Understanding the evolution of, and the interactions between, ice sheets and the global climate over geological timescales is important for being able to project their future evolution. However, direct observational evidence of past CO₂ concentrations, and the implied radiative forcing, only exists for the past 800 000 years. Records of benthic δ¹⁸O date back millions of years but contain signals from both land ice volume and ocean temperature. In recent years, inverse forward modelling has been developed as a method to disentangle these two signals, resulting in mutually consistent reconstructions of ice volume, temperature, and CO₂. We use this approach to force a hybrid ice-sheet–climate model with a benthic δ¹⁸O stack, reconstructing the evolution of the ice sheets, global mean sea level, and atmospheric CO₂ during the late Pliocene and the Pleistocene, from 3.6 million years (Myr) ago to the present day. During the warmer-than-present climates of the late Pliocene, reconstructed CO₂ varies widely, from 320–440 ppmv for warm periods to 235–250 ppmv for the early glacial excursion ∼3.3 million years ago. Sea level is relatively stable during this period, with maxima of 6–14 m and minima of 12–26 m during glacial episodes. Both CO₂ and sea level are within the wide ranges of values covered by available proxy data for this period. Our results for the Pleistocene agree well with the ice-core CO₂ record, as well as with different available sea-level proxy data. For the Early Pleistocene, 2.6–1.2 Myr ago, we simulate 40 kyr glacial cycles, with interglacial CO₂ decreasing from 280–300 ppmv at the beginning of the Pleistocene to 250–280 ppmv just before the Mid-Pleistocene Transition (MPT). Peak glacial CO₂ decreases from 220–250 to 205–225 ppmv during this period. After the MPT, when the glacial cycles change from 40 to 80 120 kyr cyclicity, the glacial–interglacial contrast increases, with interglacial CO₂ varying between 250–320 ppmv and peak glacial values decreasing to 170–210 ppmv.

中文翻译：

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重建过去360万年来冰盖，海平面和大气CO ₂的演变

了解冰盖和全球气候范围内冰盖与全球气候之间的相互作用以及它们之间的相互作用，对于能够预测其未来的演变非常重要。但是，仅在过去80万年中才存在过去CO ₂浓度的直接观测证据 和隐含的辐射强迫。底栖记录δ ¹⁸ Ø追溯到数百万年，但包含来自陆地冰量和海洋温度的信号。近年来，已经开发了逆向正向建模作为解散这两个信号的方法，从而导致了冰量，温度和CO _2的相互一致的重建。我们使用这种方法来强迫具有底栖生物的冰盖-气候混合模型 δ ¹⁸ O堆栈，重建的冰盖，全球平均海平面和大气的演化CO ₂年前到今天晚上新世和更新世期间，从360万年（MYR）。在新世末的低于现在高，气候条件，重建的CO ₂ 变化很大，从320-440  ppmv的为暖期，以235-250  ppmv的早日冰川漂移~3.3 万年前。在此期间，海平面相对稳定，冰川事件期间的最大高度为6-14  m，最小为12-26  m。两者 CO ₂和海平面处于此期间可用代理数据所覆盖的广泛值范围内。我们的更新世结果与冰芯CO ₂记录以及不同的可用海平面代理数据非常吻合。对于早更新世，2.6-1.2 秘耳前，我们模拟40个 KYR冰川周期，与次间CO ₂从280-300减小 ppmv的在更新世的开始到250-280  ppmv的只是中更新世过渡（MPT）之前。冰期的最高CO ₂从220–250 ppmv降低至205–225  ppmv在这段时期。MPT之后，当冰川周期从40转变为 80120 kyr时，冰川与冰川之间的反差增加，冰川 之间的CO ₂在250–320 ppmv之间变化 ，峰值冰川值降低至170–210  ppmv。