S K Y G L O W

light pollution & the uk’s changing skies

01/

What is Skyglow?

On a clear, dark night it’s possible to view somewhere in the region of 4,000 stars. The number of stars we can see at night depends largely on the amount of light we emit from the Earth’s surface.

Artificial light that’s excessive, obtrusive and ultimately wasteful is called light pollution, and it directly influences how bright our night skies appear. With more than nine million streetlamps and 27 million offices, factories, warehouses and homes in the UK, the quantity of light we cast into the sky is vast. While some light escapes into space, the rest is scattered by molecules in the atmosphere making it difficult to see the stars against the night sky. What you see instead is ‘Skyglow’.

02/

Mapping Light from Space

Using images from overhead satellites, we looked into how bright our night skies appear from space, and how this has changed over the last 22 years.

We used images from two different satellites, the Operational Linescan System (OLS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) to calculate the brightness of the night sky.

03/

What the Skyglow Map Shows

You can see from the map that between 1992 and 2012 ‘Skyglow’ decreased by 28%. This is surprising since the UK population increased by 10%. One possible conclusion is that ‘Skyglow’ has reduced because we’re using better designed lighting that doesn’t create as much light pollution. Another possible cause is that overall we’re consuming less energy. However, the rise of energy efficient lighting may mean we’re still generating the same amount of brightness.

It’s important to remember that just because the average amount of ‘Skyglow’ has gone down across all regions, certain areas within regions may have actually increased in brightness. This would be offset by other areas getting darker. This could happen, for example, if there was a migration of people from one location to another.

A contributing factor to the decrease in light pollution, despite the population increase, could be the rise in multiple occupant housing. If people are relocating from rural to city locations, clustering in specific areas and living in more crowded conditions, this could cause light pollution to be higher, but confined to a smaller area. This would be countered by a much lower level of light pollution in areas outside of this concentration. Overall, this has the potential to lower the average level of light pollution.

04/

How Skyglow Affects You?

When we consider the damage of other types of pollution, ‘Skyglow’ may seem relatively harmless. However, the damage is far reaching, affecting plants, animals and humans in a number of ways.

“Lighting up the world carelessly leads to the waste of energy and money, along with significant costs to our quality of life. Our biology and ecology remain ill-equipped to handle night time brightness in extreme measures, and can suffer even in the presence of relatively small amounts. We encourage everyone, from property owners up to governments, to consider carefully the need for artificial light at night and to ensure that any light used is the proper amount, at the proper time, for only the task at hand. The need to light our activities can be balanced with preservation of the night through simple acts such as shielding light fixtures and lowering light intensities to appropriate levels.”

Dr. John Barentine from the International Dark-Sky Association (IDA)