Archive for April, 2017

How is knowledge lost?

April 20, 2017

At some point in the 1950’s the physics of the Greenhouse Effect was so uncontroversial in the United States that it was the subject of a children’s song. A really great song.

WARNING: This song contains a BANJO accompanimentWARNING

The song is on the You Tube link above and the lyrics are at the end of this article.

Written by folk-singer Tom Glazer, the lyrics show an excellent appreciation of the physics of the greenhouse effect.

After first describing how a greenhouse works, the song describes how the Earth is warmed by solar radiation

The atmosphere is like a greenhouse too
It lets most of the solar rays through
The surface of the Earth absorbs these rays
And re-radiates them as long heat rays

And then, in very sophisticated terms it describes the role of water vapour in the atmosphere

There’s vapour in the air, What does it do?
It doesn’t let the long heat rays pass through
Trapped by the vapour they bounce back and forth,
Re-radiated and re-absorbed

Did you read that?

re-radiated and re-absorbed

Tom Glazer is describing the basic physics of the MODTRAN model of atmospheric transmission! (Link).

Can you imagine a world where it is OK to say “re-radiated and re-absorbed” to primary school children?

Children who learned this song would have a better operational understanding of the physics of the greenhouse effect and global warming than a fair fraction of the population of this country or the USA!

But the terrible truth is that 60 years after it was written, this song and the knowledge it embodies has been lost to popular culture and become – apparently – controversial.

How did we lose this collective knowledge?


What does the glass of a Greenhouse do?
It lets the short solar rays pass through
The objects in the house absorb these rays
And re-radiate them as long heat rays

What does the glass of a Greenhouse do?
It doesn’t let the long heat rays pass through
Trapped by the glass they bounce back and forth,
Re-radiated and re-absorbed

Stay Stay, you long heat rays, Warm up the house on cold cold days
Stay Stay, you long heat rays, Warm up the house on coooooold cold days

The atmosphere is like a greenhouse too
It lets most of the solar rays through
The surface of the Earth absorbs these rays
And re-radiates them as long heat rays

There’s vapour in the air, What does it do?
It doesn’t let the long heat rays pass through
Trapped by the vapour they bounce back and forth,
Re-radiated and re-absorbed

Stay Stay, you long heat rays, Warm up the house on cold cold days
Stay Stay, you long heat rays, Warm up the Earth on cooooooold cold days

Weather Songs

Not everything is getting worse!

April 19, 2017

Carbon Intensity April 2017

Friends, I find it hard to believe, but I think I have found something happening in the world which is not bad. Who knew such things still happened?

The news comes from the fantastic web site MyGridGB which charts the development of electricity generation in the UK.

On the site I read that:

  • At lunchtime on Sunday 9th April 2017,  8 GW of solar power was generated.
  • On Friday all coal power stations in the UK were off.
  • On Saturday, strong winds and solar combined with low demand to briefly provide 73% of power.

All three of these facts fill me with hope. Just think:

  • 8 gigawatts of solar power. In the UK! IN APRIL!!!
  • And no coal generation at all!
  • And renewable energy providing 73% of our power!

Even a few years ago each of these facts would have been unthinkable!

And even more wonderfully: nobody noticed!

Of course, these were just transients, but they show we have the potential to generate electricity which has a significantly low carbon intensity.

Carbon Intensity is a measure of the amount of carbon dioxide emitted into the atmosphere for each unit (kWh) of electricity generated.

Wikipedia tells me that electricity generated from:

  • Coal has a carbon intensity of about 1.0 kg of CO2 per kWh
  • Gas has a carbon intensity of about 0.47 kg of CO2 per kWh
  • Biomass has a carbon intensity of about 0.23 kg of CO2 per kWh
  • Solar PV has a carbon intensity of about 0.05 kg of CO2 per kW
  • Nuclear has a carbon intensity of about 0.02 kg of CO2 per kWh
  • Wind has a carbon intensity of about 0.01 kg of CO2 per kWh

The graph at the head of the page shows that in April 2017 the generating mix in the UK has a carbon intensity of about 0.25 kg of CO2 per kWh.

