Corrections to the Mann et. al. (1998) Proxy Data Base and Northern Hemispheric Average Temperature Series

2003/11/01 by Stephen McIntyre, Ross McKitrick · 7 citations
Earth and Planetary Sciences · Environmental Science · Mathematics · #Tree-ring climate responses #Climate variability and models #Plant Water Relations and Carbon Dynamics #Extrapolation #Proxy (statistics) #Northern Hemisphere #Principal component analysis #Series (stratigraphy) #Econometrics #Statistics #Collation #Environmental science #Mathematics #Climatology #Meteorology #Geography #Geology #Computer science

paper · doi:10.1260/095830503322793632

openalex publication_date 2003/11/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/14

Abstract

The data set of proxies of past climate used in Mann, Bradley and Hughes (1998, “MBH98” hereafter) for the estimation of temperatures from 1400 to 1980 contains collation errors, unjustifiable truncation or extrapolation of source data, obsolete data, geographical location errors, incorrect calculation of principal components and other quality control defects. We detail these errors and defects. We then apply MBH98 methodology to the construction of a Northern Hemisphere average temperature index for the 1400–1980 period, using corrected and updated source data. The major finding is that the values in the early 15th century exceed any values in the 20th century. The particular “hockey stick” shape derived in the MBH98 proxy construction – a temperature index that decreases slightly between the early 15th century and early 20th century and then increases dramatically up to 1980 — is primarily an artefact of poor data handling, obsolete data and incorrect calculation of principal components.

Citations

• Global surface temperatures over the past two millennia
• High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with General Circulation Model control-run temperatures
• Calculating unbiased tree-ring indices for the study of climatic and environmental change
• Climate over past millennia

Cited by

• The importance of the geophysical context in statistical evaluations of climate reconstruction procedures
• Are multiproxy climate reconstructions robust?
• Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Method, Predictor Network, Target Season, and Target Domain
• The M&M Critique of the MBH98 Northern Hemisphere Climate Index: Update and Implications
• Millennial temperature reconstruction intercomparison and evaluation
• Hockey stick graph (global temperature) [wikipedia]
• Temperature record of the last 2,000 years [wikipedia]