At a glance – Are we heading into a new Ice Age?
Posted on 2 May 2023 by John Mason, BaerbelW
On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added “At a glance” section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a “bump” for our ask. This week features “Are we heading into an ice age?“. More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.
At a glance
In something like a Day after Tomorrow scenario, the idea that a new ice-age was just around the corner was the subject of a book, a DVD and a website created in 2002. The author was a retired architect, by the way. Fortunately for us, both the movie and the quote above are figments of someone’s fertile imagination. But let’s have a quick look at ice-ages and what makes them tick, after which we hope you will agree the notion that another ice-age is just around the corner is nonsensical.
Ice-ages, also known as glacials, are cold periods that occur in a cyclic fashion within an Icehouse climate state. Earth’s climate has been mostly of the Hothouse type (no Polar ice-sheets) but on occasion has cooled down to Icehouse, as has been the case in the last few million years. There are regular variations in Earth’s orbit around the Sun, taking place over tens of thousands of years, that affect the amount of Solar radiation reaching our planet. During the Icehouse state, such variations can lower and raise planetary temperature sufficiently to trigger swings between cold glacials – when ice-sheets expand towards the Equator – and mild interglacials – when the ice retreats back polewards.
To give an idea of the time-scales involved, Europe and North America have seen glacials and interglacials come and go repeatedly over the last 2.5 million years, this being known as the Quaternary Period of geological time. The last glacial started 115,000 years ago and the Last Glacial Maximum (LGM), when the greatest ice extent was reached, was around 22,000 years ago. The current interglacial – also known as the Holocene, commenced 11,700 years ago.
A general pattern may be seen here with a long cooling towards Glacial Maximum and a relatively quick warming into an interglacial. The speed of warming is because important climate feedbacks are triggered: removal of pale, reflective snow and ice cover revealing the darker ground beneath allows more solar heat energy to be soaked up. Melting of permafrost releases carbon dioxide and methane. These – and other – feedbacks therefore amplify the warming effect.
However, our burning of fossil fuels has happened on such a vast scale that we have blown such factors apart. The atmospheric concentration of carbon dioxide (CO2) has risen well above the 180-280 ppm range typical of recent glacial-interglacial cycles. The current level, getting on for 420 ppm, is more typical of the mid-Pliocene, around a million years before the start of the Quaternary. Mid-Pliocene ice-sheets were much smaller than those of the present day. Rather than being due another glaciation, we can expect a continued transition towards Pliocene conditions.
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In case you’d like to explore more of our recently updated rebuttals, here are the links to all of them: