首页 >> 推荐阅读 >> 正文

译:Soot strategies

来源: 时间:2011/1/26 14:19:00 点击:

As the power of black carbon to accelerate ice-melt becomes clearer, climate-change policymakers are giving more time to this long overlooked pollutant. Jenny Johnson reports.


Global efforts to mitigate climate change are beginning to take aim at a once-obscure pollutant called “black carbon” in a shift that may bring policies to cool the planet to families preparing meals at home and farmers readying plots of land for planting.

A series of new scientific studies have confirmed the potent warming effects of black carbon on melting ice and snow in the Arctic and the Himalayas, spurring a new focus on attacking sources of those emissions. The latest research identifies open burning in agricultural fields in Eurasia as a key source of black carbon in the Arctic. Evidence also indicates emissions from the burning of coal, wood and other biomass for domestic cooking and heating throughout Asia are heavily impacting the Himalayas.

Black carbon is part of a chemical mix of particulate matter that has long been an air-pollution concern due to its impacts on human health. But the pollutant also acts to reduce the reflectivity of ice and snow, allowing heat absorption and hastening surface melt. Research indicates reductions could immediately help save ice and snow in the Arctic and the Himalayas, two areas of critical global importance that are proving particularly sensitive to climate change.

Melting of Arctic ice presents several dangers for the planet. The process could undermine the region’s ability to act as a cooling mechanism for Earth by reflecting incoming solar radiation back into space and disrupt global ocean circulation by decreasing the salinity of water. Greenland, meanwhile, holds enough frozen water to raise sea levels – if melted – by as much as seven metres. These scenarios are increasingly realistic, as catastrophic loss of ice in the Arctic has accelerated in recent years, well beyond the predictions of climate models.

The Arctic is warming at two to three times the rate of the rest of the planet, with its rising temperatures constituting a possible global “tipping point”, which could result in rapid global warming and a cascade of changes through the ecosystem. Black carbon may have contributed as much as 50% of the 1.9 degrees Celsius of warming seen in the region since 1890, according to a 2009 paper published in Nature Geoscience.

Research shows that black carbon is also heavily impacting the glaciers of the Himalayas, another region of global significance. The “third pole” or “Asian water tower” feeds some of the world’s biggest rivers, including the Ganges, Yangtze and Yellow River, which together supply drinking water and crop-irrigation for some 1.5 billion people across 10 countries. According to estimates published last year in the journal Atmospheric Chemistry and Physics, black-carbon emissions have caused nearly 10% of the ice-cover loss in the Himalayas from 1990 to 2000, of which about 36% is attributed to Indian coal and biofuel burning.

Previously seen as a distraction from capping and reducing carbon dioxide, the nexus of air pollution and global warming is finally coming to the forefront of the climate-policy debate as evidence grows that so-called short-lived climate forcers like black carbon have big effects.

The shift in focus also comes against a background of continuing failure to set credible global policy on carbon-dioxide emissions. Black carbon can be effectively reduced through targeted, regional programmes that can help limit warming in the near term, something that cannot be done with carbon dioxide due to its longer atmospheric lifetime. And black carbon’s large and direct human health impacts, plus the fact it is already targeted by rapidly urbanising countries, make it an attractive target.

What next?

The latest research shows that due to a seasonal shift in a climatic anomaly called the Arctic Front, smoke from the widespread open burning of grass and straw that takes place in Eurasia in the late winter and early spring efficiently travels north to the Arctic, where particles from it land on the ice and snow.

Scientists have identified open burning in northern Eurasia – Russia, Kazakhstan, Mongolia and north-west China – as the single biggest source of black carbon in the Arctic and say that, at certain times of the year, it may constitute an even bigger contribution to warming in the region than carbon dioxide.

