Archive for August, 2021

Articles about my house

August 31, 2021

Friends, I have just added a static page to this blog called “My House”.

It contains links to the all the articles I have written over the last couple of years on my efforts to reduce carbon dioxide emissions from my house.

If the link is not obvious to you – you can find the page here:



Heat Pumps: Power, Noise and Condensation

August 30, 2021

Friends, I had a visit the other day from a couple who were considering installing a heat pump in their home, but were concerned about the noise.

To get the heat pump to operate, I ran the hot water for 10 minutes and then requested a hot water ‘boost’ using the app on my phone.

We then stood around the heat pump chatting until the visitors started to get cold. The reason? The heat pump had started up and was blowing cold air over their legs. But they had not heard a thing!

I told them to wait – and slowly the heat pump speeded up and became audible. But it was not what I would call ‘noisy’. In the garden, 5 metres away – you would not be aware of it as a separate sound against the (quiet) suburban background.

In fact, the need for heat pumps to be quiet constrains their design significantly and actually determines their physical size! It would be possible to make heat pumps differently – but they would be either noisier or drippier!

Let me explain…

Click for a larger version. How a heat pump works. A fan rotates and blows air out of the heat pump cabinet. This draws in air which flows over a so-called heat exchanger. This consists of many small diameter pipes containing coolant. The coolant absorbs heat from the air which is later delivered to the house.

Thermal power and air volume

When designing a heat pump, the first thing one needs to know is the thermal power the heat pump must deliver: Let’s say its 6 kW.

If it operates with a coefficient of performance (COP) of 3, then 2 kW out of those 6 kW will be from the electrical motor, and 4 kW will be extracted from the air.

Heat pumps obtain this energy by cooling outside air by roughly 3 °C using a so-called heat exchanger. The heat capacity of air is (more or less) fixed, ~ 1 kJ/kg/°C (source) and 1 kg of air occupies a volume about 0.83 cubic metres.

So, if the heat pump extracts heat from 0.83 cubic metres of air per second, cooling it by 3 °C, then it will extract 3 x 1 kJ = 3 kJ of heat per second i.e. 3 kW.

So to achieve its target of extracting 4 kW of heat, it must pass 33% more air over its heat exchanger i.e. about 1.1 cubic metres of air.

Air speed and noise

Heat pump noise arises from air flow over and around surfaces, and the noise increases with the speed of air flow.

A heat pump can draw a given quantity of air over its heat exchanger in (broadly) two ways.

  • By increasing the speed of air flow over a given area of heat exchanger
  • Or by increasing the area of heat exchanger and keeping the air speed low.

In practice, the faster the air flows, the noisier the heat pump becomes.

So when more heating power is required, manufacturers can speed up a fan a little to increase air speed, but  generally they increase the area of the heat exchanger.

Click for a larger version. Heat pumps made by Vaillant. In order to extract more heat while keeping the air speed low, heat pumps need to be physically larger to accommodate larger area heat exchangers.

Heating Power and Condensation

The heating power of a heat pump is linked directly to the volume of air it passes across its heat exchanger, and the amount by which the air is cooled.

So one other option for increasing the heating power extracted from the air while maintaining low air speeds (i.e. low noise) is to cool the air more.

However when air is cooled, then depending on…

  • the air temperature,
  • the initial humidity, and
  • the temperature drop,

…water may or may not condense. The larger the temperature drop, the more likely water is to condense.

Water condensation is not especially harmful, but at low temperatures, condensation can freeze around the heat exchanger and stop the heat exchanger working.

Heat pumps can detect this and intermittently melt any ice on the heat exchanger – but this makes the operation of the heat pump less efficient.

To cope with condensation all heat pumps are equipped with a drain which allows condensed water to simply drip out the bottom of the casing. This is why it is important to mount heat pumps level – so the designed draining port is actually at the lowest point.

But where does the water go after it drains away?

Allowing water to just drip on the ground – and potentially freeze is not a great idea.

Plumbing the drain into an existing drainpipe may seem adequate but it is not. In winter, when the heat pump is operating below zero, this will freeze and may cause icy spillages, and blockages.

So best practice is dig a ‘soak-away’. For my heat pump we used a ground auger to drill a 15 cm diameter hole a full 1 metre deep. We then filled this with small stones.

The drain hose from the heat pump has a 30 cm long internal heater that prevents icing until the condensate is about 15 cm below ground level. Hopefully the temperature there will be above 0 °C!

Click for a larger version. Arrangement for removing condensation from a heat pump. The casing must be level and water is drained away from the lowest point in the cabinet into a soak-away. The drain is heated along its length to prevent it freezing up at low temperatures.

