英国新闻听力 飓风与全球变暖有关?（在线收听）

The hurricane season this year in the Atlantic Ocean has been the most destructive on record. There was Hurricane Katrina which devastated New Orleans in August, then Hurricane Stan sweeping through Central America and Hurricane Wilma which hit Florida last week and was at one point the strongest storm ever to have been recorded in the Atlantic. There have been so many storms this year as well that the latest had to be given the designation Beta. This is the first time meteorologists have run out of names and had to resort the Greek alphabet. Some scientists believe that global warming is the cause. Pramod Morjaria examines the evidence.

REP: It's really scary -- how it's swirling round these buildings. A couple of windows seem to have blown out; the street is covered in debris. The power cables are all down. That's about all I can see from where I'm standing. I go a little to this corner....the winds on the other side -- if I was to stand there, I would immediately be swept away. They're over 100 miles an hour. There were two cars; one of them at the front was completely lifted off its back wheels. It was moved further along the road.

RITA EYEWITNESS: This is unbelievable, unbelievable. I knew it was going to be bad, but I didn't think it would be this bad.

BBC REPORTER ON WILMA: I'm just walking through the main lobby area of the hotel. It's just a scene of complete devastation. There's a piano standing beside a window, which had been reinforced with steel girders, but which was just blown over by the force of the hurricane.

BBC REPORTER: Moving out towards the sea, there's literally no beach left any more. The sea has completely swallowed it up.

REP: BBC reporters and eyewitnesses describe the power and destruction caused by Hurricanes Katrina, Rita and Wilma: the first time three maximum strength hurricanes have been recorded in a season. They may have weakened over land, but their power was still immense, swamping coastal areas of the region within weeks of each other. People may have been shocked, but scientists say conditions in the Gulf of Mexico this summer couldn't have been more ripe for such violent storms to form.

BRENDA EKWURZEL: What is really critical is: we need warm sea surface temperatures. We need 27 degrees Celsius, to be favourable for hurricanes.

REP: Brenda Ekwurzel is a Climate Scientist from the Union of Concerned Scientists in Washington. She says that in the cases of Katrina and Rita, the sea surface temperature was almost 33 degrees celsius, a full six degrees higher than the minimum for hurricanes to form and strengthen.

BRENDA EKWURZEL: Essentially, it's the way the earth is getting rid of excess heat in the summer time. And the hurricanes are something that happen when we evaporate the water vapour from the sea surface, lift it up high and convert it into rain when it hits the cooler upper atmosphere. That heat is released, that was from the sea surface and that fuels these powerful storms. It's kind of like throwing fuel on a fire.

REP: The 2005 hurricane season can only be described as nothing short of unprecedented.

It's the first time in 50 years, when hurricane naming began, that all 21 names have been used up in a season -- one which doesn't even finish until the end of this month. Wilma was the 21st storm, so a new list, based on the Greek alphabet, had to be started. Ian Cameron, from the UK's Meteorological Office, explains the system.

IAN CAMERON: We have lists of names, running from the letter A through to the letter W. And there's a naming convention which is used and recycled about every six years.

REP: I've got the list here in front of me. And right up until 2010, the names are given. So for 2006, for next year, we've got Alberto, Beryl, Chris. So it seems like quite an efficient process.

CAMERON: What’s been happening is actually it was only women's names up to a certain point, before men joined the list. And if you look through the list, you can see there are alternate male and female names. And what the World Meteorological

Organisation does is: if there's a hurricane that has formed that has caused considerable damage, or for other reasons, they will probably drop it from the list. So Katrina and Rita and Wilma -- the three popular famous ones from this year -- will actually be dropped from the list when it's recycled.

REP: You mentioned Wilma there and that's the last one on the list of 2005, in terms of the names. So they're having to start again, and use the Greek alphabet.

CAMERON: Yes, this is quite amazing. It's the first time this has happened.

REP: So does that suggest, then, since records began, that 2005 has been the most active year in terms of storm formation?

