3.1 Climate Variables

Hydrology

Observed

The analysis of river flows is complex and subject to large variability, so it is difficult to identify impacts of climate change. During the period 1954 to 2008, summer mean flows were dominated by decreasing flows while for winter there is a tendency for increases in mean flows. Annual and winter high flows are also dominated by increasing trends.

Drier summers could have effects on summer base-flows of rivers in Cork and the recharge of underlying aquifers. This ultimately has implications for the provision of drinking water, as was evident in many areas during the prolonged drought period of summer 2018.

Summary of Change

Increasing seasonality in hydrological regimes can be expected with likely decreased summer and increased winter flows.

Flood risk will increase due to a combination of higher river-flows and increases in extreme precipitation events. These events are likely to play a greater role in climatic events in the future. An example would be high tides coupled with fluvial and pluvial events, especially in the lower reaches of the River Lee and Cork Harbour.

Climate risks for Cork

Groundwater flooding, which is the emergence of groundwater at the surface away from river channels and watercourses, under conditions where the 'normal' ranges of groundwater level and flow are exceeded.

Pluvial, or surface-water flooding, which results from rainfall-generated overland flow that may occur during or immediately after intense rainfall events and before the runoff enters Cork city’s watercourse or drainage system.

Fluvial or river flooding, which occurs when excessive rainfall causes the River Lee to exceed its capacity.

Rainfall

Observed

Throughout Ireland, annual average rainfall amounts have increased by roughly 5% relative to the 1961-1990 baseline period, with this increase observed across all seasons. However, spatially, rainfall intensity and amounts vary with no clear direction of change yet apparent.

Summary of Change

Increasing seasonality in precipitation can be expected with drier summers likely.

An increase in the occurrence and magnitude of extreme rainfall events is also likely.

Climate risks for Cork City

Groundwater flooding

Pluvial flooding

Fluvial flooding

Sea Level

Observed

Satellite observations indicate that sea level around Ireland has risen by approximately

0.04m to 0.06m since the early 1990s.

Summary of Change

Sea levels are expected to increase for all Irish coastal areas.

Climate risks for Cork City

Coastal flooding, which occurs when normally dry, low-lying land is flooded by seawater.

Coastal erosion, which is the process of wearing away material from the coast line due to imbalance in the supply and export of material from a certain section.

Sea Temperature

Observed

The seas around Ireland have been warming at a rate 0.6⁰ C per decade since 1994, which is unprecedented in the 150 year observational record. The greatest warming has been observed over the Irish Sea.

Summary of Change

In line with global trends, the seas around Ireland are expected to continue warming. Warm seawater has a greater volume than cold seawater. As ocean temperatures increase, so will the total ocean volume. Any increased volume will cause the level of the water in the oceans to rise.

Climate risks for Cork City

Coastal flooding.

Coastal erosion.

Surface Air Temperature

Observed

Observations indicate an increase in the surface temperature for Ireland of 0.8°C since 1900. In addition, the number of warm days has increased while the number of frost days has decreased.

Summary of Change

Surface air temperatures are expected to increase everywhere compared to the present.

An increase in the intensity and duration of heat waves is expected.

Climate risk for Cork City

Heat waves may lead to severe drought and violent thunderstorms which impact upon human health, physical infrastructure, river water levels and fires.

Fewer frost days and milder night-time temperatures are expected.

Waves and Surges

Observed

Analysis of satellite data for the period 1988 to 2002 shows a general increase in wave height in the northeast Atlantic.

Summary of Change

The magnitude and intensity of storm wave heights are expected to increase for spring and winter.

Climate risks for Cork City

Coastal flooding;

Coastal erosion.

Wind Speed and Storms

Observed

For Ireland, observations indicate a high degree of yearly variability in wind speeds and, due to a lack of correlation in the available data, analysis of long term trends cannot yet be determined with confidence.

Summary of change

Projections indicate a decrease in wind speeds for summer and increases for winter.

An increase in the intensity of extreme wind storms is expected.

Climate risks for Cork City

Wind storms or high winds, that are defined as a having a wind speed greater than 50 km/h which equates to a Force 7 (28–33 knots) on the Beaufort wind force scale.