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

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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.