MyGridGB’s mastermind is Andrew Crossland. On the site he has published a manifesto outlining a plan which would actually reduce our carbon intensity to less than 0.1 kg of CO2 per kWh.

What I like about the manifesto is that it is eminently doable.

And who knows? Perhaps we might actually do it?

Ahhhh. Thank you Andrew.

Even thinking that a good thing might still be possible makes me feel better.


25 years ago…

April 4, 2017

25 years ago, the atmospheric concentration of carbon dioxide was 350 ppm  – just 70 ppm higher than its pre-industrial concentration.

Oh yes. And I got married.

Objectively, I can describe this elapsed time as 9131 days. Or almost 789 million seconds.

And I can describe the way in which the atmospheric concentration of carbon dioxide has changed since then by more than 50 ppm.

And I can even describe the wonder of seeing two new human beings come into the world and evolve from being babies to being adults.

But subjectively, words fail me.

Version 2

But it is a fact that on this date, 25 years ago, friends and relatives gathered and supported Stephanie and myself as we got married.

And this post is just to say ‘Thank you’ to everyone who was there that day, and whose good wishes felt like a very tangible blessing. Our aim this year is to try to visit each of you. We have a list and you have been warned!

But whether you were there or not, I leave with you the Epithalamion written by my brother Sean and read by him at the wedding.

Epithalamion for Michael and Stephanie

Young people dance and drink a lot,
Draw close in metaphysical discussion,
Make light of commitments in making love
Celebrate the sadness of casual encounters,
Make art from them, and then repeat them.
Moments exhilarate; memory excruciates; the future’s a dream.
Years pass; what was painfully beautiful becomes untenable.
There comes time to move from testing the limits of resilience
To exploring the possibilities of permanence

Flitting is fine for adolescents and Peter Pan,
But now this woman is a woman, and this man a man.

Michael played guitar and sang a lot.
Went with women, but not a lot;
Sought the wrong thing in the wrong places,
And thus made the necessary errors;
Skirted sanity’s edge and touched insanity’s terrors.
I knew him as an orphaned six-year old; I have known
the need, and comfort of, his hand.
I have sought the warmth of his palm; welcomed his embrace;
Suffered the full force of his anger
— And see! Here I am unharmed.
And here is the baby I held in my arms
Become an adult who,
In looking for his mother, found a lover;
And in loving a lover, found a wife;
And, after a long search,
The needed even tenor of a stable life.

In seeking after women, he was never a Don Juan;
But now the child whose hand I held is become a man.

I don’t know Stephanie’s past;
However I strongly suspect
That happy women don’t jump from Aeroplanes;
And I know for a fact
That Ireland is the best
But least happy nation to stem from;
And that an uncertain constitution of your blood
Doesn’t do your humour any good.
This is not to carp, but just to establish
A youth that was below emotional perfection,
So that future adventures – this moment –
Might allow scope for improvement.
How sad, if all her relations, now full-stomached and dyspeptic,
Were also silently lamenting her deteriorating spirit,
Her vanished prospects,
The poor calibre of chap who’s landed in it!
To them I would say:
“The Chosen Path is the best!
And this is it!”

Today Stephanie puts on her Bridal Gown
To follow a dream that is her own.
Today good faith and trust may light hope’s flame;
She thus assumes perfection and a woman’s name.