Sarah Doherty of the University of Washington in the United States used field samples to trace the origins of the black carbon coating snow in the Arctic to biomass burning in Eurasia. At a St Petersburg conference in November, she cautioned that the cooling effects of other particles in the smoke are “highly uncertain” and may dampen the warming impact of black carbon in the region. However, Doherty said that decreasing biomass burning in Eurasia would likely have the biggest single impact on reducing Arctic warming in the near term.

Controlling open burning is a major challenge. Farmers in China and Russia are officially prohibited from disposing of waste, recharging the soil and ridding their fields of pests through burning, but such bans have proved ineffective.

“In order to reduce China’s springtime black carbon emissions, farmers need a viable alternative method of crop waste removal,” a May 2009 report from US-based non-profit the Clean Air Task Force stated. Researchers are testing ideas for alternatives, such as using straw as a source of bioenergy, which would result in lower emissions. Processing waste for fertiliser is another leading idea.

In Russia, fire policy is coming under the spotlight following the summer's wildfires that burned vast areas of forest amid record heat and drought, destroying 30 villages and killing dozens directly and indirectly from smoke, smog and carbon monoxide effects. While the summer blazes are unlikely to have affected the Arctic on the scale of the spring fires due to climate patterns, critics say the events demonstrated a general lack of capacity on the part of the government to control fires across its large territory. They argue that, without greater capacity, it will be impossible to control the fires in the spring.

Several researchers have reported that the Kremlin is currently reviewing its forest code, which was changed in 2007, doing away with a unified forest protection system and giving more power to the regions. Major changes to the forest code are a top priority for environmental groups in Russia today and there is international pressure on Russian officials to act in time for the next fire season.

Action to decrease the black carbon affecting the Himalayas is more advanced. Several international development programmes are focused on distributing more efficient cooking stoves that greatly reduce emissions. However, the scale of the problem and the expectation that black-carbon emissions will continue to increase alongside Asian industrial development, still hinder effective policy.

The China-based group Third Pole Environment is conducting research into the many unanswered questions about sources and effects of emissions and how the region will respond to global environmental changes and has stressed the need for further work in this area. It is clear that even beginning to address the climate impacts of activities like grass and straw burning in Eurasia will take time. There are many knowledge gaps that prevent robust policy solutions, such as basic data on the types of crops in Russia and its land cover. The willingness of the countries to act remains an open question.

At a supranational level, there is some progress. While black carbon is not among the greenhouse gases addressed under the United Nations Framework Convention on Climate Change, a separate UN convention is set to begin shaping reduction policies to mitigate climate change. In December, the Convention on Long-range Transboundary Air Pollution (under the UN Economic Commission for Europe) agreed to revise one of its protocols in 2011 to include black carbon, as well as other short-lived climate forcers, such as carbon monoxide and methane.

This step will make it the first international body to begin shaping policies that account for the air pollutant's climate effects. Europe, the United States and Russia are among signatories to the convention. China is not, but the work plan for the coming year specifies the creation of policies that could be applied outside the area currently covered by the convention.

A series of new studies on black-carbon sources, effects and mitigation options are set to be published in 2011 by the United Nations and several high-profile research institutions. As understanding of the issue improves, advocates are hoping united solutions and action will quickly follow.

(译文如有出入请联系本会,来源于chinadialogue)

译   文:

亟待出台烟尘治理策略

随着炭黑能够加速冰雪融化速度的事实日渐明朗,气候变化政策的制定者们对这一长期以来受到忽视的污染物给予了更多的关注。


曾经不起眼的污染物—“炭黑”正逐渐得到全球减缓气候变化行动的关注。这一转变或许会使那些在家做饭的家庭以及准备耕种土地的农民受到那些旨在为地球降温的政策的影响。

一系列新的科学研究已经证实,炭黑具有导致北极和喜马拉雅地区冰雪融化的潜在致暖效应。这一研究成果激发了人们对于此类排放的源头进行治理的关注。最新的调查结果发现,欧亚地区农用耕地的露天焚烧行为是北极地区炭黑的主要来源之一。此外,还有证据显示,亚洲各地人们为了烧饭和取暖而燃烧的煤炭、木材、以及其它生物燃料所产生的排放对喜马拉雅地区也造成了严重的影响。

