特定的热浪事件是否与气候变化有直接关系？

The percentage of the earth’s land surface covered by extreme heat in the summer has soared in recent decades, from less than 1 percent in the years before 1980 to as much as 13 percent in recent years, according to a new scientific paper.

根据一篇新科学论文的说法，最近几十年间，夏季被极端高温覆盖的地表面积从1980年以前的不到1%，增加到近几年的高达13%。

The change is so drastic, the paper says, that scientists can claim with near certainty that events like the Texas heat wave last year, the Russian heat wave of 2010 and the European heat wave of 2003 would not have happened without the planetary warming caused by the human release of greenhouse gases.

这篇论文称，变化如此剧烈，以至于科学家们几乎可以肯定地说，如果没有人为排放温室气体导致的地球变暖，去年德克萨斯州、2010年俄罗斯以及2003年欧洲的热浪之类的事件就不会发生。

Those claims, which go beyond the established scientific consensus about the role of climate change in causing weather extremes, were advanced by James E. Hansen, a prominent NASA climate scientist, and two co-authors in a scientific paper published online on Monday in the Proceedings of the National Academy of Sciences.

这种说法超出了科学界对于气候变化在极端天气事件中的角色的现有共识。美国国家航空航天局(NASA)知名气候科学家詹姆斯·E·汉森(James E. Hansen)和另外两人合著的这篇科学论文，周一发表在《美国国家科学院院刊》(Proceedings of the National Academy of Sciences)的网站上。

“The main thing is just to look at the statistics and see that the change is too large to be natural,” Dr. Hansen said in an interview. The findings provoked an immediate split among his scientific colleagues, however.

“主要就是观察统计数据，就能看出变化太大了，不可能是自然原因造成的，”汉森博士在接受采访时说道。然而，这些研究发现立即在他的科学界同仁中引发了分裂。

Some experts said he had come up with a smart new way of understanding the magnitude of the heat extremes that people around the world are noticing. Others suggested that he had presented a weak statistical case for his boldest claims and that the rest of the paper contained little new.

一些专家称，对于世界各地人士都在注意到的极端高温天气事件，汉森拿出了一种聪明的新方法来理解其严重性。另一些人则提出，他用孱弱的统计学理由来支持自己最大胆的结论，而论文的其他部分几乎没有新内容。

The divide is characteristic of the strong reactions that Dr. Hansen has elicited in the debate over climate change. As the head of the Goddard Institute for Space Studies in Manhattan, he is one of NASA’s principal climate scientists and the primary custodian of its records of the earth’s temperature. Yet he has also become an activist who marches in protests to demand new government policies on energy and climate.

就汉森在气候变化辩论中引发的强烈反响而言，这种分歧是典型的。作为曼哈顿戈达德太空研究所(Goddard Institute for Space Studies)的负责人，他是NASA主要的气候科学家之一，也是NASA地球温度记录的主要保管人。但他也已成为一名活动人士，参与街头抗议，要求政府出台能源和气候方面的新政策。

The latter role — he has been arrested four times at demonstrations, always while on leave from his government job — has made him a hero to the political left But it has discomfited some of his fellow researchers, who fear that he may be sowing unnecessary doubts about his scientific findings and climate science in general.

后一种角色——他四次在示威中被捕，都是在从政府工作请假期间——使他成为政坛左翼眼中的英雄。但是，这让他的一些同行不安，他们担心，他可能在公众脑海里对自己的科学发现乃至气候科学整体播下不必要的怀疑种子。

Climate-change skeptics routinely accuse Dr. Hansen of manipulating the temperature record to make global warming seem more serious, although there is no proof that he has done so and the warming trend has repeatedly been confirmed by other researchers.

气候变化怀疑论者经常指责汉森操纵温度记录，使全球变暖看似更加严重，尽管没有证据表明他这样做过，而且变暖趋势已被其他研究人员反复证实。

Scientists have long believed that the warming — roughly 2.5 degrees Fahrenheit over land in the past century, with most of that occurring since 1980 — was caused largely by the human release of greenhouse gases from burning fossil fuels. Such emissions have increased the likelihood of heat waves and some other types of weather extremes, like heavy rains and snowstorms, they say.