Today is the ceremonial,
The tip of the huge and hidden thing to come;
The speckle and glass-glint of sun on the sea’s surface,
Eye-pleasing and transient, above depths that would terrify.
Today is about sex and the containment of sex;
About fear and the overcoming of fear;
About flesh and the fact flesh is fertile;
And the fact flesh decays;
And the fact flesh is human and lovely.
Today, too, is about family,
About what your Mother and Father do to you,
And for you;
It is about fertility and the bearing of children,
About the repetition of familiar things — and old errors;
The discovery of particular new joys,
New ways of two people meeting,
The miracle, perhaps, of new human beings.
Today is about what — what no ceremony could proclaim —
Informing the mundane with a proper focus,
With the laser intensity of life, and making it last;
About enlivening the drudge of living,
The dulling-ness of day to day.

It is about making do, and doing the best you can.
It is about Stephanie being a woman, and Michael a man.

If that’s all, then what’s the point?
Why are we here?
Why not reach for our revolver
And place it in our ear?
Because… because there’s more.
Today is about this…
We need each other;
We are nothing if connected to nothing.
Today we celebrate connectedness;
Cutting the crap we acknowledge love,
And the power of love to sustain.
And love is a light thing —
Not just the fleshly decaying ponderousness of sex,
But the shock of seeing, and then seeing afresh.
Today we dignify love,
Erecting a social carapace to protect it,
To allow it, in the private vision of two lovers.
We try to fix a hope — that love is not a flimsy.
Can such a light thing — love — though ever be strong enough?
All brides and all their grooms are optimists or fools.
But. Imagine egg-shell-skating carefulness; Consider how caution kills.
Let’s learn, and be thankful for the lessons of these optimistic fools;
Aristocrats of human risk, they let love open the future.
To feed hope’s flames, their noble folly’s fuel.

Come, then let us thank them; let us now applaud;
Today, this woman is a lady; and this man a lord.

Sean de Podesta , 1992

Global Warming: we were warned.

April 2, 2017

Human beings – including the one writing this – often find it hard to grasp the rates of processes involved in Global Warming.

When thinking about the physics, there are three important rates to consider.

  • The rate at which human emissions have taken place.
  • The rate at which the emissions affect Earth’s temperature.
  • The rate on which human emissions will dissipate.

But we also need to consider one other ‘rate’:

  • The rate at which humanity can respond to a warning after it has been given.

Let’s look at each of these ‘rates’ in turn:

Rate of Emissions

We are emitting carbon dioxide into the atmosphere at an astonishing rate: about 33 billions tonnes of carbon dioxide every year.

Humanity's Cumulative Emissions of Carbon Dioxide expressed in two ways. The left-hand axis shows the data as a fraction of the emissions. The right-hand axis shows the data as billions of tones (i.e. Gt) of carbon.

The graph above shows data from the Carbon Dioxide Information Analysis Centre. It shows humanity’s cumulative emissions of carbon dioxide expressed in two ways.

  • The left-hand axis shows the data as a fraction of the emission up to 2013 (100%)
  • The right-hand axis shows the data as billions of tonnes (i.e. Gt) of carbon. Multiply this number by 3.67 to convert it to billions of tonnes (i.e. Gt) of carbon dioxide.

From the graph we can see that:

  • 80% of the carbon dioxide we have put into the atmosphere has been put there in my lifetime. I am 57.
  • Although climate emissions have stabilised in the last three years, this only means that the slope of the graph has stopped increasing.
  • Continuing at the current rate, every 7 years we will emit carbon dioxide equivalent to the entirety of human emissions from the dawn of time to the date of my birth.

Climate Impact

Below is the estimate of the Earth’s average surface temperature made by the team at the NASA GISS laboratory. Alongside the data is a trend-line smoothed over a 10 year period.

The temperature rise is shown relative to the average temperature over the period 1951 to 1980.

Global Land Ocean 10 year smoothing

  • The graph shows that since 1980, the temperature trend has been rising roughly linearly at about 0.02 °C per year i.e. 0.2 °C per decade, or 2 °C per century.

Carbon absorption

The 33 billion tonnes of carbon dioxide we emit annually into the atmosphere corresponds to about 9 billion tonnes of carbon – these are the units used in the info-graphic below.


