Saturday, 14 March 2020

COVID-19 Herd Immunity Sim

Why Herd Immunity Doesn't work for Covid-19

This is a simulation of the epidemic for the sake of working out how much herd immunity is needed to protect the population.
The answer is around 90+% (98% in this sim). Herd immunity is mistaken.


Herd immunity is designed for vaccines.
In normal epidemics, herd immunity works because the contagion distance between someone who contracts the disease and the next person who isn’t immune is large due to the number of people already immune (depending on the % immunity and infection rate). But here, no one has immunity, so the disease would distribute itself throughout the population and the contagion distance remains small even after nearly everyone has become immune. So in this case, herd immunity is incorrect, despite what you may have heard from our PM saying he’s followed the advice of the chief scientist.

How To Use

The easiest way is simply to press the StartSim button. It simulates a population of 160,000 where each person potentially infects 0.8 people in their vicinity each day until they get isolated (in the example in day 5). The default vicinity is 256 (+/-16 in each direction) and if by chance an infected person tries to infect an already infected person, it has no effect.

You can see in realtime how an infection spreads across the population. Initially it appears to be exponential, but fairly quickly isolation cuts in and people who have it tend to come into contact with those who already have it, so they don't infect so many new people.
So, the epidemic then spreads at the boundary.
As it does so, some people - a few - remain uninfected, by chance and as the disease progresses at the boundary, the mass of people now immune effective protect the very few who have never been infected. But this is a very low figure, because the whole population has no prior immunity and is not vaccinated.

You can play around with the infection rate (<=1) and mobility to simulate a ghastly pandemic that seems to spring from everywhere all at once, but ultimately it has little effect on the herd immunity as it effectively doesn't exist.

Remember, this is only a simulation to demonstrate the lack of herd immunity. It does not really project actual figures for infection, nor are the rates correct, nor the population, nor the mobility, nor the potential impact of warmer weather on the virus.


Pop: Contagion/day:
Isolate on day: Mobility:

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Monday, 30 December 2019

Monopoly Sim

Our family plays Monopoly every Boxing Day and the winner gets to keep our Monopoly trophy for a year with their name inscribed on a new lolly stick. I've never won, I should do something about that!

I wanted to simulate the game of monopoly to find out which locations are most likely. The distribution won't be even because GO TO Jail takes you back to Jail (or Just visiting Jail once you pay or throw a double to get out) and some of the other cards take you to different locations on the board (Go, Pall Mall, Marlebone station, Trafalgar Square or Mayfair.

Naturally, it's not good enough just to simulate the game, the quest is whether it's possible to do that on a 1K ZX81. We can do that by some analysis on what really counts for the simulation.

Firstly, obviously, to find out which locations are most popular, we don't need to draw a simulation of the board, simply listing the popularity of each location as a series of numbers will do. On a ZX81 we'd need to count the memory used by the screen for this. Assuming each location could have a popularity up to 255, then we need 4 locations per location: 160 bytes in total.

Secondly, we don't need to store the names of the properties; the value of the properties or rents since if we simply know the popularities, we can calculate the income we'd get from that and the card values.

Thirdly, we don't need to maintain any money, because we only care about popularity; this means we don't need to simulate the bank or money for passing GO and we don't need to simulate chance and community chest cards that involve money. So, the only cards that matter are those that take you to a new location.

Fourthly, we can note that there are only 2 Community Chest cards that don't involve money, a goto GO and goto Jail, which are also part of the Chance cards, so we can re-use two of the chance cards to simulate Community Chest.

Fifthly, we can assume that a play will get out of jail immediately by paying or by having a card - it makes little difference to distributions (though we could simulate runs where the play prefers to get out of jail using a double, this means they'd only move

This means the simulation is pretty simple:

  • We need an array of 40 locations to hold popularities.
  • We need to simulate two dice for moving parts: the sum of two random numbers 1..6.
  • We need to redirect the locations if we land on one of the 3 Chance or 3 Community Chest locations or Goto Jail.
  • The redirect locations are: 0 (GO), 10 (Jail), 11 (Pall Mall), 15 (Marlebone stations), 24 (Trafalgar Square), 39 (Mayfair) or back 3 spaces, but Community Chest is limited to the first two.
  • We could calculate going to jail if the last 3 rolls are matching pairs and this would mean an extra jail visit every 1/216 throws on average. Getting out of jail by throwing a matching pair wouldn't affect results because the throw only puts the player into the 'just visiting' location and thus doesn't affect where they land after leaving jail.
  • Periodically we should display the current popularities.
With all these rules apart from the even dice jail rule and using the normal ZX81 Basic space-saving rules we can squeeze the code into 1Kb.

