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  • Rights: Crown Copyright 2020
    Published 15 October 2020 Referencing Hub media

    A climate oscillation is a recurring climate pattern – El Niño events, for example. Climate expert James Renwick explains how natural climate variations differ from climate variations due to climate change.

    Questions for discussion:

    • What does James mean when he says natural variations just shift things (energy) around?
    • How does this differ to climate variations due to climate change?



    The climate does vary naturally for all sorts of reasons, and these so-called natural variations or oscillations involve energy. Heat is being shifted around from different parts of the world to somewhere else.

    A classic example is an El Niño in the tropics, where a whole lot of heat goes from near Australia and Indonesia and it shunts across the tropical Pacific to be closer to South America – happens over a matter of months – and it’s just moving energy, moving heat around within the oceans and the atmosphere.

    The thing about these natural variations or oscillations is they don’t change the total amount of heat in the Earth, they just shift things around. So it’s getting cooler where you are because it’s getting warmer somewhere else. When you add it up around the globe, there’s no change.

    Another kind of natural oscillation, which does actually change the total temperature or energy of the Earth, is something like the Ice Ages. This is a classic example where, over 100,000 years or so, the Earth goes from a climate like we have today to one where the continents are covered in a couple of kilometres of ice and it’s several degrees colder than present. And that happens because sunlight changes – so that the Sun basically becomes a bit dimmer.

    Professor James Renwick, Victoria University of Wellington
    El Niño weather pattern animation, NIWA
    Animations of ice age freezing across Earth globe and permafrost from The Last Time the Globe Warmed, Curiosity Stream, PBS Eons
    Woolly mammoths illustration, Mauricio Antón, released under CC BY 2.5


    This resource has been produced with the support of the Ministry for the Environment and Stats NZ. (c) Crown Copyright.

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