How much condensation is there?

The amount of condensation depends on many factors but because I knew you would ask, I wrote a spreadsheet to calculate it. (Excel .xlsx file: Calculation of Condensate Volume)

A typical output is shown below. The graph shows the number of litres per day of condensation for a heat pump which delivers 6 kW of heating when the external temperature is 0 °C.

This calculation assumes the relative humidity of the air is 85% and that the temperature drop across the heat pump heat exchanger is either 3.5 °C or 7.0 °C – potentially extracting double the heating power.

In this case the larger temperature drop causes a roughly 10-fold increase in the rate of condensation

The reason for the shape of the curves is that:

  • At low external temperatures, the heat pump must run at high power and so extract heat from a larger volume of air.
  • At low external temperatures, the amount of water in the air is much less than at high temperatures.

Together these two factors combine to produce maximum condensation at temperatures between 5 °C and 10 °C.

Click for a larger version. The graph shows the amount of condensation (litres per day) expected when a heat pump is operating at the external temperature shown so as to maintain an internal temperature of 19 °C. The thermal power at 0 °C is 6 kW and heat pump is assumed to cool the air by ΔT = 3.5 °C  or by ΔT = 7.0 °C. The relative humidity of the air is assumed to be 85%. Notice that cooling the air more drastically increases the amount of condensation.

Non-combatants may wish to stop reading here.

But for those interested, I will explain the calculation below.

Click for a larger image. Spreadsheet for calculating the amount of water which condenses from a heat pump. The text below explains each column in the calculation. The actual spreadsheet is downloadable from a link in the text.

The basic inputs are the shown in red text with a yellow background.

  • The desired internal temperature (19 °C)
  • The thermal power required to maintain 19 °C when the external temperature is 0 °C. (6000 W = 6 kW)
  • The Coefficient of performance of the heat pump (3) which is assumed to be constant.
  • The humidity of the air (85%)
  • The amount (ΔT) by which the heat pump cools the air (3.5 °C)

Column 1: shows the external temperature.

Column 2: shows the temperature demand, the difference between the internal and external temperatures

Column 3: shows the thermal power required to heat the dwelling, assuming it is proportional to temperature demand.

Column 4: shows how much thermal power must be extracted from the air based on the COP.

Column 5: shows the volume of air per second that must be cooled by ΔT in order to extract the required heating power. More air flow is required at low temperatures as the heating demand increases

Next we work on the humidity

Column 6: shows the specific humidity of saturated air with the numbers entered from a data table. This expresses the maximum density (in grams per cubic metre) of water that air can hold without condensing.

Column 7: shows the the same quantity as column 6 but derived from a formula designed to closely match the actual data. This allows me to interpolate between the points in the data table.

Column 8: shows the specific humidity of the air under consideration i.e. with relative humidity less than 100%.

Column 9: shows the specific humidity of saturated air which is ΔT colder than the external temperature.

Column 10. If the specific humidity of the actual air (Column 8) exceeds the specific humidity of saturated air at its new lower temperature, then condensation will occur.

Column 11. If condensation occurs, then the excess water (the difference between columns 8 and 9) will become liquid.

Column 12. Expresses the condensation per cubic metre in terms of condensation per second.

Columns 13, 14, 15 and 16. Expresses the condensation rate in terms of litres per second, per minute, per hour and per day respectively.

COVID 19: Wave#3. How its going.

August 29, 2021

Click for a larger image. Logarithmic graph showing positive caseshospital admissions and deaths since the start of the pandemic. The blue arrows show the dates of recent ‘opening’ events. The green dotted line shows an extrapolation from the first week of June. The blue dotted line shows an extrapolation of current trends, doubling every 42 days. Also highlighted in purple are the Euro finals, and the dates of returns to school and university in 2020 and 2021.

Friends, I last wrote about the pandemic three weeks ago on August 7th. At that point it had just become clear (to me at least) that the late July peak in cases was associated with the Euros.

In the UK we are now experiencing the third wave of the epidemic which was happening ‘underneath’ the ‘Euro surge’. Viral prevalence is high and showing slow exponential growth – with cases, admissions, and deaths doubling roughly every 42 days.

There are currently:

  • More than 30,000 cases per day (x 30 compared with ~ 1000 per day at this time last year).
  • Almost 1000 admissions per day (x10 compared with ~ 100 per day at this time last year).
  • Over 100 deaths per day (x 10 compared with ~ 10 per day at this time last year).

