Changelog

Notable changes to this site and to Without the Hot Air. Newest first.

2026-08-15 — 34 chapters revised, and a new "Has It Held Up?" overview

Since the last entry, the update work on Without the Hot Air went from a worked example to most of the book: 34 pages now carry sourced, dated updates to figures that have moved since 2008, each shown as visible <del>/<ins> markup against MacKay's original text, never a silent correction — up from the 20 in the previous entry, after a further pass through the audit ledger's lower-priority claims (LEDs, wave power, defence spending, EV efficiency, battery storage, carbon pricing, and more).

New: Has It Held Up? — not another chapter revision, but a synthesis of what the 34 pages of edits add up to: where MacKay's numbers moved (solar and wind costs collapsed further and faster than almost anyone forecast), where his method held up regardless (nuclear's safety case, his skepticism of hydrogen and biofuels), and where the world surprised him in both directions. The /changes page remains the mechanical, chapter-by-chapter list for anyone who wants the detail underneath it.

Also fixed: a rendering bug where prose mentioning two dollar amounts in the same paragraph (e.g. "$61 per MWh … $76/MWh") got silently parsed as math by the site's KaTeX pipeline, swallowing the text between them — affected both new content and some of MacKay's own 2008 text. Filed upstream: flowershow/flowershow#1359.

2026-08-08 — New foundations, and a few things quietly unbroken

This site is now a plain markdown knowledge base, published with Flowershow. The bespoke Next.js application that used to build it is gone. The pages you read are the markdown files in the repository — nothing is generated in between.

Without the Hot Air has moved to its own home: withouthotair.org. David MacKay's book had been living inside this repository since 2021, which never quite made sense; it is a book, and it deserved a book's front door. It is now a standalone community edition — his 2008 text, unchanged, in a form that can be corrected and updated. Every old chapter link here redirects to it.

Both sites now carry an "Edit this page" link at the bottom of every page. If you spot an error, fixing it is two clicks and a pull request.

Things that turned out to be broken

Rebuilding a site is a good way to find out what has been quietly failing:

• Five images had not been loading for years. They were stored with Git LFS, but the deployment never fetched LFS objects — so the site was serving a 131-byte text file where each image should have been. Recovered and restored.
• The global temperature chart was dead, twice over: the data file it referenced had never been committed, and the chart component needed a setting the page did not have. It now draws live HadCRUT5 data from 1850 to 2025.
• Four images displayed as raw text rather than as images, because the old site could not read the syntax they were written in.
• Chapter titles in the book's navigation read chap03, chap04, and so on, wherever a figure appeared before the heading.
• The site footer's "A Project of Life Itself" link went to vercel.com — a leftover from the template the site was built from in 2021.

Still to do

Most of the writing here dates from 2021 and has not been systematically revised. The temperature chart is now current while the analysis below it argues from 2018 carbon budget figures, which is a gap worth closing. That work is tracked in the open, as is the larger project of updating MacKay's numbers.