GY2436: An Introduction to Past Global Climate Changes

Overview of Quaternary Science and Palaeoclimatology

GY2436 provides an introduction to climatic change during the Quaternary Period, which spans the last $2.59 \text{ Million}$ years. This module explores the nature and causes of geological shifts to provide context for contemporary environmental changes and human impact. The Quaternary is a division of the Late Cenozoic Era and is subdivided into the Pleistocene and Holocene Epochs. It is characterized by major cyclical changes, specifically geologically recent glaciations of the Northern Hemisphere, which serve as a laboratory for studying landscape and ecosystem responses to abrupt and gradual change.

Defining Climate and Past Environments

Climate is defined by Goudie (1997) as the long-term atmospheric characteristics of an area, whereas weather pertains to short-term phenomena from minutes to months. Palaeoclimate refers to conditions prior to the instrumental record, generally exceeding $300$ years. Global climate cycles between "Icehouse" and "Greenhouse" phases; the Quaternary is currently in an icehouse phase featuring a significant cryosphere. Scientists use indirect "proxy" evidence—such as fossil, geochemical, or landscape records—to reconstruct these past conditions. Key records include the Plio-Pleistocene oceanic "stack" of $57$ globally distributed benthic $\delta^{18}O$ records by Lisiecki and Raymo (2005).

The Last Glacial Maximum (LGM)

The LGM occurred approximately $21,000$ years BP. Between $21,000$ and $9,000$ years BP, Greenland air temperatures rose by approximately $20^\circ\text{C}$, while Antarctic temperatures increased by $10\text{-}15^\circ\text{C}$. During this transition, global sea levels rose by roughly $120\,m$, and global ice coverage decreased from $40\text{ million } km^2$ to $16\text{ million } km^2$. Atmospheric $CO_2$ rose from $180\,\text{ppm}$ to $260\,\text{ppm}$, and methane increased from $350\,\text{ppb}$ to $710\,\text{ppb}$. These shifts caused a radical reorganization of Earth's biomes and changes in ocean currents and temperatures.

Historical Context and Human Factors

Early research into the Ice Age involved figures such as Charles Darwin, Louis Agassiz, and Professor T.C. Chamberlin, who created the first maps of North American glaciation in 1894. Modern scientific understanding is supported by projects like the BRITICE glacial map, which details the British-Irish Ice Sheet. In terms of human factors, the module examines the dispersal of modern humans and the timeline of Neanderthals (Homo neanderthalensis) from $300,000$ to $40,000$ BP, alongside archaeological finds like the hominin from Flores, Indonesia.

Module Structure and Assessment

The module is taught by Arnoud and Anna Joy Drury and organized into four sections: drivers of change (including Milankovitch orbital forcing), palaeoecology, geochronology, and landscape responses. Learning outcomes focus on describing global shifts, understanding ice core records from Greenland and Antarctica, and utilizing proxy data. Assessment consists of coursework analyzing ice and marine core data (50%) and a May exam (50%). Essential reading is provided by Lowe and Walker.