Line numbers take up 21*5 = 105b. The main code takes up another 305b. M$ takes about 45 bytes variables take up about 6*4 = 24 bytes. The screen takes 160 bytes, making a total of 639 bytes, which is within the limit of a 1K ZX81.


It's just a list of numbers representing the popularity of every location from GO to Mayfair:

The ZX81 is really slow when run in SLOW mode, taking 0.6 seconds per go, or about 84 seconds per round including the printing. About 4,000 runs were taken which took nearly an hour. We could speed this up by running in fast mode; removing lines 25 and replacing line 130 with GOTO 30. Then it would take 0.15s per run, so 4000 runs will take 10 minutes.

What the results mean:

Site Pop Site Pop
Old Kent 32 Whitechapel 41
King's Cross 29 Angel 40
Euston 43 Pentonville 36
Pall Mall 46 Electric 41
Whitehall 35 Northumberland 40
Marlebone 40 Bow St 47
Marlborough 51 Vine St 44
Strand 47 Fleet St 52
Trafalgar 58 Fenchurch 43
Leicester 44 Coventry 40
Water 47 Piccadilly 49
Regent 46 Oxford 39
Bond 32 Liverpool 45
Park Lane 29 Mayfair 51

In this run there were 4173 throws, so there would have been 19 extra go to jail's due to three successive pairs (boosting Electric to Strand by about 7%).

We can see that the four most popular places are Trafalgar, Fleet St, Marlborough and Mayfair and at the other end of the scale, Park Lane, King's cross, Old Kent Road, and Bond Street are significantly less likely. It's understandable that Marlborough would be likely, but I would have thought Bow Street would have been equally likely (both 5/36 probability), but Trafalgar was unexpected - except that it's an actual card destination. We know that Chance was hit (47+70+54 = 171) times without the player being redirected (11/16), so in total it was hit 248 times and therefore 15 of these involved jumps to Trafalgar (lowering the hit rate to 52). A similar number of hits redirected to Mayfair (51-15 = 45 still leaving it more popular than Park Lane).

The sample size is about 4173 across 40 locations, about 104 hits per location, so the variance will be fairly significant. Therefore I haven't deduced too many details from the results.


The main conclusion is this: it's perfectly possible to solve an interesting question by simulation on an old computer with minimal memory. Even on a 1Kb ZX81 there was spare space. It's worth considering what the minimal computing resources are to solve the same problem. It's certainly under 1Kb, so a basic Jupiter Ace or a 1Kb MSP430 should easily be possible along with a PIC16F54 or even maybe an ancient 1802-based ELF computer with the standard 256b of RAM.

Saturday, 3 August 2019

Danger! Danger! Devaluation!

Right now, Brexiters keep claiming that devaluation is good for the economy. They're almost certainly wrong.

Intuitively, a fall in the pound is a bad thing: anything we buy from overseas goes up in price and since a high proportion of what we buy comes from overseas, our cost of living will go up.

But then Brexiters jump in and say "Devaluation is great, because it means more exports and that will make the economy grow." As a general rule, because Brexiters often distort the truth, you should be skeptical. So, are they wrong here too?

It's a good question. Recently I was at my Dad's house and we were watching a TV show called "Factory Wars" on the Yesterday channel. I was surprised to find a bloke from The Institute of Economic Affairs. Why was an economist from a lobbying organisation with secretive funding (hint, Big tobacco and the climate denying US groups like the Heartland Institute) on a history show?

Basically he was using it to push free market ideology. He claimed that the UK escaped the recession in the 1930s because it implemented austerity unlike the US which implemented a Keynesian New Deal. This was completely different to how I'd understood these economies in the 1930s: on the basis that austerity empirically doesn't work; its easy to explain why, and it was the Keynesian New Deal that empowered the US to manufacture the armaments that helped the allies overcome the Nazis.

