The role of enhanced rock weathering deployment with agriculture in limiting future warming and protecting coral reefs

Negar Vakilifard,Neil R Edwards,Euripides P Kantzas,Philip B Holden,David J Beerling

doi:10.1088/1748-9326/ac1818

Abstract

Meeting the net-zero carbon emissions commitments of major economies by mid-century requires large-scale deployment of negative emission technologies (NETs). Terrestrial enhanced rock weathering on croplands (ERW) is a NET with co-benefits for agriculture, soils and ocean acidification that creates opportunities for generating income unaffected by diminishing carbon taxes as emissions approach net-zero. Here we show that ERW deployment with croplands to deliver net 2 Gt CO2 yr−1 removal approximately doubles the probability of meeting the Paris 1.5 °C target at 2100 from 23% to 42% in a high mitigation Representative Concentration Pathway 2.6 baseline climate. Carbon removal via carbon capture and storage (CCS) at the same rate had an equivalent effect. Co-deployment of ERW and CCS tripled the chances of meeting a 1.5 °C target (from 23% to 67%), and may be sufficient to reverse about one third of the surface ocean acidification effect caused by increases in atmospheric CO2 over the past 200 years. ERW increased the percentage of coral reefs above an aragonite saturation threshold of 3.5 from 16% to 39% at 2100, higher than CCS, highlighting a co-benefit for marine calcifying ecosystems. However, the degree of ocean state recovery in our simulations is highly uncertain and ERW deployment cannot substitute for near-term rapid CO2 emissions reductions.

Highlights

A rapid transition to a low-carbon economy is essential to avoid breaching the Paris Agreement climate targets
grid-enabled integrated Earth system model (GENIE) model simulations We developed three GENIE simulation experiments adopting a high mitigation baseline (RCP2.6, the postscript 2.6 denoting radiative forcing in Wm−2 in year 2100 relative to year 1750): (a) enhanced rock weathering (ERW) with 2 Gt CO2 yr−1 removal, (b) carbon capture and storage (CCS) with 2 Gt CO2 yr−1 removal, (c) co-deployment of ERW with CCS giving a total of 4 Gt CO2 yr−1 removal
negative emission technologies (NETs) help achieve the 1.5 ◦C Paris agreement target According to our Earth system simulations, application of either NET (ERW or CCS) slowed the atmospheric CO2 growth rate and lowered peak atmospheric CO2 concentrations by ∼6 ppm at 2050 and 11 ppm at 2100 (figure 2(a))

Summary

Introduction

A rapid transition to a low-carbon economy is essential to avoid breaching the Paris Agreement climate targets This transition is insufficient to meet the mid-century net-zero carbon emission commitments of major economies, including the UK, EU, China and Japan, without large-scale deployment of negative emission technologies (NETs) (Hartmann et al 2013, Board and Council 2015). The deployment of NETs with cobenefits impacting multiple economic sectors could provide valuable opportunities to incentivise continued active carbon drawdown. Such efforts might allow existing regulation and incentive schemes to be re-purposed and strengthened to encourage carbon sequestration without direct reliance on carbon pricing (Cox and Edwards 2019). The repurposing of existing policy frameworks may facilitate an earlier introduction of negative emissions, potentially another critical enabling factor in the ultimate achievement of ambitious mitigation targets

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Discussion

Conclusion