In the weeks ahead we have the return to Schools and Universities in England. Based on last year (when prevalence was about 10 times lower) we might reasonably expect an increase in the number of cases admissions and deaths over and above the current trend. See the purple arrows on the graph above.

In the face of these facts, it might surprise many readers to know that life in the UK for many non-immunocompromised people has become very normal.

Are we all OK with this?

The Daily Mail points out that current death rates from COVID are no longer the greatest cause of death in the UK. The gist of their suggestion is that we should just get used to this.

[Note: as detailed in the figure caption, their numbers are out of date]

Click for a larger version. Article from the Daily Mail on Sunday 29th August 2021. The graphic is misleading because it uses older data on deaths and the death rate has been increasing. COVID Deaths are now over 700 per week and if current trends continue will exceed 1400 deaths per week at the end of September.

I understand and sympathise with this argument. But the argument is based on numbers now.

Being an epidemic, the prevalence of COVID will continue to increase and – as we have seen repeatedly – we can make decisions which seem reasonable now, but which commit us later to large numbers of cases, hospital admissions and deaths.

One lesson of the epidemic might be that modest precautionary steps taken early can avoid the need for drastic lockdowns – the only tool for dealing with a widespread lethal epidemic in its later stages.

Recall that roughly 1700 people die each day ‘normally’. So 100 people dying each day (6% of normal) may be considered ‘acceptable’.

But if things continue on current trends, then by the end of September 2021 we may be looking at 200 people dying each day (12% of normal), alongside 60,000 daily cases and 2,000 hospital admissions per day. The death toll from Wave#3 might be have reached 8,000.

And if things continue to continue on current trends for a further month, then by the end of October 2021 we may be looking at almost 400 people dying each day (24% of normal). The death toll from Wave#3 might have reached almost 15,000. This is probably not acceptable to most people – and certainly not me.

What to do?

I don’t know!

The Government appear to be in denial about these likely projections, which are similar to predictions by much more eminent people than I.

As I look at these figures  it is clear that the growth rate of the epidemic is being limited by vaccines, but it is still growing, albeit slowly.

Vaccination of children may help, but I suspect that any program started now will be too late to prevent a ‘back-to-school’ boost in cases and further growth through the autumn. Vaccination of 18 year-olds may well be sufficient to slow viral spread at Universities.

So unless we re-introduce some additional social distancing, it seems cases and hospital admissions and eventually deaths will all continue to grow. This is not to mention any risks of other variants or ‘long Covid’.

However the government seem indifferent to these harms, and all the associated suffering.

So it seems likely that things will continue on trend until – frankly – something politically embarrassing causes the government to act.

Or have I missed something?

Journey from the Centre of the Sun

August 15, 2021

Click image for a larger version. Some of the stages in the energy conversions and transfers that allows me to have hot water in the mornings without any carbon dioxide emissions. Simple heh?

Friends, just the other day I wrote about how my heat pump produced hot water each day.

The way in which the heat pump extracts heat from the air is ingenious in the extreme.

But as I reflected on it, I realised that this ingenuity occurred in the middle of a long series of energy transformations taking – very roughly – 170,000 years.

Please allow me to explain.

#1 Where does the energy come from?

The source of nearly* all the energy humans exploit on Earth is sunlight.

Using sunlight and carbon dioxide plants produce oxygen (thank you) and carbohydrates. This so-called ‘photosynthesis‘ captures energy from the sunlight in the form of re-arranged chemical bonds within carbohydrate molecules.

When we use animals for work – horsepower and ox-power – the energy the animals use is derived from the carbohydrate molecules in their food.

When we burn plants – primarily wood – for heat, the energy released is from the reverse of the reaction that created the carbohydrate molecules. And so, the carbon dioxide which was captured when the plant grew, is released. But since burned wood is generally only a few decades old – burning plants can be (almost) neutral in the production of carbon dioxide.

Fossil fuels are all derived from plants, and the energy of the captured sunlight has been ‘distilled’ over thousands of years by a variety of physical processes into coal, oil and gas. Unfortunately, burning fossil fuels also releases carbon dioxide, but not carbon dioxide that was recently captured. It releases carbon dioxide that was captured eons ago.

Burning fossil fuels is still the main way in which we make electricity – so electrical energy is in some sense the energy of ancient sunlight. How charming.

#2 Where does the energy of sunlight come from?

That the Sun is hot has been obvious to all humans since the dawn of time.

But the source of its immense heat was a mystery until just about 100 years ago when it was suggested that hydrogen nuclei (a.k.a. protons) might ‘fuse’ together to make helium nuclei, and release energy.