It's not coincidence that the IEA offered a completely different explanation than what is normally understood: they're based at 55, Tufton Street where Vote Leave was also based. So, again we have another ideologue whose views we should suspect.

So, I checked out what really happened in the UK's economy in the 1930s? Economics Help is really useful. Basically, the crash of 1929 caused a lot of hardship in the UK, but in the mid to late 1930s we dropped the gold standard; which lead to a deflation of the pound and this lead to a mild economic recovery in the south, but the North still had it tough.

So, it looks like Brexiters might be a bit right, and the IEA were misleading as normal. But is it?

Devaluation Model

Actually we can work this out ourselves, because it's easy to model. In our model (for a business, but it can apply at a larger scale) we consider just three variables:

  1. Profits
  2. Internal costs (labour minus rises in the cost of living due to buying overseas goods, maintenance of equipment etc). We assume this is a constant.
  3. Imports (including the increases in the cost of living for employees from overseas goods).

Case A

In the first scenario, we consider a company with reasonably high import costs (50%), a profit margin of 30% and the rest is internal costs (20%). If the pound deflates by 25%, then imports go up to 50*1.25 = 62.5%. So, now our profits are 30-12.5 = 17.5% profits. This means that the company needs to sell 30/17.5 = 71% more goods, but the domestic market will buy less, and the overseas market will only find its products are 25% cheaper (due to devaluation).

So, the question is: is it like overseas customers will buy 71% more, if it's 25% cheaper? This seems unlikely to me.

Case B

Let's consider the second case: profits are 70%, internal costs 20% and imports are 10%. Imports increase by 25% => 12.5%, so we now need to sell: 70/(70-2.5) = 3.7% more. OK, so in this case our product is 25% cheaper, and we only need to sell 3.7% more for us to make more profit, this seems plausible.

So, we have to ask ourselves, what kinds of businesses are like this? Mass market manufacturing (cars, aircraft, smoke alarms) will rely a lot on imports and will make a relatively small profit. Apple, for example has margins between 20% to 30%. Dyson is also about 21%. DELL has an operating profit of just 1.1%. Companies producing consumer items such as smoke alarms have fairly low margins which explains why they would move to cheaper EU countries.

What companies are like case B? Services and financial companies are like that. However, financial companies are likely to move out of the UK due to Brexit, so this means service companies would benefit.

However, to some people, UK manufacturing companies can look good: namely, if you hold a lot of offshore wealth, then UK manufacturing companies struggling under devaluation look like a good buy. In other words, disaster capitalists with offshore accounts, such as people like Jacob Rees Mogg and a large proportion of Conservative party members and MPs.


Brexiters are wrong: it's just a front for their disaster capitalist mission. We can summarise our model and convey why in a simple table:

So, why did the UK not crash due to a double-whammy of austerity and devaluation in the 1930s? That's pretty simple, being the biggest power bloc at the time meant that although most of its food (91%?) was imported along with a significant proportion of goods, a great deal of this was essentially an internal market, with the added advantage that many resources, particularly coal were internal.

Saturday, 6 July 2019

Let the EVs Take the Strain

A recent BBC article says EVs won't solve congestion problems. It's yet another negative headline about EVs to follow from yesterday's negative EV headline where they said EVs were falling in sales for the first month in whatever (when in fact BEV sales had gone up 67%). They even go to the trouble of showing a picture of a rare EV, an 8 year old early prototype Smart ED TwoFour, rather than - say EVs hundreds of times more popular, to get across the idea that EVs are toys. Next week, watch out for the Tesla-bashing article ;-) and no mention of how sales of real EVs in the EU, the US and globally are rocketing.

Similarly, this article uses a bit of truth to hide a bigger lie. In fact EVs will go quite a long way to solving congestion.

Car Use is Falling

Car use is already going down in some parts of the UK, mostly because in London, they're not needed much and elsewhere because insurance for young drivers is prohibitive.
But actually, the nature of EVs will themselves radically change our vehicle usage, primarily because they have so few moving parts and batteries last much longer than originally expected (and will get several times better), to get sufficient wear and tear we're going to have to drive them much more often.