长期以来，科学家们认为气候变暖——过去一个世纪里陆地温度上升约2.5华氏度(合1.4摄氏度)，其中大部分发生在1980年以后——主要是由化石燃料燃烧导致的人为温室气体排放造成的。他们还说，这些排放增加了热浪和其它一些极端天气事件(如大雨和暴风雪)的发生几率。

But researchers have struggled with the question of whether any particular heat wave or storm can be definitively linked to human-induced climate change.

但是，对于某次特定的热浪或风暴能否确定的与人为导致的气候变化联系起来，这个问题一直困扰着研究人员。

In the new paper, titled “Perception of Climate Change,” Dr. Hansen and his co-authors compared the global climate of 1951 to 1980, before the bulk of global warming had occurred, with the climate of the years 1981 to 2011.

在这篇题为《气候变化的感知》("Perception of Climate Change")的新论文中，汉森博士及合著者将全球变暖主要阶段到来之前的1951年至1980年间的全球气候，与1981年到2011年间的气候做了对比。

They computed how much of the earth’s land surface in each period was subjected in June, July and August to heat that would have been considered particularly extreme in the period from 1951 to 1980. In that era, they found, only 0.2 percent of the land surface was subjected to extreme summer heat. But from 2006 to 2011, extreme heat covered from 4 to 13 percent of the world, they found.

他们分别计算了这两个时期的6、7、8三个月里，按1951年到1980年间的标准被视为极端高温的地球陆地面积比例。他们发现，在前一时期，夏季遭遇高温的陆地面积仅为0.2%;而2006年到2011年间，极端高温覆盖了世界的4%到13%。

“It confirms people’s suspicions that things are happening” to the climate, Dr. Hansen said in the interview. “It’s just going to get worse.”

汉森在采访中称，“这证实了人们的怀疑，即情况正在发生，而且会变得更糟糕。”

The findings led his team to assert that the big heat waves and droughts of recent years were a direct consequence of climate change. The authors did not offer formal proof of the sort favored by many climate scientists, instead presenting what amounted to a circumstantial case that the background warming was the only plausible cause of those individual heat extremes.

这些发现使得他的团队断言，近年来的大规模热浪和干旱是气候变化的直接后果。作者没有拿出许多气候科学家青睐的那种正式的证据，而是陈述了相当于间接证据的推论，即背景变暖是这些具体极端高温事件唯一貌似合理的成因。

Some experts said they found the arguments persuasive. Andrew J. Weaver, a climate scientist at the University of Victoria in British Columbia who reviewed the paper before publication, compared the warming of recent years to a measles outbreak popping up in different places. As with a measles epidemic, he said, it makes sense to suspect a common cause.

有些专家说，他们认为这些论证有说服力。加拿大不列颠哥伦比亚省维多利亚大学(University of Victoria)的气候科学家安德鲁·J·韦弗(Andrew J. Weaver)在论文发表之前对其进行了评审。他把近年来的变暖比作在不同地区爆发麻疹。他说，就像在麻疹疫情中一样，怀疑有同一来源是合理的。

But some other scientists described the Hansen paper as a muddle. Claudia Tebaldi, a scientist with an organization called Climate Central that seeks to make climate research accessible to the public, said she felt that the paper was on solid ground in asserting a greater overall likelihood of heat waves as a consequence of global warming, but that the finding was not new. The paper’s attribution of specific heat waves to climate change was not backed by persuasive evidence, she said.

但是，其他一些科学家形容汉森的论文是一本糊涂账。克劳迪娅·泰巴尔迪(Claudia Tebaldi)是寻求让公众了解气候研究的组织——气候中心(Climate Central)的科学家。她表示，她觉得在断言热浪总体发生几率更高是全球变暖的一个后果方面，这篇论文是站得住脚的，但这一研究发现并不新鲜。她说，这篇论文将一些特定的热浪归因于气候变化，这是缺乏有说服力的证据支持的。