Wed, Nov 07, 2018 - Page 14 News List

Oceans heating faster than previously thought
海洋暖化速度超乎預期

In this photo from July 21 last year, researchers look out from the Finnish icebreaker MSV Nordica as the sun sets over sea ice in the Victoria Strait along the Northwest Passage in the Canadian Arctic Archipelago. Studies show the Arctic is heating up twice as fast as the rest of the planet. Scientists are concerned because impacts of a warming Arctic may be felt elsewhere.
加拿大北極群島西北航道旁的維多利亞海峽,研究人員在芬蘭破冰船「諾迪卡號」上瞭望海冰上的落日。攝於二○一七年七月二十一日。研究顯示,北極氣溫上升的速度是地球其他地區的兩倍。科學家擔心,其他地方可能會因北極暖化受到影響。

Photo: AP
照片:美聯社

The world’s oceans have absorbed 60 percent more heat than previously thought over the last quarter of a century, scientists said last Thursday, leaving Earth more sensitive still to the effects of climate change.

Oceans cover more than two thirds of the planet’s surface and play a vital role in sustaining life on Earth.

According to their most recent assessment this month, scientists from the Intergovernmental Panel on Climate Change (IPCC) say the world’s oceans have absorbed 90 percent of the temperature rise caused by man-made carbon emissions.

But new research published in the journal Nature used a novel method of measuring ocean temperature. It found that for each of the last 25 years, oceans had absorbed heat energy equivalent to 150 times the amount of electricity mankind produces annually. That is 60 percent higher than previous studies showed.

Whereas those studies relied on tallying the excess heat produced by known man-made greenhouse gas emissions, a team of US-based scientists focused on two gases found naturally in the atmosphere: Oxygen and carbon dioxide. Both gases are soluble in water, but the rate at which water absorbs them decreases as it warms.

By measuring atmospheric oxygen and CO2 for each year, scientists were able to more accurately estimate how much heat oceans had absorbed on a global scale.

“Imagine if the ocean was only 10m deep,” said Laure Resplandy, assistant professor of geosciences at Princeton and lead study author. “Our data show that it would have warmed by 6.5 degrees Celsius every decade since 1991.”

That compares with a IPCC estimate of a 4.0 C rise each decade. Resplandy said the data showed mankind must once again revise down its carbon footprint, with emissions needing to fall 25 percent compared to previous estimates.

TODAY’S WORDS
今日單字

1. absorb v.

吸收 (xi1 shou1)

2. climate change phr.

氣候變遷 (qi4 hou4 bian4 qian1)

3. carbon dioxide phr.

二氧化碳 (er4 yang3 hua4 tan4)

4. soluble in water phr.

可溶於水的 (ke3 rong2 yu2 shui3 de5)

5. atmospheric adj.

大氣的 (da4 qi4 de5)

6. geoscience n.

地球科學 (di4 qiu2 ke1 xue2)

7. carbon footprint phr.

碳足跡 (tan4 zu2 ji1)


“The result significantly increases the confidence we can place in estimates of ocean warming and therefore helps reduce uncertainty,” said Ralph Keeling, a geophysicist at the University of California-San Diego and co-author of the study.

The IPCC warns that drastic measures need taking in order to limit global warming to 1.5 Celsius by the end of the century but the world produced a record amount of carbon emissions in 2017.

(AFP)

科學家上週四表示,在過去四分之一世紀中,全世界海洋所吸收的熱,比原先所認為的還要高出百分之六十,讓地球更容易受到氣候變遷的影響。

海洋覆蓋了三分之二以上的地球表面,對供養地球上的生命至關重要。

聯合國「政府間氣候變遷問題小組」(IPCC)的科學家表示,根據他們本月發表的最新評估,人為碳排放所造成的溫度升高,有百分之九十已被海洋吸收。

但是在《自然》期刊上發表的一項新研究,使用了一種新方法來測量海洋溫度。研究發現,在過去二十五年中,海洋所吸收的熱能相當於人類每年發電量的一百五十倍。這比之前的研究結果高出百分之六十。

這些研究採用的方法,是計算已知的人為溫室氣體排放所產生的多餘熱量,而美國一個科學家團隊則是聚焦於大氣中天然存在的兩種氣體:氧氣和二氧化碳。這兩種氣體都可溶於水,但隨著溫度的升高,水吸收這兩種氣體的速度會降低。

透過每年測量大氣中的氧氣和二氧化碳,科學家能夠更準確地估算出全球海洋吸收了多少熱。

「想像一下,如果海洋只有三十英尺(十公尺)深」,普林斯頓大學地球科學助理教授、該研究主要作者洛‧芮斯普蘭迪說,「我們的數據顯示,自一九九一年起,海洋每十年就會升溫攝氏六點五度」。

然而IPCC的估計卻是每十年升溫攝氏四度。芮斯普蘭迪表示,數據顯示人類必須再下調其碳足跡,要比之前所估計的再減少百分之二十五的碳排放量。

「這研究結果讓我們更有信心能夠估算海洋的暖化,因此有助於減少不確定性」,加州大學聖地牙哥分校地球物理學家、該研究共同作者洛夫‧基林說。

IPCC警告說,必須要採取嚴厲措施,才能夠在本世紀結束前,把全球暖化限制在攝氏一點五度以內;然而,二○一七年全世界卻產生了破紀錄的碳排放量。

(台北時報林俐凱編譯)

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