Collaborative Research: P2C2--Exploring the Early Anthropogenic Hypothesis

早期的人为假设（EAH）认为，农业产生的温室气体排放量大到足以扭转几千年前二氧化碳和甲烷浓度的自然下降趋势，原因是推动大气中这两种气体的含量上升，使气候异常温暖。具体来说，研究人员计划：(1)重新检查人为限制雪厚的模型参数化，以确定这种限制如何影响永久积雪的范围；(2)在考虑现代日照但二氧化碳和甲烷水平变化的情况下进行模式模拟，以确定当今冰川开始的阈值；(3)收集现代和小冰期山地冰川和冰帽的资料，与模式模拟结果进行比较；(4)收集水稻灌溉和畜牧业在南亚传播的考古资料；(5)利用NCAR CCSM4模式进行实验，包括：(a)利用植被与二氧化碳生理和动态海洋的相互作用进行“无人为”实验，以评估早期农业温室气体对气候的全面影响；(b)模拟前工业时代晚期的实验，以便划分早期农业和工业时代人为气体对气候的影响；(c)一项仅使用人类直接输入的二氧化碳和甲烷的实验，以确定来自海洋的二氧化碳反馈是否可以解释支持35-40百万分之一的大气二氧化碳异常所需的全部碳预算。这项研究具有潜在的变革性，因为它为气候强迫提供了一个新的视角，并挑战了更广泛的科学界对人类对气候影响程度的理解。该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。

Funding is provided to further test the early anthropogenic hypothesis (EAH) that agriculture produced greenhouse-gas emissions large enough to reverse natural downward trends in carbon dioxide and methane concentrations several thousand years ago by driving atmospheric levels of both gases upward and keeping the climate anomalously warm.Specifically, the researchers plan to: (1) re-examine a model parameterization that artificially limit snow thickness, in order to determine how this constraint affects the extent of permanent snow cover; (2) run model simulations with modern insolation but varying carbon dioxide and methane levels to determine the threshold for present-day glacial inception; (3) assemble data on modern and little ice age mountain glaciers and ice caps for comparison to the model simulations; (4) assemble archeological data on the spread of rice irrigation and livestock tending across southern Asia; and (5) conduct experiments with the NCAR CCSM4 model that include: (a) a 'no anthro' experiment using interactive vegetation with carbon dioxide physiology and a dynamical ocean to assess the full climatic impact of early agricultural greenhouse gases; (b) an experiment simulating late pre-industrial times in order to parcel out the climatic effects of early-agricultural versus industrial-era anthropogenic gases; and (c) an experiment using only direct carbon dioxide and methane inputs from humans to determine whether carbon dioxide feedbacks from the ocean can account for the full carbon budget needed to support a 35-40 parts per million atmospheric carbon dioxide anomaly.This research is potentially transformative because it provides a new perspective on climate forcing and challenges the broader science community's understanding of the extent of human impacts on climate.This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).