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- 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.
- 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.
- ItemA multi-model analysis of risk of ecosystem shifts under climate change(Bristol : IOP Publishing, 2013) Warszawski, Lila; Friend, Andrew; Ostberg, Sebastian; Frieler, Katja; Lucht, Wolfgang; Schaphoff, Sibyll; Beerling, David; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B.; Kahana, Ron; Ito, Akihiko; Keribin, Rozenn; Kleidon, Axel; Lomas, Mark; Nishina, Kazuya; Pavlick, Ryan; Rademacher, Tim Tito; Buechner, Matthias; Piontek, Franziska; Schewe, Jacob; Serdeczny, Olivia; Schellnhuber, Hans JoachimClimate change may pose a high risk of change to Earth's ecosystems: shifting climatic boundaries may induce changes in the biogeochemical functioning and structures of ecosystems that render it difficult for endemic plant and animal species to survive in their current habitats. Here we aggregate changes in the biogeochemical ecosystem state as a proxy for the risk of these shifts at different levels of global warming. Estimates are based on simulations from seven global vegetation models (GVMs) driven by future climate scenarios, allowing for a quantification of the related uncertainties. 5ā19% of the naturally vegetated land surface is projected to be at risk of severe ecosystem change at 2āĀ° C of global warming (ĪGMT) above 1980ā2010 levels. However, there is limited agreement across the models about which geographical regions face the highest risk of change. The extent of regions at risk of severe ecosystem change is projected to rise with ĪGMT, approximately doubling between ĪGMT = 2 and 3āĀ° C, and reaching a median value of 35% of the naturally vegetated land surface for ĪGMT = 4āĀ°C. The regions projected to face the highest risk of severe ecosystem changes above ĪGMT = 4āĀ°C or earlier include the tundra and shrublands of the Tibetan Plateau, grasslands of eastern India, the boreal forests of northern Canada and Russia, the savanna region in the Horn of Africa, and the Amazon rainforest.
- ItemThree centuries of dual pressure from land use and climate change on the biosphere(Bristol : IOP Publishing, 2015) Ostberg, Sebastian; Schaphoff, Sibyll; Lucht, Wolfgang; Gerten, DieterHuman land use and anthropogenic climate change (CC) are placing mounting pressure on natural ecosystems worldwide, with impacts on biodiversity, water resources, nutrient and carbon cycles. Here, we present a quantitative macro-scale comparative analysis of the separate and joint dual impacts of land use and land cover change (LULCC) and CC on the terrestrial biosphere during the last ca. 300 years, based on simulations with a dynamic global vegetation model and an aggregated metric of simultaneous biogeochemical, hydrological and vegetation-structural shifts. We find that by the beginning of the 21st century LULCC and CC have jointly caused major shifts on more than 90% of all areas now cultivated, corresponding to 26% of the land area. CC has exposed another 26% of natural ecosystems to moderate or major shifts. Within three centuries, the impact of LULCC on landscapes has increased 13-fold. Within just one century, CC effects have caught up with LULCC effects.