DoENI/SNIFFER Scoping Study of Climate Change Impacts in Northern Ireland

WHAT COULD THE CLIMATE OF NORTHERN IRELAND BE DURING THE 21^ST CENTURY?

Dr Nick Betts, School of Geography, Queen's University Belfast

The atmospheric concentration of carbon dioxide (the gas most heavily implicated in the enhanced greenhouse effect) has risen by some 35 per cent in less than 200 years. There is increasing evidence that a human influence on global climate, due to the enhanced greenhouse effect, has been detected. Carbon dioxide concentration at present is approximately 360 ppmv (parts per million by volume), and dependent on the emissions scenario which is adopted, is expected to increase to 498-697 ppmv by the 2080s.

Possible future climate changes for Northern Ireland have been estimated, based upon the UKCIP98 climate scenarios (UKCIP, 1998). Climate changes relate to three future thirty-year periods centred on the 2020s, the 2050s and the 2080s. The 2020s are considered to be representative of the period 2010-2039, the 2050s of 2040-2069 and the 2080s of 2070-2099. Changes during each of these periods are calculated as the change in the thirty-year mean climate with respect to the 1961-90 average.

The climate change scenarios stated here are those anticipated to result from greenhouse gas forcing of the climate system. It is important to note, however, that natural climate variability will affect this human-induced climate change. Failure to appreciate this fact may result in impacts assessments attributing the effects on social or environmental indicators of both human-induced climate change and natural climate variability as if they were the effects of human-induced climate change alone.

• Conclusions from the scenarios include:
  Annual mean temperatures show a warming of +0.5 to 1.2°C by the 2020s, +0.8 to 2.0 by the 2050s and +1.0 to 2.8°C by the 2080s. Warming above 1961-1990 mean temperatures is slightly greater in summer (JJA) than winter (DJF) until the 2050s. Thereafter the opposite applies, culminating in winter warming of +1.0 to 2.9°C and summer warming of +1.1 to 2.5°C above 1961-90 means by the 2080s.
• Annual rainfall increases up to 5 per cent by the 2050s, and 13 per cent by the 2080s. Winter rainfall increases between 6 and 13 per cent by the 2050s; summer rainfall may increase by up to 8 per cent. Rainfall intensities are expected to increase in both winter and summer.
• Potential evapotranspiration may increase by up to 12 per cent in winter and 18 per cent in autumn.
• The mean annual number of accumulated degree-days for a maximum temperature above 25°C (relevant for e.g. air-conditioning) more than trebles by the 2080s. The mean annual number of accumulated degree-days for a minimum temperature below 0°C (relevant for e.g. road maintenance) decreases more than 70% by the 2080s.
• Accumulated degree-day temperatures above 5.5°C (reflecting the intensity of the plant growing season) increases by more than 5% per decade over the 21st century.
• While the number of winter gales is expected to decrease, extreme storms may occur more often.
  

More detailed information on the present and possible future climate of Northern Ireland is available at the web pages of the DoE/SNIFFER Climate Change Impacts Scoping Study for Northern Ireland: http://boris.qub.ac.uk/sniffer/.

Reference
UK Climate Impacts Programme (1998). Climate Change for the UK: Scientific Report. UK Climate Impacts Programme Technical Report No. 1, Climatic Research Unit, Norwich. 80 pp. Available from http://www.ukcip.org.uk