Dependence on fossil fuels is causing climate change. From the perspective of physics, let us understand the mechanism of global warming and energy issues.
Basic Knowledge
Greenhouse effect: Visible light from the Sun passes through the atmosphere and warms the surface, while greenhouse gases absorb and re-emit infrared radiation emitted by the surface, thereby warming the entire Earth.
Main greenhouse gases: CO₂ (carbon dioxide), CH₄ (methane), N₂O (nitrous oxide), and chlorofluorocarbons
・The greenhouse effect itself is necessary to maintain Earth’s life-supporting average temperature (+15°C)
・The mass consumption of fossil fuels since the Industrial Revolution has caused CO₂ concentrations to rise sharply → global warming is progressing
Responses to energy issues:
・Energy conservation: Improving efficiency and saving electricity
・Promoting renewable energy
・Decarbonization: Making CO₂ emissions effectively zero (carbon neutrality)
・Hydrogen society: Producing hydrogen with renewable energy and using it as fuel
Greenhouse effect (greenhouse effect) (the atmosphere absorbs and re-emits infrared radiation to keep Earth warm)
Greenhouse gases (CO₂, CH₄, N₂O, chlorofluorocarbons, and others)
Carbon neutrality (making net emissions zero by balancing emitted and absorbed CO₂)
Renewable energy (solar, wind, hydroelectric, geothermal, and other energy)
Fossil fuels (coal, petroleum, and natural gas; carbon compounds of biological origin)
SDGs (Sustainable Development Goals; international goals that include energy issues)
Further Exploration (Background and Significance)
Earth’s average temperature has risen by approximately 1.1°C since the Industrial Revolution (around 1850). The IPCC (Intergovernmental Panel on Climate Change) indicates that temperatures could rise by as much as 5.7°C by the end of this century.
Atmospheric CO₂ concentration increased from approximately 280 ppm before the Industrial Revolution to approximately 420 ppm today (2023). 1 ppm = 1/1,000,000.
Improving energy-conversion efficiency is important for combining measures against global warming with economic efficiency. LED lighting has approximately 10 times the luminous efficiency and uses approximately 1/10 the power of incandescent bulbs. Electric vehicles have higher thermal efficiency than internal-combustion vehicles (although this depends on how electricity is generated).
The Paris Agreement (2015): Countries set reduction targets to limit the rise in global average temperature to less than 2°C above preindustrial levels, with 1.5°C as an additional effort goal. Japan has declared carbon neutrality by 2050.
- Greenhouse gases: CO₂, CH₄, N₂O, and chlorofluorocarbons
- The greenhouse effect itself is necessary (without it, Earth would freeze)
- Fossil-fuel consumption → increased CO₂ → global warming
- Measures: energy conservation, renewable energy, and decarbonization
- Carbon neutrality = net-zero emissions
- Paris Agreement: Goal of less than 2°C
- Japan: Declaration of carbon neutrality by 2050
Points to Note (Common Confusions)
① The greenhouse effect is not itself harmful. The problem is the enhanced greenhouse effect caused by human-induced increases in CO₂. ② Ozone-layer depletion (caused by chlorofluorocarbons) and global warming are separate issues, although they are easily confused. ③ Carbon neutrality does not mean zero emissions; it means that “emissions and absorption are balanced.” ④ Introducing renewable energy alone makes a stable electricity supply difficult. A combination with energy storage and hydrogen is necessary.
Practice
- Name two major greenhouse gases.
- Explain what carbon neutrality means.
- Name one method that individuals and one method that society can use to address global warming.