Archive for March, 2015

CO2 Emissions: still a BIG and GROWING problem

March 16, 2015
CO2 emissions remaining constant is the equivalent having stopped accelerating towards the 'chasm of doom'

CO2 emissions remaining constant is analogous to  having stopped accelerating towards the ‘chasm of doom’. We are still driving there at high speed!

The global elite who read this blog – you, dear reader – will not have been fooled by the vaguely positive news reports about carbon dioxide emissions in 2014.

BBC: Global CO2 emissions ‘stalled’ in 2014

But just in case you have friends who lack your special qualities, please remind them that this is still a DISASTER!

Emissions staying constant is analogous to driving rapidly towards a cliff but not actually accelerating.

It does not correspond to applying the brakes, slowing down, stopping  or changing direction.

Annual Carbon Dioxide emission in billions of tonnes since 1750. The right hand axis shows this amount as a percentage of teh amount of carbon dioxide that was in the atmosphere in 1750.

Annual Carbon Dioxide emission in billions of tonnes since 1750. The right-hand axis shows this amount as a percentage of the amount of carbon dioxide that was in the atmosphere in 1750. The ‘news’ stories point out the last two data points are equal. The red data points are from CDIAC and the blue points from the IEA – links at teh end of the article. Click for a larger figure.

The real story

Back in 1750, Earth’s atmosphere contained about 2200 billion tonnes of CO2.

Since then we have added about 1350 Gt CO2 – that’s about 60% of the amount that was originally there.

Some of our emissions have dissolved in the oceans, and some have contributed to increased growth of plants and trees.

But a little over half is still in the atmosphere giving rise to increased warming.

If anyone really believed that the graph above would now plummet, then thsi might be the start of a season of good news.

However no one really believes we have yet reached ‘peak emissions’. And that means the ongoing disaster is still getting worse.

Total Carbon Dioxide emission in billions of tonnes since 1750. The right-hand axis shows this amount as a percentage of the amount of carbon dioxide that was in the atmosphere in 1750. The 'news' stories point out the last two data points are equal. The red data points are from CDIAC and the blue points from the IEA - links at teh end of the article. Click for a larger figure.

Total Carbon Dioxide emission in billions of tonnes since 1750. The right-hand axis shows this amount as a percentage of the amount of carbon dioxide that was in the atmosphere in 1750. The ‘news’ stories point out the slope of the curve did not increase last year. Click for a larger figure.

How did I work out these numbers? 

(This bit is technical: sorry)

I looked up historical data at the Carbon Dioxide Information and Analysis Centre (CDIAC) and got the latest data from the International Energy Agency (IEA). Their pdf ‘newsletter ‘ is here and the data can be found as a (rather confusing) Excel spreadsheet here

I looked up the mass of the  atmosphere on Wikipedia: It said it was

  • 5.1480×1018 kg

The average mass of a mole of air is 28.8 ×10-3 kg and so the number of moles of air in the atmosphere must be

  • 5.1480×1018 kg/28.8 ×10-3 kg = 178.8 ×1020 moles

In 1750 we think that carbon dioxide was about 280 parts per million of the atmosphere and so the number of moles of carbon dioxide must have been:

  • 178.8 ×1020 moles  × 280 / 106 = 5.00 ×1016 moles

And 1 mole of carbon dioxide has a mass of 44.0 ×10-3 kg per mole, so the mass in the atmosphere in 1750 must have been:

  • 5.00 ×1016 moles  × 44.0 ×10-3 kg per mole = 2.20 ×1015 kg
  • 2.20 ×1012 tonnes
  • 2.20 ×103 billion tonnes
  • 2200 billion tonnes

Arctic Spring 2015: A minimum maximum?

March 12, 2015
The extent of arctic sea-ice (in millions of kilometres squared) in recent months. The figure is downloaded for the US National Snow and Ice Data Centre .It looks like this year's maximum could cover less than ever before - a minimum maximum.

The extent of arctic sea-ice (in millions of square kilometres) in recent months. The figure is downloaded for the US National Snow and Ice Data Centre .It looks like this year’s maximum could cover less than ever before – a minimum maximum.

Spring is springing into life in Teddington, and lifting my spirits.

Meanwhile, further north, the winter growth of sea-ice in the Arctic is slowing, and about to reach its maximum extent.

As the graph at the head of page shows, it looks like this years ‘sea-ice maximum’ (blue line on graph) will not cover the same extent as previous maxima.

In fact, it could prove to be a minimum maximum.

Graph showing the February monthly average of Arctic Sea-Ice Extent since 1979.

Graph showing the February monthly average of Arctic Sea-Ice Extent since 1979.

The graph above shows the trend in February monthly-averaged sea-ice extent since 1979.

The downward trend is pretty clear: typically 1.5 million square kilometres of sea-ice that used to form in 1979 no longer forms.

