Santa Maria 1902 eruption, Tunguska event 1908 and the major Novarupta eruption 1912 coincide with the MAJOR turn in temperatures that is very clear in the model of reference for temperature in the 20th century. It was the second industrial revolution (electricity, cars, heavy machinery, the first power plants…). Tephras can be highly refractive and will keep photons inside the atmosphere, they will fly over longer. See also major 1932 Cerro eruption in Chile. Because of the beginning of temperature increase due to eruptions + Tungutska event, the demand for heating of buildings might also have recessed, hence the divergence followed by a more linear increase (not exponential). Anyway, it is very clear that the progressive addition of CO2 is not the responsible because if it were there would be no sudden divergence. My theory linking it to the brutal events of 1902, 1908 and 1912 in combination with the deployment of lightbulbs, cars, motors in general (and thus massive dispersion of energy outside) sounds much more in line with the hockey stick curve. Explosions of conventional warfare (armour piercing shells, + 3000°C) during WW2 kept pushing global temperatures up until 1945, then the relative decrease in activity combined with the end of massive volcanic eruptions contributed to the end of temperature increases until the 80s (St Helens 80, El Chichon 82, and most importantly Pinatubo and Hudson 91 as well as Rabaul 94).
CO2 emissions from 1851 to 1901 compare quite well to 1901 – 1945 emissions (I’d say the 1901 – 1945 amount represents 3.5 times the 1851 – 1901 amount) whereas there is decrease until 1910 followed by sudden divergence, corresponding pretty exactly to the two major events I am pin-pointing, Tunguska and Novarupta. The last VEI 6 eruption is in 1932, then there is a relative decrease in volcanic activity until Pinatubo 1991 (and Mount Hudson 91 in Chile, a lesser known eruption, VEI 5+) which coincides very well with the “pit stop” in temperature increases in the middle of the 20th Century. WW2 of course stalled economic activity yet the 1945 – 1973 economic boom (and parallel explosion of CO2 emissions, visible in the carbon emissions graph) could have been expected to make temperatures skyrocket. It did not.
If CO2, CH4, water vapor etc. were responsible for the “greenhouse effect”, they would also bar a lot of solar energy from entering the atmosphere and the two effects (increased inertia of energy under the greenhouse, impossibility for solar energy to descend on Earth) should compensate. Tephras from explosive events such as volcanic eruptions and meteoritic impacts (atomic tests are much less significant as they mostly were done at good distance above or under the ground, limiting craters to reduce the amount of activation products), combinated with all the human energy they keep from dissipating out of the Earth, including photons as well as other radiation from lightbulbs, are a much more sensible hypothesis.
Photons have a mass (see Luo on the rest mass and my precedent blog post) and thus represent an addition of kinetic energy to the atmosphere, hence warming (kinetic energy means heat ! agitation of atoms). Then the accumulation of heat evaporates more water, keeping a lot of light yet photon-blocking tephras up air. Hence persistence of the effect.
Public policy should of course point out such dispersions of energy as industry plants, nuclear energy (where 70% of the thermal energy is not converted into electricity but lost outside) and power plants in general, cars, energy losses in general instead of CO2 and citizens should take action to demand reduction of energy losses in the atmosphere (boycott is best : state intervention is never efficient – lesson from public choice and Austrian economics !).
The main issue with all fossil fuels (oil, coal, natural gas etc) : contamination with alpha emitters. See European Commission’s first acknowledgement of the dangerosity for human health of depleted uranium (an alpha emitter).
Note : on the concordance in time and space of major eruptions, refer as well to my earlier article on supernovas and supervolcanos