Across the country, we are seeing ‘signs of spring’. The first blooms of snowdrops and blackthorn flowers; hazel, horse-chestnut and alder trees forming tiny blossoms and fluffy catkins; frogspawn in sheltered ponds and grey herons with bright orange beaks near rivers. Not all of these heralds are pleasant, with clouds of hovering grey midges, dark green shoots of stinging nettles, and a cacophonous dawn chorus of early morning birds screaming for neighbours to stay off their turf and potential mates to talk about egg babies. Winter’s come and gone (sort of) and as stubbornly as the last tendrils of cold cling on, we shiver resolutely in the knowledge that spring and sun and slightly less rain will arrive eventually. When exactly it gets here is another question, as it depends entirely on who you ask.
Meteorologists, in Ireland and around the world, split the year into four equal three-month-long seasons based on temperature. The warmest three months are summer, the coldest three winter, and the leftovers shuffled into spring and autumn. Simple and straightforward enough, by this ruling spring starts in March and continues until the end of May.
However, if you ask an astronomer (or pagan, or astrologist, or anyone from a prehistoric culture who spent a bit too much time looking upwards) that’s a bit too late. The Earth has seasons because as it spins wildly around the sun it rocks back and forth, tilting on its axis so that the North and South hemispheres can take turns sunning themselves. In early spring the tilt of the axis relative to the sun increases, the days get longer, and the temperatures warmer.
As the hours of daylight increase we gradually approach the Spring Equinox (March 20th) which is a day split evenly down the middle, with 12 hours each of light and dark. Both spring and autumn have an equinox, while summer and winter have a solstice, the longest and shortest days of the year respectively. It makes sense that the solstices should lie right in the middle of the warmest and coldest seasons, and again given the leftovers, Spring and autumn fit nicely around the equinoxes. But that means that, astronomically, the start of spring is in early February.
Why is it different? Ireland getting more sunlight would surely lead to higher temperatures one would think, logically they shouldn’t be too far behind each other. The ever-topical and tempestuous answer, is climate. Weather and temperature are indeed heavily impacted by the planet’s tilt and hours of daylight, they are simply a bit slow to respond. It takes about six weeks for the climate to catch up to the planets movements, a meteorological buffering wheel of ocean currents and warming air-fronts. Thus the difference between the two estimates for spring springing upon us, is simply a matter of lag.
If you want to add another layer of confusion, ask an ecologist! Most ecologists tend to divide the year into six seasons, adding a prevernal (or pre-spring) season just after winter when only the toughest of flowers, like the crocus, are able to bloom. These six seasons don’t have any fixed dates though, and when they arrive is determined by natural indicators and events.
In fact there is an entire field of study for the ‘first signs’ of the seasons each year, Phenology. When amateur weather predictors in Ireland say that storms are coming if a dog eats grass or seals come into the strand, or that if a hen picks at her feathers a downpour is due, you may want to take them with a tablespoon or two of salt, but it is definitely true that nature knows more than we do about the seasons.
As the days get longer and warmer in Ireland, flora and fauna will get brighter and more active around us. Oak, ash, elder and hawthorn trees will dress themselves in leaves and buds, gardens and roadsides alike will bloom with tulips, daffodils and primroses, and migratory swallows like sandmartins will return to the island just in time for warmer weather. If the days are calm and warm, early butterflies might be visible as they come out from their winter hibernation, with orange-tip and small tortise-shell butterflies among the most common. March moths show up as their name suggests, while march hares might be seen madly ‘boxing’ each other during the mating season.
Ireland is known for celebrating spring earlier than the rest of the world, with the star-gazing Celts honouring Imbolc and the goddess Brighid at the start of February. Given that we can often experience all four seasons in one day here I don’t suppose it matters much the particular day spring starts. The season is a time of new growth, new life, and new warmth, and that at least is something everyone can agree on.
Aisling Brennan – Science Writer