Climate change impacts and risks at global warming of 1.5ºC to 4ºC: latest research findings

16:15 Tuesday 28 May


Room S6


Richard Betts (United Kingdom) 1,2; Lamprini Papadimitriou (United Kingdom) 3; Michalis Vousdoukas (Italy) 4; Luc Feyen (Italy) 4; Wojtek Szewczyk (Spain) 4; Jason Lowe (United Kingdom) 2,5

1 - University of Exeter; 2 - Met Office Hadley Centre; 3 - Cranfield Water Science Institute, Cranfield University; 4 - Joint Research Centre (JRC), European Commission; 5 – Priestley Centre, University of Leeds

We will present and discuss new research findings on the impacts of climate change at global warming of 1.5°C, 2°C, 3°C and 4°C, at both global scales and in selected countries. Focus impacts will include water availability, river and coastal flooding, food insecurity and human heat stress. The research is the result of a major global interdisciplinary project, HELIX (High-End cLimate Impact and eXtremes) which finished in October 2017 and has published more than 100 peer-reviewed publications.

Target audience

Both the scientific community and policy makers. The HELIX research responded to an EU call for developing a number of future scenarios of the natural and human world as a consequence of 1.5°C, 2°C, 4°C and 6°C global warming. Using two high-resolution full-complexity Atmospheric General Circulation Models (GCMs), EC-Earth and HadGEM3, and regional climate models, we drove models of biophysical impacts of climate change such as fresh water availability, river flooding, crop yield and biodiversity loss, as well as to calculate an index of vulnerability to food insecurity, at levels of global warming of 1.5°C, 2°C, 4°C and 6°C relative to the pre-industrial climate. HELIX has delivered policy-relevant conclusions to inform EU policy makers by contributing to the IPCC Special Report on global warming of 1.5°C. the audience of our session will get an overview of the conclusions reached, the methods used and an opportunity to discuss with the panel on the conclusions presented.

Proposed format for the session

Our session will consist of seven presentations, lasting 15 minutes each including questions and discussion.

Contributing Authors abstracts

1. Richard Betts, University of Exeter and Met Office Hadley Centre, Director of the HELIX project

Outline:  Despite the Paris Agreement aiming to limit global warming to below 2°C and pursue efforts for 1.5°C, current policies related to greenhouse gas emissions are projected to lead to between 2.4°C and 4.4°C by 2100. It therefore remains vital to assess the potential impacts of high-end climate change, both in order to understand the impacts we wish to avoid by limiting warming to lower levels, and to inform adaptation to unavoidable impacts.  Two key areas of impacts on people are heat stress and food insecurity.  At 4°C global warming, tropical regions could regularly experience combination of high temperature and humidity, which go beyond the commonly-accepted maximum levels for outdoor working.  Moreover, patterns of rainfall extremes simulated for 4°C warming could lead to unprecented levels of vulnerability to food insecurity.

2. Lamprini Papadimitriou, Cranfield Water Science Institute (CWSI), Cranfield University

Outline: The simulation of hydrological impacts under a changing climate remains one of the big challenges of the Earth system sciences. Impact assessments can be in many cases a laborious process leading to inevitable methodological compromises that drastically affect the robustness of the conclusions. The quantification of the impacts becomes even more challenging due to interdependencies between physical and socio-economic systems. Research undertaken within the HELIX (High-end climate impacts and extremes) project aimed to explore the aforementioned challenges. Hydrological simulations were performed using the JULES land surface model, set up at the global scale, forced by different sets of climate data following the higher-end emission pathway (RCP 8.5).

A vulnerability based assessment of global freshwater availability was developed and applied to incorporate the socio-economic impacts on hydrology and explore the effects of adaptation options. The assessment was built on a conceptual framework, considering transient hydro-climatic impacts of crossing specific warming levels (1.5oC, 2oC and 4oC) and related socio-economic developments under high-end climate change. The combined dynamics of climate and socio-economic changes suggest that although there is important potential for adaptation to reduce freshwater vulnerability, climate change risks cannot be totally and uniformly eliminated.

