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- ItemThe limits to global-warming mitigation by terrestrial carbon removal(Hoboken, NJ : Wiley, 2017) Boysen, Lena R.; Lucht, Wolfgang; Gerten, Dieter; Heck, Vera; Lenton, Timothy M.; Schellnhuber, Hans JoachimMassive nearāterm greenhouse gas emissions reduction is a precondition for staying āwell below 2Ā°Cā global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature āovershootā in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to ārepairā delayed or insufficient emissions reduction policies unable to prevent global mean temperature rise of 2.5Ā°C or even 4.5Ā°C above preāindustrial level. Our results show that those tCDR measures are unable to counteract ābusinessāasāusualā emissions without eliminating virtually all natural ecosystems. Even if considerable (Representative Concentration Pathway 4.5 [RCP4.5]) emissions reductions are assumed, tCDR with 50% storage efficiency requires >1.1āGha of the most productive agricultural areas or the elimination of >50% of natural forests. In addition, >100āMtN/yr fertilizers would be needed to remove the roughly 320āGtC foreseen in these scenarios. Such interventions would severely compromise food production and/or biosphere functioning. Second, we reanalyze the requirements for achieving the 160ā190āGtC tCDR that would complement strong mitigation action (RCP2.6) in order to avoid 2Ā°C overshoot anytime. We find that a combination of high irrigation water input and/or more efficient conversion to stored carbon is necessary. In the face of severe tradeāoffs with society and the biosphere, we conclude that largeāscale tCDR is not a viable alternative to aggressive emissions reduction. However, we argue that tCDR might serve as a valuable āsupporting actorā for strong mitigation if sustainable schemes are established immediately.
- ItemThe worldās biggest gamble(Hoboken, NJ : Wiley, 2016) Rockstrƶm, Johan; Schellnhuber, Hans Joachim; Hoskins, Brian; Ramanathan, Veerabhadran; Schlosser, Peter; Brasseur, Guy Pierre; Gaffney, Owen; Nobre, Carlos; Meinshausen, Malte; Rogelj, Joeri; Lucht, WolfgangThe scale of the decarbonisation challenge to meet the Paris Agreement is underplayed in the public arena. It will require precipitous emissions reductions within 40 years and a new carbon sink on the scale of the ocean sink. Even then, the world is extremely likely to overshoot. A catastrophic failure of policy, for example, waiting another decade for transformative policy and full commitments to fossilāfree economies, will have irreversible and deleterious repercussions for humanity's remaining time on Earth. Only a global zero carbon roadmap will put the world on a course to phaseāout greenhouse gas emissions and create the essential carbon sinks for Earthāsystem stability, without which, world prosperity is not possible.