关于全球气候变暖的危害，有关专家指出，它引起的气候变化可能会使极端气候的出现频率和强度不断增加。在一些地区，龙卷风、强雷暴以及狂风和冰雹也会增多，世界许多地区将遭受更频繁、更持久或更严重的干旱。
    同时，由于暖冬的气温比常年偏高，这就使各种病菌、病毒活跃，病虫害滋生蔓延，很多有害动物，比如蚊子、跳蚤、老鼠等减少了被冻死的几率，此类传染病载体的数量大增，对人类健康构成了严重威胁。据估计，全球变暖会使疟疾和登革热的传播范围增加，威胁40％～50％的世界人口。

The current problems of global warming and the reduction of Earth’s natural resources such as fossil fuels, fresh water and topsoil are the most difficult challenges humankind has ever faced. Scientists have concluded that reducing the release of carbon dioxide (CO2) will lessen global warming; so in 1997 181 governments signed the Kyoto Protocol to reduce their emissions of the chemical along with five other “greenhouse gases.” Although this measure is a positive step, in the July 2005 issue of the scientific journal Physics World, British physicist Alan Calverd proposes a simpler way to eliminate global warming—stop eating meat. His article “A Radical Approach to Kyoto” has spread rapidly across the Internet and is being heatedly discussed by scientists.
Although Calverd is not a vegetarian he recognized the great waste of natural resources and energy caused by the raising of animals for food. So he calculated the various forms of CO2-producing power use, such as the burning of fossil fuels and human and livestock metabolism, and found that 21% of such power consumption involves keeping farm animals alive. Similar to automobile fuel exhaust, the livestock’s breathing generates an enormous amount of CO2, and remarkably, this agent of global warming is not included under the category of manmade emissions by climate scientists and politicians because they consider it a non-human phenomenon that can not be altered.
Further, Calverd’s figure of 21% does not include indirect sources of carbon dioxide emissions, such as feed production, mechanized slaughtering, evisceration, packaging, transport and refrigeration.

A more complete calculation of the energy cost of meat production has been done by Cornell University’s Dr. David Pimentel, an agricultural scientist, who is not involved with the vegetarian movement, but has been tracking the energy cost of ‘growing’ meat for decades and written 560 scientific papers and 23 books on the subject. Dr. Pimentel has also held numerous governmental posts overseeing the meat industry and repeatedly tells his fellow meat scientists, “I’m not making any moral judgments. I’m just giving you data.”
In his 2004 paper “Livestock Production and Energy Use,” Pimentel estimated that in the US the amount of gasoline required to sustain the average meat-based diet is an astonishing 401 gallons per year, versus 219 gallons for a vegetarian diet. These numbers increase dramatically the more meat one eats. Pimentel also calculated that if the entire world ate the way people in the US do, Earth’s petroleum reserves would be exhausted in just thirteen years.  
Most remarkable is the following observation:Even driving many gas-guzzling luxury cars can conserve energy over walking; that is, when the calories you burn walking come from the standard American diet! This is because the energy needed to produce the food you would burn in walking a given distance is greater than the energy needed to fuel your car to travel the same distance, assuming that the car gets 24 miles per gallon or better.

In addition, a similar calculation on bicycle riding from the websitehttp://www.bicycleuniverse.info/ reveals that cycling on a meat diet requires as much fossil-fuel consumption as driving a car.Another meat related emission that is often forgotten is methane, a product of anaerobic digestion generated when a cow exhales. A National Aeronautics and Space Administration (NASA) study published in the February 2005 issue of the journal Geophysical Research Letters reveals that due to its effects on atmospheric ozone methane causes twice the amount of global warming previously estimated (10%), and meat-eating is responsible for a full third of all biological methane emissions.Another surprising statistic is that the nine billion head of livestock kept in the US consume seven times the grain eaten by the country’s human population, and the percentage of grain fed to livestock is also skyrocketing in developing countries such as China, Egypt and Mexico. Furthermore, according to the Worldwatch Institute, each pound of grain-fed steak results in 35 pounds of eroded topsoil, and sustaining a meat-eater’s diet requires more than 4,000 gallons of water daily versus 300 for vegetarians.

According to the renowned ecologist Mathis Wackernagel, our animal-based diet is a major reason that humans are consuming the planet’s long term bio-capacity at an unsustainable rate. Thus, many scientists such as Wackernagel and Calverd have scientifically verified that meat consumption is draining Earth’s resources, but there are other unquantifiable but significant issues that need to be considered as well, such as animal welfare and the moral impact of mass animal slaughter on human consciousness.

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