Unfortunately this reconstruction doesn’t go all the way back to 125 million years, so we can’t see if temperatures were even higher before the peak at ~83 million years. Since the creation of the OJMHP several similar but smaller events followed, explaining the sometimes rising deep ocean temperatures in a generally cooling trend.
According to this reconstruction it is obvious that between 80 and 90 million years ago the deep ocean temperatures where at least ~15K warmer than at present, and the deep oceans have on average been cooling down about 1K every 5 million years since then.
With a very much simplified model I’ll show how these major geological events in the distant past are still influencing our current temperatures.
Simple energy balance model
- incoming solar energy is 240 W/m2 after reflection , only warming Earth’s surface - current average surface temperature is 290K (oceans, disregarding the continents).
Consider a small planet in outer space, no internal heat, fully covered with a floor heating system (FHS) to replace incoming solar energy. No heat from the FHS can escape to the inside of the planet.
And of course we can control the energy flowing to the FHS. With the FHS turned off the surface temperature of our little planet is ~2,7 K due to the Cosmic Background Radiation.
1) Turning on the heat, we begin with 0,1 W/m2, after stabilisation the surface temp is ~30K.
2) Next 240 W/m2, temperature stabilises at 255K, Earth’s generally accepted Effective Temperature, and 240 W/m2 is radiated to space.
3) More heat, 400 W/m2, temperature stabilising around 290K, and 400 W/m2 radiates to space.
Now we cover our little planet with an insulation blanket, with the same thermal resistance as our atmosphere, 290K on the inside results in 240 W/m2 loss at the outside. With the surface temperature at 290K and the blanket covering the planet, we can turn down the FHS to just 240 W/m2 and maintain the 290K for as long as we supply the same amount of energy as escapes on the outside of the insulation blanket.
Back to Earth. Note that only simple insulation (no back radiation heating or similar) is needed to explain the surface temperature, given the boost to 290K or higher by the creation of the OJMHP and that the energy budget is balanced. Recall that current climate science states that the atmosphere is even capable of WARMING the surface ~33K, so just maintaining current average surface temperatures should be an acceptable premise.
Since the peek temperature the deep oceans have been cooling down very slowly. Assuming all of the oceans had a temperature of 290K from surface to bottom at the time of the temperature peak, we see that most of that heat has already been lost to space, given the current average temperature of the deep oceans of ~275K. Every time the sun supplies less energy than escapes to space (eg Milankovitch cycles), the ocean’s surface cools down, lost heat is re-supplied by now warmer water from below and the deep oceans cool down.
This mechanism also explains the exceptionally stable temperatures on Earth. Excess incoming energy warms the surface layer, and increases outgoing radiation almost immediately. Shortage of incoming energy is buffered by the deep oceans enormous thermal mass.
Recently we started having Ice ages (last ~2.5 million years). Without a new Mantle Plume eruption Earth may well be heading towards a Snowball Earth situation. Interestingly the small 0.1 W/m2 heat flux through the oceans crust can warm all of the oceans 1K every ~5000 year when ice prevents heat loss at the surface. In this situation the small geothermal heat flux could actually be (part of) the explanation for the ending of an ice age.
Extending this setup to Earth’s early history we can envision a situation where the effect of a Faint Young Sun is offset by a much thinner crust, allowing a substantial heat flux plus a much more active Earth with many Mantle Plumes and other seismic events warming the already existing oceans.
With the inclusion of Geothermal Heat in the climate equation, the role of the atmosphere is simply that of an insulation blanket. The sun is barely able to prevent the cooling of planet Earth. With the diminishing amount of buffered heat in the deep oceans we are moving towards a colder period, unless a major re-heating by Geothermal Energy comes along. Obviously this is not a complete climate theory.
Most of the classical meteorology from before the CO2 hype is still valid. Milankovitch, Svensmark and many other theories and effects can co-exist on top of this basic climate setup. All this has serious implications for the role of CO2 and climate sensitivity, which may very well be slightly negative. Instead of worrying about humanity warming the planet, we should prepare for the Ice Age that is coming sooner or later, unless of course the next major undersea flood basalt saves the day.
Ben Wouters, Zuid Scharwoude, Netherlands.