This paper presents a preliminary assessment of the relative effects of rate of climate change (four Representative Concentration Pathways -RCPs), assumed future population (five Shared Socio-economic Pathways -SSPs), and pattern of climate change (19 CMIP5 climate models) on regional and global exposure to water resources stress and river flooding. Uncertainty in projected future impacts of climate change on exposure to water stress and river flooding is dominated by uncertainty in the projected spatial and seasonal pattern of change in climate. There is little clear difference in impact between RCP2.6, RCP4.5 and RCP6.0 in 2050, and between RCP4.5 and RCP6.0 in 2080. Impacts under RCP8.5 are greater than under the other RCPs in 2050 and 2080. For a given RCP, there is a difference in the absolute numbers of people exposed to increased water resources stress or increased river flood frequency between the five SSPs. With the 'middle-of-theroad' SSP2, climate change by 2050 would increase exposure to water resources stress for between approximately 920 and 3,400 million people under the highest RCP, and increase exposure to river flood risk for between 100 and 580 million people. Under RCP2.6, exposure to increased water scarcity would be reduced in 2050 by 22-24 %, compared to impacts under the RCP8.5, and exposure to increased flood frequency would be reduced by around 16 %. The implications of climate change for actual future losses and adaptation depend not only on the numbers of people exposed to changes in risk, but also on the qualitative characteristics of future worlds as described in the different SSPs. The difference in 'actual' impact between SSPs will therefore be greater than the differences in numbers of people exposed to impact.

Christel. 2012 Multi-year droughts in Europe: analysis of development and causes. Hydrology Research, 43 (5). 689-706. 10.2166/nh.2012.024 Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. Whilst hydrological systems can show resilience to short-term streamflow deficiencies during 9 within-year droughts, prolonged deficits during multi-year droughts are a significant threat to 10 water resources security in Europe. This study uses a threshold-based objective classification 11 of regional hydrological drought to qualitatively examine the characteristics, spatio-temporal 12 evolution and synoptic climatic drivers of multi-year drought events in 1962-64, 1975-76 and 13 1995-97, on a European scale but with particular focus on the UK. Whilst all three events are 14 multi-year, pan-European phenomena, their development and causes are contrasting. The 15 critical factor in explaining the unprecedented severity of the 1975-76 event is the 16 consecutive occurrence of winter and summer drought. In contrast, 1962-64 was a succession 17 of dry winters, mitigated by quiescent summers, whilst 1995-97 lacked spatial coherence and 18 was interrupted by wet interludes. Synoptic climatic conditions vary within and between 19 multi-year droughts, suggesting that regional factors modulate the climate signal in 20 streamflow drought occurrence. Despite being underpinned by qualitatively similar climatic 21 conditions and commonalities in evolution and characteristics, each of the three droughts has 22 a unique spatio-temporal signature. An improved understanding of the spatio-temporal 23 evolution and characteristics of multi-year droughts has much to contribute to monitoring and 24 forecasting capability, and to improved mitigation strategies. 25

No abstract

The overall global-scale consequences of climate change are dependent on the distribution of impacts across regions, and there are multiple dimensions to these impacts. This paper presents a global assessment of the potential impacts of climate change across several sectors, using a harmonised set of impacts models forced by the same climate and

The 2015 Paris Agreement commits countries to pursue efforts to limit the increase in global mean temperature to 1.5°C above pre-industrial levels. We assess the consequences of achieving this target in 2100 for the impacts that are avoided, using several indicators of impact (exposure to drought, river flooding, heat waves and demands for heating and cooling energy). The proportion of impacts that are avoided is not simply equal to the proportional reduction in temperature. At the global scale, the median proportion of projected impacts avoided by the 1.5°C target relative to a rise of 4°C ranges between 62 and 95% across sectors: the greatest reduction is for heat wave impacts. The 1.5°C target results in impacts that would be between 27 and 62% lower than with the 2°C target. For each indicator, there are differences in the proportions of impacts avoided between regions depending on exposure and the regional changes in climate (particularly precipitation). Uncertainty in the proportion of impacts that are avoided for a specific sector depends on the range in the shape of the relationship between global temperature change and impact, and this varies between sectors.