This paper endeavors to provide a broad systems perspective on the problem of greenhouse gases and the actions humanity must take to minimize the adverse climate effects being produced.
Greenhouse Gases and Their Effects
The primary natural greenhouse gases affecting Earth’s atmosphere and producing warming are carbon dioxide, water vapor, methane, nitrous oxide, and ozone. In addition to these natural gases, there are human-synthesized fluorinated gases, including hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride. The latter gases are widely used as refrigerants and are produced in various industrial processes. While their quantities are small, these gases have disproportionately large greenhouse effects.
The buildup of greenhouse gases (especially carbon dioxide) has occurred since the beginning of the Industrial Revolution, starting around 1750, mostly from the burning of fossil fuels. Up until now, more than half of human-caused carbon emissions have been absorbed by various natural carbon sinks such as the oceans and forests. However, the capacity for further absorption is decreasing. Additional emissions are less likely to be absorbed and retained.
Different greenhouse gases have varying lifespans in the atmosphere. Also, different greenhouse gases have varying effects on increasing atmospheric temperatures. The relative amounts of each greenhouse gas in the atmosphere are varying with time. Per molecule, methane has a much greater influence on atmospheric temperature than does carbon dioxide, but it is present in smaller concentrations and a methane molecule has a shorter life in the atmosphere than does a carbon dioxide molecule. Greenhouse gases that have been emitted in past years will have effects continuing for decades, even centuries to come. Even if human-caused emissions were to go to zero, the effects would still be occurring well into the future.
Human-caused greenhouse gas emissions have a number of effects in addition to increased atmospheric temperature. These include the acidification and warming of the oceans. A warmer atmosphere holds more moisture, resulting in stronger storms with greater rainfall. Simultaneously, a warmer atmosphere can also cause drought and desertification in other locations. A warmer atmosphere leads to melting of ice cover and glaciers. Loss of ice in the Arctic leads to greater absorption of sunlight there, warming the Arctic in an amplifying feedback loop that changes oceanic circulation patterns.
Greenhouse Gas Emission Sources
In addition to greenhouse gas emissions from human actions directly, there are also greenhouse gas emissions from the natural world, such as emissions of methane from melting permafrost due to increased temperatures in the high latitude regions. These emissions will continue to occur regardless of what humans do now.
It is going to be necessary to consider all the human-caused and natural sources of greenhouse gas emissions. Key questions for each one include the following.
- What is the source?
- What gas is being emitted?
- How much is being emitted?
- What are the mechanisms of emission?
- Are there mechanisms of absorption? How effective are these?
- Where are the sources of emission located?
The Imperative of Intervening to Reduce Greenhouse Gas Emissions
Understanding the emission sources, the next step is to consider what can be done to reduce them.
- What could be done to reduce or eliminate the emissions from a particular source?
- How critical to present human society is the maintenance of that source’s emissions?
- What could be alternatives to obtain the same benefits provided by that source?
- What would be the cost of using those alternatives?
It will be important to look at what is the biggest payoff for the investment for each intervention. We need to prioritize actions on the basis of the return on investment and focus on the biggest improvements first. Keep in mind that greenhouse gas emissions and consequent adverse effects are a worldwide problem. Consequently, changes must be made on a worldwide basis, not just local to a nation or a region.
What Must Be Done
In order to prevent disastrous climate change and other adverse effects, humanity has to cut back drastically on the burning of fossil fuels (coal, natural gas, and petroleum) to generate energy. Energy production needs to transition to means that do not produce and release greenhouse gases such as carbon dioxide and methane. In addition, the release of other greenhouse gases such as fluorocarbons must be greatly reduced.
The energy system needs to consider all aspects: the primary production of energy, the distribution of energy from where it is produced to where it is used, and the consumption of energy at the end point. It is critical to take the longest-term perspective possible. What can we do that will be sustainable over many human generations?
Some critical needs will require the continued burning of some fossil fuels for the foreseeable future. A primary example is aviation, where the energy density of fossil fuels is very difficult to replace. However, substitution of non-fossil fuel generation of energy is going to be vital for every application that does not have such demands. It is likely that we will need to reduce the use of applications with high impacts such as aviation.
