Arguments that dispute climate change are ignorant and contrary to geologic history.
To say that climate is always changing, that temperatures were higher during earlier periods of Earth history than today, that higher CO2 levels are good for agriculture, or that deviations from the warming trend invalidate its truth—these are wrong or hopelessly simplistic.
The debate about climate change is silly because it doesn’t matter what we think about it. The effect of the debate is to make one side or the other feel better or worse about what is happening. But climate change is happening whether we like it or not.
Climate change has been a primary factor in the history and development of human civilization. It caused the earliest migrations out of Africa. It led to the transition from hunter-gather to agricultural society.
The agricultural revolution had nothing to do with technology. It was a climate-change revolution. The agricultural revolution took place when climate stabilized and warmed 12,000 years ago at the beginning of the Holocene Epoch (Figure 1).
Figure 1. Holocene temperature variations from Greenland ice surface temperatures. Source: Dalum … [+]
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Temperatures were warmer, not colder, than today through most of geologic time—until recently. Heating is greater than it was millions of years ago. Long-term temperature has declined because CO2 has decreased—until recently.
CO2 levels were higher than pre-industrial values (278 parts per million) for most of the last 420 million years (Figure 2). In other words, the long-term decrease in CO2 largely compensated for the increase in solar output.
CO2 levels decreased because of the proliferation of land plants that converted it into oxygen. The erosion and weathering of clay minerals in granitic rocks absorbed large volumes of CO2 as the continents evolved. Long-term volcanic activity has declined as the earth has matured limiting the amount of CO2 released into the atmosphere from inside the earth.
We must focus on the deviation from these long-term trends over the last 200 years.
Figure 3 shows the same data in Figure 2 but on a logarithmic time scale to compare more recent earth history with its more distant geologic past.
Among the various projections on the right-hand side of the figure, RCP8.5 represents the “do-nothing” or business-as-usual scenario. It indicates CO2 values by early in the next century that exceed levels from more than 99% of the last 420 million years. A return to unstable climate would make agriculture impossible again.
Figure 3. Temporal evolution of CO2 and Paleogene formation of ice caps. Source: Leonard and Berman … [+]
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Regardless of the reliability of this projection or the ultimate causes for the rise of post-industrial CO2 levels, the message is clear.
What lies ahead during the lifetimes of our grandchildren will most probably not be comparable to anything since the development of multi-cellular life on Earth.
Please visit artberman.com/2020/11/21/climate-change-the-great-and-silly-debate/ for a more detailed version of this story.
