Higher temperatures, rising sea levels, heavier rain, and more severe storms will all present problems, writes Kieran Hickey
CLIMATE change, including global warming, is the biggest threat to the Earth and sets huge challenges for society going forward. There are four broad challenges: Temperature, sea levels, precipitation, and storminess.
Ireland would benefit from a modest temperature rise, in isolation. We are a relatively cool country and reliant on heating in winter, via oil, natural gas, peat, and wood, which are all major producers of greenhouse gases.
The renewable energy sector in Ireland is growing, but has a way to go before it will dominate energy production. A modest increase in temperature would shorten the winter heating season, thereby reducing greenhouse gas emissions, but some of this would be offset in summer by the increasing use of air conditioning, which uses more energy than space heating. A modest temperature rise would also be beneficial to farming, with an already much longer grass-growing season extended further and with less reliance on stored fodder and less need to bring animals indoors in winter.
However, with rising temperature come rising sea levels, as a result of a combination of the thermal expansion of water heating up (the molecules get further apart) and the melting of mountain glaciers and major ice sheets in Greenland and Antarctica. The recent 2019 Intergovernmental Panel on Climate Change Report suggested a possible sea-level rise of up to 1.1m this century, the highest estimate so far. To put this figure into perspective, for the whole of the 20th century, global sea levels rose by between 0.1m and 0.15m, and what is happening for the 21st century will be in addition to that rise.
Ireland, as an island nation with significant low-lying coastal areas, is already vulnerable to sea-level rise and this vulnerability will only increase as the century progresses. All our major urban areas are either coastal or estuarine, including Dublin, Belfast, Cork, Waterford, Limerick, Galway, and Derry. Most already have significant flood problems, compounded by risks from coastal flooding, river flooding, or a combination of both. In a modern context, cities like Cork would not have been built in their current location.
Sea-level rise of even one centimetre a year won’t be noticeable on the ground, but the cumulative rise dramatically affects the vulnerability of the coastline. This will push up the normal tidal cycle to new heights and when big storms come along, the storm surge, which is the extra height of water above the normal tidal cycle, will reach new records. On top of this will be big waves, raising the water levels even further during these storms. These new water-height changes will test coastal defence structures to their limit, will over-top others, and will flood existing flood-prone area with higher water levels than previously and, increasingly, will start to flood areas that have no history of coastal flooding.
This means that what was a one-in-100-year coastal flood event could quickly become a one-in-10-year coastal flood event, or even more frequent. In order to prevent this from happening, and from damaging urban settlements and key infrastructure and amenity areas, significant expenditure will be needed. Obviously, the cost will be high and not all areas will be protected, leading to what is known as involuntary strategic retreat, especially of rural, low-value, low-lying coastlines, which will be left to erode away.
In terms of precipitation, Ireland already gets very significant amounts of rain, which even in ordinary years can cause flooding across the country and especially in the winter. The current projections for this century are overall, increased precipitation for Ireland and increased seasonality of that precipitation. In the latter case, this will mean more rain in the winter, leading to more, and severer flood events. This may also offset the gains from an increased grass-growing season, if the lands are flooded and unusable for farming. Events like last year’s heatwave and drought are likely to increase in frequency, putting pressure on water resources in the summer, leading to water-use restrictions, which occurred in many areas last year. This water-resource deficit will be enhanced by the mismatch between water resources and human populations, with the east coast having the greatest populations, but the least water resources. This has led to calls to pump some water from the Shannon, during the winter floods, along a new channel, or pipe, across Ireland, to the east coast, to be used when needed.
In terms of storminess (and I am referring to both our normal mid-latitude storms, which mainly occur from November to February, and to the remnants of hurricanes like Ophelia and Lorenzo, which mainly occur in September and October and which appear to be affecting Ireland more frequently and with more severity).
Currently, the projection for Ireland, in terms of our vulnerability to storminess, is suggesting somewhat fewer mid-latitude storm events in total, but those that do occur will be much more severe.
Severe events, like Storm Darwin and ex-hurricane Ophelia, have the most impact, including causing loss of life, injuries, and destruction across the country.
Ireland faces a wide variety of challenges in term of climate change. How do we respond to these challenges, from a personal, familial, community, business and local and national government perspective? When people look back from 2050 or 2100, how will they judge us?
Kieran Hickey, Department of Geography, University College Cork