Chart hockey stick

Hockey stick graphs present the global or hemispherical mean temperature record of the past to years as shown by quantitative climate reconstructions based on climate proxy records. These reconstructions have consistently shown a slow long term cooling trend changing into relatively rapid warming in the 20th century, with the instrumental temperature record by exceeding earlier temperatures. Arguments over the reconstructions have been taken up by fossil fuel industry funded lobbying groups attempting to cast doubt on climate science. Paleoclimatology dates back to the 19th century, and the concept of examining varves in lake beds and tree rings to track local climatic changes was suggested in the s.

How To Make a Hockey Stick Chart

Hockey stick graphs present the global or hemispherical mean temperature record of the past to years as shown by quantitative climate reconstructions based on climate proxy records. These reconstructions have consistently shown a slow long term cooling trend changing into relatively rapid warming in the 20th century, with the instrumental temperature record by exceeding earlier temperatures.

Arguments over the reconstructions have been taken up by fossil fuel industry funded lobbying groups attempting to cast doubt on climate science. Paleoclimatology dates back to the 19th century, and the concept of examining varves in lake beds and tree rings to track local climatic changes was suggested in the s.

This was the basis of a "schematic diagram" featured in the IPCC First Assessment Report of beside cautions that the medieval warming might not have been global.

The use of indicators to get quantitative estimates of the temperature record of past centuries was developed, and by the late s a number of competing teams of climatologists found indications that recent warming was exceptional.

In Michael E. Mann , Raymond S. Bradley and Malcolm K. This showed global patterns of annual surface temperature, and included a graph of average hemispheric temperatures back to with shading emphasising that uncertainties to two standard error limits were much greater in earlier centuries.

In Hans von Storch published criticism of the statistical techniques as tending to underplay variations in earlier parts of the graph, though this was disputed and he later accepted that the effect was very small. Political disputes led to the formation of a panel of scientists convened by the United States National Research Council , their North Report in supported Mann's findings with some qualifications, including agreeing that there were some statistical failings but these had little effect on the result.

More than two dozen reconstructions , using various statistical methods and combinations of proxy records, support the broad consensus shown in the original hockey-stick graph, with variations in how flat the preth century "shaft" appears. Paleoclimatology influenced the 19th century physicists John Tyndall and Svante Arrhenius who found the greenhouse gas effect of carbon dioxide CO 2 in the atmosphere to explain how past ice ages had ended. Wilmot H. Bradley showed that annual varves in lake beds showed climate cycles, and A.

Douglass found that tree rings could track past climatic changes but these were thought to only show random variations in the local region.

It was only in the s that accurate use of tree rings as climate proxies for reconstructions was pioneered by Harold C. In Hubert Lamb , a pioneer of historical climatology , generalised from temperature records of central England by using historical, botanical and archeological evidence to popularise the idea of a Medieval Warm Period from around to , followed by a cold epoch culminating between and They used "a short-cut method" based on their earlier paper which showed that 9 instrumental stations could adequately represent an extensive gridded instrumental series, and reconstructed temperatures from to on the basis of their compilation of 20 time-series.

These records were largely instrumental but also included some proxy records including two tree-ring series. Their method used nested multiple regression to allow for records covering different periods, and produced measures of uncertainty. The reconstruction showed a cool period extending beyond the Maunder Minimum , and warmer temperatures in the 20th century. This was the first based entirely on non-instrumental records, and used tree rings. From this, they concluded that recent warming was anomalous over the year period, and went as far as speculating that these results supported the hypothesis that recent warming had human causes.

Publicity over the concerns of scientists about the implications of global warming led to increasing public and political interest, and the Reagan administration , concerned in part about the political impact of scientific findings, successfully lobbied for the formation of the Intergovernmental Panel on Climate Change to produce reports subject to detailed approval by government delegates.

The report discussed the difficulties with proxy data, "mainly pollen remains, lake varves and ocean sediments, insect and animal remains, glacier termini" but considered tree ring data was "not yet sufficiently easy to assess nor sufficiently integrated with indications from other data to be used in this report.

In Bradley , a working group of climatologists including Raymond S. Bradley , Malcolm K. Climate proxy temperature data was needed at seasonal or annual resolution covering a wide geographical area to provide a framework for testing the part climate forcings had played in past variations, look for cycles in climate, and find if debated climatic events such as the Little Ice Age and Medieval Warm Period were global.

