Environmental Physicist Dr Eiko Nemitz of the Centre for Ecology & Hydrology, who was involved in hosting the launch of the UK Government’s Clean Air Strategy, explains the role of the BT Tower Observatory in air pollution monitoring.

Environment Secretary Michael Gove, supported by Health Secretary Matt Hancock, is today (Monday 14 January) launching the UK Government’s new Clean Air Strategy at the BT Tower Observatory in central London, which is operated jointly by the Centre for Ecology & Hydrology (CEH), the National Centre for Atmospheric Science (NCAS) and the Universities of Reading and York.

The BT Tower plays a distinctive role in tracking progress towards the emission reduction targets set out in the strategy for urban emissions. First established for short-term air quality observations back in of 2006 by CEH and the Universities of Birmingham and Reading, the focus of CEH’s work at the BT Tower is on quantifying urban emissions to the atmosphere. Its unique vantage position, 190m above street-level, enables us to provide an integrated estimate of the pollutant output for much of central London and independent scrutiny of the official emission estimates.

Results to date from the BT Tower Observatory (pictured below) have indicated that our urban emission estimates for some compounds such as the greenhouse gases carbon dioxide (CO2) and nitrous oxide (N2O – known as laughing gas) as well as for carbon monoxide (CO) are pretty accurate. By contrast, emissions of methane (CH4), another greenhouse gas, appear to be underestimated, but the urban emissions are relatively minor compared with its major sources such as emissions from cattle and landfill.  

Flux measurements of nitrogen oxides (NOx) on the tower contributed to the evidence that real-world vehicle emission of NOx are significantly larger than those reported by the automobile industry under test conditions. The official emission estimates have now been revised to account for this effect.

Characterisation of the particulate matter emitted from London identified tail-pipe emissions have been identified as expected, but the measurements also found a significant contribution from the use of cooking oils and detected solid fuel burning emissions.

These crucial measurements from the BT Tower Observatory provide an important independent scrutiny and assessment of whether the emission reduction targets set out in Defra’s Clean Air Strategy are being met.