hockey stick graph

hockey stick graph is a graphical representation of the Northern Hemisphere temperature record over the past 1,000 years, showing a relatively stable temperature trend until the 20th century, followed by a sharp increase in temperatures, resembling a hockey stick. This graph was first introduced by Michael E. Mann, Raymond Bradley, and Malcolm K. Hughes in a 1998 paper published in the Nature journal, and has since been widely used by IPCC and other organizations, including the NOAA and the NASA. The graph has been the subject of much debate and controversy, with some climate change skeptics, such as Fred Singer and Richard Lindzen, questioning its accuracy and validity, while others, like James Hansen and Gavin Schmidt, have defended its findings and implications for climate change mitigation and sustainable development.

Introduction

The hockey stick graph has become an iconic symbol of climate change and its impact on the environment, with many scientists, including Stephen Schneider and Kevin Trenberth, using it to illustrate the rapid warming of the Earth's surface over the past century. The graph is based on proxy data, such as tree ring records from North America and Europe, coral reef records from the Great Barrier Reef and the Caribbean Sea, and ice core records from Greenland and Antarctica, which provide a snapshot of past temperatures and climate variability. The graph has been widely used in climate change research and has been featured in numerous reports, including the IPCC Fourth Assessment Report and the National Climate Assessment, which was conducted by the EPA and the NSF.

History of the Graph

The hockey stick graph was first developed by Michael E. Mann and his colleagues in the late 1990s, using a combination of statistical analysis and climate modeling techniques, including the Mann-Kendall test and the PCA method. The graph was initially published in a 1998 paper in the Nature journal, and was later updated and expanded in a 1999 paper published in the Geophysical Research Letters journal, which is published by the AGU. The graph quickly gained attention and was featured in the IPCC Third Assessment Report, which was released in 2001 and was chaired by Rajendra Pachauri. The graph has since been widely used and cited in the scientific literature, including papers published in the Journal of Climate and the PNAS, which is published by the NAS.

Methodology and Controversy

The hockey stick graph has been the subject of much controversy and debate, with some climate change skeptics, such as Steve McIntyre and Ross McKitrick, questioning the methodology and accuracy of the graph, and others, like Ben Santer and Phil Jones, defending its findings and implications for climate change policy and renewable energy. The graph is based on a combination of proxy data and statistical analysis, including the use of regression analysis and time series analysis, which were developed by statisticians such as Ronald Fisher and George Box. The graph has been criticized for its use of PCA, which some argue is not suitable for climate data, and for its reliance on a limited number of proxy records, which may not be representative of the entire Northern Hemisphere. However, the graph has also been defended by many scientists, including Katherine Hayhoe and Andrew Dessler, who argue that it provides a robust and accurate representation of past temperatures and climate variability, and has been supported by numerous independent studies, including those conducted by the NCAR and the UEA.

Implications and Impact

The hockey stick graph has had a significant impact on our understanding of climate change and its implications for the environment and human societies, with many policymakers, including Al Gore and Barack Obama, using it to inform climate change policy and sustainable development initiatives. The graph suggests that the 20th century warming trend is unusual and unprecedented in the past 1,000 years, and that it is likely caused by human activities, such as the burning of fossil fuels and deforestation, which were discussed at the UNFCCC and the COP. The graph has been used to support the need for climate change mitigation and adaptation efforts, such as the Paris Agreement and the Green Climate Fund, which were established by the UN and the World Bank. The graph has also been used to inform climate change research and to identify areas for further study, such as the Arctic and the Amazon rainforest, which are being studied by scientists at the NSIDC and the ACA.

Criticisms and Debates

The hockey stick graph has been the subject of much criticism and debate, with some climate change skeptics, such as Christopher Monckton and Anthony Watts, arguing that it is flawed and misleading, and others, like Michael Oppenheimer and Jennifer Francis, defending its findings and implications for climate change policy and renewable energy. The graph has been criticized for its use of statistical analysis and climate modeling techniques, which some argue are not suitable for climate data, and for its reliance on a limited number of proxy records, which may not be representative of the entire Northern Hemisphere. However, the graph has also been defended by many scientists, including Gerald North and Eric Steig, who argue that it provides a robust and accurate representation of past temperatures and climate variability, and has been supported by numerous independent studies, including those conducted by the NCAR and the UW. The debate surrounding the graph has been intense and ongoing, with many scientists and policymakers weighing in on its implications and significance for climate change research and policy, including the AMS and the EGU.

Category:Climate change