Segueing past a few decades of research and speculation, we now know for sure that nuclear fusion deep within the Sun is indeed the source of the energy that makes the Sun hot.

The environment deep within the Sun is extraordinary, with a temperature of roughly 15 million degrees Celsius.

The hot dense gas emits electromagnetic radiation – γ-rays, X-rays, ultra violet and visible light – in all directions. The nuclei and electrons in the Sun are a plasma – which is opaque to radiation. So the radiation is constantly absorbed, causing local heating, and then being re-emitted by the nuclei and electrons in the various layers of the Sun.

Because the Sun is so vast and so opaque – it takes roughly 170,000 years for the energy to travel from the core of the Sun to the surface of the Sun. Just so you know it was not a typo: I did indeed say 170,000 years.

Eventually the energy reaches the outer layers of the Sun which are at a tepid 5,500 °C (ish). The glow of this hot plasma sends visible light out in all directions and after roughly 8 minutes, a tiny fraction of it reaches Earth.

#3 My hot water: a summary

Click image for a larger version. Some of the stages in the energy conversions and transfers that allows me to have hot water in the mornings without any carbon dioxide emissions. Simple heh?

So where does the energy that heats my hot water come from? The letters in the bullet points below refer to the diagram above.

  • Nuclear fusion (A) around 170,000 years ago created energy from the fusion of hydrogen nuclei that were themselves created in the primordial ‘big bang’.
  • This energy travelled through the Sun’s layers as a variety of forms of electromagnetic radiation – γ-rays, X-rays, ultra violet and visible light – until it reached the outer layers when the radiation could travel uninterrupted into space (A, B).
  • A tiny tiny fraction of this radiation was intercepted by solar panels on my roof, which converted some of the visible light into an electrical current (B, C, D).
  • This electrical energy was stored in a battery by electrically forcing ions of lithium metal (shown in the figure as red dots) to cluster together against their desire to diffuse away from one another (E).
  • This energy was then released at night by allowing ions of lithium metal to diffuse away from one another (F), forcing electrons around an external inverter circuit that created AC currents to power a motor in a compressor (G) and electronics which ran the heat pump.
  • The heat pump then chilled a refrigerant (G) that extracted heat from molecules in the air that had also been heated by sunlight over the preceding few days.
  • This energy was transferred as heat to water flowing in a circuit through the heat pump (G).
  • And then this energy was further transferred as heat to fresh water in a hot water tank (H).

And then finally (I) a few hours later, this energy was transferred to the outer layers in my face and hands where transient receptor proteins in thermoreceptors in my skin sent signals to my brain that caused me to realise the water coming from the tap into the sink was ‘just right’.

Simple heh?

* Nearly?

Humans do exploit one source of energy which did not originate in the fusion of nuclei within the Sun: nuclear power.

Nuclear power exploits energy released by splitting the nuclei of heavy atoms that were created – as I understand it – during the last few destructive moments of a previous generation of stars.

These elements – uranium primarily – were then deposited on the primordial Earth as it formed at the same time as the Sun was ‘born’.


Heat Pump – First Operational Data

August 14, 2021

Click for a larger version. The heat meter estimates the heat delivered by the heat pump by measuring the flow of hot water [in kilograms per second] and the difference between the temperature of the water delivered by the pump (T1), and the temperature of the water returning to the pump (T2).

Friends, please let me tell you about the first data I have on the operation of the new heat pump – a 5 kW Vaillant Arotherm Plus.

[Edit 6/9/2021: Initially I stated this a 7 kW version because I had forgotten that in the end I opted for the lower power version]


As part of installation, I paid for a “Metering and Monitoring Service Package” (MMSP) which monitors: the heat delivered by the heat pump; the electrical energy it consumes; alongside the local internal and external temperatures.

All this data is measured every 2 minutes (!) and then whizzed into The Cloud where I can view and download it.

Just as importantly, the data is aggregated by Ofgem (Office of Gas and Electricity Markets) who can then assess real world performance of heat pumps ‘in the field’. And Ofgem will – I hope – eventually pay me for the data!

Aside from electrical power measurements, the key element of the monitoring system is a heat meter, whose operation is illustrated at the top of this article.

This clever device integrates several measurements:

  • The temperature of the water delivered by the heat pump
  • The temperature of the water returning to the heat pump
  • The flow rate of the water.

…to estimate the heat delivered by the heat pump.

Click for a larger version. The Sontex Superstatic 449 heat meter installed near the hot water cylinder. The meter indicates that since installation, the heat pump has delivered 78.533 kWh of useful heat.


