Assessing climate change impacts, sea level rise and storm surge risk in port cities: a case study on Copenhagen

This study illustrates a methodology to assess the economic impacts of climate change at a city scale and benefits of adaptation, taking the case of sea level rise and storm surge risk in the city of Copenhagen, capital of Denmark. The approach is a simplified catastrophe risk assessment, to calculate the direct costs of storm surges under scenarios of sea level rise, coupled to an economic input-output (IO) model. The output is a risk assessment of the direct and indirect economic impacts of storm surge under climate change, including, for example, production and job losses and reconstruction duration, and the benefits of investment in upgraded sea defences. The simplified catastrophe risk assessment entails a statistical analysis of storm surge characteristics, geographical-information analysis of population and asset exposure combined with aggregated vulnerability information. For the city of Copenhagen, it is found that in absence of adaptation, sea level rise would significantly increase flood risks. Results call for the introduction of adaptation in long-term urban planning, as one part of a comprehensive strategy to manage the implications of climate change in the city. Mitigation policies can also aid adaptation by limiting the pace of future sea level rise

A global ranking of port cities with high exposure to climate extremes

This paper presents a first estimate of the exposure of the world’s large port cities (population exceeding one million inhabitants in 2005) to coastal flooding due to sea-level rise and storm surge now and in the 2070s, taking into account scenarios of socio-economic and climate changes. The analysis suggests that about 40 million people (0.6% of the global population or roughly 1 in 10 of the total port city population in the cities considered) are currently exposed to a 1 in 100 year coastal flood event. For assets, the total value exposed in 2005 across all cities considered is estimated to be US$3,000 billion; corresponding to around 5% of global GDP in 2005 (both measured in international USD) with USA, Japan and the Netherlands being the countries with the highest values. By the 2070s, total population exposed could grow more than threefold due to the combined effects of sea-level rise, subsidence, population growth and urbanisation with asset exposure increasing to more than ten times current levels or approximately 9% of projected global GDP in this period. On the global-scale, population growth, socio-economic growth and urbanization are the most important drivers of the overall increase in exposure particularly in developing countries, as low-lying areas are urbanized. Climate change and subsidence can significantly exacerbate this increase in exposure. Exposure is concentrated in a few cities: collectively Asia dominates population exposure now and in the future and also dominates asset exposure by the 2070s. Importantly, even if the environmental or socio-economic changes were smaller than assumed here the underlying trends would remain. This research shows the high potential benefits from risk-reduction planning and policies at the city scale to address the issues raised by the possible growth in exposure

The double trade-off between adaptation and mitigation for sea level rise: An application of FUND

This paper studies the effects of adaptation and mitigation on the impacts of sea level rise. Without adaptation, the impact of sea level rise would be substantial, almost wiping out entire countries by 2100, although the globally aggregate effect is much smaller. Adaptation would reduce potential impacts by a factor 10-100. Adaptation would come at a minor cost compared to the damage avoided. As adaptation depends on socio-economic status, the rank order of most vulnerable countries is different than the rank order of most exposed countries. Because the momentum of sea level rise is so large, mitigation can reduce impacts only to a limited extent. Stabilising carbon dioxide concentrations at 550 ppm would cut impacts in 2100 by about 10%. However, the costs of emission reduction lower the avoided impacts by up to 25% (average 10%). This is partly due to the reduced availability of resources for adaptation, and partly due to the increased sensitivity to wetland loss by adaptation

Economic impacts of climate change in Europe: sea level rise

This paper uses two models to examine the direct and indirect costs of sea-level rise for Europe for a range of sea-level rise scenarios for the 2020s and 2080s: (1) the DIVA model to estimate the physical impacts of sea-level rise and the direct economic cost, including adaptation, and (2) the GTAP-EF model to assess the indirect economic implications. Without adaptation, impacts are quite significant with a large land loss and increase in the incidence of coastal flooding. By the end of the century Malta has the largest relative land loss at 12% of its total surface area, followed by Greece at 3.5% land loss. Economic losses are however larger in Poland and Germany (483 and 391 million, respectively). Coastal protection is very effective in reducing these impacts and optimally undertaken leads to protection levels that are higher than 85% in the majority of European states. While the direct economic impact of sea-level rise is always negative, the final impact on countries’ economic performances estimated with the GTAP-EF model may be positive or negative. This is because factor substitution, international trade, and changes in investment patterns interact with possible positive implications. The policy insights are (1) while sea-level rise has negative and huge direct economic effects, overall effects on GDP are quite small (max −0.046% in Poland); (2) the impact of sea-level rise is not confined to the coastal zone and sea-level rise indirectly affects landlocked countries as well (Austria for instance loses −0.003% of its GDP); and (3) adaptation is crucial to keep the negative impacts of sea-level rise at an acceptable level