ICE Drives Congestion

The problems we see with urban vehicles are problems relating to ICEs themselves. For example, you can't have a filling station at everyone's house - it's far too dangerous and far too expensive! ICEs force us to place filling stations as widely as can be tolerated and because the effort taken to fill up (compared with plugging in an EV); this in turn forces infrequent filling; large tanks and very long ranges.

But long ranges themselves have the side effect of increasing our journey lengths which impacts everything: distance travelled to shop, to our workplaces, to schools and hospitals and all this increases traffic.

EV Transformations Will Blow Our Minds

EVs will change this radically. We'll have to share cars to get the wear and tear out of them and because charging will become ubiquitous (think every forecourt where your car might hang around); we'll need cars with much shorter ranges on average than even the first generation of EVs: think 10KWh or even 5KWh for the majority of cars and in turn two person EVs will dominate for the vast majority of journeys. But in turn, because we can charge easily, we can expect journeys to shorten too.

Remember in this model, people don't own their cars as much.

Why will people choose tiny, 'under-capacity' cars? It's simple, they'll be much cheaper to build, sell and drive! My Zoe (22KWh) gets about 4 to 4.5 miles per KWh at maybe 12p/KWh. Given a gallon of petrol (4.5L) = 4.5*£1.25 = £5.63, I get 5.63/0.12*4.5 up to 210mpg running costs.

But a Renault Twizy (a 2 person EV with a 6.7KWh battery) will get 6 to 8 miles per KWh, equivalent to 300 to 400mpg running costs.

Given a typical day's travelling in the UK is only about 10 to 20 miles, about 3KWh, that's only half a Twizy's battery. And considering the sheer number of charging points there will be, the average needed journey between charges will only be 5 to 10 miles, just 1.5KWh.

On that basis, a future EV with a 5KWh will seem ample, even though right now, all the talk is about 50KWh to 100KWh batteries.

So, EVs will go a long way to reduce congestion in themselves owing to the different driving model.

Friday, 12 April 2019

Plottastic ZX80!

A guide to plotting pixels in Basic on a ZX80!


Both the ZX80 and ZX81 support 8x8 pixel character-only displays and contain 16 graphic characters that can be used to plot fat 4x4 pixel pixels on a two-by-two grid within each character:

These are called Battenberg graphics after the cake of the same name 😀

On a ZX81 it's easy to use these characters to plot (crude) graphics on the screen, the computer provides a PLOT x,y and UNPLOT x,y for this purpose. But with half the ROM on a ZX80, it's much harder - so I wondered, how much harder is it to plot pixels? It turns out it's pretty formidable!


  • The ZX80 doesn't have any PLOT or UNPLOT commands.
  • The screen on a ZX80 is like that on a ZX81, when you run a program, the screen first collapses to a minimum of 25 newline characters and expands as you display text. However, on a ZX80, unlike the ZX81, you can't print anywhere on the screen as there's no PRINT AT function, this means we'll have to poke onto the screen.
  • The memory map on a ZX81 has the display immediately after the program, but on a ZX80, the display comes after the variables and the editing workspace which means that it'll move around just by creating a new variable or possibly by performing input (which is a potential problem).
  • Ideally, to convert from pixel coordinates to Battenberg graphics you'd want to map the odd and even x and y coordinates to successive bit positions to index the character.

  • But, unlike the ZX81, the character set on a ZX80 doesn't have the characters in the right order to display Battenberg characters. Instead they contain gaps; the last 8 codes are generated from the first 8 but in reverse order; and some of the first 8 are taken from what ought to be the inverse characters!

The Solution

The solution really comes in a few parts. Firstly, the easiest way to be able to map an ideal pixel value to its Battenberg character is to create a table in RAM, by putting them into a REM statement (the ZX80 has no READ and DATA commands so it's hard to put a table of data into an array, but the first REM statement in a program is at a fixed location). However, even this presents a problem, because only 8 of the graphics characters can be typed. The easiest way to handle that is to write a program which converts a different representation of the characters into the correct ones.

