分类： 环保资讯 ECO-NEWS

人类每年消耗的自然资源都超出自然界的负荷能力，今年地球上的自然资源如水源、土壤和干净空气的配给额，提前于7月29日耗尽，透支情况每年越来越严重。

世界自然资源耗尽日，也叫地球超负荷日，是环保专家们计算出人类耗尽一年自然资源的日子。这一天之后，人类将进入“寅吃卯粮”模式，自然界的再生能力已不能满足人类的需求。

总部位于美国加州的环保组织“全球生态足迹网络”周一（29日）发布声明指出，与20年前相比，地球超负荷日已提早两个月到来，今年是有史以来最早的一次，提前至7月29日。这意味着人类现在消耗自然资源的速度，比地球生态系统能再生的速度快1.75倍，等同于需要1.75个地球才能满足人类的消费需求。

声明说：“全球生态系统超支的情形变得愈来愈明显，这体现在森林被砍伐、土壤流失、生物多样性消失及大气中二氧化碳积累。二氧化碳又导致气候变迁及更加频繁出现极端气候现象。”

全球生态足迹网络希望通过计算每一年的世界自然资源耗尽日，告诫世人自然资源被过度消耗。

自1986年开始计算以来，这个里程碑式的日子每年都提早到来。1993年的地球超负荷日落在10月21日，2003年是在9月22日，2017年提前至8月2日。

全球生态足迹网络创始人瓦克尔纳格说：“我们只有一个地球，这是最终决定人类存亡的因素。我们用了1.75个（地球）之后，不可能不产生毁灭性后果。”

联合国气候变化纲要公约第25次缔约方大会（COP25）定于12月在智利圣地亚哥举行，身为大会主席的智利环境部长施密特表示，地球超负荷日不断提前的主要原因在于二氧化碳排放量持续增加。她说：“显然的，采取果断行动变得越来越重要。”

全球生态足迹网络也发布每一个国家耗尽一年自然资源的日子。比如，德国今年5月3日已经进入自然资源的超支状态。全球范围内，四分之一国家和德国一样属于高消耗国家。如果全人类都像德国人一样消耗自然资源，那就需要三个地球才能满足人类的需求。相比之下，全球资源消耗如果平均达到美国的水平，人类则需要多达五个地球；如果平均为中国的水平，则需要2.2个地球。

Mankind will have used up its allowance of natural resources such as water, soil and clean air for all of 2019 by Monday (July 29), a report said.

The so-called Earth Overshoot Day has moved up by two months over the past 20 years, and this year’s date is the earliest ever, the study by the Global Footprint Network said.

The equivalent of 1.75 planets would be required to produce enough to meet humanity’s needs at current consumption rates.

“Earth Overshoot Day falling on July 29 means that humanity is currently using nature 1.75 times faster than our planet’s ecosystems can regenerate. This is akin to using 1.75 earths,” the environmental group, which is headquartered in Oakland, California, said in a statement.

“The costs of this global ecological overspending are becoming increasingly evident in the form of deforestation, soil erosion, biodiversity loss, or the buildup of carbon dioxide in the atmosphere. The latter leads to climate change and more frequent extreme weather events,” it added.

Calculated since 1986, the grim milestone has arrived earlier each year.

In 1993, it fell on Oct 21, in 2003 on Sept 22, and in 2017 on Aug 2.

“We have only got one Earth – this is the ultimately defining context for human existence. We can’t use 1.75 (earths) without destructive consequences,” said Mr Mathis Wackernagel, founder of Global Footprint Network.

Ms Maria Carolina Schmidt Zaldivar, Chile’s environment minister and chair of the Climate COP25 scheduled this December in its capital Santiago, said a major cause of the date falling earlier and earlier was growing amounts of carbon dioxide emissions.

“The importance of decisive action is becoming ever more evident,” she said.

Individuals can get involved by calculating their own ecological footprint at http://www.footprintcalculator.org

Source: Zaobao / The Straits Times

欧洲炎热天气蔓延到北部，北欧几个国家的气温都创新高，部分地区出现“热带夜晚”。世界气象组织警告，热浪接下来将侵袭格陵兰岛，加速冰川融化，可能打破2012年的融冰记录。

挪威气象研究所周六发推文说，挪威北部当天气温高达35.6摄氏度，追平内斯比恩于1970年创下的全国最高温纪录。南部则有20个地点出现“热带夜晚”，这意味着有关地区一整晚的气温都维持在20摄氏度以上。

瑞典多个地方上周也出现“热带夜晚”，北部气温更创下1945年以来的最高温。瑞典气象水文研究所指出，北方城镇马库斯温沙26日的气温达34.8摄氏度，是瑞典今年以来的最高温。该研究所气象专家约珀兰说：“那是自1945年以来最北地区的最高温，也是历来第三高温。”

该研究所还发布缺水预警，预告全国21个省中，有15省下个月可能面临水供不足的问题。

格陵兰岛冰层或加速融化
挪威、瑞典和芬兰当局已发布热浪警报，芬兰警方还提醒驾车人士小心驾驶，避免撞上麋鹿，因为有越来越多麋鹿穿越公路寻觅水源解渴。

此外，世界气象组织周六警告，随着席卷欧洲的破纪录热浪向北移动，位于格陵兰岛的全球第二大冰层可能会加速融化，厚度接近或低于2012年的最薄纪录，而今年的融化也开始得非常早。

丹麦气象研究所专家莫特拉姆说，热浪预计在北极上空移动，带来大量足以融化冰川的能量。“北冰洋和冰盖表面的海冰，估计会在接下来三到五天内融化。”

Nordic countries are experiencing searing temperatures as Europe’s record-breaking heatwave moves north, the Swedish Meteorological and Hydrological Institute (SMHI) said yesterday, with some areas recording “tropical nights”.

In Sweden, the most extreme heat has headed straight for the country’s far north.

On Friday, the small town of Markusvinsa in the far north recorded a temperature of 34.8 deg C, the highest mark reached in all of Sweden so far this year.

“That’s the hottest temperature in the far north since 1945 and the third-highest temperature on record,” SMHI meteorologist Jon Jorpeland told Agence France-Presse.

Last week, several places in Sweden experienced “tropical nights”, meaning that temperatures stayed above 20 deg C throughout the night.

The tropical heat was also being felt in other Nordic countries, and the Norwegian Meteorological Institute said yesterday that it had recorded “tropical nights” in 20 different locations in southern Norway.

Heat warnings have been issued in Sweden, Norway and Finland, and last week, Finnish police even warned motorists to be mindful of moose, which were increasingly crossing roads in search of water to quench their thirst.

Meanwhile, the heatwave that smashed national temperature records in Belgium, Germany and the Netherlands, and which baked Paris in its highest-ever temperature of 42.6 deg C in the middle of last week, has dissipated a little, but many travellers faced disrupted journeys.

The mercury dived in France with outbreaks of drizzle as state weather service Meteo-France lifted red alerts imposed in 20 departments.

In Germany, the country’s highest mountain Zugspitze – standing at 2,962m – was still almost completely covered in snow despite a national temperature record of 42.6 deg C in the north on Thursday.

“The thick snow cover has provided a buffer against (the mountain) absorbing the high temperatures this year,” a spokesman for the research station at Zugspitze said.

Commuters and holidaymakers saw travel plans blighted with disruption to air and rail services in several European countries.

Flights at London’s Heathrow and Gatwick airports were cancelled and delayed – some by more than two hours – with holiday destinations such as Alicante, Rome and Lisbon affected.

Elsewhere in the British capital, there was still travel havoc due to rails buckling under the heat and fires breaking out along commuter lines.

The Met Office advised against non-essential travel.

At Paris’ Gare du Nord, an electrical failure halted domestic and international high-speed trains during Friday lunchtime, including Eurostar and Thalys services, although traffic gradually resumed.

Thalys – which links Paris to Brussels, Amsterdam and Cologne – also saw disruption, with slow trains amid fears that infrastructure could overheat.

