Historical aspects of global warming

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by Dr. Fred Schueler

“Since the day that Arrhenius first did the math” in 1909, the calculated greenhouse effect of carbon dioxide has remained within the same range of values, and CO2 (not to mention methane) is what is changing. The details may vary, but the basic fact of the greenhouse effect is very robust, and the calculated effect hasn’t changed in a century.

The ‘Little Ice Age,’ which culminated in the ‘year without a summer’ of 1816, is now regarded as being due to reduced carbon dioxide levels following the regrowth of Central and North American forests. When the forest grew back on this largest abandonment of farmland in all history, producing the American ‘Wilderness,’ huge amounts of carbon dioxide were absorbed and temperatures fell.

All through the mid- and late-19th Century, and the first half of the 20th Century, it was an accepted fact that the Earth’s climate was warming and that glaciers were retreating.

“The cooling period beginning in 1945 is reproduced by current global climate models that include the physical effects of sulfate aerosols, and there is now general agreement that aerosol effects were the dominant cause of the mid-20th century cooling.” (Wikipedia, slightly edited). This period of pollution-induced cooling before the recent ‘blade of the hockey stick’ increase in temperature, seems to have erased the memory of the fact that global warming, and its association with greenhouse gases, had been well known.

The problem with the recently accelerated rates of warming is the likelihood of triggering positive feedback loops, in which warming itself releases carbon dioxide from thawing permafrost, increased wildfires, or methane release from undersea methane clathrates or permafrost.

Until the general population thinks of how their behavioural preferences originate, there’s the danger that they’ll just continue in what looks like anthropocentric status-seeking self gratification.

If climate change is to be controlled, we’ll need to change the whole tenor of society to think more globally, basing action on the consensuses that arise from scientific “faith in doubt,” and, as energy sourcing is decarbonized, also to work towards the incorporation of what’s now atmospheric carbon into living trees, agricultural soils, and wetlands.

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