How dark is your sky? Estimating artificial light in Ireland from satellite imagery 2015-2019

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Satellite data provides insight on Ireland’s light emissions from 2015-2019
  • Ireland has lower artificial light emissions than other European countries such as the UK, Portugal and the Netherlands
  • Irish cities have lower light emissions than international counterparts such as London and Paris
  • Dublin county has much higher light emissions than any other county
  • Dublin’s Pembroke South Dock and the North Inner City have high light emissions
  • South and West Kerry and West Mayo have very low light emissions

Go to release: “How dark is your sky?” Estimating artificial light in Ireland from satellite imagery, 2015-2019

The Central Statistics Office (CSO) has today (19 November 2020) released the Frontier Series publication, “How dark is your sky? Estimating artificial light in Ireland from satellite imagery, 2015-2019”.

As a CSO Frontier Series publication it uses new methods which are under development. Publishing outputs under the Frontier Series allows the CSO to provide useful new information to users and get informed feedback on these new methods and outputs whilst at the same time make sure that the limitations are well explained and understood.

Commenting on the release, Tim Linehan, Statistician, said: ‘This CSO Frontier Series publication analyses satellite data to estimate artificial light emissions in Ireland between 2015 and 2019. The source data is from the United States National Oceanic and Atmospheric Administration (NOAA) Earth Observation Group (EOG) and represents a high-quality, free source of satellite imagery. Satellite data analysis is a commonly used method measuring light emissions.

The analysis shows that Ireland in January 2019 has significantly lower average artificial light emissions with 0.92 units than the UK (1.78 units), Portugal (2.52 units) and the Netherlands (7.43 units). The units used are nW/cm2/sr.

When comparing with international cities using the EU NUTS-2/3 geographical regions, Dublin city (24.29 units) has significantly lower light emissions in January 2019 than Paris (43.52 units), Inner London West (53.27 units) and Inner London East (46.78 units)

At a county level, in January 2019, Dublin has much higher measured average emissions (11.53 units) compared to the second highest county Louth (1.70 units). The counties with the next highest emissions are Kildare (1.49 units), Meath (1.15 units), Limerick (1.03 units) and Cork (0.91 units). The counties with the lowest emissions in 2019 were Leitrim (0.53 units), Mayo (0.55 units), Kerry (0.58 units) Roscommon (0.64 units) and Sligo (0.65 units).

A similar trend is seen at Local Electoral Area (LEA) as the 10 LEAs with highest emissions were located in Dublin. Pembroke South Dock had the highest level of emissions with 69.94 units. The two LEAs with lowest emissions were South and West Kerry (0.42 units) and West Mayo (0.45 units). 

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