Global estimates of the impact of a collapse of the West Antarctic ice sheet: an application of FUND

The threat of an abrupt and extreme rise in sea level is widely discussed in the media, but little understood in practise, especially the likely impacts of such a rise including a potential adaptation response. This paper explores for the first time the global impacts of extreme sea-level rise, triggered by a hypothetical collapse of the West Antarctic Ice Sheet (WAIS). As the potential contributions remain uncertain, a wide range of scenarios are explored: WAIS contributions to sea-level rise of between 0.5 and 5 m/century. Together with other business-as-usual sea-level contributions, in the worst case this gives an approximately 6-m rise of global-mean sea level from 2030 to 2130. Global exposure to extreme sea-level rise is significant: it is estimated that roughly 400 million people (or about 8% of global population) are threatened by a 5-m rise in sea level, just based on 1995 data. The coastal module within the Climate Framework for Uncertainty, Negotiation and Distribution (FUND) model is tuned with global data on coastal zone characteristics concerning population, land areas and land use, and then used for impact analysis under the extreme sea-level rise scenarios. The model considers the interaction of (dry)land loss, wetland loss, protection costs and human displacement, assuming perfect adaptation based on cost-benefit analysis. Unlike earlier analyses, response costs are represented in a non-linear manner, including a sensitivity analysis based on response costs. It is found that much of the world’s coast would be abandoned given these extreme scenarios, although according to the global model, significant lengths of the world’s coast are worth defending even in the most extreme case. This suggests that actual population displacement would be a small fraction of the potential population displacement, and is consistent with the present distribution of coastal population, which is heavily concentrated in specific areas. Hence, a partial defence can protect most of the world’s coastal population. However, protection costs rise substantially diverting large amounts of investment from other sectors, and large areas of (dry)land and coastal wetlands are still predicted to be lost. Detailed case studies of the WAIS collapse in the Netherlands, Thames Estuary and the Rhone delta suggest greater abandonment than shown by the global model, probably because the model assumes perfect implementation of coastal protection and does not account for negative feedbacks when implementation is imperfect. The significant impacts found in the global model together with the potential for greater impacts as found in the detailed case studies shows that the response to abrupt sea-level rise is worthy of further research

Economy-wide impacts of climate change: A joint analysis for sea level rise and tourism

While climate change impacts on human life have well defined and different origins, the interactions among the diverse impacts are not yet fully understood. Their final effects, however, especially those involving social-economic responses, are likely to play an important role. This paper is one of the first attempts to disentangle and highlight the role of these interactions. It focuses on the economic assessment of two specific climate change impacts: sea-level rise and changes in tourism flows. By using a Computable General Equilibrium (CGE) model the two impacts categories are first analysed separately and then jointly. Considered separately, in 2050, the forecasted 25 cm. of sea level rise imply a GDP loss ranging from (-) 0.1% in South East Asia to almost no loss in Canada, while redistribution of tourism flows - which in terms of arrivals favours Western Europe, Japan, Korea and Canada and penalises all the other world regions - triggers GDP losses ranging from (-) 0.5% in Small Island States to (-) 0.0004% in Canada. GDP gainers are Australia, New Zealand, Western Europe, Middle East and South Asia. The impact of sea level rise and tourism were simulated jointly and the results compared with those of the two disjoint simulations. From a qualitative point of view, the joint effects are similar to the outcomes of the disjoint exercises; from a quantitative perspective, however, impact interaction does play a significant role. In six cases out of 16 there is a detectable (higher than 2% and peaking to 70%) difference between the sum of the outcomes in the disjoint simulation and the outcomes of the joint simulations. Moreover, the relative contribution of each single impact category has been disentangled from the final result. In the case under scrutiny, demand shocks induced by changes in tourism flows outweigh the supply-side shock induced by the loss of coastal land