3. Michalis Vousdoukas, Joint Research Centre (JRC), European Commission – Rising coastal flood risk in Europe and worldwide

Outline: The present contribution reports the methodology and outcome of coastal flood risk assessments done using the integrated risk assessment tool LISCoAsT (Large scale Integrated Sea-level and Coastal Assessment Tool). We assess future flood risk along Europe coupling different greenhouse gas emission and socioeconomic scenarios. Our analysis shows that by 2100, the global average 100-year extreme sea level (ESL) is projected to rise by 34-76 cm under a moderate-emission-mitigation-policy scenario and by 58-172 cm under a business as usual scenario. Rising ESLs are mostly driven by thermal expansion, followed by contributions from ice mass-loss from glaciers, and ice-sheets in Greenland and Antarctica. ESL rise would render a large part of the tropics exposed annually to the present-day 100-year event from 2050. By the end of this century this applies to most coastlines around the world. Such intensification of ESLs will drive an increase in flood losses along Europe. EAD is projected to increase 2-3 orders of magnitude, EAD/GDP% rises from 0.01% to 0.29-0.86% by 2100, and EAPE increases from 100,000 to 1.5-3.6 million people. All the above imply substantial adaptation challenges.

4. Luc Feyen, Joint Research Centre (JRC), European Commission – Projections of global drought and European and global river flood risk under different levels of global warming.

Outline: Droughts affect societies worldwide with often devastating consequences over long periods. They affect a wide range of sectors, from food security, drink water provision to energy production. Drought can cause conflicts when water restrictions are required and could trigger unwanted migration. Droughts are caused by an imbalance between the natural supply of water through precipitation and evapotranspiration demand by the earth and ecosystems. This imbalance can be exacerbated through the human use of water. Natural supply and demand depend on temperature and spatiotemporal precipitation patterns, which will alter in view of climate change.  River floods are one of the costliest natural hazards and the ongoing rise of global temperature may further increase impacts on economy and society.  Here we present the results of a global drought and flood hazard analysis at European and global scale, carried out in the framework of the HELIX project, we quantify future drought conditions and flood risk under a range of Specific Warming Levels (1.5°C, 2°C and 3°C and 4°C warming compared to pre-industrial times) and socio-economic scenarios.

Drought changes with respect to historical conditions are derived from a peak over threshold analysis using the SPEI multiscalar drought index that represents both the supply and demand sides of the surface moisture balance.  The studies combine ensemble climate projections for the current century with state-of-the-art models and datasets to quantify hazard, exposure and vulnerability. Models are used to estimate human losses, direct economic damage and subsequent indirect impacts. All studies indicate a clear positive correlation between atmospheric warming and future drought and flood risk at global scale, with a substantial increase in socio-economic impacts over a vast majority of countries. Impacts are notably higher under increased warming, but at the same time, variability between model projections also increases, leading to greater uncertainty regarding flood impacts at higher warming levels. Flood impacts are further shown to have an uneven regional distribution, with the greatest losses observed in the Asian continent at all analysed warming levels.

5. Wojtek Szewczyk, Joint Research Centre (JRC), European Commission – Global economic impacts from climate change

Outline: The HELIX project has studied the economic effects due to climate change in agriculture, energy, river floods and coastal areas. The economic analysis uses a multi-sector, multi-region general equilibrium model to assess how the direct sectoral impacts would affect the overall economy. The economic overall impacts are calculated in terms of production (GDP) and welfare (consumption). A set of climate scenario was considered, including the 2°C future.

Jason Lowe, Met Office Hadley Centre – UKCP18 and HELIX: tools for providing climate scenarios for policy and planning

Outline: Adaptation planning increasingly draws on climate change information from model simulations. In the UK a variety of model scenarios are used, including HELIX outputs and a new set of national climate scenarios, UKCP18. This talk will provide an overview of UKCP18 then begin the journey of comparing the results from UKCP18 with those from HELIX. In particular, it will consider the response from the global model simulations in HELIX alongside the global model ensemble component of UKCP18. Better understanding of how these datasets relate will allow a richer narrative to be constructed during the next climate change risk assessment as it will enable both information sources to be used alongside each other more easily.