Publicity and controversy on publication of MBH98 Hockey stick graph

release of paper on 22 april 1998 given exceptional media coverage, including questioning whether proved human influences responsible global warming. mann agree highly suggestive of inference. said our conclusion warming of past few decades appears closely tied emission of greenhouse gases humans , not of natural factors . proxy data inherently imprecise, , mann said have error bars. sizable 1 gets farther in time, , there reasonable uncertainty in given year. there quite bit of work done in reducing these uncertainties. climatologist tom wigley welcomed progress made in study, doubted if proxy data ever wholly convincing in detecting human contribution changing climate.

phil jones of uea climatic research unit told new york times doubtful adding 150-year thermometer record extend proxy reconstruction, , compared putting apples , oranges; mann et al. said used comparison thermometer record check recent proxy data valid. jones thought study provide important comparisons findings of climate modeling, showed pretty reasonable fit proxy evidence. commentary on mbh98 jones published in science on 24 april 1998. noted used available long term proxy climate series, , if new multivariate method of relating these series instrumental data paper claims, should statistically reliable. discussed of difficulties, , emphasised each paleoclimatic discipline has come terms own limitations , must unreservedly admit problems, warts , all.

the study disputed contrarian pat michaels claim of warming took place between 1920 , 1935, before increased human greenhouse gas emissions. george c. marshall institute alleged mbh98 deceptive in going 1400, , not covering medieval warm period predated industrial greenhouse gas emissions. same criticisms made willie , sallie baliunas.