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CO₂ Isn’t the Only Driver: What the Climate Change Debate Leaves Out   

As a youngster first getting about and joining the social world, others suggested avoid religion and politics when joining in conversations, saying it would be safer to merely chat about the weather.  For about the last 30 years climate change has become a topic of interest to many.  Increasingly, this has become a topic that can develop into arguments, so chatting about the weather is less advisable.  

Initially global warming caused by human activity was the concern quoted, however quantitating this requires numerous readings to measure on a global scale.  Since the year 2000, any long term trend in weather changes like drought or cyclone numbers and intensity has been blamed on climate change.    

The world, on a geological scale of millions of years, has endured several major shifts in climate, from ice ages lasting many tens of thousands of years interspersed by shorter interglacial periods. Geologists such as Plimer advocate that the world’s flora and fauna have invariably flourished during these interglacial periods.  The last ice age came to an end about 10,000 years ago which increased sea levels by 120m thus altering continent coastlines and reducing land bridges between land masses.  This extended interglacial has allowed mankind to flourish.  The Earth is said to be at a sweet spot orbital distance from the sun allowing water to exist in the liquid state and this is a key component for all living creatures.  All living matter derives energy from the sun to sustain life; plants evolved a way to convert light into growth matter by photosynthesis and other species derive their nutrients by foraging on plant matter whilst predators (including humans) consume foraging animals.   

The switch between ice ages and interglacial climate is attributed to long term variations in the Earth’s orbit about the sun.  There are three processes, one is the tilt of the Earth’s axis which can vary over long term by a degree or two and this extends the summer and winter climate pattern, the second is long term changes in the elliptical orbit of the Earth about the sun.  The sun is at one focus of this ellipse and at present the Earth is at its perigee (closest approach) during January making the southern hemisphere summer hotter than when the reverse is true due to precession.  In addition, variations elongate the exact shape of the ellipse.  If each of these variations coincide then the Earth gets a longer interglacial like we experience now.   

In the longer term of a thousand or so years the Earth will revert to another cooler glaciation period which will reduce the Earth’s capacity for sustainability for our current population level.  Much of the current debate about climate change revolves about human industrial progress and its effect on the atmosphere composition.  Currently, this consists of 21% oxygen, 78% nitrogen and 1% argon and these gases are mostly transparent to light from the sun.  Our Earth is typically 15^oC warmer than otherwise due to traces of gases like CO₂ and H₂O vapour which are transparent to visible light but absorb IR radiation giving a ‘glass house’ effect.  Preindustrial levels of CO₂ were typically 280ppm but are currently just above 400ppm.  It is postulated that this increase will enhance the glass house effect giving over 3^oC rise in global temperature and a further sea rise of 3-5m.  Much of the debate focusses on limiting or reducing CO₂ levels to limit global warming.  Very hard to achieve, but inevitable in the longer term as fossil fuel resources are consumed.  

Looking at the IR absorption spectrum of CO₂ and H₂O vapour, both have broad absorption bands. What is missing mostly from the debate is that H₂O vapour levels vary typically with humidity and temperature from between say 500ppm at colder high latitudes to up to 30,000 ppm in the tropics. Well over 90% of the glass house effect we enjoy is due to the H₂O vapour.   The counter argument is cloud formation, when a column of moist air rises, adiabatic cooling as it expands at the lower pressure creates reflective clouds when the saturation level is attained.  This reflectivity reduces the global warming due to the H₂O vapour component and therefore is rarely mentioned when discussing the rise in human induced CO₂ level.   It’s rise since preindustrial levels from 280 to 400 should only incur a rise of 30% of 10% of 15^oC (= 0.5^oC) with H₂O vapour contributing the rest.  I guess the debate should better focus on whether rises in CO₂ also creates rises in H₂O vapour levels and then we should include increased cloud reflectivity.  Too complicated for me.  

As mentioned above, our sweet spot orbit zone about the sun creates ideal life forming conditions.  However, there are concerns about other subtle effects than may affect us.  Galileo studied the planets like Jupiter and also identified sunspots.  Space weather is updated daily on the web, and this shows a regular variation in sunspot activity every 11 years.  Sunspots went quiet for over 50 years since Galileo and this coincided with a mini ice age in Europe.  Now the orbit of Jupiter is also 11years, does Jupiter and to a lesser effect Saturn have a synergistic effect on sunspots and can this also have climatic effects?  Again, this is too complicated for me but a current space weather issue makes note of the possible link (see attachment), so I’m happy to let space scientist sort it out. 

Perhaps of more concern about space weather is the effects of a severe impact of a coronial mass ejection (CME) on our developed world.  When we first started electronic communication with telegraph wires around the globe in the mid 1800s, a massive CME from the sun hit the Earth causing widespread auroras and a dangerous electrical spike in the wires for operators.  A similar CME today could seriously affect man made communication satellites and electronic equipment on earth.  Cars, banking etc these days are computer controlled and a massive CME could render many of the devices inoperative.   We are increasingly dependent on electronics, computing and internet banking nowadays, and should a massive CME devastate components essential for operation, the outcome is hard to imagine. 

Perhaps space weather is a topic for more meaningful conversation than climate change.   

References (APA 7th)

• Hausfather, Z. (2020). Explainer: How the rise and fall of CO2 levels influenced the ice ages [Image]. https://www.carbonbrief.org/explainer-how-the-rise-and-fall-of-co2-levels-influenced-the-ice-ages/
• National Oceanic and Atmospheric Administration. (2025). Climate change impacts [Image]. https://www.noaa.gov/education/resource-collections/climate/climate-change-impacts
• Westerhold, T., Marwan, N., Drury, A. J., Liebrand, D., Agnini, C., Anagnostou, E., Barnet, J. S. K., Bohaty, S. M., De Vleeschouwer, D., Florindo, F., Frederichs, T., Hodell, D. A., Holbourn, A. E., Kroon, D., Lauretano, V., Littler, K., Lourens, L. J., Lyle, M., Pälike, H., & Röhl, U. (2020). An Astronomically Dated Record of Earth’s Climate and Its Predictability over the Last 66 Million Years [Image]. Science, 369(6509), 1383–1387. https://doi.org/10.1126/science.aba6853 

Dr Ray Hodges FRACI (retired Associate Professor from Monash Gippsland)

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