This image is from Wikipedia and was adapted from U.S. DOE, Biological and Environmental Research Information System. –, Public Domain, Link All the numbers are in billions of tonnes of carbon (Multiply by 3.7 to obtain the numbers in billions of tonnes of carbon dioxide). Figures in red are human emissions.

Natural processes remove about 2 billion tonnes of carbon from the atmosphere each year by dissolving it in sea water. And a further 3 billion tonnes of carbon a year is removed by increased plant growth.

If we stopped emitting carbon dioxide now, then these processes would the lower the carbon dioxide concentration in the atmosphere back to 1960’s levels in about 100 years.

As a consequence of these slow rates of removal, we are already committed to many decades of further warming at a rate similar to that which we are experiencing already.


  • The bulk of human emissions have occurred relatively recently.
  • We are now in an era when the Earth’s surface is definitely warming.
  • When we eventually take action we will still experience warming for many decades more.

But we have known all this for a long time: at least 36 years

The process which limits our rate of response. 

Arguably, the emergence of ‘popular’ appreciation of the effect of carbon dioxide emissions can be timed to 1981, when James Hansen and colleagues published a landmark paper in Science 

The paper is complex, but readable. But in case you are busy, here are some extracts.

A 2 °C global warming is exceeded in the 21st century in all the CO2 scenarios we considered, except no growth and coal phaseout.

This is happening now.

Floating polar sea ice responds rapidly to climate change. The 5 °C to 10 °C warming expected at high northern latitudes for doubled CO2 should open the North-west and North-east passages along the borders of the American and Eurasian continents. Preliminary experiments with sea ice models suggest that all the sea ice may melt in summer, but part of it would refreeze in winter. Even a partially ice-free Arctic will modify neighbouring continental climates.

This is happening now well before CO2 concentrations have doubled.

The global warming projected for the next century is of almost unprecedented magnitude. On the basis of our model calculations, we estimate it to be ~2.5°C for a scenario with slow energy growth and a mixture of nonfossil and fossil fuels. This would exceed the temperature during the altithermal (6000 years ago) and the previous (Eemian) interglacial period 125,000 years ago, and would approach the warmth of the Mesozoic, the age of dinosaurs.

This is happening now, but the warming is faster than the ‘worst case’ scenario they envisaged.

Political and economic forces affecting energy use and fuel choice make it unlikely that the CO2 issue will have a major impact on energy policies until convincing observations of the global warming are in hand.

How true! And even after the observations have become convincing, ‘political and economic forces‘ are still resisting a change in fuel use.

In light of historical evidence that it takes several decades to complete a major change in fuel use, this makes large climate change almost inevitable. However, the degree of warming will depend strongly on the energy growth rate and choice of fuels for the next century. Thus, CO2 effects on climate may make full exploitation of coal resources undesirable.

An appropriate strategy may be to encourage energy conservation and develop alternative energy sources, while using fossil fuels as necessary during the next few decades.

In retrospect, we could not have asked for a clearer or more accurate warning or better advice.

As I look at it now, the physical rates of processes make this problem really difficult

But it is our inability to respond to warnings which makes this potentially insoluble.

All the warnings above have come to pass: Let’s hope the paper’s warnings about sea level rise prove to be less accurate.

Danger of rapid sea level rise is posed by the West Antarctic ice sheet, which, unlike the land-based Greenland and East Antarctic ice sheets, is grounded below sea level, making it vulnerable to rapid disintegration and melting in case of general warming.

The summer temperature in its vicinity is about -5°C. If this temperature rises ~5°C, de-glaciation could be rapid, requiring a century or less and causing a sea level rise of 5 to 6 m (55). If the West Antarctic ice sheet melts on such a time scale, it will temporarily overwhelm any sea level change due to growth or decay of land-based ice-sheets. A sea level rise of 5 m would flood 25 percent of Louisiana and Florida, 10 percent of New Jersey, and many other lowlands throughout the world.

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