This is the fourth in a series of seven articles aimed at describing some of the threats that humanity faces in the coming years. It is the issue of global sea rise. There are many who dispute whether carbon dioxide and methane emissions from human civilization are the primary cause of global warming. But regardless of the source of the warming climate, it is becoming more and more clear that sea level is rising in response. That will have an incredible impact upon the population of the world, since there has always been a great desire to live at or very near to the sea shore. And the level of the sea has seldom been constant over geological time, since glaciers have expanded and contracted many times over the past million years, causing the sea level to vary hundreds of feet during these oscillations.
What is different this time, is that our current civilization was developed with the current sea levels. So all of the infrastructure associated with the great cities of the world, it is mainly at sea level. And for many of the people who live in poor countries, like Bangladesh, they exist on river estuaries which are extremely susceptible to sea level rise. So whether the current rise in sea levels is due to anthropogenic greenhouse gas emissions, or whether it is merely a continuation of the cycle of ice sheet expansions and contractions that preceded our species, it becomes necessary to develop a plan for dealing with ongoing sea level rise.
The best option would be to have a controlling thermostat knob on our climate that we could use to compensate for either natural effects on the climate, or for those that humanity has caused. At present, we do not have that. If the scientists who are convinced that human emissions of greenhouse gases are responsible for increasing the temperature, then one knob would be raising and lowering the CO2 concentration of the atmosphere. As seen by the political response to this in the US, there is extremely heavy opposition to this technique from those who are invested in the status quo of the energy industries. It also will require huge investment in both research and in physical facilities to enable renewable energy resources to supplant fossil fuel sources. There is no doubt that we do need to invest in both the research and the facilities, along with redesigning of the electrical grid to be more resilient and to accept the intermittent nature of renewable energy sources.
One option for a zero carbon energy source that is not being discussed is nuclear energy. No, not the energy created from the fission of U235 atoms used in every nuclear power plant in the world at present. Instead, what is needed is to develop reactors that use the thorium power cycle. At one time, nuclear energy research considered thorium as a viable source of electric power. There is one small problem with the thorium cycle, though. It is not capable of generating plutonium as a byproduct. Back when the nuclear power industry was being developed, there was a desire to have plutonium production so that spent uranium fuel rods could be processed to remove the plutonium for weapons production. The vast majority of the research for nuclear energy used enriched uranium U235 as the source for power generation, and thus research for thorium went by the wayside.
But the U235 power cycle also produces other long-lived radioactive isotopes that keep reactor rods fatally radioactive for hundreds of thousands of years. Thus humanity is tasked with trying to isolate wastes from power generation inside of geologically stable environments for many millennia longer than humanity has had a civilization. This is scarcely a realistic model to build a sustainable civilization upon. And U235 reactors are inherently unstable. Complex neutron absorption systems have to be maintained in order to keep the reaction at the sweet spot. Too much absorption, and the nuclear fire goes out and no electricity is generated. Just right, and you can remove the excess heat with water that flashes to steam and eventually turns electric generators. Too little neutron absorption, and the system is capable of melting down into a puddle of zirconium and uranium, that will eventually break through all known containment systems. At the same time, gases generated from the reaction will likely ignite, releasing a cloud of radioactive elements out of the containment system.
Thorium, on the other hand, is an inherently stable reaction system. The active isotope of thorium (Th232) is 99.98% of all thorium in nature. When it absorbs a neutron, it eventually reacts through subsequent beta particle decay into U233. This isotope of uranium is capable of sustaining nuclear fission, but unlike its cousin U235, it does not create longer-lived radioactive isotopes as byproducts. Instead, the fission products it produces are all lighter than the starting materials, and their radioactive half lives are mainly less than a hundred years. Thus it is conceivable that waste products could be maintained in an isolation facility for a reasonable period of time and then would not be a hazard to future generations in future millenia.
The thorium cycle has another advantage. It is impossible to get a runaway reaction using thorium. Since the proposed design for a thorium reactor involves a molten salt reactor, any loss of containment would result in a salt-thorium mixture solidifying on the ground, incapable of performing further fission. All of these advantages over the existing U235 nuclear cycle says that thorium fission should be investigated thoroughly and promptly brought to commercialization. Again, another problem (reducing CO2 generation while providing stable electrical power generation) that could be solved by the investment of the government into scientific research, and opportunities for employment of nuclear engineers and metallurgical engineers and mechanical engineers. Oh, and by the way, the main ores of thorium also contain rare earth metals and phosphates. Both of these are highly desirable materials. Also, thorium is four times more abundant in Earth’s crust as is uranium.
This was a detour from the immediate problem we are intending to address, which is sea level rise. What is needed is a way to do triage for the developed world in trying to determine what infrastructure is indefensible given a certain amount of sea rise, and what infrastructure can be salvaged if we begin to take action now. For example, London installed a barrier on the Thames back in the 1980’s that serves to protect London from abnormally high tides. Would such a barrier be feasible for the Hudson to protect the NY – NJ region from ongoing sea rise? What will the implications of ongoing sea rise be for cities such as Miami, where the tourist infrastructure is at risk. As much as those who believe in karma wish for Mar-A-Lago to suffer inundation, the entire southeastern coast of Florida is at risk. And areas like Newport News and Charleston South Carolina are already going through periods of rainless flooding caused by peak tides. This will only get worse over the next few decades. What is needed to enable these highly-populated metropolitan areas to still be functional? What if it is determined that it is not feasible? How do we deal with the displaced populations?
The issues of displaced populations becomes even more dire when you consider the underdeveloped nations most at risk from rising seas. In these areas, it would be necessary to develop lower-tech means to mitigate the risk. One partial solution is to reestablish mangrove barriers as initial surge suppressors. Mangroves have the ability to capture soil in the roots, thus allowing the ground level to rise as the water level rises. But it will be necessary to develop ways to prevent salt water intrusion, and it will be extremely beneficial if the techniques used to counteract sea level rise use the local farmers and laborers as the contractors to do the work to save their own land. That way, they receive a benefit in building and maintaining these facilities, presumably receiving an income, and they then have an incentive to make sure they work, since their farming livelihood depends upon the new systems functioning properly.
The issues concerning sea level rise are longer-term in their impact and solutions. But in order to effectively deal with them, we must plan now based on what we know will happen. Otherwise we will be caught off guard, like in 2018 when the warmer and less dense waters of the Gulf of Mexico caused the extremely rapid intensification of Hurricane Michael. For one of the consequences of global sea level rise is due to the decrease of density at higher temperatures. Seawater takes up about 1% more volume at 30ºC than it does at 20°C. And the higher water temperatures from a warming climate not only act directly on the water level, they also provide more fuel for the storms that feed upon their heat. We may have been caught off-guard by a hurricane much stronger than expected, but we should not be caught off-guard by physical effects we can predict decades in advance.