Parallel Session 3.5: The Earth System and Carbon Dioxide Removal

Thursday, 11:00 - 12:30
04 I Seminarraum I/II

Scenarios limiting warming to <2°C rely heavily on Carbon Dioxide Removal. Despite this many key questions around potential efficacy, impacts and feedbacks of different proposed CDR methods remain unanswered. Our session explores the response of the Earth System, i.e., the climate system, biosphere, and the carbon cycle, to proposed CDR.

Talks:

  • Helene Muri
    • The increasing awareness of the many damaging aspects of climate change over this century and beyond has prompted research into ways of reducing and reversing the recent man-made increase of the carbon concentrations in the atmosphere. Most IPCC emission scenarios stabilising climate at low levels, such as the 1.5°C target as outlined by the Paris Agreement, require large scale deployment of Bio-Energy with Carbon Capture and Storage (BECCS).
      Here, the potential of large scale BECCS deployment in reaching the 1.5ºC global warming target is evaluated alongside associated climate consequences and carbon cycle feedbacks. An Earth system model with fully coupled carbon cycle and interactive biogeochemistry is used to assess different BECCS deployment scenarios combined with strong mitigation. Large-scale BECCS deployment influences not only the global carbon cycle, but also the feedbacks between the atmosphere and land surface. The climate implications, including changes to the hydrological cycle, of large scale BECCS deployment in pursuit of the 1.5°C target will be presented.
       
  • Sebastian Sonntag - Earth system effects, side-effects, and carbon cycle feedbacks of reforestation and ocean alkalinization
    • For the assessment of CDR methods side-effects and carbon cycle feedbacks play an important role as they may alter the methods’ mitigation potential. Here we comparatively assess a reforestation scenario and an ocean alkalinization scenario as examples for land- and ocean-based CDR methods with respect to their effects in the coupled Earth system. We perform model experiments using the Max Planck Institute Earth System Model (MPI-ESM) with prognostic carbon cycle, forced by fossil-fuel CO2 emissions according to the high-emission scenario RCP8.5. The two CDR scenarios are very different regarding their potential to reduce global warming. Yet, normalized to the same reduction in global warming, we find that more CDR is needed via reforestation than via ocean alkalinization. This lower cooling efficiency of reforestation is due to the biogeophysical effects of land cover change counteracting the cooling CDR signal and to the climate sensitivity possibly being state-dependent. Furthermore, we find a lower efficiency to remove carbon from the atmosphere for reforestation compared to ocean alkalinization, since the ocean releases more carbon in response to reforestation than the land in response to alkalinization. Overall our findings illustrate how side-effects and feedbacks in the Earth system alter the mitigation potential of CDR methods.
       
  • Jiajun Wu
    • Blue Carbon represents the photosynthetic carbon captured by marine primary producers, among which macroalgae acts as an efficient carbon fixer. However, most of the macroalgae fixed carbon is not permanently removed from the active carbon cycle because it is remineralized on solid substrate habitats.
      Here we present a carbon dioxide removal idea to mariculture massive amount of macroalgae on open ocean floats to sequester CO2 in the plant biomass. Once matured, the biomass can be directly and rapidly sunk to the deep seafloor where the carbon will remain out of contact with the atmosphere either permanently (if buried in the sediments) or for centuries to millennia if remineralized back to the overlying deep ocean water mass.
      The potential and side effects are evaluated using the University of Victoria Earth System Climate Model. To test the maximum potential, the macroalgae is simulated to grow in all ice-free deep ocean regions during RCP4.5 and RCP8.5 emission scenarios. Then, the potential of smaller regional deployments is also investigated. Because of nutrient limitation, we perform additional experiments using artificial upwelling pipes to supply nutrients from deeper waters. Sensitivity analyses are also conducted to investigate parameters uncertainties such as the seafloor remineralization.
  • Miriam Ferrer González - Impacts of Artificial Ocean Alkalinization on Rates of Change and Seasonality of Environmental Drivers of Marine Ecosystems
    • Authors: Miriam Ferrer González, Tatiana Ilyina, Sebastian Sonntag
    • Artificial ocean alkalinization (AOA) is one of the carbon dioxide removal methods proposed to mitigate the expected rapid perturbation of environmental drivers of marine ecosystems. Using the emissions-driven Max Planck Institute Earth system model and forcing according to the Representative Concentration Pathway scenarios, we explore the environmental impacts of this method and consistently compare its effects to those of stratospheric sulfur injection (SSI). We consider two different time scales: decadal rates of change and seasonal variability. Albeit indicating large internal variability, warming trends reach comparable rates to those obtained in a terminated SSI scenario regionally over the Northern hemisphere after termination of a large-scale AOA scenario. Besides, right after termination of AOA, rates of ocean acidification become up to one order of magnitude higher than in the unmitigated scenario over regions where particularly vulnerable ecosystems are located. Despite of the different modified forcings by the AOA and SSI methods, they do not present regional differences in their effects on the seasonality of surface temperatures. Further, AOA alters the seasonal variability of seawater carbonate chemistry, however these effects are rather minor compared to the associated impacts on the mean states.
       
