Should Climate Debates Begin at 1850, Or 500 Million Years BC?
Most contemporary climate arguments begin around 1850, Professor Ian Plimer begins more than 500 million years earlier
That difference in perspective is at the heart of Chapter 8, “The Geology of Climate Change”, in our new book, Canary in a Climate World: Climate Realism vs. the Net Zero Myth.
Plimer asks readers to step back from modern temperature records, computer projections and political targets and consider what the physical history of our planet reveals.
Across immense periods of geological time, Earth has experienced dramatic changes in temperature, atmospheric carbon dioxide, sea levels, ice cover and biological life. These changes occurred long before industrialization, ‘fossil-fuel’ use or modern human emissions.
What can that history teach us about the climate debate today?
Professor Ian Plimer is an Australian geologist and Professor Emeritus of Earth Sciences. He has held academic chairs at the University of Adelaide, the University of Melbourne, the University of Newcastle and the Technical University of Munich.
He has published more than 140 scientific papers, edited major scientific journals and reference works, and written 16 books for general audiences. His perspective matters because our understanding of climate is profoundly affected by the period of time we choose to examine.
A temperature change may appear highly unusual when viewed across several decades. Viewed across thousands, millions or hundreds of millions of years, it becomes part of a much larger and more complicated history.
As Plimer writes:
“Whether Earth is warming or cooling depends on the timeframe.”
Earth has repeatedly moved between warmer and cooler periods. Ice sheets have advanced and retreated. Sea levels have risen and fallen. Continents have moved, oceans have opened and closed, and volcanoes have reshaped the landscape and atmosphere.
Plimer’s central challenge is straightforward: how can we understand current climate change without first understanding the enormous natural changes that preceded it?
A climate that has never been static
Drawing upon evidence from sediments, fossils, cave deposits, ice, archaeology, isotopes and historical records, Plimer describes a planet that has never possessed a stable or ideal climate.
He points to the Marinoan glaciation more than 600 million years ago, when ice reportedly extended to sea level near the equator. He examines numerous warming events found in the marine fossil record, major ice ages and interglacial periods, and the long decline in global temperatures during the past 50 million years.
Plimer also places the present period within an ice age that began approximately 34 million years ago.
Within that larger ice age, Earth has experienced repeated glaciations and warmer interglacial periods. Human civilization developed during the current interglacial, which has itself contained warmer and cooler intervals.
These include the Holocene Climate Optimum, the Minoan, Roman and Medieval warm periods, followed by cooler intervals including the Little Ice Age.
‘Climate change’, from this perspective, is not an abnormal interruption of a previously stable planet. ‘Climate change’ is the normal condition of Earth.
What about carbon dioxide?
One of the most provocative parts of Plimer’s chapter concerns the relationship between atmospheric CO₂ and temperature. Plimer argues that the geological record does not support the simple claim that atmospheric carbon dioxide alone controls global temperature.
He points to periods when atmospheric CO₂ concentrations were considerably higher than they are today, including periods of extensive glaciation. He also cites ice-core research indicating that, during past natural cycles, changes in temperature preceded changes in atmospheric CO₂.
His argument is not merely that the climate changed before humans began burning ‘fossil fuels’. It is that Earth’s climate is governed by numerous interacting forces operating across vastly different timescales.
These include plate tectonics, changes in Earth’s orbit, solar variability, volcanism, ocean circulation and the continual exchange of heat and gases between the atmosphere, oceans and land.
Plimer therefore challenges readers to ask whether public discussion has reduced an extraordinarily complex planetary system to a single variable.
Sea level is more complicated than it appears
Sea-level change is another important part of the chapter. Plimer notes that global sea levels have risen by approximately 130 metres since the height of the last glaciation around 20,000 years ago.
But he also explains that relative sea level differs significantly from one location to another. In some places, the sea appears to rise partly because the land is sinking. Elsewhere, the land rises and relative sea level falls.
Local measurements may be influenced by subsidence, tectonic activity, sedimentation, volcanic processes, gravity, wind and the continuing adjustment of land following the disappearance of massive ice sheets.
This does not mean that sea levels never rise. It means that interpreting individual measurements requires knowledge of the geological and geographical setting in which they were recorded.
Once again, the geological perspective introduces complexity into a debate frequently presented through slogans and frightening images.
The danger of choosing the wrong starting point
- When political leaders tell us that current conditions are unprecedented, we should ask: unprecedented since when?
- The beginning of satellite measurements?
- The beginning of reliable thermometer records?
- The Industrial Revolution?
- The end of the Little Ice Age?
- The beginning of the current interglacial?
Each starting point produces a different impression. If we examine only the most recent decades, we see one picture. If we examine thousands of years, that picture becomes more complicated.
If we examine hundreds of millions of years, we encounter a planet repeatedly transformed by forces far greater than anything humanity has witnessed during recorded history. That history should encourage scientific humility.
A geological challenge to ‘Net Zero’
Plimer ultimately argues that the geological record is incompatible with claims of an unprecedented climate emergency caused primarily by human CO₂ emissions.
His arguments are grounded in the geological record and demand serious consideration. They should not be dismissed or excluded simply because they challenge the prevailing climate narrative.
Climate is not controlled by a single switch. Earth is a dynamic system shaped by the atmosphere, oceans, Sun, clouds, water vapour, geology, biology, orbital changes and forces operating deep within the planet.
This is why open scientific debate matters, particularly when climate projections are being used to justify policies that could transform energy systems, economies and living standards throughout the world.
Before governments spend trillions of dollars restructuring the global energy system, the public should be permitted to hear from accomplished scientists who question the assumptions behind those policies.
Professor Ian Plimer is one of those scientists. He is also one of 38 accomplished contributors who bring their expertise, evidence and independent perspectives to Canary in a Climate World.
His chapter asks us to look beyond decades and political cycles and examine the history written in rocks, fossils, sediments and ancient seas.
What does the climate debate look like when viewed across more than 500 million years? Very different indeed.
Professor Ian Plimer’s “The Geology of Climate Change” appears as Chapter 8 of Canary in a Climate World: Climate Realism vs. the Net Zero Myth.
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Header image: Geocraft.com