The warmer than usual weather currently being experienced in Ireland and across Europe raises important questions: is this "just" the weather or is it climate change? And how can we know? For Ireland Met Éireann forecast temperatures of up to 17C, while many places across Europe broke daily record temperatures in October, with parts of France and Spain reaching 35C. Something about this month's weather, and our understanding of what constitutes "normal" weather for this time of year, is changing.
This unseasonably high temperature is occurring because of a heat dome moving across western Europe from the east. A heat dome occurs when high-pressure atmospheric conditions persist over a particular region. This strong, high-pressure acts like a lid, trapping heat, and so the air temperature rises. As well as higher than average temperature, heat domes can result in increased humidity, weaker winds, and overall reduced rainfall. This kind of weather can then last for days or sometimes weeks, depending on the path of the jet stream.
Jet streams are fast bands of air which flow around the globe at around ten thousand metres above the Earth’s surface. They usually blow from west to east and have a significant influence on temperature patterns and storm activity. The jet stream has been meandering further north over Ireland than typical for the time of year, pulling in the plume of warm air from western Europe, and resulting in the warmer than expected weather.
A recent study led by Dr Samantha Hallam from Maynooth University has shown that the jet stream is changing. Between 1871 and 2011, the average jet stream latitude over the North Atlantic has moved northwards in all seasons with an increase of 3° from 44° to 47° north in winter, and a 10 mph increase in speed to 132mph. The poleward migration of the jet stream is consistent with the decreasing temperature difference observed between the equator and the Arctic over the period, associated with the changing climate.
Climate change or just unusual weather?
The evidence that climate change is occurring globally at accelerated rates is unequivocal according to the IPCC. A recent World Meteorological Organisation (WMO) report shows that temperatures in Europe have increased at more than twice the global average over the past 30 years, rising 1.5C in just three decades. Ireland is seeing trends that reflect this warming. Met Éireann reported that October 2022 was the 17th consecutive warmer than usual month, with recorded temperatures at 25 of its weather stations 1.2-2.2C above monthly averages.
In a recent analysis of 504 extreme weather events across the globe, 71% were found to have been more severe or more likely because of human driven climate change. Another recent study shows that, in 732 sites on six continents, an average 37% of all heat-related deaths during 1991-2018 can be directly attributed to climate change.
One way to help understand if extreme weather is a result of climate change is with the science of Extreme Event Attribution. This is a methodological examination of weather events potentially occurring outside of typical long-term climate patterns. It examines their occurrence, frequency, and severity to analyse if these are increasing or not.
Attribution sciences aims to measure how anthropogenic, or human driven, climate change directly affects recent extreme weather events. It is also valuable in linking what can sometimes seem like the abstract concept of global climate change with the immediate and very personal experience of weather; the kind of everyday experience influencing if we choose to wear a coat or not.
How changes in weather patterns change us
This is the cultural experience of weather. It is how we make sense of the world we live in. It creates meaning for us. Right now, the heat dome may bring some benefits to our immediate experience of weather and climate such as a little relief from ever increasing energy bills, or flowers still blooming in our parks and gardens.
But the longer-term impacts of changing patterns of how weather is societally experienced include cultural change. This is because the idea of weather is based on a cultural understanding of what it means to live in a stable climate. We know what to do throughout the seasons in response to weather because of our continuity of experience. We understand its meaning, and so we can respond psychologically to the winter season by adapting to darker mornings and evenings. We may anticipate cosy evenings at home, hearing rain and wind against the window.
This cultural understanding of the weather within a stable climate has influenced our practical everyday adaptations too. We know what to do at any time because it’s what we have always done. November means managing higher heating costs, stocking up on fuel, getting the winter coats out of the back of the wardrobe. Weather, the weather we know, is imbued with cultural meaning and response.
Cultural perceptions of, and responses to, the weather both impact on and are impacted by climate. Within a changing climate, we have to try and understand what this means for us as a society.
This article originally appeared on RTE Brainstorm