Ireland’s climate and weather is variable over periods of hours to days, it changes quickly and often going from showers to sunshine. However, we can get stable periods of hot or cold spells too and the storms can be strong and damaging. Prolonged droughts or freezer are rare but do happen.
The seasons bring changes, the summer is warmer than the winter and with autumn and spring being in-between. But this can vary. There are cold wet summers and dry warm winters.
So what does this all mean looking a bit more long term? By doing that, we can work out the average and the range of variability. So, if we average temperature data over a period of thirty years, we can work out how hot or cold our summers and winters might be on average and how these might vary. This is how we used to work out what our average climate was like. Some linked features such as floods and droughts were calculated over longer period such 100 years or serval 100 years. These were referred to as return periods, i.e., this event would on average occur once in a 100-years.
In a stable climate we would expect that these values would, on average, be the same decade after decade. However, we now know that is not the case. Analysis of over 100 years of observational data shows that our climate is changing. This is most evident in the temperature data and particularly over recent decades. Analysis of these data show that the global average temperature has increased by 1.0 C since pre-industrial times (IPCC, 2018).
It is not only temperature that has changed. There have been changes in rainfall and decline in snow and ice. Sea-level has increased as the oceans also heat up. These changes have been assessed by the Intergovernmental Panel on Climate Change (IPCC) in their major assessment reports.