At the peak of the heatwave, temperatures on the tracks soared to up to 15 deg C higher than that of the air.

In Switzerland, train engineers painted rails white to reflect the heat of the sun.

In northern and central France, the heatwave has been particularly brutal in the countryside, aggravating fires which have seen thousands of hectares of crops destroyed.

“More than 3,200ha have already gone up in flames since the start of summer,” Interior Minister Christophe Castaner said.

Source: Zaobao / The Straits Times

美国与欧洲近日相继出现极端热浪。科学家警告，全球极端气温已逼近人体耐热极限，当湿球温度超过摄氏35度以致人体排汗散热失调，恐让中东、南亚及中国华北平原不适宜居住。

湿球温度指的是当前环境仅通过蒸发水分所能达到的最低温度，以反映水分蒸发能力。

英国劳柏罗大学气候科学家马修斯指出，当气温超过摄氏35度，人体靠排汗让体温保持在安全值。但当湿球温度达35度时，人体的调节系统就难以运作。

马修斯说：“湿球温度包含水分蒸散的冷却作用，因此通常较天气预报的正常气温（即干球温度）低得多。一旦超过湿球温度门槛，空气里就会饱含水汽，让汗液无法蒸发。”

这意味人体无法降温到足够程度，几小时内就会身亡。

他指出：“这无关喝多少水、躲在多阴凉的地方或休息多久，无法排除体热，身体核心温度就会上升。”

马修斯说，气候变迁让世界部分人口最密集的区域恐在本世纪结束前超出湿球温度门槛，波斯湾地区、南亚以及中国华北平原首当其冲，成为不适宜居住地带，这些地区加起来，人口达数十亿。

冷气是抗暑的最后防线之一，却有大量耗电问题。马修斯表示，到了2050年，冷却系统带来的用电增加，相当于现在美国、欧盟、日本加总起来的用电量，十分惊人。

马修斯认为，眼下的挑战严峻，但人们能拿出的相应办法却有限，因此温室气体排放必须降至巴黎气候协定的限制，这样才有机会扭转致命的高温。

Extreme global temperatures are pushing the human body “close to thermal limits”, according to a climate scientist.

Record-breaking heat has swept through Europe this week with temperatures topping 40C in a number of countries.

However, in places such as South Asia and the Persian Gulf, people are already enduring temperatures reaching up to 54C.

Despite all the body’s thermal efficiencies, these areas could soon be uninhabitable, according to Loughborough University climate scientist Dr Tom Matthews in The Conversation.

When air temperature exceeds 35C, the body relies on sweating to keep core temperatures at a safe level. However, when the “wet bulb” temperature – which reflects the ability of moisture to evaporate – reaches 35C, this system no longer works.

“The wet bulb temperature includes the cooling effect of water evaporating from the thermometer, and so is normally much lower than the normal (“dry bulb”) temperature reported in weather forecasts,” Dr Matthews wrote.

“Once this wet bulb temperature threshold is crossed, the air is so full of water vapour that sweat no longer evaporates,” he said.

This means the human body cannot cool itself enough to survive more than a few hours.

“Without the means to dissipate heat, our core temperature rises, irrespective of how much water we drink, how much shade we seek, or how much rest we take,” he explained.

Some areas – which are among the most densely populated on Earth – could pass this threshold by the end of the century, according to Dr Matthews.

There is already evidence wet bulb temperatures are occurring in Southwest Asia.

With climate change starting to profoundly alter weather systems, rising temperatures could soon make parts of the world uninhabitable.

If electricity can be maintained, living in chronically heat-stressed conditions may be possible but a power outage could be catastrophic.

In a recent paper published in Nature Climate Change, Dr Matthews and his team looked at the probability of a “grey swan” event in the case of extreme heat coinciding with massive blackouts.

Mega blackouts sometimes follow powerful tropical cyclones. Researchers found that dangerously hot temperatures during a period with no electricity could have catastrophic consequences.

