12.6: Solutions

Global Emissions

Climate change is a complex problem because modern society was built around burning fossil fuels for energy. We still depend heavily on fossil fuels for everything from driving our cars and washing our laundry to charging our cell phones and heating our homes. To stabilize the climate, however, we’ll need to reach near-zero carbon emissions over the long term. Thus, the challenge is to decarbonize our economy. The longer we wait, the greater the impacts of future climate change will be, or the faster we'll need to reduce emissions. And because it is a global problem, the whole world, or at least most of it, will need to cooperate to solve it. Moreover, because we’re already committed to further climate change, we'd better prepare to adapt. This chapter discusses technological options, political efforts, and personal actions for climate mitigation and adaptation to the inevitable.

Figure \(\PageIndex{1}\) illustrates the increase in carbon dioxide (CO₂) emissions since 1750. Before the Industrial Revolution, emissions were very low. Emissions grew relatively slowly until the mid-20th century. In 1950, the world emitted 6 billion tonnes of CO₂. By 1990, this had nearly quadrupled to more than 20 billion tonnes. Emissions have continued to grow rapidly. We now emit more than 38 billion tonnes annually. Emissions growth has slowed in recent years, but they have not yet peaked. In recent years, China, the United States, and India have been the top three CO₂ emitters by total volume, with China being the largest emitter since 2006. Other major emitters include Russia, European Union (EU) member states, and Indonesia. While emissions from China and India have increased over the past few decades, their per capita emissions remain significantly lower than those of countries such as the United States and the EU.

Technology

Current global energy production relies heavily on fossil fuel burning, as illustrated in Fig. \(\PageIndex{2}\). The largest energy sources are oil, coal, and natural gas, all fossil fuels, while non-fossil fuels together account for only about 20% of total energy. In the United States, transportation is the largest source of emissions, accounting for 27%, followed by electricity generation at 25% and industry at 24%.

Most oil consumption powers transportation via internal combustion engines in cars and trucks, which are very inefficient. Only about 25% of the energy input into transportation moves vehicles, while nearly 75% is wasted as heat. Coal is mainly used in power plants to generate electricity, and this process also loses about 50% of the total energy. This loss is less than that of internal combustion engines, so electric cars have lower carbon footprints than internal combustion engine cars, even if the electricity comes from coal. Most natural gas is used to generate electricity and to heat buildings. Hydro- and nuclear power generate electricity, whereas biomass is primarily used for cooking and home heating in the developing world. Renewable energy sources, such as solar and wind, supply only a small fraction of total energy.

Nuclear Power

Nuclear power generates electricity by using heat from a controlled nuclear fission reaction to create steam, which drives a turbine connected to a generator. They provide fossil-free power that does not emit carbon dioxide (except during construction). Unlike intermittent sources such as solar and wind, nuclear power plants can operate 24/7, providing a steady, reliable baseload power supply. For this reason, some view them as an important future energy source. The Diablo Canyon Nuclear Power Plant depicted in Figure \(\PageIndex{3}\) is the only operational nuclear plant in California, as well as the state's largest single power station.

However, nuclear power has disadvantages too. They are expensive to build, dangerous to operate, and produce radioactive waste for which no long-term repository currently exists. Catastrophic accidents such as the nuclear meltdowns in 2011 at the Japanese Fukushima Daiichi plant and in 1986 at the Chernobyl reactor in what is now northern Ukraine have shown the dangers associated with nuclear power production. As a result, nuclear power remains controversial.

Renewables

In some countries, renewable energy sources have increased rapidly in recent years. Germany, for example, increased the share of renewables in total electricity production from 3% in 1990 to 45% in 2020, while its economy has remained among Europe's strongest. Denmark plans to move to 100% renewable energy by 2050. As of 2023, in the United States, renewables currently account for 9% of total energy consumption and 21% of electricity production, as illustrated in Figure \(\PageIndex{4}\). Because transportation consumes the most energy in the United States, petroleum (oil) accounts for most of that energy. Fossil fuels such as natural gas and coal still account for nearly 60% of electricity generation, with nuclear power and renewables accounting for the remainder.

Solar power is the conversion of sunlight into electricity, either directly via photovoltaic (PV) cells (also known as solar panels) or indirectly via concentrated solar power using mirrors. Wind power uses wind energy to rotate wind turbines, which are then connected to a generator to produce electricity. A renewable energy farm including solar panels and wind turbines in Germany is shown in Figure \(\PageIndex{5}\)A. Hydro power is generated by converting the gravitational potential or kinetic energy of a water source into electricity, as illustrated in Figure \(\PageIndex{5}\)B. Bioenergy is a renewable energy source derived from plants and animal waste. Unlike fossil fuels, biomass commonly used for bioenergy includes wood, food crops such as corn, energy crops, and waste from forests, yards, or farms. Geothermal power is electricity generated from Earth's core. Water or another fluid is sent down multiple miles below the surface, where the temperature increases. This boils the liquid in the pipes, which then drives a steam turbine at the surface.