So, on the ZX80, first type this:
After you run it, you'll get this:
Even this was tricky; I had to use character codes above 32, since symbols such as +, -, /, ", etc get translated into keyword codes for the Basic interpreter. The above program illustrates an interesting feature of ZX80 Basic that differs from ZX81 and ZX Spectrum Basic in that AND and OR operations are actually bitwise operations rather than short-circuit boolean operations. Thus P AND 15 masks in only the bottom 4 bits.

Once we have generated the symbols we can delete lines 10 to 30.

The next step is to actually write the code to generate pixels and plot them. Once we know how, it's actually a bit simpler. Firstly, we fill out the screen with spaces (or in my case, with '.'):
This gives us 20, full lines of characters. Because it's going to be difficult to plot a pixel by reading the screen, figuring out the plotted pixels then incorporating the new pixel; I cache a single character in the variable P and its location in the variable L. All my variables a single letters to save space if you try to run it on a 1Kb ZX80. The idea is that if the new print location in L changes, we reset P back to 0, otherwise we incorporate the new pixel.

Next we start the loop and calculations for plotting, in this case a parabola. We loop X=0 to 63 and calculate Y on each loop (it's a parabola that starts at the bottom of the screen):

Finally we perform the pixel plotting and loop round.

This involves saving the previous location in K so we can compare it later; then calculating the new location based on X and Y (since each character position is 2 pixels, we need to divide X and Y by 2 and since there are 32 visible characters and an invisible NEWLINE character on every screen line we must multiply Y/2 by 33). Note, a quirk of ZX80 Basic means that multiplies happen before divides, so Y/2*33 would calculate Y/66!

The pixel bit calculation in line 50 makes use of ZX80 bitwise operators, we want to generate 1 if X=0 (so 1+(X AND 1) will generate either 1 or 2) and then we need to multiply that by the effect of the Y coordinate, which is 1 on the top line, and 4 on the bottom: 1+(Y AND 1)*3 will do that. Hence this will generate the values 1, 2, 4, 8 depending on bit 0 of X, Y.

We must POKE the location L plus an offset of 1 (because the first character of the display is a NEWLINE) and also we must add the location of the display file (it turns out that these calculations don't make the display file move around). We poke it with the pixel value we want indexed into the right character code from the REM statement. Finally we loop round X.

This code generates this graph:
It looks reasonable even though it's generated with integer arithmetic. It's the first pixel plotted graph I've ever seen on a ZX80!

More Examples

My original reason for doing this was to see if I could generate sine waves using a simple method I once found for a Jupiter Ace. Here's the program and the result:
It looks fairly convincing, especially as it's all done with integer arithmetic. Because the code generates both the sine and cosine value, it's easy to turn this into a circle drawing program which produces the following:

It looks a bit odd, that's because the algorithm doesn't quite generate sine and cosine curves. What it's really doing is computing a rotation matrix, but only one of the terms is computed for sine and cosine each time. Hence, the circle looks a bit like an oval with a slight eccentricity.

My graph drawing algorithm has one very serious limitation. Because it doesn't read the screen in order to compute a new pixel, if the graph goes over the same part of the screen twice, the second pass will muck up what was there before. Doing the correct calculations is possible using some table lookups and bitwise operations, though it would slow down the graph generation. I didn't bother, because I only wanted to generate simple graphs.


The ZX80 and ZX81 have very similar hardware, but a number of design decisions in the ZX80's firmware made drawing circles much harder than you might expect. With a lot of effort it is possible to generate some simple graphs 😀

Saturday, 3 November 2018

The Gift of Sisyphus

George Monbiot always writes great articles on sustainability (and although this one is 6 years old it holds up well). Here, what George Monbiot is saying is that (as well as the abusive consequences of extractivism) about 50% of CO2 production is due to this kind of consumerism.

However, I would argue that the priority for everyone is simply to stop using fossil fuels asap. Imagine the same argument if we already had 100% clean energy: Monbiot would be saying that this pointless conumerism causes 0% of CO2 production. So, it would still be pointless, extractivist, and abusive, but it won't fundamentally be raising global temperatures for thousands of years.

