Climate variability

New computer model simulations identify widespread changes in climate variability under sustained anthropogenic forcing – ScienceDaily

The public is increasingly aware that climate change will impact society not only through changes in average temperatures and precipitation over the 21st century, but also in the occurrence of more pronounced extreme events, and more generally in the natural variability of the Earth system. Such changes could also have significant impacts on vulnerable ecosystems in terrestrial and marine habitats. A scientific exploration of predicted future changes in climate and ecosystem variability is outlined in a new study published in the journal Earth System Dynamics, representing the result of a broad collaborative partnership between the IBS Center for Climate Physics (ICCP ) at Pusan ​​National University in South Korea and the Community Earth System Model (CESM) project at the National Center for Atmospheric Research (NCAR) in the United States.

The team conducted a set of 100 model simulations of the global Earth system over the period 1850-2100, working with a “business-as-usual” scenario for relatively high greenhouse gas emissions during the 21st century. The simulations were given different initial conditions and, thanks to the butterfly effect, they were able to represent a large envelope of possible climatic states over 1850-2100, allowing sophisticated analyzes of changes in the variability of the Earth system over time. . The nominal one-degree (~ 100 km) resolution of the model, in conjunction with the 100-member set, represented an unprecedented set of technical challenges that needed to be addressed before moving on to the goal of assessing how variability climate is impacted by sustained anthropogenic changes in the climate system. “We addressed these challenges by using the IBS / ICCP Aleph supercomputer, one of Korea’s fastest supercomputers,” says Dr Sun-Seon Lee of ICCP, co-author of the study that carried out the simulations with his NCAR colleague Dr Nan. Rose flower. For the project, approximately 80 million hours of supercomputer time were used and approximately 5 petabytes of disk space (approximately 5,000 normal hard drives) were required to store the model output.

The main finding of the study is that the impact of climate change is apparent in almost all aspects of climate variability, from extreme temperatures and precipitation over land to increasing fires in California. , changes in the amplitude of phytoplankton flowering in the North Atlantic. Ocean. Each of these changes has significant impacts on the sustainable management of resources. For example, the occurrences of extreme precipitation events during the 21st century (between 2000-2009 and 2090-2099) indicate that extremes are expected to become more frequent in many regions. These projected changes in extreme precipitation are in fact representative of the pervasiveness of changes in extremes in the future across a wide range of climatic and ecosystem variables, which has important implications for future adaptation strategies.

“In addition to large-scale changes in extreme events, our study also identified large-scale changes in the structure of the seasonal cycle during the 21st century, showing increased growing season length over mainland areas north of 50 ° N, ”says Dr Keith Rodgers of ICCP, lead author of the study and co-lead of the CESM2 Large Ensemble Project. Largely due to the average warming condition and the ensuing changes in the timing of retreating and advancing winter snow cover, by the end of the 21st century, the length of the growing season is expected to increase by three weeks.

Taken together, computer simulations reveal that across our planet we can expect widespread changes in climate variability, ranging from synoptic storms to seasons to El Niño and decades. Dr Gokhan Danabasoglu, co-author of the study and co-leader of the project, says that “an important step for the future will be to identify in more detail the potential societal impacts and to communicate the implications for the strategies of development. ‘adaptation”. This larger study has already motivated a number of more specialized scientific investigations using the huge volume of output from the simulations, covering topics ranging from impacts on marine ecosystems to hydrological changes that affect water supply.

The National Center for Atmospheric Research is sponsored by the US National Science Foundation and managed by the University Corporation for Atmospheric Research.

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