Areas where more data was needed were to be identified, and there was a need for improved data exchange with computer-based archiving and translation to give researchers access to worldwide paleoclimate information.

The IPCC supplementary report, , reviewed progress on various proxies. These included a study of 1, years of tree ring data from Tasmania which, like similar studies, did not allow for possible overestimate of warming due to increased CO 2 levels having a fertilisation effect on tree growth.

It noted the suggestion of Bradley et al. Archives of climate proxies were developed: in Raymond S. Bradley and Phil Jones composited historical records, tree-rings and ice cores for the Northern Hemisphere from up to the s to produce a decadal reconstruction. It concluded that the "Little Ice Age" period was complex, with evidence suggesting the influence of volcanic eruptions. It showed that temperatures since the s were higher than earlier in the year period, an indication of other factors which could most probably be attributed to human caused changes increasing levels of greenhouse gases.

This paper introduced the "Composite Plus Scaling" CPS method which was subsequently used by most large-scale climate reconstructions of hemispheric or global average temperatures.

In this method, also known as "Composite Plus Scale", selected climate proxy records were standardized before being averaged composited , and then centred and scaled to provide a quantitative estimate of the target temperature series for the climate of the region or hemisphere over time.

This method was implemented in various ways, including different selection processes for the proxy records, and averaging could be unweighted, or could be weighted in relation to an assessment of reliability or of area represented. There were also different ways of finding the scaling coefficient used to scale the proxy records to the instrumental temperature record. John A. Eddy had earlier tried to relate the rarity of sunspots during the Maunder Minimum to Lamb's estimates of past climate, but had insufficient information to produce a quantitative assessment.

A reconstruction of Arctic temperatures over four centuries by Overpeck et al. It stated that in this record, warming since the late 19th century was unprecedented. The section proposed that "The data from the last years are the most useful for determining the scales of natural climate variability".

Recent studies including the reconstruction by Hughes and Diaz questioned how widespread the Medieval Warm Period had been at any one time, thus it was not possible "to conclude that global temperatures in the Medieval Warm Period were comparable to the warm decades of the late 20th century. In at least some areas, the recent period appears to be warmer than has been the case for a thousand or more years".

Tim Barnett of the Scripps Institution of Oceanography was working towards the next IPCC assessment with Phil Jones , and in 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".

Tree ring specialist Keith Briffa 's February study showed that this problem was more widespread at high northern latitudes, and warned that it had to be taken into account to avoid overestimating past temperatures.

Variations on the "Composite Plus Scale" CPS method continued to be used to produce hemispheric or global mean temperature reconstructions. From this was complemented by Climate Field Reconstruction CFR methods which could show how climate patterns had developed over large spatial areas, making the reconstruction useful for investigating natural variability and long term oscillations as well as for comparisons with patterns produced by climate models.

The CFR method made more use of climate information embedded in remote proxies, but was more dependent than CPS on assumptions that relationships between proxy indicators and large-scale climate patterns remained stable over time.

Related rigorous statistical methods had been developed for tree ring data, with Harold C. Fritts publishing a study and a book showing methodology and examples of how to produces maps showing climate developments in North America over time. These methods had been used for regional reconstructions of temperatures, and other aspects such as rainfall. As part of his Phd research, Michael E. They then teamed up with Raymond S. 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 years in the surrounding region.

Their study did not calibrate these proxy patterns against a quantitative temperature scale, and a new statistical approach was needed to find how they related to surface temperatures in order to reconstruct past temperature patterns.

For his postdoctoral research Mann joined Bradley and tree ring specialist Malcolm K. Hughes to develop a new statistical approach to reconstruct underlying spatial patterns of temperature variation combining diverse datasets of proxy information covering different periods across the globe, including a rich resource of tree ring networks for some areas and sparser proxies such as lake sediments, ice cores and corals, as well as some historical records.

Their global reconstruction was a major breakthrough in evaluation of past climate dynamics, and the first eigenvector -based climate field reconstruction CFR incorporating multiple climate proxy data sets of different types and lengths into a high-resolution global reconstruction. Their method was based on separate multiple regressions between each proxy record or summary and all of the leading principal components of the instrumental record.