The key thing to remember is that it's the total amount of CO2 emissions since the industrial revolution that matters, not the rate we emit. So, Reduce/ Re-use / Recycle (RRR) by itself won't fix global warming if we still use fossil fuel energy at all: it's simply like a bath that's trickling instead of gushing - it'll still overflow eventually.

But eliminating our fossil fuel usage and employing RRR makes it easier and quicker to get to 0 emissions. This still means the priority is clean energy now.

It's possible for most of us to cut out around 66+% of our domestic CO2 production by making just a few big decisions that keep paying both us and the world back. Listed in order of lowest to highest investment:

  1. Switch over to a 100% renewable energy supplier, like Ecotricity, or Good Energy. Pick a big supplier that actually owns Wind turbines, solar power and is starting to invest in baseload energy storage. This will cut out 30% of your emissions.
  2. Radically switch over any gas appliances to electricity. This will probably take a few years, but will include your gas fire and cooker / oven. This will probably address another 15% of your emissions (up to 45% now).
  3. Buy solar power for your house or invest in an Energy4All renewable cooperative. This will make other people's decisions for them, by removing some of the market for the existing fossil fuel industry and placing energy production power in your hands rather than theirs.
  4. Switch to an electric vehicle as soon as you can afford it. This will cut out another 30% of CO2 emissions. Even if you cut down on car driving and cycle or walk instead (a good thing), it's a false economy to believe that it's less polluting to keep an old fossil fuel car going as long as possible, because all it does is delay the time when you go clean: because the emissions involved in the new car will be a fixed cost. Every year we delay on this is a year the fossil fuel car industry has less incentive to switch: vote with your bank account.

The total here amounts to about 75% of your CO2 production and up to 30% of other's CO2 production. I cover this in a bit more detail in this post.

By contrast, difficulty with putting Monbiot's argument into practice is that to address it, we have to change our lifestyles in hundreds of small ways and a few big ways:

  1. To eliminate the consumerism we generate (though it's hard to predict when we'll stop using new things and there are also multiple ways of addressing consumerism, e.g. sharing as many consumables as possible).
  2. To eliminate the consumerism others generate for us (e.g gifts) without appearing to be kill-joys.
  3. To campaign for governments and world organisations to address the root causes, like conflict minerals. This is needed, because time and time again we're going to be suckered by cheaper products that we think we do need, and we don't have the time or knowledge to fully (or even partially) analyse the supply chains and ethics involved. Regulations are needed to shift the playing field in favour. Consider the effort involved by the company Fairphone (I have a fairphone 1) in tracing mineral sources.

So, the probability is that we'll try to do these things for a while, but slowly get overwhelmed by the market forces pushing us in the opposite direction.

This is really just an application of Every Big Helps from Sustainability Without the Hot Air.

Sunday, 8 July 2018

Three steps to Carbon Free Me (part 1)


Recently I posted a comment to my cousin's post about the heatwave:

Ok, so no comments on the elephant in the room here. It’s not just us, much of the world is in the grip of a heatwave right now. 33 people have died in Quebec. We need to start addressing the underlying causes - talking about it is a good start. And it will help us if we understand this will get worse. In a few decades, this will be a normal summer. Sorry I bang on about it all the time.

Citing this Guardian article:

And she replied:

I think people (including myself) don't know what to say because it's such a big issue that we feel quite helpless about it... I don't think the majority are in denial that climate change is a real danger. It's more just that it feels so far out of our control that it's hard to think about it.. "10 things you can do now to reduce your impact on climate change" type articles would probably get more people on board

Sigh, I can really see her point. So, this is my first shot at an article like that.


I think, to be able to respond at a personal level is to be clear about what the plan is. If we don't know what we're aiming for we won't know what to do and wouldn't even know how successful we've been. So, the goal here is very, very simple. It's not about plastic or planting trees, or a million things you can do that make a small difference. it's about relatively easy things you can do that will make literally a huge difference, like 30% to 60% of the whole way, for you.

The plan, globally, is to cut down on the emissions of CO2. To Zero. You may have heard talk of a low-carbon economy. A low-carbon economy will still be a disaster. Globally we have to cut down to nothing and then beyond. We have roughly 50 years to do this and in developing countries we have 30 years.

