change/earths-natural-defences-against-climate-change-beginning-to-fail-449340.html , DS] The earth's ability to soak up the gases causing global warming is beginning to fail because of rising temperatures, in a long-feared sign of "positive feedback," new research reveals today. Climate change itself is weakening one of the principal "sinks" absorbing carbon dioxide - the Southern Ocean around Antarctica - a new study has found. As a result, atmospheric CO2 levels may rise faster and bring about rising temperatures more quickly than previously anticipated. Stabilising the CO2 level, which must be done to bring the warming under control, is likely to become much more difficult, even if the world community agrees to do it. The news may give added urgency to the meeting in three weeks' time between the G8 group of rich nations and the leading developing countries led by China, at Heiligendamm in Germany, when an attempt will be made to put together the framework of a new world climate treaty to succeed the current Kyoto protocol. "This is a timely warning in advance of Heiligendamm and the G8 that the climate clock is beginning to tick faster," said the leading environmentalist Tom Burke, visiting professor at Imperial College London. "The shift that has been detected in a four-year study by researchers from the University of East Anglia, the British Antarctic Survey and the Max-Planck Institute for Biogeochemistry, published in the journal Science, is one of the most ominous in the development of climate change. It implies a breach in the planet's own defences against global warming. Human society has hugely benefited from the earth's natural carbon absorption facility, which means oceans and forests take up roughly half of the CO2 pumped into the atmosphere, in the so-called carbon cycle. What is left in the atmosphere is known as the "airborne fraction". If sinks weakened, the airborne fraction would be likely to get bigger. Although supercomputer models of the climate have for some time predicted the weakening of the ocean and terrestrial sinks, no example of it happening has actually been detected - until now. Now the research team has found the vast Southern Ocean, which is the earth's biggest carbon sink, accounting for about 15 per cent of the total absorption potential, has become effectively CO2-saturated. The level of the gas it is absorbing has remained static since 1981 - but in that time the amount emitted has grown by 40 per cent, so it has stopped keeping pace and much more CO2 is left over to trap the sun's heat. The effect - revealed by scrutinising observations of atmospheric CO2 from 40 stations around the world, is thought to have been caused by an increase in ocean wind speeds. Stormier weather and stronger waves are churning up the sea and bringing natural CO2 stored there closer to the surface - which reduces the ability of the surface to absorb the gas from the air. The increased winds are believed to be caused by altered atmospheric temperature regimes produced by two separate processes - the depletion of the ozone layer over Antarctica by chlorofluorocarbon gases from aerosol spray cans (now phased out), and global warming. It is thus a positive feedback - an effect of climate change which itself makes climate change worse. Some researchers fear that feedbacks may make global warming happen much faster, and harder to control, than generally appreciated. The pessimism of scientists such as James Lovelock is largely based on the fact that most feedbacks in the earth's system are likely to work against us. "This is the first unequivocal detection of a carbon sink weakening because of recent climate change," said the lead author of the study, Corinne Le Quéré, of the University of East Anglia. "This is serious. Whenever the world has greatly warmed in the past, the weakening of CO2 sinks has contributed to it." Professor Chris Rapley, director of the British Antarctic Survey, said: "Since the beginning of the Industrial Revolution the world's oceans have absorbed about a quarter of the 500 gigatons [millions of tonnes] of carbon emitted by humans. The possibility that in a warmer world the Southern Ocean is weakening is a cause for concern." The Government's chief scientific adviser, Sir David King, said: "We have quite a large number of positive feedbacks to worry about, and this appears to be another one. But the seriousness of it would depend on if it was affecting the whole ocean, or merely the Southern Ocean." In recent years it has become clear that the rate at which CO2 was accumulating is itself increasing. The level currently stands at about 382 parts per million by volume (ppm), up from 315 ppm in 1958. In the past decade the rate has jumped from about 1.6ppm annually to well above 2ppm - a fact which, as The Independent reported in October 2004, may well signal that the earth's absorption ability is shrinking. Asked if this rate increase could now be linked to weakening sinks, Dr Le Quéré said: "I think we are just at the border of detecting that." She added: "All the carbon cycle experts have their eyes on it." Directory: files files -> Answer True False 2 points Question 2 files -> Integer programming and game theory files -> 4 Integer Programming files -> Bpa vehicle Window Repair Scenario #1 task: Procure vehicle window relacement. Objective files -> Pop Warner History files -> North Carolina Inclusion Initiative Mapping Where Children with ieps are Being Served Purpose files -> Fall 2013 Spring 2014 Program Data: Standard 1 Exhibit 4d files -> Hanban – asia society confucius classrooms network 2010 request for proposal files -> Northern England’s set-jetting locations Download 1.74 Mb. Share with your friends:
|