Most reconstructions shared some data series, particularly tree ring data, but newer reconstructions used additional data and covered a wider area, using a variety of statistical methods. (1998), with a third curve to 1400 from Briffa's new paper, combined with modern temperature data bringing the lines up to 1999: in 2010 the lack of a clarity about this change of data was criticised as misleading. [19] [68] The AR4 SPM statement was that "Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years. It reached the conclusion that peak Medieval warmth only occurred during two or three short periods of 20 to 30 years, with temperatures around 1950s levels, refuting claims that 20th century warming was not unusual. [9] In 2003, as lobbying over the 1997 Kyoto Protocol intensified, a paper claiming greater medieval warmth was quickly dismissed by scientists in the Soon and Baliunas controversy. It typically outlines where the startup begins, their first couple of years hustling, and then a turning point. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. Variations on the "Composite Plus Scale" (CPS) method continued to be used to produce hemispheric or global mean temperature reconstructions. At this broad scale, they found widespread warmth from the 9th to 11th centuries approximating to the 20th century mean, with dominant cooling from the 16th to 18th centuries. The Past, Present and Future of Global Inequality, http://www.ted.com/talks/erik_brynjolfsson_the_key_to_growth_race_em_with_em_the_machines, http://www.ted.com/talks/robert_gordon_the_death_of_innovation_the_end_of_growth, http://www.economist.com/briefing/2013/01/12/has-the-ideas-machine-broken-down, http://www.fastcompany.com/90269483/how-ai-software-could-help-fight-future-wildfires, http://www.npr.org/programs/ted-radio-hour/522858434/the-digital-industrial-revolution, Bhatia, Anshu, et al. In my study of 172 startups, all but eleven companies had hockey stick-shaped growth curves. For the past 1700-1800 years, global production has been a flat line, but the industrial revolution in the 19th century spiked the growth rate up for the last 200-300 years.

[32], Tim Barnett of the Scripps Institution of Oceanography was working towards the next IPCC assessment with Phil Jones, and in 1996 told journalist Fred Pearce "What we hope is that the current patterns of temperature change prove distinctive, quite different from the patterns of natural variability in the past". They were able to detect that the multiple proxies were varying in a coherent oscillatory way, indicating both the multidecadal pattern in the North Atlantic and a longer term oscillation of roughly 250 years in the surrounding region. [22] This showed global patterns of annual surface temperature, and included a graph of average hemispheric temperatures back to 1400 with shading emphasising that uncertainties (to two standard error limits) were much greater in earlier centuries. These methods had been used for regional reconstructions of temperatures, and other aspects such as rainfall.

[94] The von Storch et al. The section proposed that "The data from the last 1000 years are the most useful for determining the scales of natural climate variability". The resulting reconstruction went back to 1400, and was published in November as Mann, Park & Bradley 1995. Mann carried out a series of statistical sensitivity tests, removing each proxy in turn to see the effect its removal had on the result. [126], In a study published in November 2004 Edward R. Cook, Jan Esper and Rosanne D'Arrigo re-examined their 2002 paper, and now supported MBH. Mann used comparisons with other tree ring data from the region to produce a corrected version of this dataset. He reported that Edward R. Cook, a co-author on the paper, had confirmed agreement with these points,[74] and a later paper by Cook, Esper and D'Arrigo reconsidered the earlier paper's conclusions along these lines. The least squares simultaneous solution of these multiple regressions used covariance between the proxy records. [140], Further support for the "hockey stick" graph came from a new method of analysis using Bayesian statistics developed by Martin Tingley and Peter Huybers of Harvard University, which produced the same basic shape, albeit with more variability in the past, and found the 1990s to have been the warmest decade in the 600-year period the study covered. [28] Their study also used the modern instrumental temperature record to evaluate how well the regions covered by proxies represented the northern hemisphere average, and compared the instrumental record with the proxy reconstruction over the same period. [7] Jones et al. [7] Mann describes this as the least scientifically interesting thing they could do with the rich spatial patterns, but also the aspect that got the most attention.