Urban Heat Islands - Planet Earth Online

Chris - If summer ever arrives in Britain, the nation will need to switch from worrying about potential floods to the effects of excess heat.

Cities and towns experience elevated temperatures compared to rural areas because artificial surfaces, such as roads and buildings, absorb solar radiation during the day, store this heat up and then slowly release it during the evening.  It results in some parts of the city - so-called urban heat islands - getting warmer than others.

Catherine Muller, from Birmingham University's Urban Climate Laboratory, is studying the problems of urban heat in a project called 'Hi Temp'.

Planet Earth podcast presenter Sue Nelson went to meet Catherine in a fenced off piece of grass in the City, containing various pieces of equipment, and asked her how urban temperatures can compare to surrounding areas...

Catherine - During heat wave events you can get them up to five, six, seven degrees warmer, for a city like London you could be looking at, maybe, 10 degrees warmer.   One of our partners is the Birmingham City Council and they are particularly interested in where the high risk areas are within Birmingham.  For example, if you cast your mind back to the 2003 heat wave, which does seem a long time ago today, we had in the UK alone about 2,000 excess deaths. Most of those were occurring within the city centre and that was always attributed to the increase in temperatures.  So you are seeing a big impact on human health in these regions.

Sue -   So you've got to measure temperatures certainly for a start, so I'm assuming then that some of these bits of equipment, quite a few of which I've not actually seen before, and couldn't quite tell what it is although I'm suspecting that the spinning cups on some of them are measuring wind speed...

Catherine -   That is correct.  We've got rain gauges which are monitoring rainfall...

Sue -   And next to it is that a...it looks like a long temperature-

Catherine -   These are surface temperature probes. We have a few on the grass which is measuring grass temperature and we've got a few on the concrete which is just giving us the artificial surface temperatures.

Sue -   Now, this is just one weather station in one part of Birmingham.  We're talking about Britain's second largest city here, how are you measuring across the city itself in terms of so that you understand the differences in temperature and other effects that cross the city?

Catherine -   This site here is essentially measuring urban background conditions, it's not completely in the city centre it's just slightly out in leafy Edgbaston, so we call this an urban background site.  At Paradise Circus within the city centre the Met Office have just opened up a truly urban weather station site.  That's bang in the middle of town, so that will give us some urban readings but that has just opened up in the last 12 months or so.  What has traditionally happened in terms of getting an idea of these urban heat islands is we've actually used the data from this site here and we've compared it to the Met Office's rural station site which is just outside of the Birmingham conurbation.  So what we've done is actually just taken those pairs of data sets and actually looked at how they differ to get an indication of how temperatures vary.  Obviously that's not good enough to be able to assess how weather and air temperatures vary across a region as big as Birmingham. We've got so many different land uses in the area; we need to get a better indication of how they actually do vary.

Sue -   And how have you done that?

Catherine -   This is where Hi Temp comes in. We're setting up the Birmingham Urban Climate Laboratory which will be a very dense network of weather equipment across Birmingham.  In fact we think it should be the world's densest urban network once it's actually completed.  So it's a big thing for the UK, let alone Birmingham.  What we will do is we will have 25 automatic weather stations very similar to some of the equipment you can see here.  They will be located in primary electricity substations.  The reason we've gone for electricity sub stations is that one of our partner is Eon, specifically Western Power, a part of Eon.  They are actually interested in how urban heat and excess temperatures can actually have an impact on energy supplies.  In the future with changing climate obviously temperatures will increase and this could have an impact on energy supplies.  We've got 130 or so going out into schools across the region.  These are Wi-Fi battery powered so all the data gets sent across the school Wi-Fi.  We are putting them into school sites so that they are secure, we can use their Wi-Fi to transmit the data and also to get the school kids involved because it's really nice to get kids at school actually involved in some real science.

Sue -   This is quite an exciting stage you're at now, it's getting it underway.

Catherine -   It's just taking off at the moment.  We're starting to install the equipment.  That's a big job in itself.  Once we've got that set up though it shouldn't take too much to actually look after them because all the data is coming in automatically to us every hour, all we need to do is process the data, quality check it and then we can upload it onto a website that anyone can actually access if they want to have a look at what the temperatures and the weather is actually doing across the region.

Sue -   And as you've already highlighted this will give you an insight into a whole range of procedures, be it energy usage, temperature, buildings...

Catherine -   Well we've mentioned about the health and the energy impacts of urban heat.  Obviously that has an impact on the transport infrastructure so we get rails that can buckle under excess heat, even tarmac can be melted on the roads.  So we obviously need to know what areas of the city have a higher risk of these things occurring and then we can actually think about ways to mitigate and adapt to any kind of changes that are going to occur with climate change.