Chapter 1

CHAPTER 1:  

Mechanisms of Global Warming – how methane and carbon dioxide keep infrared heat in the atmosphere – how plants absorb carbon - percentage of global climate change to greenhouse and solar irradiance.

Before deciding what to do about climate change, it’s important to understand the physics and biology that are involved. While the consequences are complex, both basic mechanisms are simple: Carbon dioxide and methane are transparent to visible light, but opaque to the infrared radiation light becomes when it’s re-radiated from the surface of the Earth, so when they are at higher concentrations they trap more of the sunlight’s energy in the atmosphere and warm it up. 

Plants obtain the energy they need to grow, and the substance of their bodies, by absorbing carbon dioxide and entraining energy from sunlight in carbon compounds, initially sugars, by photosynthesis, which releases oxygen. When their bodies are eaten or burned the carbon the photosynthesis has “fixed” into organic material returns to the atmosphere as carbon dioxide, and the energy is released, by oxidative metabolism or combustion. If the plant bodies are buried in some way, the carbon they have captured is taken out of circulation and “sequestered.”

Methane is the simplest hydrocarbon, and it arises on Earth when microbes metabolize organic matter in situations where there’s not much oxygen: wet soils, the guts of animals, the buried seafloor deposits that are exploited for petroleum, and cold seabeds under the Arctic Ocean. Atmospheric methane is eventually degraded by oxidation, but while it lasts it’s a stronger greenhouse gas than carbon dioxide.

Atmospheric circulation (“weather”) is complex, and affected by many factors other than the interactions of greenhouse gases and solar radiation. It’s this complexity that inspired the change of terminology from “global warming” to “climate change” or “climate crisis:” many of the experienced effects of climate change are perceived as changes in precipitation – drought or flooding – or wind speed rather than just temperature. 

Because our human mentalities are mostly attuned to the short-term exigencies of day-to-day life, human memory is an unreliable guide to long-term changes in climate, which can only be studied in long stretches of records or data. 

Among the complicating factors are the way water vapour, which is a powerful greenhouse gas, comes and goes from the atmosphere, while clouds and snowcover reflect sunlight back into space. Particulate air pollution and aircraft contrails also reflect light, and the amount of radiation that reaches the Earth varies with the solar sunspot cycle, and with the position of the Earth in its orbit.