CAMERON: It certainly appears to be one of the more active years for turning into the hurricanes and tropical depressions that are named.

REP: Thankfully the majority of hurricanes that occur, blow themselves out at sea. Although this year has seen the highest number, it's not their frequency which is being highlighted, but their intensity. A study published in the science journal Nature in September of hurricane activity points to a link between the strength of storms and global warming. Climate Scientist, Brenda Ekwurzel, supports its findings.

BRENDA EKWURZEL: When we look worldwide, the percentage of Category 4 and 5 hurricanes or typhoons or cyclones, depending on the ocean basin they're in, has almost doubled in the past 30 years -- where we see a precipitous rise in ocean temperatures, which is directly related to the heat trapping gases that we've accumulated in the atmosphere at unprecedented levels. It shows us that Nature is delivering more powerful punches.

REP: And she says the evidence is compelling.

BRENDA EKWURZEL: We've had very high-quality ocean temperature measurements. And we're not just talking about the sea surface, in the upper several hundred metres in the ocean surface over the past 45 years. And when you look at the models, we cannot calculate the warming of the ocean if we do not include the heat-trapping gases from the dirty emissions -- the cars and trucks -- and the methane and other heat-trapping gases in the atmosphere. When we add those into the models, we get the exact temperature rise that we see worldwide in the oceans.

REP: There isn't consensus, is there, amongst the scientific community about just how much of a driver global warming in all of this? There are scientists who just basically say: well, it's cyclical.

BRENDA EKWURZEL: What you hear being discussed in detail are the debates of where we don't understand how strong it is going to be, what are going to be the local variations of the impacts on the ground. Because we do have this warming superimposed upon the natural cycles. And the natural cycles -- it's sort of like you see a lot of wiggles, but those wiggles are now tilted in an upward direction.

REP: But this view isn't universally accepted.

BARRY KEIM: I'm more of the ilk to say that the last ten years are just a part of a cycle that's related to changing sea-surface temperatures, and I'm not so quick to point the finger at global warming.

REP: Dr Barry Keim is from the Hurricane Research Centre at Louisiana State University.

BARRY KEIM: The period of record that they are examining was the past 30 years. And basically what's transpired from about 1965 to 1995 was a period of calm in the hurricane climatology -- in particular, in the North Atlantic basin. And then, in the last ten years, conditions have changed, and we've had noticeable increases in both the frequencies and intensities of storms since about 1995. So, if you only take the record back 30 years, of course you're going to find a long-term trend towards increasing values. However, if you extend the record back to about the 1920s or earlier, you'll find that the last ten years actually look very much like the '30s, '40s and 1950s in the North Atlantic.

REP: And the key to unlocking what will happen in the future could lie in opening up the past to closer scrutiny. And that's exactly what Cary Mock, Associate Professor at the Department of Geography at the University of South Carolina, is about to do when he visits the UK later this year. He'll be looking at naval ship records, weather charts, and old newspaper reports, for evidence of tropical cyclones. He's currently analysing evidence from 1837 when four hurricanes hit Florida. He also says that in 1886 seven hurricanes made it on to shore in the US, a figure that has not been repeated since. I asked him how this kind of research can help.

CARY MOCK: Cycles, for example, these natural cycles -- we would generally expect active versus inactive hurricane activity over 40 to 60 year time-frames. We have a much longer perspective, seeing everything else fluctuates in a 40 or 50 year cycle. Cycle we know that can't be global warming, for example.

REP: The North Atlantic is perhaps the most widely researched ocean for hurricane activity, but other parts of the world are subject to the brute force of tropical storms. In east Asia they're known as typhoons and in the Indian subcontinent as cyclones.

REP: The most recent, just a few days ago, killed over a hundred people in three Indian states and dumped 20cm of rain in one day on the city of Chenai, flooding many parts of it. Thousands of people were evacuated from low-lying parts of India's south-east coast, with fishing boats returning to dry land as the cyclone whipped up fierce winds in the Bay of Bengal.

