Description of The Medieval Warm Period and Little Ice Age in IPCC Reports - 1995 Report (SAR)

1995 Report (SAR)

By 1995, research in the subject had advanced and hemispherical reconstructions of temperature were available, though only for the summer season (because tree rings are often most strongly influenced by summer temperatures). The 1995 IPCC report used a northern hemisphere summer temperature reconstruction (fig 3.20) from 1400 to 1979 by (Bradley and Jones 1993). This too shows no MWP (it only goes back to 1400) and colder temperatures otherwise before the 20th century, of the order of 0.5 °C colder. Fig 3.21 shows 8 ice core records from 1200 to present, which display a mixed pattern.

The MWP and LIA are introduced, in the text, as "two periods which have received special attention... These have been interpreted, at times, as periods of global warmth and coolness, respectively. Recent studies have re-evaluated the interval commonly known as the Medieval Warm Period to assess the magnitude and geographical extent of any prolonged warm interval between the 9th and 14th centuries (Hughes and Diaz, 1994). The available evidence is limited (geographically) and is equivocal." After discussing the evidence, it concluded "a clearer picture may emerge as more and better calibrated proxy records are produced. However, at this point, it is not yet possible to say whether, on a hemispheric scale, temperatures declined from the 11-12th to the 16-17th century. Nor, therefore, is it possible to conclude that global temperatures in the Medieval Warm Period were comparable to the warm decades of the late 20th century."