Carbon Emissions: Stating the obvious

Since the dawn of time we have emitted approximately 1271 billions tonnes of carbon dioxide and we show no signs of slowing down. In 2008 we emitted approximately 32 billion tonnes of carbon dioxide. The BBC figure for 2012 is 35.6 billion tonnes.

Friends – I am barely keeping my head above water – work has never been busier – and there never seems to be a moment to reflect on things. But it is quarter-to-midnight on Sunday, and even though I have just spent several hours answering the Protons for Breakfast feedback, I feel like have a few more minutes of attention in me.

This week Protons for Breakfast was about Global Warming, and as I was answering the feedback I looked up the latest data on carbon dioxide emissions. By chance the BBC covered the same story with more recent data and the gloriously obvious headline

Carbon emissions are ‘too high’ to curb climate change

The numbers are astounding. Each year we collectively emit more than 1% of the total amount of carbon dioxide in the atmosphere. And an annual figure of 35 billion tonnes is an almost inconceivably large amount of ‘stuff’. If we wanted to do this for some other reason – then the task would seem overwhelming!

I got the impression that people at Protons for Breakfast really wanted to do something about this phenomenon – but they wanted guidance as to what would make a difference!. At it is at times like this that it is worthwhile to remember the words of Mahatma Ghandi who said:

“You may never know what results come of your actions, but if you do nothing, there will be no results.”

I wish I could find something more inspiring to say. I do feel that people’s consciousness is changing, and it does seem inevitable that we will – eventually – begin to face up to this problem. At some point in time, the graph at the top of the page will peak – and we will begin move beyond the carbon age. Let’s hope it is sooner rather than later.

Carbon Emissions from Planes: I eat my words

A Boeing 747: How much fuel does it use?

At the end of March I will be attending the 9th International Temperature Symposium, a conference that takes place once every 10 years. Sadly the event takes place at DisneyLand, California, roughly 5,500 miles away :-(. I am looking forward to spending a week discussing arcane details of temperature measurement and taking morning coffee in the Magic Kingdom East Foyer, but I am concerned at just how much carbon dioxide I will emit travelling to the conference.

I had worked this out before – and my answer was very roughly that the flight to LA from Heathrow emitted around 2 tonnes of carbon dioxide per passenger. But at the last Protons for Breakfast someone questioned this – and said it was nearer to half that! It took me ages to figure out that the reason we disagreed was simply in our estimation of how much fuel a Boeing 747 uses. I have looked hard to find the answer and… – I was wrong. The flight will ‘only’ emit around 1 tonne of carbon dioxide per passenger each way. Great!

The key information that led me to this conclusion was a post on this chat site that sounded trustworthy – it seemed to be from a 747 crew member.

Fuel burn (planning) 747-200s or 747-300s…

• Taxi/Takeoff : 1 tonne
• Assuming a heavy aircraft at 377 tonne takeoff weight, it will burn some 15 tonnes to initial cruise.
• First hours of cruise, expect some 13 tonnes per hour
• As the plane gets lighter, this will decrease to under 10 tonnes per hour.
• Descent, approach, landing, generally burn 3 tonnes.
• Taxi-in will be anywhere from 0.500 to 1 tonne
• Our company policy is to plan landing at destination with 14 tonnes reserve.
• The capacity of these airplanes is generally 155 tonnes with the 7 tanks configuration, or 165 tonnes  with 9 tanks…

So for a flight to LA from Heathrow taking roughly 11 hours and 5500 miles. Fuel use is therefore:

• Taxi/Takeoff : 1 tonne 
• 15 tonnes to initial cruise.
• 9 hours of cruising at an average of 11 tonnes per hour = 99 tonnes
• Descent, approach, landing, 3 tonnes.
• Taxi-in 1 tonne
• Total is approximately 120 tonnes 

I had previously assumed that the fuel used was nearer to 200 tonnes. We can work out the carbon dioxide emissions from this much fuel in several stages as follows:

• Fuel 120 tonnes = 120,000 kg
• Fuel is kerosene which has an approximate formula C12H26
• Molecular weight is 12 x 12 + 1 x 26 = 170
• Carbon fraction is roughly 144/170 ~ 84.71% by weight
• Mass of Carbon in fuel 101,640 kg
• Mass of CO2 from carbon in fuel 373,019 kg. This is a factor 44/12 = 3.67 larger than the mass of carbon in the fuel because of the addition of oxygen.
• Passengers on the plane is typically 350
• CO2 per passenger 1066 kg, or just over 1 tonne.

After thoughts. Firstly, I had checked that calculation several times, but my error was in the very first step: I >am< an idiot. Secondly, one tonne is still a large amount of carbon dioxide to emit in 11 hours. And thirdly, it’s important to get these things right. If the Protons’s attendee is reading this: sorry.

Time for more honesty and openness: this time on Carbon

UK Greenhouse Gas Emissions 1990 to 2009 in millions of tonnes of carbon equivalent. Also shown is the extrapolated linear trend and target

The Climate Change Act of 2008 commits the UK to reducing greenhouse gas by 80% from their 1990 levels by the year 2050. This is a pretty drastic statement of ambition and you might be wondering how we are doing now that we are 2 years into the 42 years set to achieve this. If you look up the Emissions Targets web page of the Department for Energy and Climate Change (DECC) and click around and you will be able to download data to allow you to plot a graph like the one at the  top of the page. And hey! we are pretty much on target! Looking at this you could feel proud of our National Achievement. You might wonder just exactly what we did to achieve this since you didn’t remember anything other than being irritated by compact fluorescent light bulbs, but then again maybe that’s all that it takes?

Alas the situation is not so rosy. The first clue comes when we look at UK electricity consumption (sorry: second-hand source). This has just gone up by 20% since 1990!

UK Electricity Generation (TWh) 1980 to 2008

Now the additional electricity we are using has not resulted in too much additional carbon emissions because since 1990 we have switched off a large number of coal-fired power stations  and brought on-line a large number of gas-fired stations. Gas-fired stations emit about half the carbon dioxide of an equivalent coal-fired station. However one important cause of the downward trend was recently identified by the esteemed Robert Watson in a BBC story. He pointed out simply that we have exported the manufacturing of a vast fraction of our national requirements to China. Individually this has saved us all money. It has also ‘saved’ us carbon, since the emissions associated with the manufacture of these goods are now associated with China, even though it is we who consume them! And additionally, the goods now have to be shipped half-way around the world.

The article just brought home to me how complex the problem of reducing emissions is. Although it may seem impossible to make progress when complexities such as attribution of emissions to particular countries arises, the first step is simply to openly and honestly account for the carbon emissions as they are now. Once we are clear about what is actually happening, then I have confidence that it will become possible to imagine the next step. But without clarity on the emission data, no progress is possible.