最新研究指出(2014-02-21)，火山噴發可反射陽光的粒子至大氣層中，稍微有助在過去15年間抵消人類碳排放的影響。

1998年來所謂的暖化暫緩時期，向來是氣候變遷懷疑派與主流科學家爭論不休之處。

溫度的確一直上升，自有紀錄以來14個溫度最高的年份，有13個年份是在21世紀，不過增幅不及人造溫室氣體排放增加的程度。

懷疑論者以預期和實際溫度的差異為理由，表示人造全球暖化現象是心理恐慌與科學錯誤下的產物。

不過，刊登在「自然地球科學」期刊（NatureGeoscience）中的研究指出，火山爆發有助解釋暖化似乎減緩的現象。

研究團隊說，火山爆發出的硫磺粒子反射陽光，有助於降低低層大氣層溫度。

根據研究團隊數據，1998年至2012年間的預測與實際測量溫度當中多達15%的差異，可歸因於這些懸浮微粒。

研究主筆、美國勞倫斯利佛摩國家實驗室（Lawrence Livermore National Laboratory）的桑德（Ben Santer）告訴法新社：「1998年的『暖化暫緩』現象有不同成因，像是21世紀初期火山爆發，造成降溫。」

不過火山在「暖化暫緩」爭論中並未居於要角，主要是因自爭論1998年開始以來，並沒有火山大規模爆發，而小規模的火山爆發影響較難測量。

研究也指出：「目前還需要更多觀察懸浮微粒在火山噴發時的特性。」

（譯者：中央社蕭倩芸）

延伸閱讀: 

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2098.html

http://www.reuters.com/article/2014/02/23/us-climate-volcanoes-idUSBREA1M0W920140223

(Reuters) - Small volcanic eruptions help explain a hiatus in global warming this century by dimming sunlight and offsetting a rise in emissions of heat-trapping gases to record highs, a study showed on Sunday.

Eruptions of at least 17 volcanoes since 2000, including Nabro in Eritrea, Kasatochi in Alaska and Merapi in Indonesia, ejected sulfur whose sun-blocking effect had been largely ignored until now by climate scientists, it said.

The pace of rising world surface temperatures has slowed since an exceptionally warm 1998, heartening those who doubt that an urgent, trillion-dollar shift to renewable energies from fossil fuels is needed to counter global warming.

Explaining the hiatus could bolster support for a U.N. climate deal, due to be agreed by almost 200 governments at a summit in Paris in late 2015 to avert ever more floods, droughts, heatwaves and rising sea levels.

"This is a complex detective story," said Benjamin Santer of the Lawrence Livermore National Laboratory in California, lead author of the study in the journal Nature Geoscience that gives the most detailed account yet of the cooling impact of volcanoes.

"Volcanoes are part of the answer but there's no factor that is solely responsible for the hiatus," he told Reuters of the study by a team of U.S. and Canadian experts.

Volcanoes are a wild card for climate change - they cannot be predicted and big eruptions, most recently of Mount Pinatubo in the Philippines in 1991, can dim global sunshine for years.

Santer said other factors such as a decline in the sun's output, linked to a natural cycle of sunspots, or rising Chinese emissions of sun-blocking pollution could also help explain the recent slowdown in warming.

The study suggested that volcanoes accounted for up to 15 percent of the difference between predicted and observed warming this century. All things being equal, temperatures should rise because greenhouse gas emissions have hit repeated highs.

TEMPORARY RESPITE

"Volcanoes give us only a temporary respite from the relentless warming pressure of continued increases in carbon dioxide," said Piers Forster, Professor of Climate Change at the University of Leeds.

A study by the U.N. Intergovernmental Panel on Climate Change last year suggested that natural variations in the climate, such as an extra uptake of heat by the oceans, could help explain the warming slowdown at the planet's surface.

The IPCC projected a resumption of warming in coming years and said that "substantial and sustained" cuts in greenhouse gas emissions were needed to counter climate change.

It also raised the probability that human activities were the main cause of warming since 1950 to at least 95 percent from 90 in 2007. Despite the hiatus, temperatures have continued to rise - 13 of the 14 warmest years on record have been this century, according to the World Meteorological Organisation.