特定的熱浪事件是否與氣候變化有直接關系？

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.

根據一篇新科學論文的說法，最近幾十年間，夏季被極端高溫覆蓋的地表面積從1980年以前的不到1%，增加到近幾年的高達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.

這篇論文稱，變化如此劇烈，以至于科學家們幾乎可以肯定地說，如果沒有人為排放溫室氣體導致的地球變暖，去年德克薩斯州、2010年俄羅斯以及2003年歐洲的熱浪之類的事件就不會發(fā)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.

這種說法超出了科學界對于氣候變化在極端天氣事件中的角色的現有共識。美國國家航空航天局(NASA)知名氣候科學家詹姆斯·E·漢森(James E. Hansen)和另外兩人合著的這篇科學論文，周一發(fā)表在《美國國家科學院院刊》(Proceedings of the National Academy of Sciences)的網站上。

“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.

“主要就是觀察統計數據，就能看出變化太大了，不可能是自然原因造成的，”漢森博士在接受采訪時說道。然而，這些研究發(fā)現立即在他的科學界同仁中引發(fā)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.

一些專家稱，對于世界各地人士都在注意到的極端高溫天氣事件，漢森拿出了一種聰明的新方法來理解其嚴重性。另一些人則提出，他用孱弱的統計學理由來支持自己最大膽的結論，而論文的其他部分幾乎沒有新內容。

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.

就漢森在氣候變化辯論中引發(fā)的強烈反響而言，這種分歧是典型的。作為曼哈頓戈達德太空研究所(Goddard Institute for Space Studies)的負責人，他是NASA主要的氣候科學家之一，也是NASA地球溫度記錄的主要保管人。但他也已成為一名活動人士，參與街頭抗議，要求政府出臺能源和氣候方面的新政策。

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.

后一種角色——他四次在示威中被捕，都是在從政府工作請假期間——使他成為政壇左翼眼中的英雄。但是，這讓他的一些同行不安，他們擔心，他可能在公眾腦海里對自己的科學發(fā)現乃至氣候科學整體播下不必要的懷疑種子。

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.

氣候變化懷疑論者經常指責漢森操縱溫度記錄，使全球變暖看似更加嚴重，盡管沒有證據表明他這樣做過，而且變暖趨勢已被其他研究人員反復證實。

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.

長期以來，科學家們認為氣候變暖——過去一個世紀里陸地溫度上升約2.5華氏度(合1.4攝氏度)，其中大部分發(fā)生在1980年以后——主要是由化石燃料燃燒導致的人為溫室氣體排放造成的。他們還說，這些排放增加了熱浪和其它一些極端天氣事件(如大雨和暴風雪)的發(fā)生幾率。

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，對于某次特定的熱浪或風暴能否確定的與人為導致的氣候變化聯系起來，這個問題一直困擾著研究人員。

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.

在這篇題為《氣候變化的感知》("Perception of Climate Change")的新論文中，漢森博士及合著者將全球變暖主要階段到來之前的1951年至1980年間的全球氣候，與1981年到2011年間的氣候做了對比。

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.

他們分別計算了這兩個時期的6、7、8三個月里，按1951年到1980年間的標準被視為極端高溫的地球陸地面積比例。他們發(fā)現，在前一時期，夏季遭遇高溫的陸地面積僅為0.2%;而2006年到2011年間，極端高溫覆蓋了世界的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.”

漢森在采訪中稱，“這證實了人們的懷疑，即情況正在發(fā)生，而且會變得更糟糕。”

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.

這些發(fā)現使得他的團隊斷言，近年來的大規(guī)模熱浪和干旱是氣候變化的直接后果。作者沒有拿出許多氣候科學家青睞的那種正式的證據，而是陳述了相當于間接證據的推論，即背景變暖是這些具體極端高溫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.

有些專家說，他們認為這些論證有說服力。加拿大不列顛哥倫比亞省維多利亞大學(University of Victoria)的氣候科學家安德魯·J·韋弗(Andrew J. Weaver)在論文發(fā)表之前對其進行了評審。他把近年來的變暖比作在不同地區(qū)爆發(fā)麻疹。他說，就像在麻疹疫情中一樣，懷疑有同一來源是合理的。

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，其他一些科學家形容漢森的論文是一本糊涂賬?？藙诘蠇I·泰巴爾迪(Claudia Tebaldi)是尋求讓公眾了解氣候研究的組織——氣候中心(Climate Central)的科學家。她表示，她覺得在斷言熱浪總體發(fā)生幾率更高是全球變暖的一個后果方面，這篇論文是站得住腳的，但這一研究發(fā)現并不新鮮。她說，這篇論文將一些特定的熱浪歸因于氣候變化，這是缺乏有說服力的證據支持的。