Extreme Weather Events In Europe: Preparing For Climate Change Adaptation

By Norwegian Meteorological Institute

27 October, 2013
Dnva.no

This study arises from the concern that changes in weather patterns will be one of the principal effects of climate change and with these will come extreme weather. This is of considerable consequence in Europe as it impacts on the vulnerability of communities across the continent and exposes them to environmental risks. It is now widely recognised that failures in international efforts to agree on the action necessary to limit global climate change mean that adaptation to its consequences is necessary and unavoidable (Solomon et al., 2007).

The changes anticipated in the occurrence and character of extreme weather events are, in many cases, the dominant factor in designing adaptation measures.

Policy communities within the EU have begun to consider appropriate responses to these changes and an EU adaptation strategy is under active development and implementation. There are also sectoral EU initiatives, for example on water shortages and heat waves, and, at a regional level, on planning for floods and storms.

The basic and unavoidable challenge for decision makers is to find workable and cost-effective solutions when faced with increased probabilities of very costly adverse impacts. Information about the nature and scale of these changes is essential to guide decisions on appropriate solutions.

Agenda-setting for climate change and adaptation has to take place in a social or/and political setting. Scientific information about temporal changes in the probability distributions of extreme weather events over Europe, the main focus of this report, is important for informing the social and political processes that it is hoped will lead to adequate climate-change adaptation measures in Europe.

This report is focused on providing a working-level assessment of the current state of the quantitative understanding of relevant extreme weather phenomena and their impacts.

Given the current state of scientific knowledge and the requirement to deliver a timely input to policy processes, the scope of this report is inevitably limited and it does not set out to provide a comprehensive coverage of all extreme weather phenomena and impacts in the EU. However, there are crucial aspects of additional risk and uncertainty from extreme weather that are highly relevant to the work of EU policy makers and we aim to cover them in this report.

The report has been prepared by a Working Group sponsored by the Norwegian Academy of Science and Letters under the chairmanship of Professor Øystein Hov. EASAC has collaborated on this work and published a condensed version of the report as part of its work on climate change and public policy issues which can be found on www.easac.eu

The objective of the present document is to provide a handy tool for policy makers to whom the background science may not be immediately accessible. The report starts with a description of the way in which extreme weather phenomena are characterised, in particular through the use of statistics. Subsequent chapters then describe the state of knowledge about the key extreme weather phenomena, the impacts they have and some of the broad approaches that have been taken, within sectors and at different geographic scales, to reduce these impacts through adaptation measures. In a final chapter we consider the particular case of adaptation within European agriculture. The report concludes with a summary of major findings and some broad recommendations for strengthening the information available for decision makers in Europe.

Executive Summary

The current position:recent changes in extreme weather patterns

1. The Earth’s climate has changed in the past due to geophysical factors, including the oscillation of its axis as it travels round the sun. Over recent years, however, human activity has been the cause of more profound and rapid change. Since the industrial and agricultural revolutions, the use of fossil fuels as energy sources, together with intensive agriculture and deforestation, have led to an increase in atmospheric carbon dioxide (CO2) and methane (CH4) levels which are now higher than at any time in the last 800 000 years. This will have a profound effect on the Earth’s climate, which will warm as a result.

2. Meteorological and climatological measurements of climatic change in Europe show that intense precipitation has become more severe and more frequent, with complex variability in the sense of a non-uniform spatial pattern. However, the lack of a clear large-scale pattern can be expected when dealing with extremes, as the number of events is small and they take place at irregular intervals and with irregular intensity.

3. Winter rainfall has decreased over Southern Europe and the Middle East, and has increased further north. The latter increase is caused by a pole-ward shift of the North Atlantic storm track and a weakening of the Mediterranean storm track. Short and isolated rain events have been regrouped into prolonged wet spells.

4. Some recent changes in the pattern of weather extremes have been considerable: in some parts of Europe, observed trends to more and longer heat waves and fewer extremely cold days and nights have been observed. Since the 1960s, the mean heat wave intensity, length and number across the Eastern Mediterranean region have increased by a factor of five or more. These findings suggest that the heat wave characteristics in this region have increased at higher rates than previously reported (Kuglitsch et al., 2010).

5. Increasing summer dryness has been observed in Central and Southern Europe since the 1950s, but no consistent trend is found over the rest of Europe. In a study of river flows in Europe by Stahl et al. (2010), a regionally coherent picture of annual stream-flow trends emerged, with negative trends in southern and eastern regions, and generally positive trends elsewhere – especially in northern latitudes – suggesting that the observed dryness is reflected in the state of rivers.