“We looked at tropical cyclones, which have already caused the biggest blackouts on Earth, with the months-long power failure in Puerto Rico after Hurricane Maria among the most serious,” Dr Matthews wrote.

“We found that as the climate warms, it becomes ever more likely that these powerful cyclones would be followed by dangerous heat, and that such compound hazards would be expected every year if global warming reaches 4C.

“During the emergency response to a tropical cyclone, keeping people cool would have to be as much a priority as providing clean drinking water.”

Heat-stressed countries are likely to see the largest absolute increases in humid-heat and they are often the least well-prepared to deal with the hazard. This could drive mass migration, which would make heat a worldwide issue – even for countries that are not experiencing scorching temperatures.

Dr Matthews wrote: “The challenges ahead are stark. Adaptation has its limits. We must therefore maintain our global perspective on heat and pursue a global response, slashing greenhouse gas emissions to keep to the Paris warming limits.

“In this way, we have the greatest chance of averting deadly heat – home and abroad.”

Source: Zaobao / Independent

挪威国营广播机构NRK周六（27日）报道，挪威研究人员在挪威斯瓦尔巴的北极群岛发现超过200头已经饿死的驯鹿。

挪威极地研究所三名研究员说，气候的变化以及粮食的缺乏是导致这场悲剧发生的原因，而且这是前所未见的规模。

研究员佩特森说：“看到那么多动物死亡是很恐怖的。这是气候变化对环境造成影响的一个可怕例子。”

据佩特森，12月发生在斯瓦尔巴的豪雨让这些动物在寻找食物时，非常困难。

她相信，虽然这些驯鹿远离文明社会，也不受人类干扰，但它们的死亡却显示，一个较为温和的气候对这些野生动物可造成巨大影响。

Some 200 reindeer have been found dead from starvation in the Arctic archipelago Svalbard, an unusually high number, the Norwegian Polar Institute said Monday (July 28), pointing the finger at climate change.

During their annual census of the wild reindeer population on the group of islands in the Arctic ocean, about 1,200 kilometres from the North Pole, three researchers from the polar institute identified around 200 deer carcasses believed to have starved to death last winter.

Ashild Onvik Pedersen, head of the census, said the “high degree of mortality” was a consequence of climate change, which according to climate scientists, is happening twice as fast in the Arctic as the rest of the world.

“Climate change is making it rain much more. The rain falls on the snow and forms a layer of ice on the tundra, making grazing conditions very poor for animals,” she told AFP.

In winter, Svalbard reindeer find vegetation in the snow using their hooves, but alternating freezing and thawing periods can create layers of impenetrable ice, depriving the reindeers of nourishment.

According to Onvik Pedersen, a comparable death toll has only been recorded once before – after the winter of 2007-2008 – since monitoring of the reindeer population started 40 years ago.

The increased mortality is also due in part to a significant increase in the number of reindeer in the Norwegian archipelago. That is partly thanks to climate change and the warmer summers, meaning more individuals compete in the same grazing areas.

Since the 1980s, the number of reindeer has doubled in Svalbard, and now stands at around 22,000, according to the Norwegian Polar Institute.

Source: Zaobao / The Straits Times

气候变化正使全球很多物种面临生存挑战。一个国际研究团队发现，尽管动物会“自我调节”来适应环境变化，但它们的适应能力总体上还是赶不上气候变化的速度。

德国莱布尼茨动物园与野生动物研究所学者领衔的团队近日在英国《自然·通讯》杂志发表报告说，他们分析了此前发表的1万多项科研成果，结果发现，动物通常会尽力“自我调节”去适应气候变化，比如调整冬眠、繁殖和迁徙时间等，只要适应得足够快，它们还是可以在气候变化时在自己的栖息地生活。

不过研究人员说，按照如今的气候变化速度，即便是那些“自我调节”较快的动物，适应速度也不足以保证生存。

莱布尼茨动物园与野生动物研究所教授沙特说，新研究主要针对鸟类，而且是大山雀、喜鹊等常见而且已知能较好地应对气候变化的物种。其他动物群体的完整数据较少。研究人员预计，一些稀有或濒危物种的生存前景更不容乐观。

动物灭绝可能会对生态系统造成严重破坏。研究人员说，希望他们的分析和数据整理能够促进气候变化与物种适应能力相关研究，为制定更好的环境保护措施贡献力量。

The speed of climate disruption is outstripping many animals’ capacity to adapt, according to a study that warns of a growing threat to even common species such as sparrows, magpies and deer.

