During the annual ritual of Earth Hour:

...around one billion people are expected to switch off their lights for one hour as a political statement against climate change and fossil fuels, and in support of carbon cuts and renewable energy.

Bjorn Lomborg thinks the ritual is a feel-good exercise for the rich that does nothing meaningful to improve the planet. Whether he is right to make this judgement is probably too much a matter of opinion to be asked as a question here. But during his argument he makes the very specific claim (I've highlighted the specific part of the claim worth addressing):

In fact, a small decline in electricity consumption does not actually translate into less energy being pumped into the grid, and therefore does not reduce emissions. While any significant drop in electricity demand means a temporary reduction in CO2 emissions, this is partly offset by the surge from firing up coal or gas stations to restore electricity supplies afterward...

Those ‘environmentally friendly’ candles that many participants light? They are a fossil fuel — and burn almost 100 times less efficiently than incandescent light bulbs. (That’s why you won’t ever find a modern hospital using them instead of electricity). Using one candle for each switched-off bulb actually cancels out even the theoretical CO2 reduction; using two candles means that you emit more CO2.

Is he right that lighting one or more candles per bulb turned off cancels out any possible gain from turning off your lights?

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    A bit of a false equivalence since major landmarks and office buildings don't light up thousands of candles to offset the thousands of light-bulbs they shut off. But it is, as said in the first quote, a political statement, not an actual attempt to reduce carbon emissions.
    – Kevin Fee
    Mar 30 '17 at 19:54
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    "That’s why you won’t ever find a modern hospital using them instead of electricity" Even if electric lighting is more expensive I suspect most hospitals use electric lights rather than candles/torches/oil lamps due to safety and reliability factors.
    – JAB
    Mar 30 '17 at 20:01
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    Closely related question: skeptics.stackexchange.com/questions/8708/… Mar 30 '17 at 20:45
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    The claim that Earth Hour doesn't reduce emissions may be a straw man: I yet have to see a statement by the initiators of that event that it's the intention of the event to save energy by switching of the light for an hour. I spent some time on their website, and according to the material that I found there, it seems just to be about awareness raising. If that is true, the premise of Lomborg's claim would be invalid.
    – Schmuddi
    Mar 31 '17 at 5:49
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    @matt_black: Errr.... no. Fossil fuel is just that, fossil. Oil, gas, coal. Wood, animal fat, or beeswax are not fossil fuels. The CO2 released from them has, geologically / environmentally speaking, only just been bound. It's the CO2 that is currently in circulation anyway. The issue with fossil fuels is that they release additional CO2, which has been bound in times when there was quite a lot more of it around.
    – DevSolar
    Apr 7 '17 at 12:21

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