6. The risk of and vulnerability to floods have increased over many areas in Europe, due to a range of climatic and non-climatic impacts, whose relative importance is sitespecific. Flood damage has increased substantially, however observations alone do not provide conclusive and general proof as to how climate change affects flood frequency. An ubiquitous increase in flood maxima is not evident.

7. The insurance industry reports a pronounced increase in the number of weather-related events, which have caused significant losses, for example, wind-storms and floods globally and, to a somewhat lesser degree, in Europe. There is still insufficient knowledge about the extent to which these changes can be found in wind and precipitation observations and whether they are driven by global warming. Some of the hazard-driven increases of loss events may have been masked by human prevention measures, in particular in the case of flood loss data, as these can be influenced much more by preventive measures than wind-storm losses.

8. In some regions, low-lying coastal zones are considered to be particularly vulnerable to climate change, especially through sea-level rise, changes in wave climate and in storminess. In Portugal, one of the European countries most affected by coastal erosion, the shoreline is retreating at an annual average of as much as 9 m in places, mainly as a result of weakening of river sediment supplies due to dams and embankments. However, the question of past trends in storm number and intensities is still open. More North European wind storms are seen when the state of the North Atlantic Oscillation (NAO) is in a positive phase, but the causes determining the phase of the NAO are still unclear.

The outlook

1. The main tool for providing insights into possible climate futures is computer modelling. Using modelling studies with other inputs, some of the likely trends for the future can be seen. In particular, a consensus is emerging about the likely future pattern of extreme weather events in Europe. Heat waves are very likely to become more frequent, with increased duration and intensity, while the number of cold spells and frost days are likely to decrease. Fewer cold extremes are expected, but occasional intense cold spells will still occur, even in the second half of the 21st century. Southern Europe and the Mediterranean Region may expect a combination of a reduction in annual precipitation and an increase in average temperatures. Summer dryness is expected to further increase in Central and Southern Europe during the 21st century, leading to an enhanced risk of drought, longer dry spells, and larger soil moisture deficits.

2. Climate model simulations also suggest more frequent droughts throughout Europe, although flash and urban floods triggered by local intense precipitation events are also likely to be more frequent. Other likely consequences of climate change include decreased annual river flow in Southern Europe and increased water stress in regions that are already vulnerable to reductions in water resources.

3. Studies suggest higher precipitation intensity for Northern Europe and increased dry-spell lengths for Southern Europe. High intensity and extreme precipitation are expected to become more frequent within the next 70 years. The increased frequency is estimated to be larger for more extreme events, but will vary considerably from region to region. The seasonality and structure of precipitation is expected to change.

4. It is currently not possible to devise a scientifically sound procedure for redefining design floods used, for example, in planning for food defence (for example, 100- year floods) due to the large range of possible outcomes. For now, adjusting design floods using a climate-change factor is recommended, but flood-risk reduction strategies should be reviewed on regular basis, taking new information into account.

5. Climate model simulations indicate an increase in windstorm risk over Northwestern Europe, leading to higher storm damage when there is no adaptation. Over Southern Europe, severe wind storms are projected to decline. Economic impacts of extreme weather events

1. Much of the information about the economic impacts of extreme weather events comes from data on insured losses compiled by the insurance industry such as that held by the Munich Re company in its NatCatSERVICE, comprising about 30 000 data sets of individual loss events caused by natural hazards. This analysis shows that, in general, the frequency of weather-related loss events has increased significantly at a global level, in contrast with losses from geophysical hazards such as earthquakes or tsunamis, which have shown only a slight increase.

2. In Europe the increase in losses from extreme weather events has been about 60 % since the 1980s. This is low compared with the number of loss events suffered in other continents, which, in the case of North America, are now 3.5 times the number of the early 1980s. Of the loss events registered in the NatCatSERVICE database, the great majority, 91 %, are from extreme weather and, of these, 75 % are from storms and floods.

3. The pattern of loss events varies across Europe, with larger numbers in the United Kingdom and West-Central Europe and lower numbers in Scandinavia and Northern Europe. In Southern Europe, heat waves, droughts and wildfires are the most numerous events, whereas in Western and Central Europe floods and storms predominate.

4. The economic loss burden has been considerable, with an estimated loss of € 415 billion (€ 415×109) since 1980 (2010 values). The most costly hazards have been storms and floods, amounting to a combined total of almost € 300 billion.

5. Weather events have also been responsible for considerable loss of life in Europe, estimated at around 140 000 lives lost since 1980. The largest impacts on life have come from heat waves such as those in Central Europe in 2003.

Adaptation strategies: responses to changes in extreme weather

1. At the European level, climate-change adaptation is part of the strategies for improving the resilience of specific sectors, such as health and transport, reflecting the expected impacts of climate change on them. It is expected that the severity of climate change will be greatest in the Southern and Mediterranean parts of Europe and that there will be particular problems in some specific geographical areas including mountain areas, coastal zones and islands. Agriculture, fisheries, human health, water resources, biodiversity and ecosystems and physical infrastructure, including transport and energy are expected to be particularly affected.

