路由器抓包:what is environment problem

有什么环境问题

什么是环境问题

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The Greenhouse problem

A number of the gases we are putting into the atmosphere have the effect of trapping energy that comes to the earth as sunlight but which would otherwise be radiated back into space. The main contributor is carbon dioxide, accounting for about half the greenhouse effect. Humans generate about 24 billion tonnes of carbon dioxide each year, mostly from the burning of fossil fuels (coal, oil and gas) in rich countries.

The carbon dioxide content of the atmosphere has increased by about 25% since humans began to use fossil fuels in large quantities 150 years ago. The concentration is now around 350 ppm and increasing by about 1.5% p.a. The effects can't be predicted with confidence but this increase could result in a 1-2 degree rise in average global temperature by 2030. The expected rise at the poles is much greater. If the greenhouse effect continues into the 22nd century then polar ice would begin to melt eventually bring about a sea rise of perhaps a hundred metres. Even a half metre rise would cause huge problems for the many people who live on low lying islands and in coastal regions.

Probably the most undesirable effects will be hotter and drier climates in many Third World regions such as the African Sahel, where millions of people even now have difficulty growing enough food, and more frequent occurrence of extreme climatic events such as storms, floods, droughts and cyclones. These can devastate food production.

It is possible that positive feedback effects from several sources could suddenly produce a catastrophic runaway greenhouse effect. For example,

- As the warming dries out the Arctic tundra it begins to rot, releasing greenhouse gases.

- As the tropical rainforest is destroyed we lose the cloud their moisture generates. That cloud presently reflects much solar energy back into space, cooling the earth.

- As the warming reduces the formation of polar ice each year less salt is separated to fall to the bottom causing the huge currents that take carbon-rich water down.

- As these currents diminish less nutrients are brought up to feed the plankton which take in much carbon.

- As the oceans warm and become more polluted coral reefs dissolve, ceasing to take carbon from the atmosphere and releasing their carbon to the ocean.

It seems that the global atmospheric system can flip from one state to another fairly quickly. Some ice ages have come and gone relatively suddenly. The worry is that human activity could tip the system into a new state, for example, bringing on a new ice age. Nature moves 100 times as much carbon into and out of the atmosphere as humans do, so we might trigger or lever huge shifts and runaway effects in nature's processes.

PLANT MANY TREES?

It doesn't take long to realise that there is no realistic chance of solving the greenhouse problem by planting trees to remove carbon dioxide from the atmosphere. Firstly we'd have to plant something like the area of Australia, and secondly this would only take carbon from the atmosphere while the trees were growing.

Similarly, increasing the use of nuclear energy in order to cut coal use would not make much difference. Burning coal to produce electricity contributes only a small fraction of the carbon input, carbon constitutes only about half of the greenhouse problem, and to build all the reactors needed would require a great deal of energy and would therefore help to make the greenhouse problem worse for possibly 50 years.

...AND ENERGY GROWTH?

If the CO2 content of the atmosphere continues to increase at the present rate then late next century it will probably have risen to around 8 times the present level.

World energy consumption is growing at about 2% p.a. Remember that the Third World is far below rich world energy use levels and wants to catch up. In fact half the world's people average only 1/17 the rich world average per capita use. If all the people likely on earth late next century were to rise to the present per capita use levels in rich countries world energy use would be about 8 times its present amount.

The atmospheric scientists have been telling us for years that if we are to stop the level of carbon in the atmosphere from rising any higher, we must cut carbon inputs by 60-80%. If we were to cut them by 60% and share the quantity of energy between all the people we would have on earth by 2060 you and I would have to get by on only 1/18 of the energy we use now. Most people have no idea of the magnitude of the overshoot and therefore the magnitude of the reductions in resource use and in consumption that will have to be made if the problems are to be solved.

The greenhouse problem provides strong support for the "limits to growth" argument. There is no plausible way of solving the problem without accepting drastic reduction in per capita levels of production and consumption and thus shifting to The Simpler Way, including a zero-growth economy. (The assumption that changing to renewable energy can solve the problem is not plausible; See on this website the Renewable Energy section in The Limits to Growth.)

THE OZONE PROBLEM.

In the mid 1980s it was realised that the ozone in the atmosphere is being depleted. There is only a very small quantity of this gas. If all the molecules of ozone were brought together at normal pressure they would make up a layer around the earth less than 3 mm thick. Yet ozone performs the extremely important function of blocking out much of the ultraviolet light that comes from the sun and is harmful to life. Life on earth was only able to emerge from the seas on to the land after plants had released enough oxygen to create an ozone shield.

In the late 1980s scientists observed a large hole forming each year in the ozone over the antarctic. More recently another hole has appeared over the Arctic. By the early 1990's there had been about a 3-5% reduction in the amount of ozone in the whole atmosphere. The main destructive gases, CFC's, remain active in the atmosphere for 100 years.

The ozone problem illustrates the most important aspect of the general environment problem, i.e., the damage being done to the life support systems of the planet. Increased ultraviolet light coming to earth will have undesirable effects on various biological systems, including the productivity of broad leaf plants (and therefore agriculture) and the micro-organisms in the sea which account for a considerable proportion of the world's oxygen and which take much carbon from the atmosphere. Processes such as these are crucial in maintaining the conditions necessary for the health of the entire planet, and the most worrying aspect of the environment problem is that in many ways human activity is degrading these systems and processes that make life on earth possible.

ACID RAIN.

In the heavily industrialised areas of North America and Europe the rainfall has become acidic due to the amount of nitrogen and sulphur entering the atmosphere especially from cars and power stations. As a result forests and lakes are dying. This is one more factor reducing the productivity of agriculture and more importantly degrading the life support systems of the planet. There will be strong pressure to increase use of fossil fuels and fertilisers in coming decades, increasing the release of acid to the atmosphere.

SOIL DAMAGE

All life on earth depends on the earth's fragile "life jacket" made up by the thin layer of topsoil (average depth only 30 cm) from which all living things derive their sustenance. We are treating this vital resource in a way that cannot continue for many more decades. Our agriculture is one of the most unsustainable aspects of our society. Consider the main damaging effects.

- Erosion takes 24 billion tonnes of soil from the world's farms every year (and there are more than 80 million additional people to feed every year). Our agriculture involves ploughing and this leaves the ground open to erosion by wind and rain.

环境问题是什么

环境问题

面临着什么样的环境问题