A model-based estimate of the climate and carbon cycle response to negative CO2 emissions over multi-centennial timescales

Anthropogenic emissions of carbon dioxide since the beginning of industrialization have led to an increase in global surface temperature. This rapid increase in global surface temperature is unprecedented over the past 2000 years. The increase in frequency of natural disasters such as extreme rainfall, floods and heatwaves indicate that immediate action is required to prevent further impact of climate change. The Paris agreement targets to keep warming below 2°C above the preindustrial state, while pursuing efforts to limit the increase to 1.5°C . While climate mitigation strategies such as reducing fossil fuel emissions and deforestation are currently implemented, recent studies show that artificially removing atmospheric CO₂ (negative emissions) might be necessary to achieve the targets set by the Paris agreement. Therefore, understanding the response of climate system towards artificial removal of atmospheric CO₂ or equivalently negative emissions is essential.

In this study, using a coupled climate and carbon cycle model, we simulate the response of the climate system to net negative emissions in 9 idealized simulations each having a positive emission phase and an equal and opposite negative emission phase such that the cumulative emissions since preindustrial period is zero in each simulation. We specifically address the following two questions: 1) For the same total emissions in the positive phase, does the timescale of emissions have any impact on the long-term response of the climate system? 2) If the timescale of emissions is the same, what is the sensitivity to the magnitude of total emissions in the positive phase? The results from our nine climate-carbon model simulations will be discussed at the meeting.