Millions of people in countries in the Northern Hemisphere, including the United States and India, suffer from heat waves even before the summer solstice, which marks the first day of summer.
Daylight periods will shorten after the solstice, while nights will become longer, but there will likely be little respite in the period of high temperatures.
Climate activists on Wednesday painted the Stonehenge monument in the United Kingdom to demand the phase-out of fossil fuels, which contribute to climate change blamed for prolonged heatwaves and extreme weather conditions around the world.
Revelers gather at one of the world’s most famous prehistoric sites to celebrate the summer solstice. Stonehenge is believed to have been built with a specific alignment with the summer solstice sunrise.
So what is the significance of the summer solstice, which marks the longest day of the year?
Here’s what you should know.
When is the summer solstice in 2024?
The 2024 summer solstice falls on Thursday, June 20, at 8:50 pm GMT. People across the Northern Hemisphere will experience the solstice at the same time.
The Northern Hemisphere summer solstice typically falls between June 20th and 22nd. This year’s solstice is the first in 228 years and last occurred on June 20, 1796.
The last solstice on June 22nd was in 1975 – since then and until last year, it had been occurring on June 21st.
The date changes occur because the time it takes Earth to orbit around the Sun each year doesn’t exactly line up with our calendar year.
Although Earth’s orbital cycle and tilt on its axis remain relatively constant over short periods, gradual and natural variations create a slight shift in the solstice date every few decades.
Why is it the longest day of the year?
During the summer solstice, the Northern Hemisphere will experience the longest period of sunlight in a day, or the longest day of the year.
This is due to the Earth’s position in its orbit around the Sun and the way the North Pole is tilted closer to the Sun during the summer solstice. The sun’s rays reach the Northern Hemisphere at their most direct angle, resulting in the longest period of daylight.
Areas further from the equator will have more daylight hours than those closer. For example, parts of India closest to the equator will have almost 14 hours of sunlight.
The Arctic Circle will experience a polar day, also known as midnight sun, with 24 hours of sunlight.
Is it the hottest day of the year?
Despite the long hours of sunshine, it won’t be the hottest day of the year.
This is due to a concept called “seasonal delay”. The Earth and its atmosphere take time to warm. This is similar to how the hottest part of the day usually occurs in the afternoon rather than midday when the sun is highest in the sky.
The oceans, which cover about 70% of the Earth’s surface, absorb, store and slowly release heat. Ocean warming contributes to the overall delay in reaching maximum temperatures.
Why will it get hotter now?
The hottest days of summer are likely to occur several weeks after the summer solstice, usually in July or August in the Northern Hemisphere.
The heat from the long daylight hours will have accumulated on Earth. Additionally, although the days begin to get shorter immediately after the solstice, they are still quite long and the sun remains relatively high in the sky, meaning the solar energy received remains substantial.
Earth’s surface and atmosphere are efficient at absorbing this solar energy, but they release heat gradually.
Due to these factors, temperatures will continue to rise until the end of July or August, when the energy balance points to more energy lost than gained.
Aren’t there already several heat waves?
From India to Greece and the USA, heat waves have hit several countries in the Northern Hemisphere.
A heat wave is marked by at least two or more days of unusually high temperatures compared to typical averages for a location during that period or month.
A heat wave in the northeastern US, for example, occurs when the temperature reaches or exceeds 32.2 degrees Celsius (90 degrees Fahrenheit) for three consecutive days.
In India, a heat wave is declared when the maximum temperature reaches at least 40ºC (104ºF) in the plains, or 30ºC (86ºF) in mountainous regions, according to India’s meteorological department.
In the US, heat domes – trapped high-pressure hot air masses – are exacerbating heat waves.
Humidity can also cause certain areas to feel hotter.
And the Southern Hemisphere?
At the same time as the summer solstice in the North, the Southern Hemisphere will experience the winter solstice.
This is because the seasons are reversed there, so while the astronomical start of summer occurs in the north, astronomical winter begins in the south.
Astronomical events are related to the Earth’s position in space, while the meteorological start of a season is based on the calendar year and the annual temperature cycle.
The Southern Hemisphere will have the shortest day of the year, or the one with the shortest duration of sunlight.
This story originally appeared on Aljazeera.com read the full story
