Modelling the effect of natural and human altered nitrogen and phosphorous cycles on the global carbon cycle and climate warming

自工业革命开始以来，人类通过燃烧化石燃料、改变土地利用和生产人工肥料，对碳、氮和磷循环产生了深远的影响。燃烧化石燃料向大气中释放二氧化碳，成为全球变暖的主要驱动力。然而，排放到大气中的碳只有大约45%留在大气中，其余的被海洋和陆地生物圈吸收。预计在未来很长一段时间内，海洋仍将是碳汇，但陆地生物圈能否继续吸收碳，还是会转变为向大气排放碳的净来源，目前尚不清楚。氮和磷是生命的关键元素，这些元素可得性的限制可能会限制陆地生物圈吸收碳的能力，导致排放的二氧化碳在大气中残留的比例更大。虽然氮和磷限制的潜在影响已经被了解了十多年，但将这些元素纳入地球系统模型的进展缓慢。这项研究计划的目的是提高对生物地球化学反馈循环与物理气候系统之间相互作用的认识。该项目的五年目标是将氮和磷循环纳入地球系统模型，以研究氮和磷可用性的限制将如何影响全球变暖的程度。改进后的模型还将允许对沿海富营养化、海洋死亡区的发展以及广泛的海洋缺氧的可能性进行调查，这可能是由持续的气候变化和人工肥料的生产造成的。拟议的研究将改善地球系统模型中碳循环反馈对气候变化的表现，从而有助于减少与国际协议中概述的1.5℃和2.0℃温度变化“围栏”兼容的累计碳排放总量的不确定性。总的来说，拟议的研究方案旨在增进对地球系统和人类对该系统功能的影响的了解。

Since the beginning of the industrial revolution, humans have had a profound impact on the carbon, nitrogen and phosphorus cycles through the burning of fossil fuels, land use change, and artificial fertilizer production. Burning of fossil fuels releases CO2 to the atmosphere where it becomes the primary driver of global warming. However, only about 45% of the carbon emitted to the atmosphere remains in the atmosphere, the remainder is absorbed by the oceans and by the land biosphere. The oceans are expected to remain a sink for carbon far into the future, but whether the land biosphere can continue to take up carbon or will transition to a net source of carbon to the atmosphere remains unclear. Nitrogen and phosphorous are critical elements for life, and limitations in the availability of these elements may limit the ability of the land biosphere to take up carbon, leading to a larger fraction of emitted CO2 remaining in the atmosphere. Although the potential effect of nitrogen and phosphorous limitations has been understood for over a decade, progress in incorporating these elements into Earth System Models has been slow. The objective of this research programme is to improve the understanding of the interaction between biogeochemical feedback cycles and the physical climate system. The five-year goals of the project are to incorporate the nitrogen and phosphorous cycles into an Earth System Model to study how limitations in the availability of nitrogen and phosphorus will effect the magnitude of global warming. The improved model will also allow for the investigation of coastal eutrophication, development of ocean dead zones, and potential for widespread ocean anoxia, that could result from sustained climate change and production of artificial fertilizers. The proposed research would improve the representation of carbon cycle feedbacks to climate change within Earth System Models and therefore contribute to reducing the uncertainty in the total cumulative carbon emissions compatible with the 1.5oC and 2.0oC temperature change guardrails outlined in international agreements. Overall, the proposed research programme aims to improve understanding of the Earth system and humanity's impact on the system's functioning.