REP: But experts here are also sceptical about making a connection between global warming and the strength of storms in the Indian Ocean. S. K. Subramanian is the Deputy Director General of India's Meteorological Department, with specific responsibility for cyclone warning. He cites a survey by the Intergovernmental Panel on Climate Change which found no link.

S. K. SUBRAMANIAN: That authentication is not seen over the north Indian Ocean. In fact, in the IPCC's (third assessment report, which was published recently) -- also they have shown that there are no discernable global trends, in number, in intensity and the location of tropical cyclones, due to the impact of climate change. And the changes, if any year to year, decade to decade, etc., what we see is the inherent variability of the tropical cyclone formation, the intensity part of it, over this part of the ocean basin.

REP: So are you ruling out any link between global warming and the intensity of tropical cyclones completely?

SUBRAMANIAN: Yes. As far as the north Indian Ocean is concerned, we don't have any foreseeable trend, due to global warming or due to the impact of climate change.

REP: 2004 was a record year for typhoon activity in East Asia, with 20 storms forming, six of which hit Japan. This year, the number of storms was down to ten, but half of these were category 4 or 5 in strength. One of them, Typhoon Nabi, was by some measurements, as strong as Hurricane Katrina. But Nabutaka Mannouji, the Head of the Typhoon Centre at Japan's Meteorological Agency, says this year has been a normal one in the North West Pacific Ocean. And predictions about the effects of global warming can't be made with accuracy.

NABUTAKA MANNOUJI: Look, the warming effect is only recent, ten or 20 years. So it's too early to say. And also, if you look at the data from 1950 to 2000, the data in the early part is different from the later part.

REP: But you wouldn't rule out global warming as a factor, would you?

MANNOUJI: We cannot detect the effect of global warming so far.

REP: Last year a team of international climate scientists fed their data on typhoons into one of the world's most powerful supercomputers in Japan, to produce a simulation of the effects of global warming. They were looking at how rising sea temperatures could affect storm activity in the decades ahead. The results suggest Japan can expect to be battered by typhoons of even more ferocity than now. But it's a suggestion, and the scientists themselves admit, not a confident prediction. Global warming may be a factor in increasing hurricane strength, but most experts agree that much more research needs to been done to establish any possible link, as conclusive proof.

今年，大西洋的飓风带来了前所未有的破坏。八月份，飓风卡特里娜破坏了新奥尔良；飓风斯坦席卷了中美洲；上周，飓风威尔玛袭击了佛罗里达。根据大西洋风暴记录显示，这是最强烈的一次。而最近一次的风暴是贝塔年发生了很多规模类似于此的风暴。气象学家第一次用遍了所有用来表示此类气象的名称，而不得不借用希腊字母表来表示。一些科学家认为风暴是由于全球气候变暖引起的。记者普拉蒙德? 莫贾里带来详细报道。

记者：建筑物被强烈的风暴包围着，这情景非常可怕。大风摧毁了窗户玻璃，街道上布满了碎片，电缆也受到破坏。这就是从我站的地方所能看到的一切景象。我走近拐角，风在另一边吹着。如果我站在原地，我会马上被吹跑。风速达到每小时100英里。我看到两辆车，其中在前边的一辆完全被掀翻，被风吹到远处。

飓风目击者：不可思议，真是不可思议。情况比我想象的要糟得多。

威尔玛飓风现场记者：我正穿过宾馆的大厅。这里完全受到了破坏。钢架固定住了放在窗边的钢琴，结果钢架也遭到了飓风的破坏。

BBC记者：我向海边靠近，发现海滩根本就不存在了。大海完全吞没了它。

记者：BBC记者和目击者描述了飓风卡特里娜、丽塔、威尔玛的力量和它的破坏力：第一次，规模最大的三个飓风同时出现在一个季节。上岸后，它们的力量有所减弱，但是仍然强大。几周内，席卷了海边地区。人们可能会很震惊，但是科学家说，今年夏天墨西哥湾的条件不足以形成如此巨大的风暴。

