Topic 6 Atmosphere and Climate

At the end of this subtopic 6.1 you should understand:

• The atmosphere forms the boundary between Earth and space. It is the outer limit of the biosphere and its composition and processes support life on Earth. (6.1.1) 

• Differential heating of the atmosphere creates the tricellular model of atmospheric circulation that redistributes the heat from the equator to the poles. (6.1.2)

• GHGs and aerosols in the atmosphere absorb and re-emit some of the infrared (long-wave) radiation emitted from the Earth's surface, preventing it from being radiated out into space. They include water vapour, carbon dioxide, methane and nitrous oxides (GHGs), and black carbon (aerosol). (6.1.3)

• The greenhouse effect keeps the Earth warmer than it otherwise would be due to the broad spectrum of the Sun's radiation reaching the Earth's surface and infrared radiation emitted by the warmed surface then being trapped and re-radiated by GHGs. (6.1.4) 

At the end of this  subtopic 6.2  you should understand:

• Climate describes the typical conditions that result from physical processes in the atmosphere. (6.2.1) 

• Anthropogenic carbon dioxide emissions have caused atmospheric concentrations to rise significantly. The global rate of emission has accelerated, particularly since 1950. (6.2.2) 

• Analysis of ice cores, tree rings, and deposited sediments provide data that indicates a positive correlation between the concentration of carbon dioxide in the atmosphere and global temperatures. (6.2.3)

• The greenhouse effect has been enhanced by anthropogenic emissions of GHGs. This has led to global warming and, therefore, climate change. (6.2.4) 

• Climate change impacts ecosystems at a variety of scales, from local to global. This impacts the resilience of ecosystems and leads to biome shifting. (6.2.5) 

• Systems diagrams and models can be used to represent cause and effect of climate change with feedback loops, either positive or negative, and changes in the global energy balance. (6.2.7)

• Evidence suggests that the Earth has already passed the planetary boundary for climate change. (6.2.8) 

• Climate change has an impact on (human) societies at a variety of scales and socio-economic conditions. This impacts the resilience of societies. (6.2.6) 

• Perspectives on climate change for both individuals and societies are influenced by many factors. (6.2.9) 

At the end of this subtopic 6.3 you should understand: 

• To avoid the risk of catastrophic climate change, global action is required, rather than measures adopted only by certain states. (6.3.1) 

• Dec0arbonization of the economy means reducing or ending the use of energy sources that result in CO₂ emissions and replacing them with renewable energy sources. (6.3.2) 

• A variety of mitigation strategies aim to address climate change. (6.3.3) 

• Adaptation strategies aim to reduce adverse effects of climate change and maximise any positive consequences. (6.3.4) 

• Individuals and societies on a range of scales are developing adaptation plans, such as National Adaptation Programmes of Action (NAPAs), and resilience and adaptation plans. (6.3.5) 

By the end of section, you should understand:

• The Sun emits electromagnetic radiation in a range of wavelengths, from low frequency radio waves to high frequency gamma radiation. (6.4.1)

• Shorter wavelengths of radiation (UV radiation) have higher frequencies and, therefore, more energy, so pose an increased danger to life. (6.4.2)

• Stratospheric ozone absorbs UV radiation from the Sun, reducing the amount that reaches the Earth's surface and, therefore, protecting living organisms from its harmful effects. (6.4.3) 

• The relative concentration of ozone molecules has stayed constant over long periods of time due to a steady state of equilibrium between the concurrent processes of ozone formation and destruction. (6.4.5)