Scientists behind the research described the results as alarming because they showed a dangerous lag between a human-driven shift in the seasons and behavioural changes in the natural world.

Previous academic work has shown that species respond to warming temperatures by earlier timing of biological events, for example egg-laying by birds, budding of plants and flying of insects. The new metastudy, published in Nature Research, examines how effective this is in terms of reproduction and survival.

Based on 10,090 abstracts and extracted data from 71 published studies, it found a clear lag in the majority of species studied and none could be considered safe. “The probability that none of the study species is at risk is virtually zero,” the paper notes.

The authors said hundreds of thousands of species were not covered by their study, which was weighted heavily towards birds in the northern hemisphere, but they said the problems of adaptation to climate change were likely to be even greater for other animals already deemed at risk of extinction.

Viktoriia Radchuk of the Leibniz Institute for Zoo and Wildlife Research in Germany, said: “Personally I find the results alarming. Species attempt to adapt to changing environment, but they cannot do it at a sufficient pace to ensure that populations are viable. Climate change has caused irreversible damage to our biodiversity already, as evidenced by the findings of this study. The fact that species struggle to adapt to the current rate of climate change means we have to take action immediately in order to at least halt or decrease the rate.”

A similar message was delivered to the UK parliament on Tuesday as senior conservation figures warned that the nation’s natural infrastructure – which provides fresh water, clean air, carbon sequestration and human wellbeing – was being undermined by the climate crisis, pollution, urban sprawl and budget cuts.

Tony Juniper, the chair of Natural England, which is the government’s main advisory body on conservation, said: “The 21st century will be characterised by our success or not in wrestling with these huge challenges. If we carry on as we are, I fear biodiversity will continue to decline in this country.”

He told the Environmental Audit Committee that the present system of monitoring and protecting nature reserves and sites of special scientific interest had been undermined by a 60% budget cut over the past 10 years, which had left a stressed and demoralised skeleton crew.

It was not too late to reverse this, he said, and outlined plans for a “nature recovery network” that would rebuild woodlands and peatlands, and work with farmers to protect species and restore soil quality, which can draw down the carbon dioxide that causes global heating.

“This is the soundest investment we can make in the future of the country,” Juniper said. “Unlike other assets – like roads and bridges, which depreciate over time – you get more value in the future,” he said, citing economists’ estimates of a 10 to 100-fold return in terms of better food, water and carbon sequestration.

His views were echoed by the head of the Committee on Climate Change, John Gummer, who said it would be impossible for the UK to reach its goal of “net zero” emissions by 2050 without investing in biodiversity protection and renewal.

Source: Zaobao / The Guardian

气候变化带来的威胁迫在眉睫，全球若不采取行动，继续对当前温室气体排放情况置之不理，新加坡到了2100年将面对更炎热天气、海平面上升问题，以及南极冰架倒塌带来的强大破坏力。

联合国政府间气候变化专门委员会将在2022年发布第六次评估报告，我国已经准备检讨规划范围，将报告中的新预测纳入考量，以更好地应对气候变化带来的影响。

国务资政张志贤星期四（7月4日）在蚬壳石油公司举办的”共创未来”论坛上致辞时，详述我国在应对气候变化所做的方方面面准备，包括减排、促进与利益相关者的合作，以及加强我国面对气候变化的抵御能力。

也是国家安全统筹部长的张志贤说，我国资源有限，早在1960年代发展初期，气候变化仍未成为关注点之前，已经致力于打造一个绿色环境，而这份长期规划理念一直不变。

新加坡目前应对气候变化所采取的对策，是参考了新加坡气候研究中心所进行的第二份全国气候变化调查。这份调查是以联合国政府间气候变化专门委员会2014年发布的第五次评估报告预测为依据，从而为新加坡制定对策。