At this time of year, we don’t need any space heating so the only way to assess the performance of heat pump is for heating domestic hot water (DHW).

The MMSP can detect whether electrical power is applied to the 3-way valve (see picture at the top) and so can tell if the hot water is being delivered to the radiators or the DHW tank.

The heat pump is set to heat the DHW tank between 3 a.m. and 4 a.m. each day. The data below is from the early hours of 13th August 2021.

The graph below shows electrical power drawn by the heat pump (watts), the thermal power delivered (watts), and the temperature of water (°C) versus time. The water temperature should be read against the right-hand axis.

Technical Note I have smoothed the power data by averaging it over 10 minutes to make it easier to see what’s happening.

Click for a larger version. Graph showing the operation of DHW heating cycle. The electrical power drawn by the heat pump (watts) and thermal power delivered (watts) are shown against the left-hand axis, and the temperature of the water (°C) is shown against the right-hand axis.

The first thing to notice is that the thermal power delivered by the heat pump is larger than the electrical power consumed. This is the ‘magic’ of heat pumps. The extra energy is drawn from the outside air which is cooled by about 3 °C in the process.

The second thing to notice is that initially the thermal power delivered is high (peaking at nearly 3.8 kW) and the electrical power is low (just under 1.0 kW). But as the water temperature increases from 30 °C to above 50 °C, the heat pump has to work harder (electrical power increases) to deliver slightly less heat.

This is the nature of heat pumps – they work best when heating lots of water through small temperature differences rather than heating small amounts of water through large temperature differences.

The ratio of the heat energy delivered to the electrical energy used is called the Coefficient of Performance or COP. This is shown on the graph below.

Click for a larger version. Graph showing the operation of DHW heating cycle. The Coefficient of Performance (COP) is shown against the left-hand axis, and the temperature of the water (°C) is shown against the right-hand axis.

For most of the heating cycle the COP is above 3 and almost reaches 4 when the water temperature is about 40 °C. The spike in COP at the end of the heating cycle is probably an anomaly caused by the smoothing of the data, and the fact that heat is delivered from pre-warmed pipes after the electrical energy was reduced.

Averaging the electrical power drawn by the pump over the whole day – the standby power is 12 W – the effective COP is around 2.8 i.e. the heat pump provided me with 2.8 times more thermal energy than the electrical energy I used to power it.

For those of you unaware of other household developments, this electrical energy came from a battery which stored solar power generated earlier in the day. So our hot water is 100% carbon dioxide free in the summer.

Future Improvement 

I am pretty happy with this performance. But I think it can still be improved.

Firstly, there is a four metre section of pipes between the heat pump and the DHW cylinder which are still not insulated. After insulation, more heat should be delivered and the overall COP should increase.

Secondly, I need to see how the temperature of the hot water in the taps and showers is affected by lowering the hot water storage temperature. I think somewhere between 45 °C and  50°C might be acceptable and that should improve the COP still further.

Finally, when used for space heating I am hoping to keep the temperature of the water circulating through the radiators as low as possible – perhaps 45 °C will be possible – which should again improve the overall COP. To achieve this I may need to change one or two of the older radiators. But that is a problem for the autumn.

For now I am enjoying the wonder of thermodynamics in action.

IPCC Assessment Report 6: The spin begins

August 9, 2021

So Assessment Report 6 (AR6) has been published. It represents the scientific consensus that should form the basis for the Glasgow meeting of the COP in November.

But an even shorter summary was published by Gavin Schmidt, a Brit who heads NASA’s Goddard Institute for Space Studies and who was recently appointed a presidential advisor on Climate Change.

  • It’s real,
  • It’s us,
  • Experts agree,
  • It’s bad,
  • But there is still time to do something about it.
  • Our climate future is, ultimately, up to us to decide

AR6 is a triumph. It is the culmination of a massive scientific effort that has produced a deluge of irrefutable evidence that has extinguished the acrid fires set by Climate Change deniers.

But these ex-deniers have not gone away. They have conveniently forgotten that all their years of confuscation have been shown to be not genuine scepticism, but malicious nonsense and simply wrong.

And now they are now trying to stop action on climate change by any other means. These include:

  • Ad hominem attacks on the people involved in Climate Research and Climate Activism.
  • Arguments that acting against climate change would cost too much and be unfair on the poorest in society.
  • Or that it is not the UK’s problem – but a problem for the USA or China, or India.
  • Suggesting spurious technical alternatives – such as ‘hydrogen boilers’.

