In This Article Extreme Weather and Climate

  • Introduction
  • General Overviews
  • Societal Relevance of Extreme Weather Events
  • Attributing Extreme Events to External Drivers
  • Predicting Extreme Events on Seasonal and Decadal Timescales
  • Importance and Implications of Understanding, Attributing, and Predicting Extreme Weather

Environmental Science Extreme Weather and Climate
by
Friederike Otto
  • LAST MODIFIED: 24 May 2017
  • DOI: 10.1093/obo/9780199363445-0067

Introduction

Natural disasters and extreme weather events have been of great societal importance throughout history and often brought everyday life to a catastrophic halt, in a way sometimes comparable to wars and epidemics, only without the lead time. Extreme weather events with large impacts serve as an anchor point of the collective memory of the population in the affected area. Every northern German of the right age remembers the storm surge of 1962 and where they were at the time and has friends or family effected by the event. The “dust bowl” of the 1930s with extensive droughts and heat waves shaped the life of a generation in the United States, and the Sahel droughts in the 1960s and 1970s led to famine and dislocation of population on a massive scale the region arguably never quite recovered from. Hurricane Hyian in 2013 is said to have directly influenced the outcome of the annual Conference of the Parties (COP) United Nation Framework Convention for Climate Change Negotiations in Warsaw, leading to the inclusion of a mechanism to deal with loss and damage from climate-related disasters. Though earthquakes are still fairly unpredictable on short timescales, this is not the case for weather events. Weather forecasts today are so good that we normally know the time and location of the landfall of a hurricane within a 100-mile radius days in advance. Improvements in the prediction of slow-onset events such as droughts (which depend on the rainfall over a large region and whole season) are less striking but have still improved dramatically in the late 20th and early 21st centuries. One of the major reasons for the large increase in the accuracy of weather forecasts is the exponential increase in computing power, which allows scientists to predict and study extreme weather events using complex computer models, simulating possible weather events under certain conditions to understand the statistics of and physical mechanisms behind extreme events. Extreme events are by definition rare and thus impossible to understand from historical records of weather observation alone. Despite the progress on our understanding of and ability to predict extreme weather events, substantial uncertainties remain. Two aspects are of particular importance. Firstly, we know that the climate is changing, having observed almost a one-degree increase in global mean temperature. However, global mean temperature doesn’t kill anyone, extreme weather events do. Their frequency and intensity is changing and will continue to change, but the extent of these changes depends on a host of both global and local factors. Secondly, whether or not a rare weather event leads to extreme impacts depends largely on the vulnerability and exposure of the affected societies. If these are high, even a perfectly forecasted weather event leads to disaster.

General Overviews

The global scientific community brought together under the Intergovernmental Panel on Climate Change (IPCC) has published five assessment reports since its formation in the early 1990s and with our increased understanding of extreme events their trends in frequency and magnitude are included in different chapters in the fifth assessment report (AR5), in both, Stocker, et al. 2014 and its assessment of the physical science basis and Field, et al. 2014 on the impacts of climate change. The two working group assessments particularly report on the most certain findings on observed trends in extreme weather events and their impacts with Field, et al. 2014, providing a succinct overview of key terms such as hazard, vulnerability, and exposure. It is important to put 21st-century understanding of extreme weather events into the context of the general state of knowledge about the climate system and its impacts on society while providing essential background information on methodologies of climate research. Yet the assessment reports do not provide a general overview of the 21st-century state of knowledge on extreme weather events. Given that at least in the short term the largest impacts and highest damages of human-induced climate change will be through extreme weather events, the IPCC saw this shortcoming and published Field, et al. 2012. The SREX report gives an overview of observations and predictions of extreme weather events and their impacts and highlights particularly the social dimension of extreme events. The latter are notably relevant when defining extreme events and trying to identify comprehensive indices (Zhang, et al. 2011). While SREX provides the best overview of the state of the science of extreme events, this subfield of climate science has seen an enormous increase in research activity and has also been recognized by the World Climate Research Programme (WCRP) as a field of science requiring a considered scientific effort and with major breakthroughs expected in the next few years; thus the WCRP asked a team of leading scientists in the field under the Grand Challenge on Extreme Events to coordinate the worldwide research activity to accelerate and enable breakthroughs (WCRP Grand Challenge). (The website does not provide an overview of the impacts of extreme events as the science of understanding these events is only beginning to develop.) A particular development with respect to putting extreme weather events in a climate context is the emerging of the science of extreme event attribution reviewed by the American National Academy of Science (NAS) and dedicated to answering the question whether and to what extent anthropogenic climate change has played a role in recent events. In the following section a brief overview of publications on these impacts is given; however, the rest of the article is focused on extreme weather events from a climatological point of view.

  • Field, C. B., V. R. Barros, D. J. Dokken, et al., eds. 2014. Climate change 2014: Impacts, adaptation, and vulnerability. Part A: Global and sectoral aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge Univ. Press.

    E-mail Citation »

    IPCC WG2 report on the impacts of climate change provides an overview of impacts, including from extreme weather.

  • Field, C. B., V. Barros, T. F. Stocker, et al., eds. 2012. Managing the risks of extreme events and disasters to advance climate change adaptation. A special report of working groups I and II of the Intergovernmental Panel on Climate Change. Cambridge, UK, and New York: Cambridge Univ. Press.

    E-mail Citation »

    Offers a good overview of research on extreme weather events and their impacts.

  • NAS National Academies of Sciences, Engineering, and Medicine. 2016. Attribution of extreme weather events in the context of climate change. Washington, DC: National Academies Press.

    E-mail Citation »

    An overview of the science of extreme event attribution that explains the science and highlights the current state of knowledge depending on the type of extreme event (e.g., heat, drought, flood).

  • Stocker, T. F., D. Qin, G.-K. Plattner, et al., eds. 2014. Climate change 2013: The physical science basis. Contribution of working group I to the fifth assessment report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge Univ. Press.

    E-mail Citation »

    IPCC WG1 report on the physical science basis provides an overview in particular on the methodologies used in climate science and extreme event research as well as the latest findings.

  • WCRP Grand Challenge.

    E-mail Citation »

    Website from the WCRP grand challenge on extreme events that provides a brief overview of some key aspects of extreme events and a list of relevant papers and reports on the topic.

  • Zhang, X., L. Alexander, G. C. Hegerl, et al. 2011. Indices for monitoring changes in extremes based on daily temperature and precipitation data. WIREs Climate Change 2:851–870.

    DOI: 10.1002/wcc.147E-mail Citation »

    A review on indices used to define extreme events.

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