布伦达? 伊库泽：更严重的是，海水表面温度有所升高。27摄氏度就能够形成飓风。

记者：华盛顿气象学家联合会的科学家布伦达? 伊库泽表示，卡特里娜和丽塔到来时，海水表面温度将近33摄氏度，整整比飓风形成所需要的温度高出6摄氏度。

布伦达? 伊库泽：实质上，在夏季，地球需要通过飓风来摆脱多余的热量。水蒸汽从海水表面蒸发，遇到冷空气时，会形成雨，这时可能会产生飓风。海表面释放出的热量对风暴起到推波助澜的作用。这就好比向火中投掷燃料一样。

记者：2005年的飓风只能用史无前例来描述。为飓风命名的50年来，今年是第一次，一个季节中将21个名字全部用到了。飓风直到这个月末才结束。威尔玛是第21个飓风。借用希腊字母表来命名的飓风已经开始了。英国气象局的伊恩?卡梅伦对这个方法做出了解释。

伊恩?卡梅伦：我们使用的名字从字母A到字母W。我们使用命名有一个惯例，并且每六年为一个循环。

记者：我手中拿到了名单。这里包括直到2010年飓风所会使用到的名字。下一年，也就是2006年，我们使用Alberto，Beryl，Chris。这看起来是一个比较有效的方法。

卡梅伦：事实上，在男性名字加入到名单中之前，仅使用女性名字。如果你纵览名单，就会发现这里有可以交替的男性和女性名称。世界气象组织是这样考虑的：如果飓风引起较大的破坏，或是由于其它的某些原因，它们可能会从名单中清除。所以今年三个最出名的飓风名称，卡特里娜、丽塔、威尔玛在以后的循环名单中将不会被使用。

记者：刚刚提到的威尔玛飓风是2005年飓风名单中最后的一个。所以，他们又将重新开始，而且使用希腊字母表来命名飓风。

卡梅伦：是的，这十分惊奇，因为是第一次发生这样的情况。

记者：根据飓风记录信息显示， 2005年是飓风最为活跃的一年。

卡梅伦：今年是已记载的飓风和低气压比较活跃的年份之一。

记者：很庆幸，已发生的多数飓风只是在海上活动。虽然今年的数量最多，但是我们要注意的不是飓风发生的频率，而是它的强度。科学杂志《自然》9月份发表了一篇有关飓风活动内容的研究文章。文中指出了暴风强度与全球变暖之间的关系。气候学家布伦达? 伊库泽支持这个发现。

布伦达? 伊库泽：我们所看到的是：放眼全球，依靠海洋盆地而形成的4、5级飓风、台风和气旋的百分比在过去的30年里翻了一番。海洋温度陡然上升，这与吸收热量的气体有关。这些气体以前所未有的水平在大气中累积。《自然》杂志提供了更详尽的说明。

记者：她表示证据能够引人关注。

布伦达? 伊库泽：我们进行了高质量的海洋温度测量。我们不是在讨论海水表面温度。我们可以发现：过去的45年中，海水上层几百英里的温度变暖现象巨大。我们只看模型，不能计算来自于尘埃性放射物（如汽车、卡车）以及甲烷所释放的吸收热量的气体，或是大气中所释放的其它吸收热量的气体，我们也很难估算海洋的变暖情况。当我们将这些加入到模型中时，我们就可以获得全球海洋温度的准确升高度数。

记者：到底司机对发生这种情况负有多大的责任，科学团体并没有达成一致的意见。有些科学家只是说：是的，它是循环性的。

布伦达? 伊库泽：讨论的细节集中在以下方面：海洋变暖温度为何如此之高，局部变化对地面有何影响。我们将变暖强加于自然循环之上。如果把自然循环看成一个波形，那么这些波形正向上方发展。

