Extreme events attributable to climate change: past and future
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Extreme weather events such as life-threatening heat waves and record-breaking downpours are part of the natural climate system, but some kinds of extreme weather events have become more common in recent decades. Scientific advances are allowing researchers to determine the extent to which climate change contributed to some extreme weather events. This is the science of extreme event attribution.
What recent extreme weather events can be attributed to climate change?
The Bulletin of the American Meteorological Society (BAMS) publishes an annual collection of attribution studies it has judged to be rigorous. Ten reports exist so far, describing extreme events that can be attributed at various levels to climate change, including some that, based on analyses of historical data and natural variation, would not have occurred if not for the added influence of climate change.
Would not have happened without climate change:
- a spring drought in South China (2018)
- high surface temperatures during a Tasman Sea heatwave (2017)
- the overall global atmospheric heat record (2016)
- a persistent area of unusually warm water that lingered off the Alaskan coast, causing reduced marine productivity and other ecological disruptions (2016)
Made more severe or likelier to happen because of climate change:
Studies gathered in the BAMS reports have found that climate change contributed to the occurrence or intensity of many recent extreme events, including:
- extreme rainfall in Hurricane Dorian (2019)
- a November cold outbreak in the eastern United States (2019)
- the total rainfall during mid-Atlantic warm-season flooding (2018)
- a heat wave in the Four Corners region of the United States (2018)
- a summer drought in the U.S northern Great Plains (2017)
- warm temperatures in the central equatorial Pacific during El Niño, which disrupted coral reefs and seabird populations (2016)
- tropical cyclones in the western North Pacific Ocean (2015)
- high-tide floods in southeastern United States (2015)
- record-breaking fires in California (2014)
- drought and a deadly heat wave affecting Texas and other U.S. states (2011)
How climate change is projected to affect extreme weather in the future
Scientists’ confidence about how weather and climate extremes will change is growing. Projections from the Intergovernmental Panel on Climate Change’s 2021 report suggest that as human-caused global warming increases:
- In North America, heat extremes (including warm days, warm nights, and heat waves) will become more common and more intense. Cold extremes (including cold days and cold nights) will become less common and less intense.
- Heavy precipitation like rainfall and snowstorms will happen more often and more intensely, and this will cause more flooding. In North America specifically, these increases are “likely” if global warming increases up to 3.6 degrees Fahrenheit (or 2.0 degrees Celsius) over pre-industrial levels, and “very likely” if warming exceeds that level.
- Over the 21st century, only some parts of the world are projected to see more flooding. Many of these regional projections are not very certain, but globally there is a larger fraction of regions with a predicted increase than a decrease over the 21st century.
- Greater land area will be affected by droughts, which will happen more commonly and more intensely. In much of the United States, such as the central Great Plains, summer conditions will be drier.
- Tropical cyclones (a category that includes hurricanes) will likely become less common or stay the same globally, but a greater fraction of those storms will be more intense. These especially strong cyclones will become more common in particular in some parts of the western North Pacific Ocean.
- Severe springtime thunderstorms will become more frequent in the United States and occur over a longer season.
- Compound events, such as when heavy rain causes flooding or drought contributes to wildfires, will become more frequent. Unprecedented extremes will be more likely.
- Attribution of Extreme Weather Events in the Context of Climate Change (2016) is a comprehensive look at the topic from the National Academies of Sciences, Engineering, and Medicine.
- Explaining Extreme Events of 2020 from A Climate Perspective (2021) is the most recent in a series of annual reports produced as a special supplement to the Bulletin of the American Meteorological Society, and includes links to the previous nine reports.
- Climate Science Special Report (2017) is an authoritative assessment of the science of climate change, with a focus on the United States. Produced by scientists representing federal agencies, national laboratories, universities, and the private sector, with administrative oversight by the U.S. Commerce Department’s National Oceanic and Atmospheric Administration, it represents the first of two volumes of the Fourth National Climate Assessment, mandated by the Global Change Research Act of 1990. It includes a chapter on Detection and Attribution of Climate Change. The fifth national climate assessment is scheduled for release in 2023.
- The U.S. National Climate Assessment’s fourth and latest report on climate impacts (2018) includes a discussion of natural variation and attribution research in Chapter 2.
- AR6 Climate Change 2021: The Physical Science Basis is a report produced by the Intergovernmental Panel on Climate Change. It includes a chapter on how human influence is affecting the climate (Chapter 3) and a chapter on weather and extreme climate events that outlines trends and projections (Chapter 11). Climate Change 2022: Impacts, Adaptation and Vulnerability, another IPCC report, evaluates the effects of climate change on ecosystems, biodiversity, and human communities.
- The science of attributing extreme weather events and its potential contribution to assessing loss and damage associated with climate change impacts, produced by researchers at the Environmental Change Institute at the University of Oxford’s School of Geography and the Environment, is a brief summary of attribution science and its value, including some details about how attribution modeling works.
- Extreme event attribution: the climate versus weather blame game, updated in 2021, is a useful fact sheet produced by Climate.gov, the climate-change information site of the U.S. Commerce Department’s National Oceanic and Atmospheric Administration (NOAA).
- The National Center for Atmospheric Research (NCAR) is a federally funded research and development center sponsored by the National Science Foundation. Its website offers numerous evidence-based resources on atmospheric and related sciences, including climate modeling.
- The World Weather Attribution Initiative is a collaboration with scientific partners from the University of Oxford Environmental Change Institute (ECI), the Royal Netherlands Meteorological Institute (KNMI), the Laboratoire des Sciences du Climate et de l’Environment, NOAA, Princeton University, NCAR, and the Red Cross and Red Crescent Climate Centre. The Initiative is developing tools and methodologies to perform real-time assessments of whether and to what extent human-induced climate change played a role in the magnitude and frequency of extreme weather events.
- climateprediction.net is a nonprofit, collaborative effort led by climate scientists, computing experts, and others, that performs climate modelling experiments using the home computers of thousands of volunteers to answer questions about how climate change is affecting the world now and may affect the world in the future.
- Extreme weather is of deep concern to the insurance industry, which has produced a number of documents describing those concerns and strategies for lowering risk. Among them: the National Association of Insurance Commissioners’ Assessment of and Insights from NAIC Climate Risk Disclosure Data, and Climate Change Risk Assessment for the Insurance Industry, by the Geneva Association, an insurance industry think tank.
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