  • Andrew Lenton - Climate Reversibility: Results from CDR-MIP C1 Experiment
    • Authors: Andrew Lenton, David Keller, Vivian Scott, Naomi Vaughan, Roland Seferian, Jerry Tjiputra
    • There is an urgent need to assess how Carbon Dioxide Removal (CDR) could help either mitigate climate change or even reverse it, and to understand the potential risks and benefits of different options. To explore this, the Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP) was created to coordinate and advance our understanding of CDR in the earth system.  The first CDR-MIP experiment (C1) focusses on climate reversibility, here atmospheric carbon dioxide levels are raised from the pre-industrial levels (~280 ppm) to 4x CO2 at 1% per annum, and then returned back to pre-industrial levels, before being then held at this level.  Results show that some climate variables such as temperature return quickly to their pre-industrial value as atmospheric CO2 decreases, but others such as ocean overturning circulation, which plays a critical role in controlling weather and climate, peak several decades later, and can take hundreds to thousands of years to return to their pre-industrial state. Spatially we see that even for variables that return quickly to global pre-industrial values such as land net primary production and upper ocean acidification the spatial distributions are significantly altered. These results have profound implications on our ability to reverse climate change through reducing atmospheric CO2 levels, and for maintaining key ecosystems services such as food production, as well as on societal responses and strategies for adapting to a changing climate.
Convened by: 

David P. Keller

Organisation: 
GEOMAR Helmholtz Centre for Ocean Research Kiel
Country: 
Germany

David Keller is a scientist at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany.  His research interests include marine biogeochemistry, the climate system, and assessing proposed climate engineering methods.  Although he has conducted experimental field work in the past in estuarine systems, he currently mostly uses Earth system models to understand interactions between biogeochemical cycles and the climate system.  David Keller is one of the coordinators of the Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP).  He has a PhD from the University of Maryland in Marine, Estuarine, and Environmental Science with a specialization in biological oceanography.

Andrew Lenton

Organisation: 
CSIRO Oceans and Atmosphere & Antarctic Climate and Ecosystems Cooperative Research Centre
Country: 
Australia

Vivian Scott

Organisation: 
University of Edinburgh
Country: 
United Kingdom

A researcher at the University of Edinburgh, Vivian Scott works on carbon capture and storage (CCS), energy and climate policy, and assessing the potential and consequences of 'negative emissions' technologies and approaches to support mitigation.

His research focuses on technical and policy development to support deep decarbonisation of the economy, the potential for CCS principals and technologies to be applied to manage carbon in the climate system; understanding the development of climate and energy policy and the interaction between technical and political perspectives; and understanding the role and implications of large amounts of CO2 or carbon removal and storage on the climate system. He is co-leader of the Carbon Dioxide Removal Model Inter-comparison project (CDR-MIP). More generally, he is interested in the interactions between society, the carbon cycle and climate system, and the inter-generational responsibilities and feedbacks these generate. 

Naomi Vaughan

Organisation: 
University of East Anglia
Country: 
United Kingdom

Naomi (Nem) Vaughan is a lecturer at the Tyndall Centre for Climate Change Research in the School of Environmental Sciences at the University of East Anglia.  Her research interests focus on possible societal response options to climate change; mitigation, adaptation, carbon removal or ‘negative emissions’ and ideas of climate engineering.  Her focus is on these issues at a global scale and over a long time (e.g. centuries), how they are constrained by the Earth system (including climate-carbon cycle feed-backs) and how they interact with one another.  Nem is an interdisciplinary scientist working from a physical science background with colleagues across a range of disciplines.

Speakers: 

Helene Muri

Organisation: 
University of Oslo
Country: 
Norway

Helene Muri is a researcher at the University of Oslo’s Meteorology and Oceanography Section. Current work is focused on Earth system modelling of various climate geoengineering techniques including BECCS, SRM and cirrus cloud thinning, and actively participates in GeoMIP (Geoengineering Model Intercomparison Project) and CDR-MIP. Furthermore, she contributed towards the EuTRACE climate geoengineering assessment report. Previously, she held an ERC Advanced grant post-doc at Université catholique de Louvain working on climate model - data comparisons for paleo-climate studies. She gained her D.Phil degree from the University of Oxford’s Atmospheric Oceanic and Planetary Physics department in 2009 on the topic of forcing evaluation in climate model ensembles, as part of the climateprediction.net project.

Sebastian Sonntag

Organisation: 
Max Planck Institute for Meteorology
Country: 
Germany

Sebastian Sonntag is a scientist at the Max Planck Institute for Meteorology, Hamburg, Germany. He has a background in physics, he holds a PhD in geoscience, and his research involves understanding interactions and feedbacks in the Earth system using models of different complexity. He is working on both SRM as well as land- and ocean-based CDR methods with a focus on the climate and carbon cycle response as simulated with an Earth system model.

Jiajun Wu

Organisation: 
GEOMAR Helmholtz Centre for Ocean Research Kiel
Country: 
Germany

Jiajun is a first-year Ph.D candidate with spectacular interest in Blue Carbon and global climate change. Jiajun moved to Kiel after finishing undergraduate study in marine biology at Ocean University of China, Tsingtao. Back then, he had intensive training in marine biology and oceanography. Afterwards, Jiajun spent 3 years in his Master program Biological Oceanography at GEOMAR, in which several seminars and lectures made Jiajun interested and inspired in marine biogeochemistry modelling. In November 2016, he started his Ph.D career. By estimating Blue Carbon (CO2marine photosynthesis) climate engineering ideas in computational models, he looks forward to efficient and sustainable solutions to mitigate the climate change via enhancing the carbon capture & storage (CCS) in the ocean.

Miriam Ferrer González

Organisation: 
Max Planck Institute for Meteorology
Country: 
Germany

Miriam Gonzalez studied fundamental physics at La Laguna University in Canary Islands, Spain. In 2010, she moved to Hamburg to enter the interdisciplinary master's program Integrated Climate System Sciences. Miriam finished her Ph.D. at the ocean biogeochemistry group of the Max Planck Institute for Meteorology in Hamburg, where she currently has a postdoctoral position.