Department of Applied Mathematics, University of Washington, Seattle, WA 98195, USA.
Proc Natl Acad Sci U S A. 2013 Feb 5;110(6):2058-63. doi: 10.1073/pnas.1212471110. Epub 2013 Jan 23.
The observed global-warming rate has been nonuniform, and the cause of each episode of slowing in the expected warming rate is the subject of intense debate. To explain this, nonrecurrent events have commonly been invoked for each episode separately. After reviewing evidence in both the latest global data (HadCRUT4) and the longest instrumental record, Central England Temperature, a revised picture is emerging that gives a consistent attribution for each multidecadal episode of warming and cooling in recent history, and suggests that the anthropogenic global warming trends might have been overestimated by a factor of two in the second half of the 20th century. A recurrent multidecadal oscillation is found to extend to the preindustrial era in the 353-y Central England Temperature and is likely an internal variability related to the Atlantic Multidecadal Oscillation (AMO), possibly caused by the thermohaline circulation variability. The perspective of a long record helps in quantifying the contribution from internal variability, especially one with a period so long that it is often confused with secular trends in shorter records. Solar contribution is found to be minimal for the second half of the 20th century and less than 10% for the first half. The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07-0.08 °C/decade, with superimposed AMO-related ups and downs that included the early 20th century warming, the cooling of the 1960s and 1970s, the accelerated warming of the 1980s and 1990s, and the recent slowing of the warming rates. Quantitatively, the recurrent multidecadal internal variability, often underestimated in attribution studies, accounts for 40% of the observed recent 50-y warming trend.
观测到的全球变暖速度并不均匀，每个预期变暖速度放缓的事件的原因都是激烈争论的主题。为了解释这一点，每个事件通常都分别援引了非重现事件。在回顾了最新的全球数据（HadCRUT4）和最长的仪器记录——英国中部气温（Central England Temperature）中的证据之后，出现了一幅新的图景，为最近历史上每一个多十年的变暖与变冷事件给出了一致的归因，并表明在 20 世纪后半叶，人为全球变暖趋势可能被高估了一倍。人们发现，一种反复出现的多十年振荡延伸到工业化前的英国中部气温 353 年记录中，可能是与大西洋多年代际振荡（AMO）有关的内部变率，可能是由热盐环流变率引起的。长记录的视角有助于量化内部变率的贡献，特别是对于与较短记录中的长期趋势经常混淆的周期如此长的变率。发现太阳对 20 世纪后半叶的贡献最小，对前半叶的贡献不到 10%。发现自 1910 年以来，工业化时代的人为净增暖率一直稳定在 0.07-0.08°C/decade，叠加了与 AMO 相关的上下波动，其中包括 20 世纪初的变暖、20 世纪 60 年代和 70 年代的冷却、20 世纪 80 年代和 90 年代的加速变暖以及最近变暖速度的放缓。从数量上看，经常在归因研究中被低估的反复出现的多十年内部变率，解释了最近 50 年观测到的变暖趋势的 40%。