I urge you to beware of people adopting these arguments because delay in acting increases the costs of action and the final extent of the damage caused.

Conveniently, today’s Daily Mail coverage of AR6 shows these failed denialists in action

The Daily Mail covers the IPCC report with 3 pieces which exemplify their agenda to stymie meaningful action.

Daily Mail#1

The first piece is straight news of AR6 with comments. It’s alarming reading because what is happening is alarming!

But at the end there is a Daily Mail political context piece which is designed to make it seem like a strong response may be – unfortunately – unaffordable because of compassion for the poorest in society.

Click for a larger version

Daily Mail#2

The second piece is a series of frankly bizarre ad hominem attacks by Dominic Lawson. The key points are that:

  • Chris Packham is a hypocrite.
  • The BBC is “a pulpit for eco-fanatics and their doomsday climate cult“.
  • Alok Sharma (President of the COP26) is a hypocrite for travelling to countries for face-to-face negotiations.
  • There then follows a deranged fantasy in which he attacks church leaders and Greta Thunberg for trying to stop global climate change.
  • He then brings in the ‘It’s China not us’ argument for good measure.

In short he suggests these people are all nutty doom-mongers who should not to be trusted.

In contrast, his exemplar of a responsible citizen is Ian Botham, photographed while hunting, shotgun in hand.

Nowhere does he acknowledge the reality of the science in the AR6 and nowhere does he propose any alternative course of action. In this he seems to be morally retarded – acknowledging no responsibility for the emissions this country has made – massive on a historical per capita basis – which are warming the planet for the very poorest and most desperate people.

Daily Mail#3

The third piece reports on infighting within the Conservative Party. The piece first outlines the party’s glorious achievements and grand commitments, but then highlights the views of Tory rebels and adds irrelevant confuscation around the use of hydrogen for heating.

  • “Kent MP Craig Mackinlay has launched a group to to push back at plans to outlaw sales of new petrol and diesel cars and replace gas boilers within the next 20 years: ‘We don’t want to be on the wrong side of the electorate, that just will not wear this.'”
  • “Senior Tories fear the crisis could prove politically ruinous in so-called Red Wall seats
  • “According to the Sunday Telegraph, [there are] fears that working class families will bear the heaviest share of the burden. Last month experts advising the Government on infrastructure warned Britain’s families face paying hundreds of pounds more a year on food, flying and shipping costs to help industries remove greenhouse gases from the atmosphere.
  • “If hydrogen is part of a zero-carbon future….

This kind of discussion frames the problem which faces us in solely political terms – with no acknowledgement of the need for action. It brings up appalling ideas like hydrogen boilers in order to distract people from the undeniable need for action.


AR6 is a great achievement – a stepping stone on a path to a possible sustainable future.

But as I mentioned just last week in discussing COP in the context of the collapse of Arctic Sea Ice, the previous five assessment reports and the previous 25 COPs have not been followed by any noticeable decline in carbon dioxide emissions. In fact the rate at which carbon dioxide is being emitted has increased decade on decade.

Click for  larger version. The graph shows the Mauna Loa record of atmospheric carbon dioxide since 1959 in black. The dotted lines are extrapolations of the trend from each decade, the 1960s, 1970s etc. Also shown are the dates of COP meetings – the Conference of Parties to the UN framework convention on climate change and the dates of the scientific assessment reports AR1to AR6.

We have reason for hope – but despair is still an understandable option.

Know your onions

August 9, 2021

Click for a larger image. New Zealand onions were on sale in my local supermarket at the same price as UK onions. How?

Friends, while shopping in my local supermarket, I noticed that there were two crates of onions next to each other.

Both offered onions for sale at a very reasonable 85p per kg.

I have been trying recently to preferentially buy produce from the UK, and so I looked at the labels to see if the onions were from England or Spain.

I was pleased to see that one crate of onions was indeed from the UK.

But I was shocked to see that the other crate of onions was not from Spain, but from New Zealand!


Click for a larger image. New Zealand is literally on the other side of the Earth from the UK. It is a very long way for onions to travel.

Friends. I am not a xenophobe.

And I welcome the import of New Zealand produce to the UK. It makes perfect sense for us to import kiwi fruits for example, or wine. I can even understand a seasonable argument for apples.

But importing onions from New Zealand makes no sense to me.

I am, literally, lost for words

COVID 19 Wave#3: Trends become clearer

August 7, 2021

Click for a larger image. Logarithmic graph showing positive caseshospital admissions and deaths since the start of the pandemic. The blue arrows show the dates of recent ‘opening’ events. The green dotted line shows an extrapolation from the first week of June. The purple area shows the period of the Euros finals.