张志贤指出，如果全球各国不采取行动应对当前温室气体排放情况，到了2100年，我国可能面对平均每日气温比1980年至2009年间，上升4.6摄氏度的情况，而到时的全球海平面相比于1986年至2005年间，将上升达一公尺。

到时的这个情景还未将南极冰架倒塌可能带来的冲击纳入考量，而它所带来的影响一直备受全球科学家关注。不少外国媒体去年底也报道了南极冰架倒塌恐引发全球大规模水患等隐忧。

新加坡在这方面早已未雨绸缪，采取行动，包括在2011年已把新填海土地的最低填海水平调高一公尺，而未来的大型基础建设如樟宜机场第五搭客大厦和大士码头也都会建在更高平台。同时，政府也在探讨需要进一步采取哪些填海、建造防波堤（sea wall）等措施，更好地保护我国沿岸地带。

张志贤说：”这些是我国必须做出的重大投资，以保障我们的未来，应对未来几十年海平面上升所带来的影响。”政府会谨慎探讨各项措施的成本效益（cost-benefit）。

此外，新加坡也正在透过让资源来源更多元化和自给自足能力的加强，来强化我国气候变化应对能力。

张志贤说：”在我们加强韧性的同时，也会积极帮助企业将挑战转变为机遇，建造绿色建筑与研发节能科技，推动节能节水及节省土地的城市耕作”

例如，吉宝岸外与海事正在与本地研究机构合作设计可抵抗北极海洋与冰川情况的钻探平台（rig）和其他岸外设施。新科工程最近也获颁合同，为美国海岸卫队设计和建造能穿越极地冰区的新重型破冰船。

另一方面，蚬壳石油公司也在”共创未来”论坛上宣布于本地设立旗下首个全球城市解决方案生活实验室。

蚬壳石油公司将与政府、私人企业和各地社群紧密合作推动创新概念与先进科技，改善能源与资源的使用方式，朝更节能减碳的未来迈进。

张志贤说：”气候变化无疑是我们现在面对的最棘手全球挑战之一。我们现在就须要采取行动减低碳排放量并培养应变能力，以在这个世纪末和更长远的未来保护好我们自己。”

SINGAPORE – As a small, low-lying island state, Singapore will continue to take preventive action against the impact of climate change, Senior Minister Teo Chee Hean said on Thursday (July 4).

Mr Teo drew attention in particular to the Republic’s efforts in going low-carbon and managing rising sea levels in a speech at the sixth Asian edition of the Shell Powering Progress Together forum.

Singapore raised the minimum level for newly reclaimed land by 1m in 2011, a move that preceded the Intergovernmental Panel on Climate Change’s (IPCC) most recent report in 2014 by three years.

The report projected that global sea levels – relative to Singapore’s sea levels from 1986 to 2005 – will rise 1m by 2100 if the world’s current carbon emission trajectory remains unchanged.

But sea waters could potentially rise even further, Mr Teo noted, as the report did not factor in the impact from the possible collapse of melting Antarctica ice shelves.

“We are currently studying what further measures we need to take, such as reclamation, sea walls or pumping stations, to better protect our coastal areas,” said Mr Teo, who is also Coordinating Minister for National Security.

“By planning early, we can phase in the necessary measures so that the cost can be spread out over many years.”

For example, the new mega-port at Tuas Terminal and Changi Airport Terminal 5 will be built 1m and 1.5m above the minimum level required respectively.

The focus of this year’s forum was on sustainable energy use in future cities. At the forum, Shell launched its first global City Solutions Living Lab, to be located here.

A multidisciplinary team will develop technological solutions aimed at helping cities move people and goods with lower emissions and switch to cleaner energy options, while working together with city authorities.

Shell said it chose to base the lab in Singapore due to the city-state’s active push for energy transition and sustainability, its pro-business environment and Shell’s longstanding presence here, going back to 1891.