The least squares simultaneous solution of these multiple regressions used covariance between the proxy records.

The results were then used to reconstruct large-scale patterns over time in the spatial field of interest defined as the empirical orthogonal functions , or EOFs using both local relationships of the proxies to climate and distant climate teleconnections. A balance was required over the whole globe, but most of the proxy data came from tree rings in the Northern mid latitudes , largely in dense proxy networks.

Since using all of the large numbers of tree ring records in would have overwhelmed the sparse proxies from the polar regions and the tropics , they used principal component analysis PCA to produce PC summaries representing these large datasets, and then treated each summary as a proxy record in their CFR analysis. The primary aim of CFR methods was to provide the spatially resolved reconstructions essential for coherent geophysical understanding of how parts of the climate system varied and responded to radiative forcing , so hemispheric averages were a secondary product.

Their original draft ended in as most reconstructions only went that far, but an anonymous peer reviewer of the paper suggested that the curve of instrumental temperature records should be shown up to the present to include the considerable warming that had taken place between and The paper announced a new statistical approach to find patterns of climate change in both time and global distribution, building on previous multiproxy reconstructions.

The authors concluded that "Northern Hemisphere mean annual temperatures for three of the past eight years are warmer than any other year since at least AD", and estimated empirically that greenhouse gases had become the dominant climate forcing during the 20th century. Hegerl described their method as "quite original and promising", which could help to verify model estimates of natural climate fluctuations and was "an important step towards reconstructing space—time records of historical temperature patterns".

Release of the paper on 22 April was given exceptional media coverage, including questioning as to whether it proved that human influences were responsible for global warming. Mann would only agree that it was "highly suggestive" of that inference. Most proxy data are inherently imprecise, and Mann said "We do have error bars. They are somewhat sizable as one gets farther back in time, and there is reasonable uncertainty in any given year.

There is quite a bit of work to be done in reducing these uncertainties. Phil Jones of the UEA Climatic Research Unit told the New York Times he was doubtful about adding the year thermometer record to extend the proxy reconstruction, and compared this with putting together apples and oranges; Mann et al.

Jones thought the study would provide important comparisons with the findings of climate modeling , which showed a "pretty reasonable" fit to proxy evidence. He noted that it used almost all the available long term proxy climate series, "and if the new multivariate method of relating these series to the instrumental data is as good as the paper claims, it should be statistically reliable.

The study was disputed by contrarian Pat Michaels with the claim that all of the warming took place between and , before increased human greenhouse gas emissions. Marshall Institute alleged that MBH98 was deceptive in only going back to , and so not covering the Medieval Warm Period which predated industrial greenhouse gas emissions.

In October the borehole reconstruction published by Pollack, Huang and Shen gave independent support to the conclusion that 20th century warmth was exceptional for the past years. Jones, Keith Briffa , Tim P. Barnett and Simon Tett had independently produced a "Composite Plus Scale" CPS reconstruction extending back for a thousand years, comparing tree ring, coral layer, and glacial proxy records, but not specifically estimating uncertainties. Jones et al. As Bradley recalls, Mann's initial view was that there was too little information and too much uncertainty to go back so far, but Bradley said "Why don't we try to use the same approach we used in Nature, and see if we could push it back a bit further?

We can actually say something, although there are large uncertainties. In considering the Jones et al. Mann carried out a series of statistical sensitivity tests , removing each proxy in turn to see the effect its removal had on the result. He found that certain proxies were critical to the reliability of the reconstruction, particularly one tree ring dataset collected by Gordon Jacoby and Rosanne D'Arrigo in a part of North America Bradley's earlier research had identified as a key region.

To find out why, Mann compared the two datasets and found that they tracked each other closely from to , then diverged until around when they again tracked each other. He found a likely reason in the CO 2 " fertilisation effect " affecting tree rings as identified by Graybill and Idso, with the effect ending once CO 2 levels had increased to the point where warmth again became the key factor controlling tree growth at high altitude.

Mann used comparisons with other tree ring data from the region to produce a corrected version of this dataset. Their reconstruction using this corrected dataset passed the validation tests for the extended period, but they were cautious about the increased uncertainties. The Mann, Bradley and Hughes reconstruction covering 1, years MBH99 was submitted in October to Geophysical Research Letters which published it in March with the cautious title Northern Hemisphere temperatures during the past millennium: inferences, uncertainties, and limitations to emphasise the increasing uncertainty involved in reconstructions of the period before when fewer proxies were available.

Though substantial uncertainties exist in the estimates, these are nonetheless startling revelations.

Hockey stick graphs present the global or hemispherical mean temperature record of the past to years as shown by quantitative climate. In the hockey stick controversy, the data and methods used in reconstructions of the temperature record of the past years have been disputed.

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A hockey stick chart shows a long flat period on a chart which precedes either a sharp decline or steep rise.

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Hockey Stick Chart

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Hockey Stick Growth for Entrepreneurs

In the hockey stick controversy , the data and methods used in reconstructions of the temperature record of the past years have been disputed. Reconstructions have consistently shown that the rise in the instrumental temperature record of the past years is not matched in earlier centuries, and the name " hockey stick graph " was coined for figures showing a long-term decline followed by an abrupt rise in temperatures. These graphs were publicised to explain the scientific findings of climatology , and in addition to scientific debate over the reconstructions, they have been the topic of political dispute. The issue is part of the global warming controversy and has been one focus of political responses to reports by the Intergovernmental Panel on Climate Change IPCC. Arguments over the reconstructions have been taken up by fossil fuel industry—funded lobbying groups attempting to cast doubt on climate science. The use of proxy indicators to get quantitative estimates of the temperature record of past centuries was developed from the s onwards, and found indications that recent warming was exceptional. In , Michael E. Mann , Raymond S. Bradley and Malcolm K.

The hockey stick is a growth chart that shows some inflection point at which revenue goes up at an extremely high angle and continues in that direction forever.

Search this site. Hockey Stick Curve Chart hockey stick The temperature record of the 2nd millennium describes the reconstruction of temperatures since CE on the Northern Hemisphere, later extended back to 1 CE and also to cover the southern hemisphere. A hockey stick is a piece of equipment used in field hockey, ice hockey or roller hockey to move the ball or puck.

Hockey stick controversy

A hockey stick chart is a line chart in which a sharp increase occurs suddenly after a short period of quiescence. The line connecting the data points resembles a hockey stick. Hockey stick charts have been used in the world of business and as a visual to show dramatic shifts, such as global temperatures and poverty statistics. A hockey stick is comprised of a blade, a small curve, and a long shaft. A hockey stick chart displays data low-level activity y-axis over a short period of time x-axis , then a sudden bend indicative of an inflection point , and finally a long and straight rise at a steep angle. The chart is typically observed in science labs, such as in the field of medicine or environmental studies. Scientists, for example, have plotted global warming data on a chart that follows a hockey stick pattern. Social scientists are also familiar with the chart. Some observations about the rate of increase in poverty have been delineated by this shape. The hockey stick chart can command immediate attention. A sudden and dramatic shift in the direction of data points from a flat period to what is visible in a hockey stick chart is a clear indicator that more focus should be given on causative factors. If the data shift occurs over a short time period, it is important to determine if the shift is an aberration or if it represents a fundamental change. Groupon Inc. It accomplished this in about two-and-a-half years, half the time of even Amazon and Google. This is the blade part of the hockey stick.

Many entrepreneurs see flat linear growth when starting a new business before they see any drastic changes. This flat or stagnant growth would be the blade part of the hockey stick and the rapid growth is the actual stick, or handle. This could be user rate , bounce rate , new customers , sales , or any metric that determines business growth. The idea is that when you start a business, you begin to see a normal rate of growth until a certain point is hit and growth begins to accelerate at a fast pace. For example, when looking at the user growth rate for our digital market agency during the past year, we see stagnant growth for ten months until there is a major growth spurt. This accelerated pace of growth can come from many different strategies including paid advertisements, search engine optimization, sales, brand awareness, and simply just word-of-mouth. For our digital marketing agency , this inflection point was due to implementing search engine optimization SEO in all our content for our website. Once we began to take the time to plug in SEO to our website and began crafting relevant content, we saw our active users increase drastically. Beginning in , the revenue growth of the company was stagnant for about 10 years before they started seeing any big changes.