Friends, I last wrote about the pandemic 11 days ago on July 27th. Then I said:

… [the] decline in daily cases is really welcome. However since I don’t know why it has happened I can’t really imagine what will happen next.

If I had to guess, I think I would expect the rapid decline to be temporary. I think daily cases  will fall to a still high level, perhaps 10,000 cases per day, but hopefully less.

And then I would expect daily cases to either increase again or decrease, but much more gradually. But that is just a guess.

So in the coming weeks I will be looking to see if the hospitalisations and deaths show the same peak in  cases, and then trying to discern the ongoing trend in cases.

Things have now become clearer, and the rapid decline in daily cases was indeed temporary and the timing indicates that it was associated with the Euro 2021 championship.

Click for a larger image. Logarithmic graph showing positive cases, since the start of 2021. The blue arrows show the dates of recent ‘opening’ events.  The green dotted lines show (a) an extrapolation from the first week of June, and (b) a guess for the ‘underlying’ spread showing the ‘Euros Effect’.

The peak in daily cases occurred on 21 July and daily hospital  admissions  peaked 10 days later on 31 July. This correlated peak in admissions indicates that the peak in cases was not a measurement effect but arose from a real increase in viral prevalence.

As I write (7 August) the number of deaths per day has not yet reached its peak but the 7-day retrospective average is currently 90 deaths per day.


By looking at the data at the peaks (7-day retrospective averages) we can estimate how many cases result in hospital admissions and how many hospital admissions result in deaths.

  • Around 47,700 cases per day resulted in about 930 admissions to hospital per day i.e. a ratio of roughly 2%
  • Around 930 admissions resulted in at least 90 deaths per day i.e. a ratio of roughly 10%
  • So 47,700 cases per day results in at least 90 deaths per day i.e. a fatality ratio of roughly 0.2%

These figures are much lower than earlier in the pandemic, but they are still – in my opinion – worryingly high. For comparison, in the UK we normally expect about 1700 deaths per day from ‘non-pandemical’ causes.

Ongoing Trends

Recently daily cases have fallen to around 27,000 cases per day – a very high level by either a historical or an international comparison.

Worryingly daily cases still appear to be slowly increasing. Measures to restrict viral spread appear to be ad hoc at best and so we might reasonably expect Wave#3 to continue for several weeks – or even months – at a similar level.

Based on the ratios above, 27,000 cases per day will result in roughly 55 deaths per day or around 1600 deaths per month.

27,000 cases day probably corresponds to very roughly 1 million infections per month which is similar to the rate at which first doses of vaccine are being administered.

Click for a larger image. The progress of vaccination amongst the UK population. The left-hand axis shows the population in millions and the right-hand axis shows the fraction of the entire population – not just adults. The dark blue line shows first doses and the light blue line shows second doses.

What do I think about this?

I don’t know!

I hate to say it – and readers in New Zealand and Australia and South Korea and Taiwan may find this extraordinary – but in the UK at the moment, this level of infection and death is ‘politically acceptable’.

The alternative – re-imposing restrictions and re-doubling vaccination efforts – is not being considered.

  • If we are lucky, then the death rate will remain at 50 or so people per day for just a month or two – perhaps increasing when schools and universities restart – and then slowly reducing as the long-sought ‘herd immunity’ is achieved. The death toll from Wave#3 might be below 10,000.
  • If we are unlucky, then this death rate will continue for several months, and the widespread prevalence amongst the several million immunocompromised people might result in a new variant against which vaccines are not as effective.

This is not the policy I would have chosen – I would have been less inclined to rely on ‘luck’ as an ally. But given where we are, if the death rates and hospitalisations rates remain low enough then I can’t see this policy being changed.

On the plus side – for the non-immunocompromised – a reasonably normal life is possible.

In contrast with the UK’s ‘Total COVID’ strategy, countries which have adopted a zero-COVID strategy – such as China, New Zealand or Australia – will have to retain strict border controls until their populations are fully vaccinated.

But since no border controls are perfect, they will probably have to periodically impose lockdowns as new infections are imported: And in democracies, there is a limit to the amount of restrictions citizens are prepared to accept – and colloquially – many people seem to feel we are close to that limit. For example restrictions on Australians leaving Australia seem extraordinary!

Over the coming year or so, COVID might become endemic in the UK, and so there might not be too many restrictions for entering the UK – but countries worldwide might retain especially tight restrictions for passengers from the UK.