Singapore’s commitment to a green environment dates back to the 1960s and going low-carbon is an extension of that, said Mr Teo.

Singapore introduced a carbon tax earlier this year and is investing in infrastructure for more electric vehicles to reduce the nation’s carbon footprint.

The tax, currently set at $5 per tonne of greenhouse gas emissions in carbon dioxide equivalent, will be reviewed in 2023 with a view to increasing it to between $10 and $15 by 2030.

Mr Teo added that Singapore is happy to work with businesses like Shell who have adopted significant measures to reduce their carbon footprint.

“Businesses need to transform their business models for a world that demands corporate climate responsibility, and take advantage of the opportunities that this offers,” he said.

Source: Zaobao / The Straits Times

研究指出，南极洲海冰面积在数十年来不停扩大，原因不明后，在仅仅数年内消融的面积是法国的4倍多，如今海冰面积创新低。

在1979至2014年间，科学家观察到一个有趣且令人松口气的现象，那就是南极洲海冰面积正在扩大。

但美国国家航空暨太空总署（NASA）气候学家巴金生（Claire Parkinson）表示，自2014至2017年，南极融化的海冰几乎与北极一样多，面积缩水至近40年来新低。

南极洲海冰面积自1280万平方公里缩减了200万平方公里，但原因仍不清楚。

巴金生表示：“南极洲海冰面积在2014年创下40年新高，到2017年一路缩水至40年新低。”巴金生的研究结果发表于“美国国家科学院学报”（PNAS）。

研究团队分析了这段期间美国国家航空暨太空总署和军方卫星的微波测量，以建立至今关于海冰面积的最精确描绘，但仅为涵盖面积，而非冰层厚度。

南极洲先前面积扩大及当前缩减的原因都仍不清楚。

WASHINGTON (AFP) – After mysteriously expanding for decades, Antarctica’s sea ice cover melted by an area four times greater than France in just a few years and now stands at a record low, according to a study published on Monday (July 1).

Scientists already knew Antarctica was thawing at an increasing rate, like the Arctic, because of accelerating discharge from glaciers, the rivers of ice that push up slowly against the shore.

But between 1979 and 2014, they observed a phenomenon that was both intriguing and reassuring: the sea ice cover was expanding.

From 2014 to 2017, however, “the Antarctic lost almost as much as the Arctic” over almost 40 years, NASA climatologist Claire Parkinson told Agence France-Presse, and the trend has continued ever since.

From a peak area of 12.8 million square kilometres, the sea ice cover receded two million square kilometers for reasons that remain unknown.

“It went from its 40-year high in 2014, all the way down in 2017 to its 40-year low,” said Parkinson, whose findings were published in the Proceedings of the National Academy of Sciences (PNAS).

The team analysed microwave measurements from NASA and military satellites over the period to build up the most precise picture to date of the historic sea ice cover, measuring only area but not thickness.

Neither the reason for the earlier expansion nor the current decline are well understood.

Competing hypotheses exist, pinning the changes on everything from the hole in the ozone layer to shifting winds and ocean currents, but it’s far from clear cut.

“None of the hypotheses are good in my opinion,” said Douglas Martinson, an oceanographer from Columbia University, one of the paper’s peer reviewers.

But he cautioned against trying to apply findings from the Arctic to the Antarctic, saying it would be “like comparing apples to army trucks.”

The Arctic is an ocean surrounded by land, while Antarctica is a continent surrounded by oceans, where icebergs are less constrained.

While parts of western Antarctica are warming, the continent remains the coldest place on Earth, as well as its largest source of freshwater.

Its mountains are covered in ice are capable of raising the level of the oceans by 57 meters, according to a 2013 study.

Chris Rapley, a climate scientist from the University College of London, said the previous gains did not in any way undermine the thesis of global warming.

“It simply demonstrates that in a complex, interconnected system, counter-intuitive outcomes can occur – at least for a while.

“We have a tendency to seek simplistic explanations of cause and effect, when in reality the situation is much more complicated and nuanced.”

Source: Zaobao / The Straits Times