Ireland in a warmer world; scientific predictions of the Irish climate in the twenty-first century

Abstract

The challenge of global climate change, and its potentially devastating consequences, are now widely acknowledged.Climate scientists throughout the world are working to increase our knowledge of climate processes and our ability to anticipate the nature and magnitude of changes resulting from increased concentrations of greenhouse gases.In Ireland, the C4I Project (Community Climate Change Consortium for Ireland) has been in operation for five years.A substantial national climate modelling capability has been built, and a comprehensive data-base of results on the future climate of Ireland is now available on the C4I website (http://www.c4i.ie) for the benefit of Irish scientists, policy makers and other users.This report describes Ireland's changing climate, based on a comprehensive series of computer simulations.The computations were carried out by the C4I team of scientists at Met ireann and at the UCD Meteorology & Climate Centre.The first phase of the C4I Project finished in December, 2007, but the collaborative work is continuing.The background to the project, and the regional climate model (RCM) approach to predicting changes in the climate, are reviewed in the opening chapter.Using a regional climate model, a range of climate simulations for the twenty-first century has been completed.Uncertainties in the predictions are reduced by combining several different model simulations in an ensemble.This ensemble procedure is reviewed in Chapter 2. The EU-funded ENSEMBLES Project is also described.A complete review of the principal results emerging from the Project is presented in Chapter 2. For a brief summary of the key results and conclusions, see box following this summary on page (v).The impact of climate change on storm surges is discussed in Chapter 3. Surge data were produced using the Regional Ocean Model System (ROMS) of Rutgers University.This model consistently reproduces the sea level variability in Irish waters.The results show an increase in storm surge events around Irish coastal areas in a warmer climate.In Chapter 4, the impact of climate change on North Atlantic wave heights is investigated, with a particular focus on coastal regions surrounding Ireland.While the impact is seasonally dependent, there is evidence that extreme wave heights may increase by up to 10% in some Irish waters.Chapter 5 describes an investigation into the impact of warmer ocean temperatures on storminess.The results show an increase in the frequency of very intense cyclones, and also increases in the extreme values of wind and precipitation associated with them.This implies an increased risk of storm damage and flooding in vulnerable Irish coastal areas.The observed trends in sea level and sea surface temperature around Ireland are studied in Chapter 6.Since the 1980s there has been a general warming trend of 0.3-0.7Cper decade in Irish waters, comparable to the trend over land.This is consistent with what has been observed globally and is expected to continue over the coming decades.Sea level rise will also exacerbate the impacts of changing storm surge and wave patterns in coastal areas and may also affect water tables through salt intrusion. page IIIThe impacts of climate change on hydrology are considered in Chapter 7. Nine Irish river catchments are modelled, and an amplification of the seasonal cycle across the country, with a rise in winter stream flow and a reduction in summer flow, is found.Increased winter flow means an elevated risk of flooding.Decreases in summer stream flow will have significant consequences for water availability, water quality, fisheries and recreational water use.A comparison between statistical downscaling and dynamical downscaling is presented in Chapter 8.The two methods are directly compared for their ability to predict precipitation over Ireland.There are differences in detail of the results produced by the two approaches, but the overall signal of wetter winters and drier summers is reflected consistently by both methods.Renewable energy sources are of growing importance.The impact of climate change on available wind energy is considered in Chapter 9.The simulations show an increase of about 10% in available wind power in future winter months in the middle of the century and a decrease of a comparable magnitude in the summer months.Increasing the horizontal resolution of the downscaling grid has a positive impact on the quality of the winds, since local effects, such as the distortion of the airflow by surface features, are better resolved.Chapter 10 describes some high-resolution experiments using the MM5 model, a limited-area non-hydrostatic model.The benefits of higher resolution for these simulations was not as clear as expected, and suggest that much more work to develop parameterization schemes suitable for this resolution is required.Until this is done, the substantial additional computational cost of the highest resolution simulations is probably not justified. The influence of climate change on ozone concentrations and ultra-violet radiation inIreland is described in Chapter 11.This study relates ozone concentrations to stratospheric circulation and temperature patterns.It suggests that the recovery in the atmospheric ozone may be slower than anticipated from a reduction in CFC emissions.Risk of skin cancer in Ireland will remain significant.Moreover, a warmer Irish climate is likely to increase outdoor leisure activities and potentially increase the exposure to damaging UV-B.The following chapter investigates the influence of climate change on heating and cooling energy demand in Ireland.Energy demand has already slightly decreased in the south of the country.A clear, continuing decrease in demand is predicted for the rest of this century.In Chapter 13, the expertise that has been developed through the C4I Project, and the climate modelling capability that has been built, is reviewed.Strong international links have been made with other climate-related projects, such as ENSEMBLES and the EC-Earth Project.Met ireann, in collaboration with the UCD Meteorology and Climate Centre and the Irish Centre for High-End Computing (ICHEC), will continue the collaborative modelling work to predict Ireland's future climate with increasing precision and confidence.Some of the key scientific issues to be addressed in future work are reviewed in this chapter.A full list of publications, conference presentations, and other outputs of the C4I Project, completes the report.The primary output is the comprehensive data-base of model results, which can be accessed on the C4I website (http://www.c4i.ie).This provides a wide range of simulation data (e.g.time series and maps of weather elements for individual simulations).We plan to develop and extend the range of products in this resource as the climate modelling collaboration continues.