The positive news is that can cut out the majority of this or a substantial fraction of 30% to 60% pretty quickly. Cutting out 30% jumps us into the 2030s; cutting out 60% jumps us into the 2040s and we can feasibly do this in a fraction of the time. And the great thing about that is that the sooner we make these steps, the more breathing room we'll have along with other benefits. The principle here is "Every Big Helps".

This is a plan for domestic emissions.

Domestic emissions fall into 3, roughly similar sections: Electricity, Heating and Transport.

I obtained these values from some simple searching on the internet with phrases like "average electricity UK per year" etc. I'll update with proper links later, but for now, I found this CO2 calculator web page handy.

The total is: 7084Kg, 7 Tonnes for an average household! Wow! But a few decades ago in the UK it was 10 tonnes, and even a decade ago it was noticeably higher, so we've progressed. Let's deal with this from the easiest to the hardest. But before that...


We can't divorce politics from choices about energy. This should be obvious. Energy gives us (quite literally) power. Globally, 80% of that power currently comes from the fossil fuel industry. To put it another way, 80% of global power resides with the fossil fuel industry, an industry that has spent decades covering up the fact that their product is adding a blanket of heat to the world. To decarbonise means deliberately taking power away from them.

Here's an example, of how much power they have. The Church of England has a mission statement that says we have to look after the earth. It's called Stewardship. It means we think it's wrong to wreck God's creation, because God thinks his creation (which includes us) is good.

However, the Anglican church also has over £100 million pounds of investments in the fossil fuel industry and some sectors of that church have realised that's in conflict with the mission statement (really?). One of the most promising Christian movements to resolve this is Bright Now, which campaigns for churches to divest from fossil fuels.

So, in February 2014, in the Church's global get-together (the General Synod), they tabled a motion to promise a debate on divestment for the following year's Synod and in the meantime, they'd divest from the Alberta Tar Sands investments, the worst fossil fuels in the world, an industry so bad that the eminent ex-Nasa climate scientist, James Hansen said if the pipelines go ahead it's game over for the climate. So, the CofE divested from the worst of worst in 2015. Good on them - that's the way to show leadership, and I'm sure it had nothing to do with the crash in oil prices in 2014, making tar sands completely uneconomical.

Then I found out in early 2015 that the debate on divestment was being replaced by a debate on engagement with the fossil fuel industry, i.e. a commitment to the fossil fuel industry - with a wagging investment finger. How did this happen? Well, I found out directly from one of the key members of the Ethical Investment Advisory Group, Richard Burridge at a fringe meeting at that 2015 Synod in York. He explained that after the resolution in 2014, Rex Tillerson personally phoned them up to propose an alternative arrangement. And then the resolution was dropped. What this means is Rex Tillerson although not a member of the CofE, has more power over it than the Synod itself. Then after the meeting, in conversation, Richard Burridge started singing from the fossil fuel industry hymn sheet, explaining why divestment itself was bad for everyone and why developing countries needed fossil fuels. It's not, as Katherine Hayhoe explains.

Never underestimate the deviousness of the fossil fuel industry.


This blog ignores efficiency. That's because people concentrate on that so much I figure you probably know about some efficiency issues: LCD TVs, LED lights, that kind of thing. But also, because I want to focus on the key issue: efficiency by itself won't lead us to our zero-carbon future; we have to actively switch our energy sources. Also, I want to concentrate on the stuff that makes a huge difference: a huge difference is a big psychological boost as well as a practical action.


Step 1: Electricity Provider

By far the easiest way to cut down on your emissions is to choose a renewable energy company for your electricity. All it involves is switching supplier. It requires no investment and because renewable energy is getting cheaper thanks to economy of scale, these suppliers are relatively and increasingly competitive. The three main 100% renewable electricity suppliers in the UK are:

  1. Ecotricity - run by the visionary Dale Vince. They have their own (onshore) wind and solar farms. They also source renewable energy from overseas to meet demand.
  2. Good Energy - a well-established 100% renewable energy supplier and they're great for feed-in-tariff support.
  3. Cooperative Energy - their green pioneer electricity tariff is now 100% renewable. They have their own wind and solar farms.
There are other pop-up renewable companies such as bulb, but until you know where they get their renewable energy from I wouldn't recommend them, though they may be perfectly fine.