But there is also the variability – typically ± 0.3 million square kilometres of sea-ice either forms or doesn’t because of the weather: the arctic too can have ‘mild’ and ‘harsh’ winters.

There  is still time for a little more sea-ice growth before the summer melt commences. So this might not be an minimum maximum, but it will be close.

Will a minimum maximum lead to a minimum minimum?

One might think that a smaller extent of sea-ice would automatically lead – after a summer of melting – to a minimum sea ice extent this September.

This is a possibility, but the data suggests there is not a direct link.

For example, in summer 2012, the sea-ice extent ‘collapsed’ to a new record minimum. However, the March before that ‘collapse’, the  winter maximum in the sea-ice extent had been ‘on the high side’ of the recent trend.

Charctic Amusement?

You can review the data yourself over at the US National Snow and Ice Data Centre.

They have a clever ‘Charctic’ tool for plotting the data year by year. Enjoy 🙂

Peak Apple: The Apple Watch will fail.

March 9, 2015
Some Apple Watches

Some Apple Watches

Today marks the launch of the Apple Watch. And I  would just like to say this:

  • It will fail.

Why?

  • It’s expensive.
  • It’s pointless.
  • It is not as useful as an actual watch which actually displays the time all the time.

Am I prepared to be wrong? Of course I am: I’ve been specialising in that in recent weeks.

And I take no pleasure in saying it. But since I am thinking it, I just thought I would I say it out loud

  • I think this is start of the end for Apple.

You heard it here first.

 

 

Why I love weighing

March 5, 2015
The UK's kilogram shown in its storage case. It matters more than you think.

The UK’s kilogram shown in its storage case. It matters more than you think. Image Courtesy of NPL

Weighing is probably not the most glamorous field of metrology, but nonetheless it forms the bedrock of many measurements: more than you might think.

I was reminded of this recently while visiting the Scottish Enterprise Technology Park in East Kilbride near Glasgow

I had two visits to make:

  • The first was to the Scottish Universities Environmental Research Centre (SUERC) with whom we are hoping to carry out some measurements of the isotopic composition of argon gas.
  • And the second was to the National Engineering Laboratory (TUV-NEL) who are the UK’s national centre of excellence in flow measurement.

As I walked across the park from one site to the other I realised that SUERC needed to weigh samples of just a few milligrams in order to count atoms, and TUV-NEL needed to weigh – literally – tonnes of fluid in order to measure flow.

Both these institutions relied ultimately on weighing procedures to tell them ‘the truth’ – but they weighed amounts that differed by a factor one billion!

SUERC

As I mentioned in the previous posting, I am working with SUERC to measure the relative  amounts different argon isotopes in some samples of argon gas.

SUERC have a mass spectrometer, called ARGUS devoted entirely to measuring argon isotopes, but there is no simple way to prove that it is equally sensitive to each type of argon isotope.

A photograph of the ARGUS mass spectrometer. Argon molecules enter on the left and are ionised and accelerated towards the magnet. The trajectories of the lighter argon-36 molecules are more strongly affected by the magnetic field than the heavier argon-40 moleculs - and so end up in a different detector at the end of their flight.

A photograph of the ARGUS mass spectrometer. Argon molecules enter on the left and are ionised and accelerated towards the magnet. The trajectories of the lighter argon-36 molecules (shown as a red line) are more strongly affected by the magnetic field than the heavier argon-40 molecules (shown as a blue line) – and so end up in a different detector at the end of their flight. The process is analogous to the way white light is split into different colours – that’s why this is called a ‘spectrometer’. Courtesy SUERC

In order to evaluate the sensitivity of the spectrometer to different types of argon isotope it is necessary to first create a sample in which the relative amounts of the different types of argon isotope is already known.

And to achieve that it is necessary to very carefully weigh samples of gas containing just a single argon isotope – typically weighing just a few milligrams – and mix them together. So the ultimate accuracy of this super sophisticated instrument is assessed, in the end, by weighing.

TUV NEL

Measuring the rate of uniformly flowing liquid or gas down a pipe is hard. But not too hard.

Measuring the rate of flow of (say) oil when it is mixed with water and air is very, very hard.

At TUV NEL they calibrate flow meters, and their ultimate measure of the accuracy of a flow meter is to place the meter in a pipe and flow fluid past: and then have the pipe empty into a giant tank.

They then weigh the tank as the water pours in – tonnes of it! – and measure how much fluid arrives as a function of time.

It’s a pretty basic measurement – but how else can you ultimately know that your flow meter is reading correctly?

The kilogram

And if SUERC and TUV NEL want to make sure that their measurements will be comparable internationally, then they need to make sure their measurements are traceable to the SI definition of the kilogram.

