Global average temperature has increased by 0.6^oC ±0.2^oC since 1860 with accelerated warming apparent in the latter decades of the 20^th century. A further increase of 1.5-6.0^oC from 1990 to 2100 is projected, depending on how emissions of greenhouse gases increase over the period.

The last century was the warmest of the last millennium in the Northern Hemisphere, with the 1990s being the warmest decade and 1998 being the warmest year. Warming has been most pronounced at night than during the day.

Reductions in the extent of snow cover of 10% have occurred in the past 40 years with a widespread retreat also of mountain glaciers outside the polar regions.  Sea-ice thickness in the Arctic has declined by about 40% during late summer/early autumn, though no comparable reduction has taken place in winter.  These trends are considered likely to continue.  In the Antarctic, no similar trends have been observed.

One of the most serious impacts on global sea level could occur from a catastrophic failure of grounded ice in West Antarctica.  This is, however, considered unlikely over the coming century.

Global sea level has risen by 0.1-0.2m over the past century, an order of magnitude larger than the average rate over the past three millennia.  A rise of approximately 0.5m is considered likely during the period 1990-2100.

Precipitation has increased over the landmasses of the temperate regions by 0.5-1.0% per decade. Frequencies of more intense rainfall events appear to be increasing also in the Northern Hemisphere. In contrast, decreases in rainfall over the tropics have been observed, though this trend has weakened in recent years.  More frequent warm phase El Niño events are occurring in the Pacific Basin.  Precipitation increases are projected, particularly for winter, for northern middle and high latitudes and for Antarctica.

No significant trends in the tropical cyclone climatology have been detected. 

As a mid latitude country, these global trends have implications for the future course of Irish climate, and with it for a range of impacts which it is judicious to anticipate.  This report from Maynooth University presents an assessment of the magnitude and likely impacts of climate change in Ireland over the course of the present century.  It approaches this by firstly establishing scenarios for Irish climate based on global climate model projections for the middle and last quarter of the present century.  Secondly these projections are then used to assess probable impacts in key sectors such as agriculture, forestry, water resources, the coastal and marine environments and on biodiversity.

The purpose of the report is to firstly identify where vulnerability to climate change exists in Ireland, and what adjustments are likely in the operation of environmental systems in response to such changes.  In many sectors, such as in agriculture, some new opportunities are likely to arise for optimising climatic resources.  In other instances e.g water resource management, long term planning strategies will be necessary to avoid adverse impacts.  Long lead in times for adjustment characterise many sectors e.g. forestry and it is important to provide as much advance warning of likely changes as possible to enable adaptation to commence early.  By anticipating change it is possible for a country such as Ireland to position itself better to minimise the adverse impacts and maximise the positive aspects which global climate changes may present.

Current mean January figures are predicted to increase by 1.5^oC mid century with a further increase of 0.5^oC-1.0^o C by 2075.  By 2055, the extreme south and south west coasts may have a mean January temperature of 7.5-8.0^oC.  By then, winters in Northern Ireland and in the north Midlands will be similar to those presently experienced along the south coast.

Since temperature is a primary meteorological parameter, secondary parameters such as frost frequency and growing season length and efficiency can be expected to undergo considerable changes over this time interval.

July temperatures will increase by 2.5^oC by 2055 and a further increase of 1.0^oC by 2075 can be expected.  Maximum July temperatures in the order of 22.5^oC will prevail generally with areas in the central Midlands experiencing maximum July temperatures of 24.5^oC.

Overall increases in precipitation are predicted for the winter months of December- February. On average these amount to 11%. The greatest increases are suggested for the north west where increases of approximately 20% are suggested by mid century.  Little change is suggested as occurring on the east coast and in the eastern part of the Central Plain.

Marked decreases in rainfall during the summer and early autumn months across eastern and central Ireland are predicted.  Nationally, these are of the order of 25% with decreases of over 40% in some parts of the south-east.

Agriculture

The scenarios produced were used as input to crop simulation models for a range of present and potential future crops. The simulation results show that the expected climate changes will have a major impact on Irish agriculture which, though significant, cannot be regarded as potentially catastrophic.

For livestock production, the expectation of more frequent summer droughts will require significant supplementation of grazed grass.

Maize silage is increasingly likely to replace grass silage, potentially increasing grazing land areas. At the same time, increased production of grain maize is expected.  Barley is another potentially important source of energy for supplemental feeding of livestock.  The expected increases in cereal grain production may be expected to reduce the cost of feed barley.  However, the extra costs associated with irrigation may offset this if it proves necessary thereby bringing the economic viability into question, especially if barley is in competition with maize as a forage crop.

Soy-bean is an important supplemental source of livestock protein and is currently imported. Soybean has the potential to replace maize as the marginal crop in Irish agriculture.

Although warmer temperatures would be expected to result in shorter winter housing times for livestock, a trend towards wetter winters may result in problems of poaching and soil damage which may negate this.  The balance of grazing season length against winter rainfall will dictate the stored feed requirement, and the actual climate will dictate the choice of forage crop grown.  Opportunities to spread slurry or dirty water in winter will be substantially reduced and increased slurry storage requirements are likely to be needed.  Drought stress will become increasingly important.

Irrigation will become important for all crops in the eastern half of the country. This will have a major impact on the economics, machinery requirement and labour demand in both tillage and livestock systems.  Irrigation in dairying in the drought-prone southeast is currently justified economically only if water is available without charge and without the construction of farm reservoirs.  With the projected scenarios, a much greater area of agricultural land will be affected by drought loss, and the quantities of water involved to compensate by irrigation will be large.  Given that agriculture may have to compete for scarce summer water extraction with other users, the consequent economic effects may make crops with good potential uneconomical.

For potato, drought stress will be the most important limiting factor determining its viability and it is likely that potatoes will cease to be a commercially viable crop over much of Ireland.

Spring barley yield increases of approximately 25% are likely by 2055 with harvesting time earlier than today.  Maize grain yields are expected to increase dramatically, in western areas by more than 150% on today’s national average value.  Later harvest dates may pose an increased risk factor. 

Soybean will remain a marginal crop with the projected changes in climate.  Although temperature conditions become more favourable, precipitation changes mean that any gains could be negated by drier summers.

Irish agricultural land use distributions will alter in response to climate change.  A sharpening of east-west contrasts is likely to occur with livestock production dominating more to the west, and arable production dominating east of the Shannon.  Planning for irrigation is needed, particularly in the east, to ensure that water costs are acceptable and summer surface and ground water resources are not overused.

Using the climate scenarios as input to a hydrological model a number of likely impacts were suggested:

A widespread reduction in annual runoff is likely that will be most marked in the east and south-east of the country.  Winter runoff is predicted to increase in most of Ireland.

All areas will experience a major decrease in summer runoff, particularly in the east of the country. These reductions are likely to average approximately 30% over large parts of eastern Ireland by mid century.

The magnitude and frequency of individual flood events will probably increase in the western half of the country.

Seasonal flooding may occur over a larger area and persist for longer periods of time. Areas such as the Shannon basin will be vulnerable to these changes. Turloughs in western Ireland will also be particularly vulnerable to these changes.

During the summer months, long term deficits in soil moisture, aquifers, lakes and reservoirs are likely to develop.  It is likely that the frequency and duration of low flows will also increase substantially in many areas.

Since evaporative losses are also likely to increase during summer months, the water resource changes projected will have a significant effect on reservoir yields.  Water supply infrastructure is expected to come under growing pressure particularly in the Greater Dublin Area and the strategic implications of this are profound for a number of areas, particularly spatial settlement strategy.

The projected changes in water availability pose potential problems for the dilution of water-borne effluent.  With a greater frequency of low flow conditions, additional precautions will be required to ensure that concentrations of water pollutants do not give rise to acute effects.  It is recommended that minimum flow constraints are determined more conservatively, particularly where new urban or agricultural discharges are envisioned.  Greater incorporation of groundwater protection considerations is also recommended as aquifers assume increasing importance as sources of water supply as competition for reduced surface resources intensifies.

Forests cover 9% of the land area of Ireland, a figure which is planned to double by 2030.  In planning for the future, foresters must select species that will perform optimally over a full rotation of 40-50 years.  The time span that this report addresses is therefore highly relevant in influencing decisions being taken today in the forestry area.

Increased CO² concentrations and warmer temperatures are expected to benefit Irish forest growth.  Decreased summer rainfall, however, would negate this, as would any increase in storm frequency.  Secondary effects of climate change on forest productivity are also expected to be considerable.  Increased nutrient mineralisation in warmer temperatures is likely, though so also are changes in pest and disease incidence.

 Among the more significant of the latter are:

Green spruce aphid (winter warmth may encourage large population increases)

Pine Weevil (favoured by warmer temperatures)

Great Spruce Bark Beetle (currently a major problem in continental Europe)

European Pine Saw Fly (outbreaks occur on a series of three consecutive dry summers)

Fomes (optimum temperature for the growth of this fungus is 22.5^oC)

Phytopera Disease of Alder (recently identified in Ireland, may thrive in warmer, drier summers)

Honey Fungus (grows optimally at temperatures 20-25^oC; drought conditions renders trees more liable to infection).

Increased fire damage and increased deer and squirrel populations may also constitute negative indirect impacts of climate change on forestry. The interaction of different effects on forest growth is difficult to model, and different species will respond differently to changed climatic conditions.  However, there is no reason to believe that Sitka Spruce will not continue to be viable as the mainstay of commercial forestry in Ireland.  Despite this, there is a need to assess different provenances and species in long term research trials.  Particular attention should be given to alternative provenances for Douglas Fir and Western Red Cedar.  It is also recommended that the national tree-breeding programme should be re-assessed in the light of current knowledge on potential climate change with a view to the selection of traits that will accommodate and capitalise on these changes.  The potential for the production and transplanting of containerised nursery stock should also be reassessed.  Finally, it is urged that climate change scenarios should be included in the Forest Inventory and Planning System currently operated by the Forest Service in the Department of Marine and Natural Resources.

Changes in climate zonation were identified as having a range of impacts for natural ecosystems and biodiversity in Ireland, with considerable gaps in knowledge and data requiring further research to enable definitive conclusions in key areas.

The projected increases in temperature, combined with a longer growing season, were found to have the potential to cause distributional and behavioural changes on Irish species.  These are summarised below.

Climate changes are also likely to result in significant alterations to habitat conditions, though movement of habitats in Ireland will be restricted by non-climatic considerations.  Salt marshes and sand dune habitats are vulnerable to sea-level and climate changes and may experience significant changes in species composition.  Montane heaths are suggested as being particularly sensitive to climate change since many montane species are at the lower altitude/southern latitude edge of their distribution, with limited migration potential and an increase in temperature combined with summer drying may prove detrimental for this habitat in Ireland.  Similarly, peatlands are expected to suffer considerably from summer drying. An increase in decomposition, a reduction in peat formation, more erosion, changes in species composition, loss of carbon storage and an increase in acid runoff may occur in this already fragile resource.

 The existence of many marine species in the seas around Ireland is temperature controlled. However it is difficult to extrapolate predictions for land temperature increase to determine likely changes in sea temperatures, particularly for sub surface temperature changes which may be controlled by larger oceanographic circulation patterns.  Thus, although species which are sensitive to climate change may be identified quite easily, the extent to which actual changes will happen is difficult to predict.  Many of the impacts are likely to be indirect, where the reduction of one species allows for an increase in another through reduced competition.  A notable impact exists with respect to salmon farming, however, where an increase in sea temperature may have serious consequences. Salmon are near the southern range of their distribution and any increases in temperature could harm the commercial viability of farms and render them subject to increased algal bloom, pest and disease problems.
 

 
The coast is a dynamic environment which is constantly responding to processes operative on a range of time scales.  The single most important control on these processes is sea level which has varied considerably over the past 20,000 years.  Global sea level is projected to rise by approximately 0.5 metres by the end of the century, predominantly due to warming and expansion of the ocean water body.  In Ireland this figure will be modified by local land level changes, though a higher platform for wave attack will inevitably mean greater erosion of ‘soft’ coastlines, formed of glacial drift or unconsolidated materials. As a general approximation, about 1 metre land retreat can be anticipated on sandy coastlines in Ireland for every centimetre rise in sea level.

Inundation risk must also take into account storm surge events and high tide frequencies.  A value of 2.6m for extreme water level presently occurs with a return frequency of 12 years on the west coast and 100 years on the east coast.  These return periods of extreme water level are likely to reduce considerably as sea levels rise.  Combining these extreme water levels with a sea-level rise of 0.49m places approximately 300km² of land in Ireland at risk of inundation.

The loss of agricultural land cannot economically be defended against, and should not be contemplated. Where infrastructure is at risk of inundation, cost beneficial solutions may exist. This is particularly the case in the cities of Dublin, Cork, Limerick and Galway, and for assets such as railway lines, airports, power stations etc.  ‘Hard’ engineering solutions should be viewed as a last resort outside of these categories, however, as the evidence suggests this type of engineering can have dramatic effects further along the coastline.  Recommendations for coastal management policies to cope with sea-level rise would include the following:

no building or development within at least 100 metres of ‘soft’ coastline  

no further reclamation of estuary land

no removal of sand dunes, beach sand or gravel. Measures to protect and rehabilitate dune systems should be implemented.

all coastal defence measures to be assessed for environmental impact

where possible the landward migration of coastal features such as dunes and marshes should be facilitated
 

Conclusions
 

Climate changes over the next half century can be anticipated and their regional dimensions can be projected using statistical downscaling techniques.  While considerable uncertainty remains, especially with respect to precipitation changes, forward planning is now required to accommodate climate change in Ireland.

 

In key areas such as agriculture, water resources, coasts, marine and the natural environment, climate change impacts are likely to be considerable and significant adjustment of present management practices will be required to ensure a sustainable future.