炭黑作为化学颗粒混合物的一部分,鉴于其对人类健康造成的影响,长期以来都被当做一种空气污染物而备受关注。然而,这种污染物却能够降低冰雪的反射率,增加热量的吸收,加快其表面的融化。研究发现,减少炭黑可以迅速挽救北极和喜马拉雅地区的冰雪层。经证明,这两个地区对于气候变化尤为敏感,因此,它们对于全球而言具有举足轻重的重要意义。

北极冰的融化使地球面临着若干危险。通过将太阳入射辐射反射回太空,这一地区发挥着地球冷却机制的作用。北极冰的融化会使该地区的这一功能遭到破坏。此外,北极冰的融化还会导致海水盐度的降低,从而对全球海洋环流造成干扰。同时,格陵兰岛的冰川如果融化,其所凝结的冰水足以使海平面上升达7之多。随着近年来北极冰灾难性地减少,其速度不断加快,甚至超出了气候模型所预测的速度,上述那些情境正越来越真实地展现在我们的眼前。

北极正以地球其它地区两到三倍的速度。而其不断升高的温度有可能会推动全球走向“临界点”,由此导致全球快速变暖,并通过生态系统引发一系列的变化。据2009年《地球自然科学》发表的一篇文章称,该地区1890年至今所观察到的1.9摄氏度温升中,差不多有50%的可能是由炭黑造成的。

研究表明,炭黑还对另一个具有全球重要意义的地区——喜马拉雅地区的冰川造成了严重的影响。这一地区被称作“第三极”或“亚洲的水塔”,为一些世界上最大的河流提供着水源补给。这些河流中有恒河、长江、黄河等。它们为10个国家的约15亿人口提供着饮用水和灌溉用水。据《大气物理化学》杂志今年发表的研究估计,1990年到2000年间,喜马拉雅消失的冰盖中有大约10%是炭黑的排放所致,而其中约36%的炭黑排放来自于印度的煤炭及生物燃料的燃烧。

空气污染与全球气候变暖之间的联系曾被视为是偏离了二氧化碳的总量控制及减排的宗旨。然而,随着炭黑等被称为短期气候刺激因素的物质具有重大环境影响的证据不断涌现,这一联系最终站在了气候政策争论的前沿。

由于一直以来都未能对二氧化碳排放制定可行的全球性政策,而这一背景也促使治理的重心发生了转移。通过具有针对性的区域项目可以有效降低炭黑排放,从而能够在短期内限制温度的升高。而对于二氧化碳而言,由于其在大气中的留存时间较长,因此无法在短期内达到限制温度升高的目的。 此外,炭黑还会直接对人类的健康产生重大的影响,再加上一些快速城市化的国家实际上已经将其作为减排目标等因素都让炭黑成为一个非常具有吸引力的治理目标。

下一步该怎么办?

最近的研究显示,由于一种被称为北极锋的异常气候的季节性变化,欧亚大陆地区冬末早春时节大范围露天焚烧干草和秸秆所产生的烟尘几乎全部向北扩散到了北极,烟尘中的颗粒飘落在冰雪的表面。

科研人员发现,包括俄罗斯、哈萨克斯坦、蒙古、以及中国西北部地区在内的欧亚大陆北部地区的露天焚烧现象是北极炭黑污染的最主要的单一来源,并且认为,在一年中的某些特定时节,该地区由于炭黑所造成的温度升高甚至超过了二氧化碳。

美国华盛顿大学的莎拉·多哈蒂通过采样,发现覆盖在北极积雪表面上的炭黑的源头是欧亚地区燃烧生物燃料所致。十一月份在圣彼得堡召开的一次会议上,她提醒说,烟尘中的其它颗粒物所带来的降温效应具有“很高的不确定性”,可能会抑制炭黑对该地区造成的暖化效应。然而,多哈蒂还表示,减少欧亚地区生物燃料的燃烧将有可能在短期内对减缓北极气候变暖产生重大影响。