Seeing how these diverse measurements in different realms  related back to the mass of a lump of metal we keep in a safe at NPL, made me reflect that the work we do at NPL really does matter. And often in ways that perhaps even we don’t realise.

A bad month at the office…

March 2, 2015
My badge for the Fundamental Constants Meeting

My badge for the Fundamental Constants Meeting

An expert is a someone who has made all the mistakes which can be made, in a narrow field.

Niels Bohr

Some time ago  – together with colleagues at NPL and SUERC – I made a very accurate estimate of the Boltzmann constant.

The Boltzmann constant is the number that specifies how much energy particles have at a particular temperature. It provides a numerical link between thermal and mechanical energy.

The work took 6 years of my life, and possibly took six years off my life!

But at the start of February, at an international conference in Germany on the value of Fundamental Constants I had to admit that our estimate was wrong. And wrong by more than the margin of error that we had anticipated.

I have been feeling terrible about this all month.

I am aware that there are lots of reasons why I shouldn’t feel bad: For example:

  • We had in fact considered the possibility that this type of major error could occur. And we mentioned in our paper how to correct our estimate if it did occur.
  • And also the difference isn’t much in the grand scheme of things: our answer was wrong by 2.7 parts per million, which is  equivalent to estimating a distance of 1 kilometre incorrectly by 2.7 millimetres.
  • And also nobody will die as a result of the mistake.
  • And as it happens, it was revealed at this meeting that all the ‘best’ recent estimates of the Boltzmann constant suffered from a similar error – so it was not just me.
  • And our revised estimate is still the most accurate ever made in human history!

But nonetheless, I have felt absolutely terrible all month.

What went wrong?

[The next bit gets technical:sorry]

In the experiment we had to estimate the average kinetic energy of a molecule in argon gas at a known temperature.

To estimate the average kinetic energy of a molecule we needed to estimate the  average speed of the molecules of the gas, and their average mass.

We estimated the average speed of the molecules from measurements of the speed of sound in the gas. This part of the experiment worked very well.

Our mistake was with our estimate of the average mass.

Natural argon in the atmosphere consists of 3 different types of argon, called  isotopes. Most of the argon molecules weigh 40 times as much a hydrogen atom and so are referred to as argon-40.

But roughly 1 molecule in 300 is only 36 times as heavy as a hydrogen atom and so is referred to as argon-36.

And roughly 1 molecule in 1500 is 38 times as heavy as a hydrogen atom and so is referred to as argon-38.

A representation of the distribution of istopes in natural argon. For every 1500 molecules of argon-40 (green) there is on average 1 molecule of argon argon 38 (purple) and 5 molecules of argon 36 (black). We seem to have mis-estimate the exact ratio of argon 40 to argon 36 molecules in our sample.

A representation of the distribution of istopes in natural argon. Very roughly, for every 1500 molecules of argon-40 (green) there is on average 1 molecule of argon argon 38 (purple) and 5 molecules of argon 36 (black). We seem to have mis-estimate the exact ratio of argon 40 to argon 36 molecules in our sample.

Argon is captured from atmospheric air, purified and sold in pressurised cylinders. We  had previously shown that the amount of argon-36 and argon-38 varied from one cylinder to the next. So we needed to analyse gas from the actual cylinder we used.

Colleagues at SUERC compared the relative amounts of the different isotopes with the relative of amounts of those isotopes in atmospheric air.

And then we used a previous measurement of the relative amounts of the different isotopes in the air by a laboratory in Korea, KRISS, to work out how much of each isotope was in our samples.

And somewhere along that chain of measurements, there was an error.  This was finally revealed when we sent a sample of our gas directly to KRISS (something that wasn’t possible when we published otherwise we would have done it already!) .

We had estimated that the ratio of argon-40 molecules to argon 36 molecules was close to 298.9. In fact it now seems likely to have been closer to 296.9. So there was slightly more argon-36 than we thought in our experimental gas – and hence the gas was a little less dense than we thought.

Heigh Ho.

What will we do?

The first thing I will do  is to apologise to everyone I meet for having been so unjustifiably confident.

Then I will catch my breath, and remind myself of the words of Niels Bohr at head of this article: truly I am becoming an expert.

And then I hope to be able to persuade my colleagues to allow me to finish this measurement properly.

What we will do is to obtain some samples of gas each consisting of just a single type of argon isotope. These gases are very expensive which is partly the reason we didn’t try this in the first place.

We will then weigh these very carefully and mix them together in precisely known amounts to produce a sample of gas in which we know the relative amounts of the different isotopes

We will then ask our colleagues at SUERC to compare our experimental gas – we still have some gas from that bottle – against our isotopically-prepared sample of gas.

And then finally we will have an estimate for the average mass of a molecule of argon in our samples of gas.

And hopefully that answer will make sense!


%d bloggers like this: