It is a big job to take away a city’s rubbish. Most rubbish is made up of things we can’t eat or use. If we kept these things, we would soon have mountains of rubbish.

In some cities the rubbish is collected and taken outside of the city to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system. The sewage system takes away the used water from toilets, bathrooms and other places.

To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbish-filled land. Finally, a house or a school may be built there, and then you’d never know that this was an old rubbish dump before.

In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly changes into something called humus, which looks like black earth. It is rich with kinds of things that feed plants and help to make them grow.

It’s 2076 and the skies are looking decidedly milky. On windy plains and in parts of the seas that have been turned over to wind farms, a different kind of tower has been built alongside the turbines (涡轮). They take in CO₂ out of the atmosphere. Vast parcels of land have been given over to forest. Trees are grown, harvested and burned for energy in power plants that don’t let CO₂ escape to the atmosphere. Instead, emissions are captured and driven underground. Powdered minerals are put into the water to absorb CO₂ and reduce ocean acidification.

All these technologies are a desperate action to reverse more than two centuries of greenhouse gas emissions. But they are not entirely up to the task and, anyway, we are still releasing greenhouse gases. “I think it’s very likely that in 60 years we’ll be using both technologies,” says John Shepherd of the University of Southampton, UK. He is referring to the two flavors of geoengineering: absorbing CO₂ out of the air and using a sunshade to reflect some of the sun’s rays back out into space.

There is no denying that climate talks are going too slowly and not so smoothly. Even if industrial emissions were to drop rapidly — a big if — some sections pose an intractable problem. We have no real replacement for aeroplane fuel and feeding people demands intensive agriculture, which accounts for a quarter of global emissions.

Computer models suggest there will be winners and losers. While a sunshade could lower global average temperatures to pre-industrial levels, there would be regional differences. Northern Europe, Canada, Siberia and the poles would remain warmer than they were, and temperatures over the oceans would be cooler. Global warming is predicted to make wet regions wetter and dry ones drier. Models suggest a sunshade would correct this, but, again, not in a uniform way.

Shepherd fears all this will feed into international arguments. He imagines some kind of global council where governments seek a climate that meets their needs. Some might prefer a slightly warmer temperature, for tourism or agriculture. But nations whose coral reefs (珊瑚礁) draw in visitors will probably want more CO₂ absorbing technologies.

In spite of all these concerns, most scientists hold that revolutionary technology and people’s awakening can shine a light on solutions in ways that are impossible now. There is undoubtedly a long way to go when we address problems facing mankind, but we can always anticipate something.

United Nations Climate Change Conference

The U.N. Climate Change conference opened in Copenhagen, Denmark on Dec.7th with some 15,000 delegates and observers from nearly 200 countries attending what is called the last best chance for an agreement to combat (与……战斗) global warming.

Their aim is to find common ground, including on reduction of greenhouse gas emissions, promotion and transfer of new more eco-friendly technology and the necessary funding to make this possible, especially for the less developed and poorer nations. It also means coming up with long term vision and cooperation for the future.

Most scientists believe the warming trend is mainly caused by human activity, especially the use of fossil fuels (矿物燃料) and the cutting down of forests. Skeptics (怀疑论者) say global warming is part of a natural cycle of climate change.

In Copenhagen, experts and officials alike are putting the emphasis on what people and governments can do to cut the emission of greenhouse gases.

Scientists say a 25 to 40 percent cut in carbon-dioxide emissions is needed to control global warming. The European Union, China, and India have already pledged (保证) reductions. The United States is waiting for Congressional (国会的) approval for a proposal put forward by the Obama administration.

Barack Obama, President of the United States said, “Each of us must do what we can when we can to grow our economies without endangering our planet -- and we must all do it together. We must seize the opportunity to make Copenhagen a significant step forward in the global fight against climate change.”

Desmond Tutu, Archbishop of South Africa said, “Worldwide, we have the chance to start turning the tide of climate change, but only if all governments commit themselves to a fair, binding (有约束力的) and sustainable climate agreement in Copenhagen.”