控制露天焚烧是一项重大的挑战。中国及俄罗斯均明令禁止农民以焚烧的方式处理垃圾、进行土壤培肥、及消灭田中害虫等。然而,这些禁令却难见成效。

美国非营利组织—净化空气任务组织在其2009年5月发表的一份报告中曾这样写道: “为了降低中国春季的炭黑排放,农民们需要一种可行的替代方式来清除农作物秸秆。”研究人员正在对一些替代性理念进行测试。比如说,将秸秆作为生物能源的来源,从而可以产生较少的排放。而另外一个主导理念就是通过垃圾处理,将其变为肥料。

而在俄罗斯,罕见的夏季高温和干旱引发了森林大火,吞噬了大片的森林,焚毁了30座村镇。大火所产生的烟、雾、及一氧化碳直接或间接导致数十人死亡。而消防政策也随之成为人们关注的焦点。受气候模式的影响,夏季火灾对北极造成的影响从程度上而言无法与春季大火相比。尽管如此,评论家依然认为,这些事件表明,政府普遍缺乏在大范围内控制火情的能力。他们认为,如果不具备更强的能力就无法控制春季火灾。

一些研究人员的报告称,克林姆林宫目前正对曾在2007进行过修改的林业法规进行复核,取消了统一的森林保护系统,并赋予各地方更多的权利。其中重大变化就是给予俄罗斯目前的环保团体优先权。而且,国际社会的压力也迫使俄罗斯的政府官员在下一次火灾高发季节来临时及时采取行动。

相对于法规而言,为了降低影响喜马拉雅地区的炭黑排放所采取的行动则先行一步。一些国际发展项目已经开始关注这一问题,并开始向人们配送能效更高的厨灶,从而大大减少了排放。然而,问题的波及面以及人们对于炭黑排放将随着亚洲工业化发展继续增长的预期都将阻碍政策的有效实施。

中国的第三极环境组织就针对许多待解的问题展开了研究,如关于排放的源头及其产生的影响、以及当地将如何应对全球环境变化、该如何在这一地区着重深入开展工作等。显然,即便是着手应对欧亚地区焚烧杂草和秸秆之类的行为所带来的气候影响都需要时间,更毋庸说由于存在着许多理论缺口而无法从政策层面给出有效的解决方案,例如缺乏俄罗斯境内种植的作物种类及种植面积的基本数据等。此外,各国是否愿意采取行动也还是个未知数。

然而,在国际范围里还是取得了一些进展。虽然《联合国气候变化框架公约》中提到的温室气体中并未包括炭黑,但是,联合国却单独制定了一份公约,旨在开始为减缓气候变化制订减排政策。12月,(联合国欧洲经济委员会下属的)《距离越境空气污染公约》同意于2011年修改其中的一个条款,将炭黑及一氧化碳和甲烷等其它短期气候刺激因素也包括在内。

这一举措使其成为首个为应对空气污染物所造成的气候效应而制定政策的国际组织。欧洲、美国、以及俄罗斯都参与了该公约的签署。中国虽然没有参与,但是却在来年的工作计划中明确表示要制订相应的政策,并且这些政策所覆盖的地区并不在公约所涵盖的范围之内。

联合国及多家著名研究机构都针对炭黑的来源、所产生的影响、以及降低其影响的方式等问题开展了一系列新的研究,并将于2011公布其结果。随着人们对这一问题理解的加深,支持者们希望能够随后尽快推出统一的解决方案,并采取一致行动。

                                                


浙江正泰公益基金会 浙ICP备11034570号 2000-2011 THE COMMONWEAL FOUNDATION OF CHINA
浙江省杭州市滨江区月明路560号正泰大厦2号楼6F 热线电话:0571—89710110 89710106 邮编310014 电子邮箱:dtxd@ztgy.org