A

B

The advantage of renewable energy is its nearly unlimited supply potential and minimal carbon emissions. Some emissions occur during the production and installation of solar panels and wind turbines. Renewables are also not associated with the dangers of nuclear power. Their main disadvantage used to be their high up-front investment costs. Once installed, however, solar panels and wind turbines require minimal maintenance because solar energy and wind are free. During the past 10 years, the cost of solar panels has decreased dramatically by 80%. Thus, over a system's lifetime, renewables become competitive with fossil fuels. Other renewable energy sources include geothermal, tidal, and wave energy, as well as hydropower. Another issue with renewable energy is its intermittent supply. Solar panels operate during daylight, whereas wind turbines operate only when the wind blows. However, recent studies, such as Shaner et al. (2018) have found that 80% of total electricity demand could be met by wind and solar, as quoted from the abstract of the paper:

Assuming minimal excess generation, lossless transmission, and no other generation sources, the analysis indicates that wind-heavy or solar-heavy U.S.-scale power generation portfolios could in principle provide ∼80% of recent total annual U.S. electricity demand. -Shaner et al. (2018)

Many companies are moving toward electric or hybrid vehicles. Because they are much more efficient (80-90%), their energy use is much lower than for internal combustion engine vehicles, and their carbon footprint can be close to zero (some is associated with vehicle production) if they use renewable electricity. Even when electricity is generated from fossil fuels, the carbon footprint of electric cars remains lower than that of internal-combustion-engine vehicles. Given the transportation sector's substantial carbon emissions and significant losses, transitioning to an electric vehicle fleet could substantially reduce future emissions. Although electric cars are more expensive to purchase, their total life-cycle costs are lower than those of gasoline-powered vehicles. Electric cars also offer additional advantages—no oil changes, no tailpipe emissions, and greater torque. However, manufacturing electric cars is not without environmental and human impacts, including those associated with mining the raw materials used in battery production.

Personal Actions

Each of us can take individual actions to reduce carbon emissions and the impacts of climate change. Conserving energy, e.g. by switching off lights when they are not needed. Switching to energy-efficient appliances, such as LED lights. Recycling also helps. Driving less or choosing an energy-efficient car, such as a hybrid, electric, or smaller vehicle, will reduce your carbon footprint. Even better is riding your bike. Eating less meat is another way to reduce your carbon footprint, since meat production generates more carbon emissions than vegetarian food. Homeowners can weatherize their homes or install solar panels. You can assess your carbon footprint on various websites to help you get started.

Ultimately, however, individual actions have limited effects. For example, imagine you start using less gas by riding your bike instead of driving your car. If many people did, demand for gas would decrease, lowering its price, assuming supply remains constant. Lower gas prices lead people to buy larger cars and drive more, thereby diminishing or erasing the effects of their personal emission reduction. That is not to say that we shouldn't take individual actions. However, collective action is also needed. Large-scale government actions, such as a carbon tax or a cap-and-trade system, can accelerate the transition to renewable energy sources that are necessary to avoid potentially dangerous climate change.

Adaptation

Climate change already affects us. It is not only a future problem or a faraway issue. It is a present issue. Since we cannot avoid further climate change in the immediate future, we must adapt to avoid its consequences. Perhaps the most important thing is to recognize that it is happening. This will prompt us to consider the potential implications for our region. If regional projections are available, we can consider them in planning. If not, we can still extrapolate from past changes, assuming we'll see more of what we’ve observed recently.

Adaptation can help manage impacts and risks to people and nature. The four types of adaptation actions are infrastructural, institutional, behavioral, and nature-based options. Some examples are building seawalls to combat rising sea levels, as shown in Figure \(\PageIndex{6}\), or inland flood defenses. Other options include providing new insurance schemes for populations threatened by climate-related disasters, adjusting crop planting times or varieties based on temperature and precipitation changes, and installing green roofs or green spaces in cities to combat the Urban Heat Island effect. Adaptation can be reactive, i.e., responding to climate impacts as they happen, or proactive, i.e., taking steps in anticipation of future climate change.

Cited Source:

Shaner, M. R., S. J. Davis, N. S. Lewis, and K. Caldeira, 2018: Geophysical constraints on the reliability of solar and wind power in the United States. Energy Environ. Sci., 11, 914–925, https://doi.org/10.1039/C7EE03029K.