记者：但是这个观点并没有被普遍接受。

巴里?凯：我更倾向于认为，过去10年发生的情况仅仅是改变海水表面温度循环的一部分。我并不急于认定这是由全球变暖造成的。

记者：巴里?凯博士来自于路易斯安那州立大学飓风研究中心。

巴里?凯：我们研究的记录是过去30年的。飓风气候学表明，1965年至1995年是飓风比较平静的时期。这种情况特别出现在北大西洋盆地。过去的10年里，条件发生了变化。1995年后，我们注意到风暴的频率和强度都有了增强。所以，如果只看过去30年里的纪录，当然你会发现一个长期增长的趋向。然而，如果你回顾20世纪20年代或更早一些时候的记录，就会发现过去10年的情况事实上同北大西洋30、40、50年代的情况十分相像。

记者：解读未来会发生什么的关键在于详细研究过去的记录。南卡罗来纳大学地理系副教授卡里?莫克准备今年晚些时候访问英国时，做这样的工作。他会翻看海上货运记录、天气图表、旧的报纸报道，从中寻找发生热带气旋的原因。当四个飓风袭击佛罗里达时，他正在分析1837年的证据。他还说，1886年7个飓风登陆美国海滨，之后就没有出现过这样的情况。我问他这种研究会起到怎样的作用。

卡里?莫克：这些自然循环，比如，我们可以对比过去40到60年里飓风的活跃与不活跃情况。我们可以做较长时间段的观察，看40或50年为一个循环内的各种变化情况。我们可以确定这是不是全球变暖。

记者：北大西洋可能是最广泛进行飓风活动研究的地区，但是世界上其它的一些地区也受到了强烈风暴的影响。东亚的台风和印度次大陆的气旋就是例子。

记者：最近，就是几天前，飓风使印度100多人丧生，一天20厘米的降水冲毁了黔奈（Chenai）市大部分地区。数千人从印度东南部海岸的低洼地带撤离。孟加拉湾的气旋带着猛烈的风将渔船吹到干燥的土地上。

记者：全球变暖和印度洋强烈风暴之间存在联系，但是专家对此观点表示怀疑。印度气象局的副局长S. K. 萨布拉曼伊恩对气旋警报表示了特殊的关注。他引用了政府间气候变化委员会的一个调查，说明它们之间不存在联系。

萨布拉曼伊恩：北印度洋的情况也未得到证实。事实上，政府间气候变化委员会最近发布的第三份评估报告表明，从数量、强度、热带气旋的位置方面来看，并没有发现气候变化影响带来了可辨别的全球变暖趋势。年复一年，如果发生变化，我们看到的也是部分海洋盆地范围内热带气旋群系内在的变化和强度的变化。

记者：那么就可以完全排除全球变暖与热带气旋强度之间的关系了吗？

萨布拉曼伊恩：是的。就目前北印度洋情况考虑，我们没有看到由于全球变暖或是气候变化影响而产生的任何可预见的趋势。

记者：2004年，飓风在东亚的活动达到了一个纪录，共形成了20次风暴，其中有6次袭击了日本。今年，风暴的数量不到10个，但是有一半在强度上达到了4或5级水平。据测量，其中的一次台风彩蝶（Nabi）强度赶上了卡特里娜台风。但是日本气象局台风中心主任纳布塔卡?曼诺基表示，今年台风在西北太平洋地区活动正常。关于全球变暖的预测还不能准确证实。

纳布塔卡?曼诺：变暖现象仅仅出现在最近10年或20年，所以不能轻易下结论。如果查看1950年至2000年的记录，会发现早期记录和后期的不同。

记者：但是你不会排除全球变暖这个因素吧？

曼诺：我们至今还没有发现全球变暖的影响。

记者：去年，一队国际气候科学家将台风数据输入到日本一台全世界最强大的超级计算机里，分析全球变暖的影响。他们正在研究长高了的海水温度如何影响几十年前的风暴活动。结果表明，日本可能受到更加猛烈的台风袭击。 但是这只是一个可能，科学家们自己承认这不是一个有信心的预测。全球变暖可能是增加飓风强度的一个因素，但是多数专家同意如果想要建立两者之间的联系，需要进行更多的研究，作为有力的证据。