It is well known that large volcanic1 eruptions2 contribute to climate variability. However, quantifying these contributions has proven challenging due to inconsistencies in both historic atmospheric3 data observed in ice cores andcorresponding temperature variations seen in climate proxies4 such as tree rings. Published today in the journal Nature, a new study led by scientists from the Desert Research Institute (DRI) and collaborating5 international institutions, resolves these inconsistencies with a new reconstruction6 of the timing7 and associated radiative forcing of nearly 300 individual volcanic eruptions extending as far back as the early Roman period."Using new records we are able to show that large volcanic eruptions in the tropics and high latitudes8 were the dominant9 drivers of climate variability, responsible for numerous and widespread summer cooling extremes over the past 2,500 years," said the study's lead author Michael Sigl, Ph.D., an assistant research professor at DRI and postdoctoral fellow with the Paul Scherrer Institute in Switzerland."These cooler temperatures were caused by large amounts of volcanic sulfate particles injected into the upper atmosphere," Sigl added, "shielding the Earth's surface from incoming solar radiation."The study shows that 15 of the 16 coldest summers recorded between 500 BC and 1,000 AD followed large volcanic eruptions - with four of the coldest occurring shortly after the largest volcanic events found in record.This new reconstruction is derived10 from more than 20 individual ice cores extracted from ice sheets in Greenland and Antarctica and analyzed11 for volcanic sulfate primarily using DRI's state-of-the-art, ultra-trace chemical ice-core analytical12 system.These ice-core records provide a year-by-year history of atmospheric sulfate levels through time. Additional measurements including other chemical parameters13 were made at collaborating institutions."We used a new method for producing the timescale," explained Mai Winstrup, Ph.D., a postdoctoral researcher at the University of Washington, Seattle. "Previously14, this has been done by hand, but we used a statistical15 algorithm instead. Together with the state-of-the-art ice core chemistry measurements, this resulted in a more accurate dating of the ice cores."词汇解析表：1 volcanicadj.火山的；象火山的；由火山引起的参考例句：There have been several volcanic eruptions this year.今年火山爆发了好几次。
Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。
2 eruptionsn.喷发，爆发( eruption的名词复数 )参考例句：There have been several volcanic eruptions this year. 今年火山爆发了好几次。
来自《简明英汉词典》Over 200 people have been killed by volcanic eruptions. 火山喷发已导致200多人丧生。
来自辞典例句3 atmosphericadj.大气的，空气的；大气层的；大气所引起的参考例句：Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
4 proxiesn.代表权( proxy的名词复数 )；（测算用的）代替物；（对代理人的）委托书；（英国国教教区献给主教等的）巡游费参考例句：SOCKS and proxies are unavailable. Try connecting to XX again? socks和代理不可用。
尝试重新连接到XX吗？来自互联网All proxies are still down. Continue with direct connections? 所有的代理仍然有故障。
继续直接连接吗？来自互联网5 collaborating合作( collaborate的现在分词 )；勾结叛国参考例句：Joe is collaborating on the work with a friend. 乔正与一位朋友合作做那件工作。
He was not only learning from but also collaborating with Joseph Thomson. 他不仅是在跟约瑟福？汤姆逊学习，而且也是在和他合作。
6 reconstructionn.重建，再现，复原参考例句：The country faces a huge task of national reconstruction following the war.战后，该国面临着重建家园的艰巨任务。
In the period of reconstruction,technique decides everything.在重建时期，技术决定一切。
7 timingn.时间安排，时间选择参考例句：The timing of the meeting is not convenient.会议的时间安排不合适。
The timing of our statement is very opportune.我们发表声明选择的时机很恰当。
8 latitudes纬度参考例句：Latitudes are the lines that go from east to west. 纬线是从东到西的线。
It was the brief Indian Summer of the high latitudes. 这是高纬度地方的那种短暂的晚秋。
9 dominantadj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因参考例句：The British were formerly dominant in India.英国人从前统治印度。
She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。
10 derivedvi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取参考例句：Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。
来自《简明英汉词典》He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。
来自《简明英汉词典》11 analyzedv.分析( analyze的过去式和过去分词 )；分解；解释；对…进行心理分析参考例句：The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。