SAJC Cluster 3.2 Lecture 8 Notes (The Science of Climate Change)

St Andrew’s Junior College H2Cluster3: Sustainable Future and Climate Change H2_Cluster3 Lecture 8_2025/pg1 Lecture 8 The Science of Climate Change (I): Past Climates KEY QUESTION: Is climate variability a new phenomenon in Earth’s history? With the completion of this lecture, attached readings and tutorial, you should be able to understand the: • Episodes of warming and cooling of Earth during the Quaternary period • Evidence of past climate variability derived from proxy indicators through the study of ice and ocean cores Lecture Outline 8.1 Climate Variability Is Nothing New 8.1.1 The Pleistocene 8.1.2 The Holocene 8.2 Evidence of Past Climate Variability 8.2.1 Ice Core Records (a) Greenhouse gas concentrations (b) Oxygen isotopes 8.2.2 Ocean Core Records (a) Shells of marine microorganisms (b) Materials removed from land 8.3 Conclusion In a project called Climate: Long -Range Investigation, Mapping, and Prediction (CLIMAP) in the 1970s, researchers reconstructed the climate of the Earth about 20,000 years ago, during a time many refer to as the Ice Age. This map shows the difference in temperatures between then and now (blue areas were colder, red areas warmer). The most obvious feature is perhaps the presence of much colder water in the North Atlantic. Ocean cores proved invaluable in this project. What are ocean cores and how did they help? What else do we know about Earth’s climate in the past?

St Andrew’s Junior College H2Cluster3: Sustainable Future and Climate Change H2_Cluster3 Lecture 8_2025/pg2 8.1 Climate Variability Is Nothing New • 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 b e due to natural internal processes within the climate system or to variations in natural or anthropogenic external forcing. • Contemporary climate change in recent years is deemed as a global challenge, but it is important to note that climate variability itself is not a new phenomenon. Climate of the Earth has been varying over a long period of time. • In this section of the syllabus, we shall first outline the changes in global climatic patterns as far back as 2.6 million years ago (mya). We then proceed to examine the evidence that suggest that these changes did occur (Section 8.2) and find out why these changes occur (Lect. 9). • The Earth is more than 4.5 billion years old. This vast span of time is called geologic time . Geologists have divided the geologic time into a series of time intervals. Of most relevance to us is the time interval known as the Quaternary Period. The Quaternary period extends from 2.6 million years ago till