Back in 2010 a booklet called Seven Theories of Climate Change by Joseph L. Bast was published by the Science and Public Policy Institute.
It lists seven climate change theories, one of them being the AGW CO2 theory. The booklet is worth reading not so much because it delimits what we know of climate drivers, but because it highlights how exceedingly complex the issue is. Vastly more complex than popular journalism would have us believe.
Climate science is dominated by uncertainty and there are also highly uncertain connections between these theories, so I’ll merely summarise them below. Additional theories and ideas from readers are very welcome – this is an evolving, not an evolved science.
1 Anthropogenic Global Warming
The mainstream theory of climate change heavily promoted for reasons beyond the scope of this post. Greenhouse gases, primarily carbon dioxide, methane, and nitrous oxide are said to be causing a catastrophic rise in global temperatures.
The second theory of climate change is really a number of theories bundled together. Feedbacks from biological and chemical processes are said to contribute towards global temperature stability by suppressing temperature increases. These are :-
- Enhanced carbon sequestration by plants as atmospheric CO2 increases, thereby causing increased rates of plant growth.
- Carbonyl sulphide (COS) produced biologically is said to form sulphate aerosols in the atmosphere which reflect solar radiation and lead to a cooling effect.
- Biosols are biologically derived plant compounds which circulate in the atmosphere and may act as condensation nuclei for clouds. They may also diffuse solar radiation close to the ground, reducing the effect of shade and increasing photosynthesis and CO2 uptake.
- Iodine containing compounds formed in sea air by marine algae may act like biosols.
- Dimethyl sulphide is emitted by oceans and may be a source of cloud condensation nuclei.
- Other aerosols. There are other natural aerosols which may also have an impact on climate.
3 Cloud Formation and Albedo
A third theory says that the climate is controlled by the formation and albedo of clouds.
4 Land Use
A fourth theory is that climate is affected by large scale changes in land use such as forestry, irrigation and building cities.
5 Ocean Currents
The fifth theory claims that climate cycles are the result of changes to ocean circulation patterns.
6 Planetary Motion
The sixth theory is that gravitational and magnetic oscillations of the solar system cause solar variations and/or other influences which change the terrestrial climate.
7 Solar Variability
The seventh theory is that solar variability accounts for most or all climate change.