The 20th Century Reanalysis Project (20CR), a joint project between the National Oceanic and Atmospheric Administration and the University of Colorado, has brought together 27 international climatologists to create a comprehensive reanalysis of all global weather events from 1871 to present day, effectively creating an accessible time machine for climate scientists.
The project allows researchers to understand the long-term impact of extreme weather, as well as providing key historical comparisons for our own changing climate.
“Producing this huge dataset required an international effort to collate historical observations and recordings from sources as diverse as 19th century sea captains, turn of the century explorers and medical doctors, all pieced together using some of the world’s most powerful supercomputers at the US Department Energy’s National Energy Research Scientific Computing Center in California and the Oak Ridge Leadership Computing Facility in Tennessee,” said lead author Dr Gil Compo.
“The resulting weather maps, called reanalyses, provide a much longer record of past weather variability than is currently available to compare present and projected weather variability in a warming climate. They also provide a valuable insight into extreme weather and climate events that were historically important, such as the 1930’s Dust Bowl.”
The 20CR team follows in the footsteps of the US Historical Weather Map Series creators, who under the direction of the US Weather Bureau wanted to find a better understanding of weather events which preceded the Second World War.
“A preliminary version of this project (20CRv1, Compo et al., 2008) spanned the period 1908 to 1958,” said Compo. “In this second and complete version (20CRv2), the global atmospheric fields for 1871 to 2008 have been generated. We hope, as Wexler and Tepper of the US Weather Bureau said in 1947, that this project can ‘breathe life into a mass of inert data’ while providing an indispensable aid to future research.”
The 20CR dataset for the first time provides climate scientists with long-term estimates of global variability in the troposphere – the lowest point in Earth’s atmosphere – weather maps from the Earth’s surface to the level of the jet-stream – located near the atmospheric boundary between the troposphere and the stratosphere – and of their time-varying quality, from 1871 to the present at 6-hourly intervals.
“The new dataset will allow climate scientists to put current weather extremes in a historical perspective and determine how extremes are changing,” said Compo. “Just how extreme is the recent European cold wave, for example, or the blizzard in the US Northeast?”
The scientists also hope that the dataset will allow scientists and governments to look back at events that may have misinformed early-century policy decisions, such as the wet period in central North America that led to overestimates of rainfall and over-allocation of water resources in the Colorado River basin n the years before the US Dust Bowl of the 30s.
“This reanalysis data will enable climate scientists to rigorously evaluate past climate variations compared to climate model simulations, which is critical for building confidence in model projections of regional changes and high-impact, extreme events,” concluded Compo. “We hope that this 138 year reanalysis data will enable climate researchers to better address issues such as the range of natural variability of extreme events, including floods, droughts, extratropical cyclones, and cold waves.”
Understanding climate isn’t always easy (but then again, neither is understanding time). This project seems to have done a lot to improve our understanding… of the climate, that is.
Image Source: Arthur Rothstein for the Farm Security Administration (public domain)