As many people have said until COVID vaccination becomes available world-wide, COVID will remain a threat everywhere in one way or another.

Good luck wherever you are.


“A Farewell to Ice” by Peter Wadhams: Review

August 4, 2021

I have just finished readingA Farewell to Ice” by Peter Wadhams. And I found it a deeply uncomfortable read.

It can be considered as a first-hand account of the Arctic Death Spiral summarised in the figure below.

Click for a larger version. The Arctic Death Spiral – copied from this link. Proceeding clockwise from the top, each line charts the estimated volume of Arctic Sea Ice in thousands of cubic kilometers for a specific month of the year. The centre corresponds to no sea ice, and the maximum radius corresponds to 30,000 cubic kilometers. The precise date at which the Arctic will be ice-free in September (black line) is not clear, but you will likely live to see it happen.

Sometimes when reading a book, one does not learn any basic new facts. This can serve as confirmation that’s one’s prior understanding was (broadly) OK.

Contrariwise, one sometimes learns a fact so basic that one realises the depth of one’s prior ignorance.

Significantly, in this book I learned that the formation of Arctic Sea-Ice is MUCH more complicated than I had hitherto appreciated.

How Seawater Freezes

Firstly, when seawater cools, it does not – like freshwater – exhibit a density a maximum at around 4 °C. How did I not know that?

Click for a larger version. The density of pure water as a function of temperature. The maximum density occurs approximately 4 °C above the freezing point.

This density anomaly is small – amounting to just 0.02% – but it plays a critical role in how open water freezes in lakes.

  • Imagine that the air above the water is very cold – say -10 °C – but that the lake water is initially warm, say + 10 °C.
  • The cold air cools the surface water which consequently becomes denser and sinks. As it sinks it lowers the temperature deeper in the lake.
  • But when the surface water cools below 4 °C, it becomes less dense and so floats at the surface. When this happens the surface layer freezes quickly, but most of the lake remains at 4 °C.
  • Hence freshwater fish are not frozen each winter.

But in water with a salt content higher than 2.47% this density maximum does not occur. Consequently, seawater – with a typical salinity of around 3.3% – cools in quite a different way to fresh water.

In seawater, the cold air can cool the entire water column down to the freezing temperature which – for saltwater – is depressed to around -1.8°C.

But this analysis only applies to still water: the action of waves on freezing water is complex and can give rise to many different structures in sea ice, including the fascinating ‘pancake’ ice.

And ‘piles’ of ice on top of the ice sheet arising from wind-driven collisions between different sections can act effectively as ‘sails’ on top of the ice.

And below these ‘sails’, equivalent ice structures develop which can act as ‘keels’, dramatically affecting sensitivity to sea currents and grounding the ice in shallow waters.

Overall, I learned that the apparently simple process of ‘water freezing’ is much more complex than I had appreciated. And significantly, I understood that accounting for this complexity was important if models of the processes were to be realistic.

The Wider Context

Peter Wadhams’ continuing fascination with the details of how sea-ice freezes and melts is evident in this book. But his fascination now evokes the same sadness as zoologists studying species which they know will soon be extinct: the behavioural details are fascinating but the more one understands, the greater the tragedy of their inevitable loss.

Peter Wadhams points out that when he began studying the polar regions in the 1970’s, it was generally accepted that the oceans were an unchanging environment, there to be mapped and studied.

And reading his accounts of his early adventures, I could share his sadness, shock and eventual horror at finding that the polar ecosystem was disappearing before his eyes (and other instruments).

Given his knowledge of the complexities of sea-ice formation it is perhaps understandable, but concerning nonetheless, that he is sceptical of the predictions of climate modelers who expect that summer sea-ice will remain for many decades. His view is that “summer’s lease has all too short a date“.

But whoever is correct, the state of the Arctic Ocean in the middle of this century is clear – there will be clear water at the North pole for several months of the year.

And so…

The book points out that the loss of sea ice (and snow cover on nearby land) affects the Earth’s overall albedo so much that it will be equivalent to an additional 50% of the warming caused by carbon dioxide emissions.

And that even if we reduced carbon dioxide emissions to zero overnight (which will not happen) this albedo warming would continue as long as the ice was gone – probably for centuries.

He stresses the importance of keeping the Arctic frozen both to reduce the overall warming, to prevent methane emissions, and to stabilise climate patterns in the Northern hemisphere.

He thus calls for geo-engineering (by low-level cloud formation) to re-freeze the Arctic now and buy time for longer term solutions.

I am generally a geo-engineering sceptic, but with regard to the Arctic, I found it difficult to disagree.

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