Detailed measurements of the thermal pollution in Greater London and a look at the long term trend.

WHO: Mario Iamarino, Dipartimento di Ingegneria e Fisica dell’Ambiente, Università degli Studi della Basilicata, Potenza, Italy
Sean Beevers,  Environmental Research Group, King’s College London, London, UK
C. S. B. Grimmond, Environmental Monitoring and Modelling Group, Department of Geography, King’s College London, London, UK

WHAT: Measuring the heat pollution of London with regards with to both the space and time the emissions occur in.

WHEN: July 2011 (online version)

WHERE: International Journal of Climatology (Int. J. Climatol.) Vol. 32, Issue 11, September 2012

TITLE: High-resolution (space, time) anthropogenic heat emissions: London 1970–2025 (subs. req)

Cities have a rather unique position in our world when we think about climate change. They are both the source of the majority of emissions, but also due to their dense nature they are the sites where the greatest innovations and reductions in emissions can occur fastest.

If you want to be able to harness the creativity and innovation of cities to be able to reduce emissions, you need to know what emissions are coming from where and when. You need data first.

That’s where these scientists from Italy and the UK stepped in to work out exactly how much waste heat the city of London was emitting. Waste heat is an issue because it contributes to the Urban Heat Island effect where the temperatures in cities can be higher than the surrounding area, which can be deadly in summer heat waves and lead to greater power usage.

Something interesting that I hadn’t considered before is that concentrated emissions can also change the atmospheric chemistry in a localised area.

The researchers looked at some very detailed data from between 2005-2008 for the city of London and broke it down into as accurate a picture as they could. They looked at heat from buildings looking at the differences between residential and commercial buildings and the different ways the different building uses would emit heat.

They looked at transport data using traffic congestion, the London Atmospheric Emissions Inventory, and data from several acronym-happy government departments to work out from what kinds of vehicles at what times of the day the waste heat was being emitted and at what temperature each different type of fuel combusted. They didn’t count trains (underground or overground) because they are mostly electric (and some of them recover waste heat from breaking) or small boats which didn’t emit enough to be counted.

They looked at the heat emitted by people at various stages of activity, age and time of day assuming a 1:1 ratio of females to males. They even looked at the standard metabolic rates of people to work out how much heat a person emits exercising, resting or sleeping!

What all that number and formula crunching told them was the total average anthropogenic heat flux for London was 10.9 Wm^-2 (watts per square metre). This calculates to be 150 Terawatt hours of waste energy (in the form of heat), which as a comparison is all of the electricity used in Sweden in 2010.

Of that total, 80% came from buildings with 42% being domestic residences and 38% being industrial buildings. The next biggest source of heat was from transport, at 15% of the 10.9 Wm^-2. Of the transport category, personal cars were the biggest contributor (64% of the transport portion).

Human heat only contributed 5.1% of the total (0.55 Wm^-2), so maybe they’re not doing enough exercise in London? The information had peaks and valleys of heat loss – winter releases more waste heat than summer, because heating systems for winter are more widespread than air conditioners in summer. The industrial building emissions were concentrated in the core of the City of London (especially Canary Wharf where there are many new centrally heated/cooled high rise offices) while the domestic building emissions were much more spread around the centre of London.

Once they got all the data from 2005 to 2008, they considered trends from 1970 projected out to 2025 to see how great a role heat emissions could play in climate change. Using data from the Department of Energy and Climate Change, the London Atmospheric Emissions Inventory (LAEI) and data on population dynamics and traffic patterns, they estimated that there would be an increase in all contributors to heat emissions unless the UK Greenhouse gas reduction targets are fully implemented.

The reduction targets are for 80% reduction by 2050 (against the baseline of 1990 emissions). From the research indicating that buildings are the biggest heat emitters (and are therefore burning more energy to keep at the right temperature), this would mean there’s a great need for increasing building efficiency to meet those targets.

The paper notes that if the Low Carbon Transition Plan for London is implemented, the average waste heat emissions for London will drop to 9 Wm^-2 by 2025, but in the central City of London, the best emissions reductions are likely to only be to 2008 levels, due to the expected growth in the area.

So what does any of this mean? It means London now has the data to know where they can find efficiencies that can complement their greenhouse gas mitigation programs. Because that’s the thing about combating climate change – it’s not a ‘one problem, one solution’ kind of issue. We need to do as many different things as possible all at once to try and add up to the levels of decarbonising that the world needs to be doing to avoid catastrophic climate change. So go forth London, take this data and use it well!