Olivia Serdeczny

The Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP): project framework.

The Inter-Sectoral Impact Model Intercomparison Project offers a framework to compare climate impact projections in different sectors and at different scales. Consistent climate and socio-economic input data provide the basis for a cross-sectoral integration of impact projections. The project is designed to enable quantitative synthesis of climate change impacts at different levels of global warming. This report briefly outlines the objectives and framework of the first, fast-tracked phase of Inter-Sectoral Impact Model Intercomparison Project, based on global impact models, and provides an overview of the participating models, input data, and scenario set-up.

A multi-model analysis of risk of ecosystem shifts under climate change

Climate 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. 5‐19% of the naturally vegetated land surface is projected to be at risk of severe ecosystem change at 2 C of global warming (1GMT) above 1980‐2010 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 with1GMT, approximately doubling between1GMTD 2 and 3 C, and reaching a median value of 35% of the naturally vegetated land surface for1GMTD 4 C. The regions projected to face the highest risk of severe ecosystem changes above1GMTD 4 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.

Social vulnerability to climate change: a review of concepts and evidence

This article provides a review of recent scientific literature on social vulnerability to climate change, aiming to determine which social and demographic groups, across a wide range of geographical locations, are the most vulnerable to climate change impacts within four well-being dimensions: health, safety, food security, and displacement. We analyze how vulnerability changes over time and ask whether there is evidence of critical thresholds beyond which social vulnerability drastically changes. The review finds that climate change is expected to exacerbate current vulnerabilities and inequalities. The findings confirm concerns about climate justice, especially its intergenerational dimensions. For example, deficiencies in early childhood may limit future educational and income generation opportunities. Evidence of clear thresholds is rare and is mainly related to the vulnerability of different age groups, household income level, and the impacts of different degrees of global warming.

Turn down the heat: regional climate change impacts on development

The Paris Agreement, a landmark in international climate policy, advocates Bholding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels^. Achieving the Paris agreement is ambitious, because time for bringing humanity on a sustainable development pathway is short. Warming in 2016 has reached 1.1 °C as compared to the pre-industrial (1880– 1900) average (WMO 2017) and current emission reduction pledges presented for the COP21 in Paris will lead with 50% probability to a global warming of about 2–3 °C, and with 34% probability to about 3–4 °C until 2100 compared to pre-industrial levels (Fawcett et al. 2015). Climate change impacts in a broad range of physical, biological and human systems have already been attributed to the observed warming for most regions of the World and are projected to further intensify (IPCC 2014). Particular risk is being attributed to climate change impacts that interact across sectors and spatio-temporal scales and lead to a cascade of impacts threatening development endeavours (Schellnhuber et al. 2012; Piontek et al. 2014). However, currently, there is still a lack of detailed knowledge about the progression of climate change impacts from environmental systems to human systems in different world regions as the world moves from current warming towards a 1.5 °C, 2 °C or even a 4 °Cworld. This pertains not only to the frequency, intensity and magnitude of impacts but also to their mutual interaction and reversibility. Impacts may for example be non-linearly related to temperature increase and/or may result in a cascade of impacts where biophysical impacts trigger crucial impacts in human systems across different sectors that may turn out to be irreversible at least on human timescales. Henceforth, assessing the vulnerability of social systems towards climate change is a crucial knowledge gap that may threaten current and future development initiatives. This special feature builds on and extends the data and literature collected for the Turn Down the Heat report II and III (Schellnhuber et al. 2013, 2014), commissioned by the World Bank, to answer the following questions in different regions of the world:

The Challenge of a 4°C World by 2100

As evidenced by the Fifth Assessment Report of the IPCC, our understanding of the Earth System and the climate change impacts expected in the coming decades is developing at a rapid pace. Contributing to this progress, the first ever Inter-Sectoral Impact Model Intercomparison (ISI-MIP) has helped to paint a clearer picture of potential impacts at different levels of global mean warming. However, along with such advances the limitations of our understanding become more apparent. A number of processes are scarcely or not at all reflected in current assessments of the risks associated with significant levels of warming. These include critical thresholds in the Earth system which, once breached, can give rise to non-linear impacts. Recent insights from West Antarctica indicate that we have already ‘tipped’ several large glacier systems there, suggesting that the risk of crossing such thresholds might be much greater than previously thought. Also excluded from a sectoral perspective are the intricate interdependencies between systems and the potential for an initial impact to cascade into a chain of impacts, or for impacts to occur simultaneously and interact in complex ways. Finally, we need to take into account the different degrees of vulnerability not only across but also within nation states. The ramifications of non-linear impacts and their uneven distribution are likely to be deleterious to the stability and wellbeing of our societies and will, we hope, never be realized. However, if we wish to understand the challenges associated with a 4°C world2, such a world needs to be imagined.

Piecing Together the Adaptation Puzzle for Small Island States

Island states are especially at risk of climate impacts and are already feeling the effects of rising sea levels, acidification, climate extremes and other impacts. Small islands face several unique challenges: They usually have limited resources to react, but are exceptionally exposed due to their physical setting and limited livelihood options. In addition, they are remote and not easily reached in time of crisis, making adaptation an imperative. This contribution presents the concept for an integrated database on climate impacts and adaptation, focussing specifically on the requirements of small island states. The database contains information on climate impact projections, linked to examples of existing adaptation projects. The database provides a structured overview of success-factors and limitations, piecing together fragmented knowledge and fostering knowledge exchange across regions in order to support science-based adaptation. While adaptation experience is increasing, including an evolving understanding of prerequisites and limitations to specific forms of adaptation, knowledge is still fragmented, due to the mostly local nature of adaptation. Island states across the world can benefit from a structured exchange, focussing on the transferability of success-criteria for adaptation. An improved knowledge base is also important for other regions, which will face similar challenges in the coming years.