NOAA/WDS Paleoclimatology - Tarawa Atoll Mn/Ca, westerly wind index, and d18O Data and Jarvis Island Sr/Ca Data from 1890-1982

Of the rise in global atmospheric temperature over the past century, nearly 30% occurred between 1910 and 1940 when anthropogenic forcings were relatively weak. This early warming has been attributed to internal factors, such as natural climate variability in the Atlantic region, and external factors, such as solar variability and greenhouse gas emissions. However, the warming is too large to be explained by external factors alone and it precedes Atlantic warming by over a decade. For the late twentieth century, observations and climate model simulations suggest that Pacific trade winds can modulate global temperatures, but instrumental data are scarce in the early twentieth century. Here we present a westerly wind reconstruction (1894-1982) from seasonally resolved measurements of Mn/Ca ratios in a western Pacific coral that tracks interannual to multidecadal Pacific climate variability. We then reconstruct central Pacific temperatures using Sr/Ca ratios in a coral from Jarvis Island, and find that weak trade winds and warm temperatures coincide with rapid global warming from 1910 to 1940. In contrast, winds are stronger and temperatures cooler between 1940 and 1970, when global temperature rise slowed down. We suggest that variations in Pacific wind strength at decadal timescales significantly influence the rate of surface air temperature change.

过去一个世纪以来的全球大气升温中，近30%发生在1910年至1940年间，彼时人为强迫（anthropogenic forcings）相对较弱。这一早期升温曾被归因于内部因素（如大西洋区域的自然气候变率）与外部因素（如太阳活动变率与温室气体排放）。然而，该升温幅度仅凭外部因素无法完全解释，且其出现时间比大西洋升温早十余年。针对20世纪后期，观测与气候模式模拟结果均表明太平洋信风可调节全球温度，但20世纪早期的仪器观测数据较为匮乏。本研究基于西太平洋一处珊瑚中锰钙（Mn/Ca）比值的季节分辨测量数据，重建了1894年至1982年的西风序列，该序列可反映年际至年代际尺度的太平洋气候变率。随后，我们利用贾维斯岛（Jarvis Island）一处珊瑚的锶钙（Sr/Ca）比值重建了中太平洋温度，并发现1910年至1940年的快速全球升温与弱信风及暖温事件相吻合。与之形成对比的是，1940年至1970年间全球升温速率放缓，此时信风更强、温度更低。我们提出，年代际尺度上的太平洋风强变化会显著影响地表气温的变化速率。