As a top priority, we need to phase out the burning of coal as soon as possible. We also need to replace burning natural gas and petroleum as rapidly as feasible. This is particularly important for electrical energy generation and heating. We must look for wherever waste occurs in the production, distribution, and utilization of energy and seek to eliminate or greatly reduce that waste. We need to drastically reduce all human releases of methane.
In general, energy utilization must move to all-electric systems wherever possible, where the primary production comes from renewable/inexhaustible sources and the utilization of the energy at the end point uses electrical forms. Electrification needs to be applied to transportation systems (road, rail, and waterway), construction equipment and processes, heating systems of all forms, industrial and chemical processes, agricultural equipment and processes, and many other utilizations. Electrical energy efficiency needs to be paramount in each of these applications, such as the use of LEDs for lighting.
A major focus will need to be the responsible retirement of existing systems that contribute to global climate change. They need to be taken out of service as quickly as they can be replaced by sustainable systems. This means that many will be removed before their normal end-of-life period while they still function well. It will be important that as much of their materials as possible be captured for recycling and reuse rather than being simply discarded. Extracting new non-renewable materials from the Earth has to be curtailed as much as we can.
Renewable Means of Energy Generation
There are in fact only a few primary sources of energy that are effectively inexhaustible. One is the energy impinging on the Earth from the sun. A second is heat coming from sources deep in the Earth, mostly produced by radioactive decay. A third is tidal forces from the gravitational influence of Earth’s moon. Renewable energy systems tap one of these three sources, in one way or another. Systems to exploit these sources tend to fall into a small number of types:
- Solar energy systems, either photovoltaic or solar-thermal
- Wind energy systems
- Wave energy systems
- Tidal energy systems
- Hydroelectric energy systems tapping water flow on a river system
- Geothermal energy systems
- Ocean thermal gradient systems
Energy Distribution and Conversion From Renewable Sources
In addition to producing energy at a source location, it is typically necessary to distribute the energy to other distant locations where it is to be used for human purposes. Two primary mechanisms have dominated the transportation of energy from renewable sources:
- Electric energy transmission via electric power lines
- Non-carbon-based gaseous fuel distribution via pipelines or tank transport. Candidate gaseous fuels that do not contribute to greenhouse gas emissions themselves are hydrogen and ammonia. They may be distributed as gases or liquids.
Finally, it is necessary to do conversion of the energy distributed to its use location into either other forms of energy or into work. For example, if the energy produced by solar or wind energy systems is distributed as hydrogen or ammonia, it may need to be converted back into electrical energy by a fuel cell or some form of a combustion engine-generator set.
Energy Storage
In most cases, the renewable energy sources have varying outputs over time. Solar energy systems don’t produce energy at night, wind energy system outputs vary with the wind velocity, and wave energy systems are variable with the weather. As a consequence, we must emphasize development of approaches to store the energy produced by these systems. Many options must be pursued, including batteries of many types, pumped hydro and pumped air systems, gravitational storage systems, molten salt thermal energy storage, etc.
Some Other Associated Needs
It will be important to phase out dangerous old technology pressurized water uranium-based nuclear power plants. If nuclear power is to continue to be used, we should focus on safer thorium-based new technology reactors. We need to finally deal with the radioactive waste storage/disposal problem.
A key approach will be to drastically revamp food production practices to reduce greenhouse gas emissions, such as from beef production. We will need to make agriculture much more conservation-oriented for all resources used, particularly water. Water is currently being used in a highly non-sustainable manner, and a significant portion of society’s energy consumption is connected with the movement of water.
Basic Societal Changes
Taking a long-term view, a number of basic societal changes will be required to reduce greenhouse gas emissions sufficiently:
- Move populations away from locations that inherently require high energy consumption to live.
- Work to reduce transport needs of all kinds.
- Emphasize circular economy concepts where everything possible is recycled and reused—nothing is thrown away and little new material needs to be mined.
- Get away from consumerism in general.
- Get away from the imperative for growth in a capitalistic economy.
Ultimately, the size of the human population needs to be brought in line with the long-term carrying capacity of the Earth’s natural systems. Hopefully this can be done by reducing human birth rates, rather than increasing human death rates.