Background
The term “hockey stick” refers to a specific reconstruction of global temperatures over the last millennium, highlighting significant trends in historical climate data. The graph acquired its name due to its shape, which closely resembles a hockey stick: a long, flat shaft representing relatively constant temperatures over a substantial pre-industrial period, followed by a sharp upward curve in the 20th century, indicating a steep rise in global temperatures.
Historical Context
The “hockey stick” graph gained prominence after its inclusion in the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report in 2001. The temperature reconstruction was primarily developed through principal components analysis of proxy data sources such as tree rings, ice cores, and other historical climate indicators.
Definitions and Concepts
- Proxy Data: Indirect measurements of climate variables derived from tree rings, ice cores, and other historical records.
- Principal Components Analysis (PCA): A statistical technique used to simplify complex datasets by reducing their dimensions, often utilized for patterns in proxy climate data.
Major Analytical Frameworks
Historical Climate Data Analysis
Historical climate data analysis involves combining various forms of proxy data to simulate past climate behavior and identify long-term trends. Methods utilized include principal components analysis and other statistical techniques to create models like the hockey stick graph.
Comparative Analysis
Early Criticisms
Criticism of the hockey stick graph arose around methodological concerns. Initial scrutiny emphasized potential inaccuracies in the dataset, raising questions about the reliability and robustness of conclusions derived from the principal components analysis.
Later Developments
Subsequent reviews and re-analyses unveiled additional complications, including potential data selection biases and issues regarding statistical significance. As a result, various experts, including A. W. Montford, challenged the validity of the hockey stick graph, describing it as a “corruption of science.”
Case Studies
Empirical evaluation of the hockey stick graph has prompted significant academic discourse, culminating in a diverse array of studies, both supporting and critiquing its methodology and conclusions.
Suggested Books for Further Studies
- “The Hockey Stick and the Climate Wars” by Michael E. Mann
- “Hockey Stick Illusion,” by A.W. Montford
Related Terms with Definitions
- Climate Change: Long-term alteration in Earth’s climate, often associated with global warming and other global-scale environmental changes.
- Global Warming: The gradual increase in Earth’s average surface temperature due to high levels of carbon dioxide, chlorofluorocarbons, and other pollutants.
- Principal Components Analysis (PCA): A statistical procedure that converts a set of correlated variables into uncorrelated variables called principal components, useful in reducing the complexity of climate data.
