Carbon Cycle Response to Temperature Overshoot Beyond 2°C: An Analysis of CMIP6 Models

Melnikova, I., Boucher, O., Cadule, P., Ciais, P., Gasser, T. ORCID: https://orcid.org/0000-0003-4882-2647, Quilcaille, Y., Shiogama, H., Tachiiri, K., et al. (2021). Carbon Cycle Response to Temperature Overshoot Beyond 2°C: An Analysis of CMIP6 Models. Earth's Future 9 (5) 10.1029/2020EF001967.

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Project: Constraining uncertainty of multi decadal climate projections (CONSTRAIN, H2020 820829)

Abstract

There is a substantial gap between the current emissions of greenhouse gases and levels required for achieving the 2°C and 1.5°C temperature targets of the Paris Agreement. Understanding the implications of a temperature overshoot is thus an increasingly relevant research topic. Here we explore the carbon cycle feedbacks over land and ocean in the SSP5-3.4-OS overshoot scenario by using an ensemble of Coupled Model Intercomparison Project 6 Earth system models. Models show that after the CO2 concentration and air temperature peaks, land and ocean are decreasing carbon sinks from the 2,040s and become sources for a limited time in the 22nd century. The decrease in the carbon uptake precedes the CO2 concentration peak. The early peak of ocean uptake stems from its dependency on the atmospheric CO2 growth rate. The early peak of the land uptake occurs due to a larger increase in ecosystem respiration than the increase in gross primary production, as well as due to a concomitant increase in land-use change emissions primarily attributed to the wide implementation of biofuel croplands. The carbon cycle feedback parameters amplify after the CO2 concentration and temperature peaks due to inertia of the Earth system so that land and ocean absorb more carbon per unit change in the atmospheric CO2 change (stronger negative feedback) and lose more carbon per unit temperature change (stronger positive feedback) compared to if the feedbacks stayed unchanged. The increased negative CO2 feedback outperforms the increased positive climate feedback. This feature should be investigated under other scenarios. © 2021. The Authors. Earth's Future published by Wiley Periodicals LLC on behalf of American Geophysical Union.

Item Type: Article
Uncontrolled Keywords: Carbon cycle; carbon-climate feedback; carbon-concentration feedback; CMIP6; overshoot; SSP5-3.4-OS
Research Programs: Advancing Systems Analysis (ASA)
Advancing Systems Analysis (ASA) > Exploratory Modeling of Human-natural Systems (EM)
Energy, Climate, and Environment (ECE)
Energy, Climate, and Environment (ECE) > Integrated Assessment and Climate Change (IACC)
Depositing User: Luke Kirwan
Date Deposited: 07 Jun 2021 07:14
Last Modified: 07 Jun 2021 07:14
URI: http://pure.iiasa.ac.at/17240

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