For an average household this will remove 23% of your emissions in one go. This takes you to November 2025 (if we lowered emissions steadily - in reality it'll take us a bit further than that, because it will be a curve).

Step 2: Heating and Cooking

The next easiest thing to do is to replace as many heating and cooking devices with electrical ones as the opportunity arises. For example, if you have the money, replace a gas fire with an electric fire. It won't be as warm, since they're limited to 2KW, but if you can tolerate it; then that's a way to go.

Also replace gas cookers with ceramic or induction electric cookers.

This is different to most of the advice you'll see, because they'll be comparing the CO2 emissions of an average electricity supplier with gas, but we are comparing renewable energy heating and cooking with gas. It will be more expensive, since electricity per KWh is more expensive than gas; so this requires an initial outlay, and an ongoing cost. We haven't found a massive increase in our electricity bills as a result.

Also, when I get figures for this, I'll update it in this blog post. Until then I'll assume that - based on these two items alone, you can save maybe 50% of gas emissions: 1565Kg of CO2, nearly as much as for electricity itself.

This would take 45% of the way, to the year: 2032.

Step 3: Transport

The next 'easiest' thing to do is to switch to electric vehicles as soon as you get a chance. An EV, running from a renewable electricity supply will save 100% of your transport emissions. Switching to electric transport involves a cost outlay, but the costs of running an EV are less than for a fossil fuel car, so it will pay back in the long term. There are many ways you can partially or fully achieve this and they're all based on the observation that most of our journeys are short.

  1. Buy an electric bicycle! Most EBs can suffice for journeys up to 45Km, enough for a visit to a friend, maybe a journey to work and back. They're limited to 15Km/h. Of course if you can handle a normal bicycle, then you'll get fitter too (but it won't save emissions, if you already have renewable electricity). Let's assume this deals with 30% of your journeys.
  2. If you have two cars, make one of them a second-hand EV and use it as the run-around: for shopping and shorter journeys. Second-hand EVs are increasingly available via auto-trader or ebay from about £5500 upwards. Most of them are first generation Nissan Leafs, some will be Zoes and BMW i3s; a few will be MiEv's (with a more limited range). These cars can carry a family on a journey 20 miles out and back, or 40 miles if you can charge it at your destination or will carry you on a 50 to 70 mile journey in total. Perhaps this will handle 70% of your journeys.
  3. If you're prepared to adapt your lifestyle, replace your car with an EV (100% of your journeys).
    1. For first generation EVs (like the 2016 Zoe we own), practical journeys will be in the 60 to 120 mile range (with one en-route re-charge) or 240 miles if you can charge at either end. We bought a second-user EV for £7500, but essentially it was new, so similar bargains may be possible. In essence, the vast majority of your journeys will fit these rules.
    2. For second generation EVs practical journeys will be in the range of 150 to 200+ miles either way. These vehicles start at £19K for the Zoe (with a leased battery); £20K for a Smart EQ; £25K or so for a new Leaf; about £34K for an i3; or similar for a Tesla model 3 (available from 2019), going up to £60K to £115K for a Tesla model S, Roadster or X.
With option 1, that saves: 700Kg of CO2 per year (assuming you use it consistently).

With option 2, it's 1623Kg of CO2 per year (assuming you use it consistently).

With option 3, you save 2319Kg of CO2 per year.

This takes us to a maximum potential of 78% of your emissions cut, ie. from 7084Kg to 1565Kg. It's equivalent to living in the year 2042. In other words, it gives us another 25 years to plan to eliminate the other 22%


This guide gives you actual figures. Things you can attain; that tell you roughly how far along the path to decarbonisation you've done. You can quote it in years so you know what year you're really living in. For me, that's a way to bring practical hope to the challenge.

Don't burn yourself out. It took us about 3 or 4 years to get as far as we have (which is about 2042), but we bought Solar Panels in the meantime and started on a mortgage. It might take you a bit longer, or you might have the resources to make major shifts now (the renewable energy shift is the easiest). Whatever you do, take a positive angle and encourage others to do the same :-)

Here's to a happy Carbon Free You!