How warm was the medieval warm period?
How warm was the medieval warm period?
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DOI：
10.1579/0044-7447-29.1.51
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发表时间：
2000-02-01
期刊：
影响因子：
6.5
通讯作者：
Lowery, TS
中科院分区：
文献类型：
--
作者：
Crowley, TJ;Lowery, TS
一个常见的结论是基于对所谓的中世纪温暖时期（类似于公元1000-1300年）的个人记录的研究。20（th）世纪目前的温暖并不罕见，因此不能被视为温室气体排放导致气候变化的迹象。这一结论并没有得到已发表的北方气候变化综合结果的支持，但这种综合结果往往被忽视或受到质疑。在本文中，我们重新审视的争议，纳入额外的时间序列没有使用在早期的半球汇编。另一个不同之处是，目前的重建使用的记录只有900-1000年长，从而避免了潜在的问题，不确定性所引入的使用不同数量的记录在不同的时间。尽管有明确的证据表明，中世纪的温暖程度高于目前的一些个别记录，但新的半球合成图支持了早期半球重建的主要结论，并进一步表明，中世纪的最大温暖程度仅限于20-30年的两到三个时间间隔，这些时间段的合成值只能与世纪中期的温暖时间间隔相比较。未能证实半球温暖度大于现在一直发生在复合材料中，因为不同地区温暖的时间存在显著的偏移;忽略这些偏移可能导致关于中世纪温暖程度及其与世纪后期变暖解释相关性的推断出现严重错误。
A frequent conclusion based on study of individual records from the so-called Medieval Warm Period (similar to 1000-1300 A.D.) is that the present warmth of the 20(th) century is not unusual and therefore cannot be taken as an indication of forced climate change from greenhouse gas emissions. This conclusion is not supported by published composites of Northern Hemisphere climate change, but the conclusions of such syntheses are often either ignored or challenged. In this paper, we revisit the controversy by incorporating additional time series not used in earlier hemispheric compilations. Another difference is that the present reconstruction uses records that are only 900-1000 years long, thereby, avoiding the potential problem of uncertainties introduced by using different numbers of records at different times. Despite clear evidence for Medieval warmth greater than present in some individual records, the new hemispheric composite supports the principal conclusion of earlier hemispheric reconstructions and, furthermore, indicates that maximum Medieval warmth was restricted to two-three 20-30 year intervals, with composite values during these times being only comparable to the mid-20(th) century warm time interval. Failure to substantiate hemispheric warmth greater than the present consistently occurs in composites because there are significant offsets in timing of warmth in different regions; ignoring these offsets can lead to serious errors concerning inferences about the magnitude of Medieval warmth and its relevance to interpretation of late 20(th) century warming.