Climate Action — Methods

Footprints are confusing.

Measuring emissions from individual actions

  1. If you buy and use a computer, most of the emissions caused will come from the manufacturing process rather than from the electricity used when it’s on. If we don’t include these ‘embodied’ emissions in measurements, they’re meaningless. There are two ways of counting embodied emissions: life-cycle analysis (LCA) and the Leontief Input-Output method (IO). LCA underestimates emissions, perhaps by a factor of two. That is to say, life-cycle sucks. We want to use sources that use IO wherever possible.
  2. Not all emissions are from CO₂. It causes maybe 75% of warming, but other greenhouse gases matter. We want sources that include these. The right unit of emissions is tons of CO₂ equivalent (t CO₂e), which includes all gases, weighted according to how much warming they cause by 2100. I’ll generally refer to 8t CO₂e as 8 tons of emissions for readability. (See the start of this for what I mean by a ‘ton’.)
  3. Any national statistics you use need to be for consumption rather than production. That means that if a computer is built in China and exported to the UK, it counts in the UK emissions statistics, because it’s an individual in the UK who benefits from the computer.

How Bad are Bananas?

How Bad are other Greenhouse Gases?

  • We’re looking at 2100 rather than 2120.
  • We’re interested in a measure of the final temperature increase. Bizarrely, global warming potential doesn’t measure that! Instead it’s (roughly) a measure of the average temperature increase over, say, 100 years. What we’re after is the global temperature change potential.
  • For reasons I don’t understand, Berners-Lee doesn’t account for the CO₂ eventually formed from other greenhouse gases, called climate-carbon feedbacks.
Calculations for methane are on the wonderfully named page 8SM-17 of this supplement.



From IPCC Mitigation Pathways Compatible with 1.5°C… (2018), p105

Greenhouse gases

From here.

The Little Planet

The Future

The future is another country. They emit things differently there.

Computing Lifetime Emissions

  • 1% annual reduction: lifetime emissions are 39.5x those in 2020.
  • 1.5% annual reduction: lifetime emissions are 35.4x those in 2020.
  • 2% annual reduction: lifetime emissions are 31.8x those in 2020.

Yearly Rule

Well, I thought it was meant to be a planet. Credit: NASA

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