[MUSIC] In this session, we're going to talk about the units and the yardsticks that we're going to use in order to, for the treatment that is going to follow. It is not going to be a very exciting session, is not going to get our pulses racing. But since we want to do something which is based in science, it is important to have these basic tools and ways of communicating. So we're going to introduce units. And and the problem is then when you deal with climate science, you have a huge number, you have gigatons, you have terrible lattes. And these are such big numbers that we tend to stare at the name of the number of the size of it. And we don't really get a feel for how big it is. So I try as much as possible to reduce everything to human sizes, perhaps sometimes very often by dividing by the population of the earth and using tricks like that. So I'm trying as much as possible to relate these big numbers to human size chunks. We're also going to introduce measures that are linked to changes in temperature and to explain why direct temperature measures are not appropriate. And finally, I'm going to introduce the concept in this session or we see you to equivalent emissions. So as I said, let's get our tape measures in place. We are going to measure energy in kilowatt hour, careful. This is a common but strange unit. If I were to start from scratch, I will not use this unit. But it is used by everybody. So there is no point in swimming against the tide. And why is it a strange unit? Because the kilowatt is not a unit of energy is a unit of power. Power is energy per unit time. Therefore, if you want energy, you have to say kilowatt hour, kilowatt day, kilowatt year or whatever. So when I say kilowatt hour, I do not mean kilowatt per hour, but I mean kilowatt times our. And while using this kilo, what measure at all? Well, one reason is because it is almost universally use. It has become ingrained in the usage, especially when we talk about climate change. But also because if we turn it down to one kilowatt hour, reducing the size is, as I always said, it is a nice human size and I can explain easily how you can get a feel for it. One kilowatt hour is called one unit on your electricity bill in the U K, one unit of electricity costs 10 p. And one kilowatt hour per day is the size of energy, which is easy to understand. Take a 40 watt light bulb, regular sized light bulb and leave it on all day. This will use one kilowatt hour per day. So by leaving on your 40 watt light bulb all day, it will cost you 10 p. A toaster is a lot more expensive in energy usage. It uses one kilowatt. This is power. So this is energy per second. It is fantastically expensive. One nuclear power station produces about one gigawatt, so one nuclear power stations only powers one million toasters active all the time anyhow. I will try to explain to express energy usage using kilowatt hour per day. Measuring emissions now. Greenhouse gases, including carbon dioxide, methane, nitrous oxide, also water vapor, but for reason they will explain, we will leave that to one side. All these different gases have different warming up characteristics. In order to get a common yardstick, we're going to express all emissions in equivalent amounts of carbon dioxide. Equivalent in this context means having the same warming effect as Co2 over the period of 100 years. One billion tons of CO2 or CO2 equivalent is called it gigatons. Careful, a common mistake. There is a distinction between carbon and Co2 and sometimes when you see, wait, you have to be careful what is the weight of carbon or weight of Co2. Dominic Lawson in the Independent, we go over his article later in this book, but right that we sent seven gigatons of Co2 in the atmosphere. That is wrong. We sent seven gigatons of carbon in the atmosphere. Co2 is made up of two oxygen's, each one atomic weight 16 and one carbon atomic weight 12. So we are actually sending two times 16 plus 12, divided by 12, 44 divided by 12 hour seven gigatons are actually 26 gigatons of Co2 in the atmosphere. I've run over 26. I seem to remember it is something like 25.6 but between friends, let's call it 26. And finally some terminology. Scientific notation is very handy, meaning 10 to the 3rd, 10 to the 5th, 10 to the 10th is very handy. Unfortunately, it is not used a lot in climate science and people like to use these greek words, kilo, mega, giga and tera. So it is good to have. Or perhaps you can write it on a piece of paper and keep it as a cheat sheet kilo. We all know is 10 to 3. And the symbol is K mega is 10-6. It's a million. And the symbol is M, a billion is giga. And the symbol is G and A trillion. 10 to the 12, a thousand billion is tera. And the symbol is T. So this concludes our not very exciting but hopefully useful session about units [MUSIC]