2. Much of the adaptation action required in the EU will be carried out by individual Member States. The European Environment Agency (EEA) is collaborating with the European Commission (EC) to establish a European climate adaptation platform (Climate-Adapt), which aims to support Member States in the development of National Climate Change Adaptation Plans.

3. Some adaptation measures will require action at a European level, including where there are shared resources such as sea-basins and rivers or geographic features such as mountain ranges that cross national borders. There will also be a particular requirement for EU action where sectors or resources have strong EU integration, for example, agriculture and fisheries; water, biodiversity and transport; and energy networks.

4. For many of the adaptation measures that will require EU-level action, some are sector-specific requiring the general improvement of storm resilience in electricity networks. Some have regional and cross-sectoral implications such as flood-risk management along the courses of the great rivers of Europe with implications for
agriculture and for physical infrastructure.

5. The current EU strategy rests on information sharing and integrating adaptation into EU policies.

Conclusions

1. A regional European pattern in recent trends in extreme weather and their impacts has been discerned. Some of the extreme weather phenomena associated with climate change are increasing in frequency and intensity within Europe. In some cases the impacts of these changes have had a significant effect on societies and economies throughout Europe, although at very different scales in different regions.

2. There is an observed trend to more and longer heat waves and fewer extremely cold days and nights in some parts of Europe. In the past, estimates of changes have suggested that they are modest, but a recent re-analysis of data showed that, since the 1960s, the mean heatwave intensity, length and number across the Eastern Mediterranean region had increased by a factor of five or more (Box 3.1). It is expected that the trends towards longer and more intense heat waves will continue with further climate change.

3. Increasing summer dryness, which is associated with drought, has been observed in Central and Southern Europe since the 1950s, but no consistent trend has been found over the rest of Europe. For some areas, notably Central and Southern Europe and parts of Northwestern Europe, it is expected that this trend will continue with global warming.

4. Extreme precipitation, often associated with floods and damage to infrastructure and crops, appears to be increasing in severity and frequency.

5. Climatic and non-climatic factors such as human settlement have increased flood-risk vulnerability over many areas. Flood damage and the number of large floods have increased substantially in Europe, however a ubiquitous increase in observed records of annual flood maxima is not evident.

6. Projections for the future indicate increases in flood risk over much of Europe. However, the projections are uncertain, partly because information about the future evolution of precipitation is uncertain but also because of confounding non-climatic factors.

7. The question of past trends in storm numbers and intensities is still open. More North European wind storms are seen when the state of the NAO is in a positive phase, but the causes that determine the phase of the NAO are still unclear.

8. In some regions, low-lying coastal zones are considered to be particularly vulnerable to climate change, especially through sea level rise, changes in wave climate and in storminess.

9. Insurance industry data clearly show that the number of loss-relevant weather extremes has increased significantly globally and to a smaller, but still relevant, degree in Europe. There is increasing evidence that at least part of these increases is driven by global warming. Some of the hazard-driven increases in loss events may even have been moderated by human activities through loss prevention measures.

10. Human factors play a part in moderating the impactsof heat waves. Extreme heat has had a considerable impact on human health in Europe with significant mortality, notably during the heat waves of 2003 and 2010. However, in many parts of Southern Europe, heat waves of a similar scale occur frequently for years without the same level of impact.

11. For many crops in Europe, weather extremes are the major factor in climate-change impacts on production. An increased frequency of extreme weather events is likely to be unfavourable for crop production, horticulture and forestry.

Recommendations

It is recommended that science-driven climate services need to be developed on national and regional levels in Europe. As the societal risk related to climate change is significant, research into the processes and drivers of the climate system need to intensify, with a particular emphasis on manifestations that carry the largest risk to humans and society. These manifestations are related to the extremes of the weather-parameter probability distributions, rather than on their mean. Climate services should evolve in an interactive way with the public and private user communities in order to devise effective adaptation measures and to:

• provide easy access to relevant meteorological and hydrological observations, climate projections and climate products, with climate adaptation as the main focus;

• facilitate the production of clear information about national/regional climate;

• provide updated information on historical, current and future climate trends;

• facilitate and disseminate relevant quality-controlled analyses of the present climate and projections of climate change to governments, counties, municipalities, business interests and research. When there are events that focus attention on impacts of extreme weather events, individual efforts to assimilate the lessons learned into planning should be encouraged. The use of real-world indicators, such as recurring problematic conditions and external expertise where municipalities or organisations are involved in relevant research projects, should also be encouraged as ways of raising the local profile of climate-change adaptation.