'Asian Brown Cloud' poses global threat (2002)

The lives of millions of people are at risk, both from the toxic haze and the weather change it brings, the study showsA dense blanket of pollution, dubbed the "Asian Brown Cloud," is hovering over South Asia, with scientists warning it could kill millions of people in the region, and pose a global threat.

In the biggest-ever study of the phenomenon, 200 scientists warned that the cloud, estimated to be three kilometers thick, is responsible for hundreds of thousands of deaths a year from respiratory disease.

By slashing the sunlight that reaches the ground by 10 to 15 percent, the choking smog has also altered the region's climate, cooling the ground while heating the atmosphere, scientists said.

The potent haze lying over the entire Indian subcontinent -- from Sri Lanka to Afghanistan -- has led to some erratic weather, sparking flooding in Bangladesh, Nepal and northeastern India, but drought in Pakistan and northwestern India.

"There are also global implications, not least because a pollution parcel like this, which stretches three kilometers high, can travel half way round the globe in a week, " U.N. Environment Program chief Klaus Toepfer told a news conference in London on Sunday.

The U.N.'s preliminary report comes three weeks before the Earth Summit in Johannesburg, which opens on August 26, where all eyes will be on how not to overburden the planet.

Global threat
While haze hovers over other parts of the world, including America and Europe, what surprised scientists was just how far the cloud extended, and how much black carbon was in it, according to India's National Physical Laboratory.

A cocktail of aerosols, ash, soot and other particles, the haze's reach extends far beyond the study zone of the Indian subcontinent, and towards East and Southeast Asia.

While many scientists once thought that only lighter greenhouse gases, such as carbon dioxide, could travel across the Earth, they now say that aerosol clouds can too.

"Biomass burning" from forest fires, vegetation clearing and fossil fuel was just as much to blame for the shrouding haze as dirty industries from Asia's great cities, the study found.

A large part of the aerosol cloud comes from inefficient cookers, where fuels such as cow dung and kerosene are used to cook food in many parts of Asia.

Acid rain
Using data from ships, planes and satellites to study Asia's haze during the northern winter months of 1995 to 2000, scientists discovered not only that the smog cut sunlight, heating the atmosphere, but also that it created acid rain, a serious threat to crops and trees, as well as contaminating oceans and hurting agriculture.

The report suggested the pollution could be cutting India's winter rice harvest by as much as 10 percent.

The report calculated that the cloud could cut rainfall over northwest Pakistan, Afghanistan, western China and western central Asia by up to 40 percent.

While scientists say they still need more scientific data, they suggest the regional and global impact of the haze will intensify over the next 30 years.

In the next phase of the project, scientists will collect data from the entire Asian region, over more seasons with more observation sites and refine their techniques.

But because the lifetime of pollutants is short and they can be rained out, scientists are hopeful that if Asians use more efficient ways of burning fuel, such as better stoves, and cleaner sources of energy, time has not run out.

由于环境污染严重，如今亚洲南部的上空笼罩着污浊不堪的空气层，被称作"亚洲褐云"。科学家警告说这种情况将造成亚洲地区上百万人丧生，同时还会对全世界的环境造成威胁。

在这次大规模的研究中，200位科学家提出警告，认为这朵厚达三公里的"亚洲褐云"正是导致每年成千上百人死于呼吸道疾病的真正"杀手"。

科学家们说，这层令人窒息的烟雾阻挡住了10％到15％射向地面的阳光，而且业已改变了南亚地区的气候，使得地面温度下降而大气温度升高。

这一大片黑压压的烟雾笼罩了从斯里兰卡到阿富汗的整个印度半岛，导致了该地区气候反常，造成的直接恶果是孟加拉、尼泊尔和印度东北部洪水泛滥，相反巴基斯坦和印度西北部却是大旱成灾。

联合国环境署主席克劳斯·特普费尔8月11日在伦敦一个新闻发布会上说："全世界范围内的环境污染已经初见端倪，仅仅亚洲上空这一片三公里厚的乌云，就可以在一周之内迅速蔓延，笼罩半个地球。"

8月26日将要在南非约翰内斯堡召开地球首脑会议，届时与会各国将共同商讨如何为我们生活的星球"减负"。联合国的初步环境调查报告将于大会召开前三周提交。

全球风声鹤唳

印度国家物理实验室称，如今这片污浊的烟雾已经蔓延到了世界其他地区，包括美洲和欧洲，科学家们对这片褐云能够覆盖如此大的范围深感吃惊，此外，还有烟雾里面的黑色碳的含量之高也是让人触目惊心的。

这片烟雾里夹杂着悬浮颗粒、灰尘、煤烟灰和其他污染物。如今这片褐云的覆盖范围早已超出了印度半岛的研究地带，正在向亚洲东部和东南部蔓延。

从前许多科学家认为只有那些较轻的能够引起温室效应的气体，例如二氧化碳，才能够围绕地球游动，但是现在看来带有悬浮颗粒的烟雾也是可以的。

研究发现，除了亚洲大城市中一些污染环境的工业之外，森林大火、植被清除和燃料燃烧对环境同样造成了严重的污染，因而也是这片亚洲褐云形成的原因之一。

这片烟雾中的悬浮颗粒主要是由于燃料的不充分燃烧造成的，因为亚洲许多地区人们还在使用牛粪和煤油作燃料来做饭，这样的燃料往往是不能充分燃烧的。

严重的环境污染引起酸雨

酸雨横行肆虐

科学家们通过飞船、飞机和卫星发回的1995年到2000年亚洲北部冬季期间的有关气象数据来对亚洲脏雾进行分析研究。研究发现，这片烟雾不仅仅能阻断阳光射入和引起大气层升温，而且还能够引起酸雨，这就对农作物和树木构成了威胁，而且还会对海洋造成污染，对农业造成伤害。

研究报告分析这样的环境污染能够造成印度冬季稻米减产10％。

此外，据报告统计，这片脏雾能够使得巴基斯坦西北部、阿富汗、中国西部和中亚西部的降雨量减少40％。

尽管对脏雾的研究还需要更多的科学数据，但是科学家们认为这片亚洲脏雾对亚洲地区乃至全球的恶劣影响将会在今后的30年内逐渐恶化。

这项研究计划的下一个阶段中，科学家们将从整个亚洲地区收集数据，扩大观测季节和观测地点的范围，并且使用更先进的科技手段。

但是由于污染物的存活时间短，而且能够被雨水冲洗掉，因此科学家们认为，如果亚洲人民在使用燃料的时候能够换用更为有效的方法，例如使用更高级一些的火炉，改用更为清洁的能源等等，这样人类就还能有时间拯救我们的地球。