Recent mild weather in the UK has most of us looking forward to the spring. The days are clearly getting longer and most of us are waking up in the daylight and getting home from work in daylight. Around a month from now, the clocks go forward for seven months of lighter evenings. The question of when spring really starts in the northern hemisphere is a matter of some debate with two major schools of thought.
1st March: The Meteorological Start of Spring
The start of spring is just over a week away if you go by the meteorological calendar. This is how the MET Office and their equivalents around the northern hemisphere define spring. It is simply easier to break down the seasons into complete months: March-May is spring, June-August is summer, September-November is autumn and December to February is winter.
But with climate change and other natural erratic changes in the seasons, meteorologists state that we cannot truly define when spring (or any other season for that matter) really starts. In December 2015, some areas in southern England were growing daffodils. We didn’t get a proper winter as we might understand them. This is why The MET Office and their equivalents have a set three-month period each year regardless of what the weather does. They need cut off dates to measure weather and temperature cycles against which to compare trends.
Yet those who disagree that something as arbitrary as the modern calendar should determine spring, this system is not really much use to anybody except meteorologists in tracking month by month trends over the years.
20th-23rd March: The Astronomical Start of Spring
The astronomical start of spring for the northern hemisphere is the date when the hours of daylight and darkness are equal. Our planet is tilted at a roughly 23.5-degree angle. It wobbles on its orbit around the sun. During this wobble, there are two points of the year when it is practically upright – late March and late September. This is how we get equal daylight in both hemispheres and why we even have an equinox.
Yet the date varies every year because the orbit around the sun is not precisely 365 days. It’s 365 days, 6 hours and a few extra minutes. It’s the reason we have a leap year every fourth year and why the atomic clock adds a leap second every so often. In this case, spring is determined by the day that the plant is upright in its orbital plain when weather patterns are mildest no matter where you are in the world. It is the beginning of autumn in the southern hemisphere and the start of spring for the north.
There is also a cultural reason to continue with this date for the northern hemisphere – it is generally the time when ancient cultures began their agricultural season including spring festivals to mark the return of the sun.
Are They Both Right or Both Wrong?
Both dates feel quite arbitrary from a certain point of view. After all, especially in the modern age, we will have noticed a warming of the temperature for some time. Most of us are not as reliant on the agricultural year as we used to be. We live in a surplus economy in a global market and not a subsistence economy that depends heavily on the seasons.
Besides which, it would be impossible (and pointless) to calculate the true beginning of any season each year. Such a task may be useful for climate scientists to mark the erratic nature of the changing seasons, but for the rest of us, it will make very little difference. However you choose to mark the beginning of spring, you are neither right nor wrong.