SAJC Cluster 3.2 Lecture 10 notes (The Science of Climate Change (III))

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 10_2025/pg1 Lecture 10 The Science of Climate Change (III): Human Activities and Contemporary Climate Change KEY QUESTION: How significant is the influence of human activities on Earth’s climate compared to natural factors? With the completion of this lecture, attached readings and tutorial, you should be able to understand that: • The consensus with the scientific community, represented by the IPCC, is that climate change in the last two centuries is unequivocal, and it is very likely contributed by human activities • Human activities influence the global carbon cycle by increasing carbon emissions and reducing carbon sinks • The enhanced greenhouse effect is due to the increased concentration of greenhouse gases by human activities • Human activities have a role in accelerating warming through positive feedback and suppressing warming through negative feedback Lecture Outline 10.1 Contemporary Climate Change: Global Warming 10.2 Greenhouse Effect versus Enhanced Greenhouse Effect (a) How the Earth is heated up: The Greenhouse Effect (b) Global Warming: The Enhanced Greenhouse Effect 10.2.1 Per Capita GHG Emissions by Sector 10.2.2 Relative Contribution of Countries to GHG Emissions 10.3 Role of Carbon Cycle and Carbon Sinks in Contemporary Climate Change 10.4 Influence of Human Activities on the Global Carbon Cycle 10.4.1 Increasing Carbon Emissions 10.4.2 Reducing Carbon Sinks 10.5 The Impact of Human Activities on the Feedback Mechanism 10.5.1 Accelerating Warming through Positive Feedback 10.5.2 Suppressing Warming through Negative Feedback 10.6 The IPCC: Contemporary Climate Change is Unequivocal 10.6.1 What is the IPCC? 10.6.2 What is IPCC’s assessment about our climate today? 10.6.3 Significance of Anthropogenic Activities in Contemporary Climate Change 10.7 Conclusion

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 10_2025/pg2 10.1 Contemporary Climate Change: Global Warming • Climate variability refers to variations in the mean state and other statistics such as standard deviations and the occurrence of extremes of the climate on all spatial and temporal scales beyond that of individual weather events . Climate variability may be due to natural internal processes within the climate system or to variations in natural or anthropogenic external forcing. • We have learnt that climate variability is not a new phenomenon. In fact, the climate of the Earth has been varying over a long period of time. We have studied the patterns of climate variability from the past (that is, during the Pleistocene and the Holocene) till the present. This knowledge is important to help us understand the