The public is increasingly aware that climate change will impact society not only through changes in average temperatures and rainfall during 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 projected future changes in climate and ecosystem variability is described in a new study published in the journal Earth System Dynamics, which represents 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 global Earth system model simulations over the period 1850-2100, working with a “business as usual” scenario for relatively high greenhouse gas emissions during the 21st century. The runs were given different initial conditions and, thanks to the butterfly effect, they were able to represent a wide envelope of possible climate states over the period 1850-2100, allowing sophisticated analyzes of changes in Earth system variability over time. time. The nominal one-degree (~100 km) resolution of the model, in conjunction with the 100-member test set, represented an unprecedented set of technical challenges that needed to be addressed before moving on to the goal of evaluating how climate variability is affected by long-lasting anthropogenic changes in the climate system. “We overcame these challenges using the IBS/ICCP Aleph supercomputer, one of Korea’s fastest supercomputers,” says ICCP’s Dr Sun-Seon Lee, co-author of the study who performed the simulations with his NCAR colleague, Dr Nan. Rose flower. For the project, approximately 80 million supercomputer hours were used and approximately 5 petabytes of disk space (approximately 5,000 normal hard drives) were required for storage of model output.
The main conclusion of the study is that the impact of climate change is apparent in almost every aspect of climate variability, ranging from extremes of temperature and precipitation on land to the increase in the number of fires in California, to changes in the magnitude of phytoplankton blooms 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, see attachment Fig. 1) indicate that extremes are expected to become more common in many regions. These projected changes in precipitation extremes are in fact representative of the ubiquity of changes in extremes in the future across a wide range of climate 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 seasonal cycle structure during the 21st century, showing increased growing season length in continental regions north of 50°N,” says ICCP’s Dr Keith Rodgers, first author of the study and co-lead of the CESM2 Large Ensemble Project. Largely due to mean state warming and resulting changes in the timing of retreat and advancement of winter snow cover, by the end of the 21st The length of the century growing season is expected to increase by three weeks.
Taken together, the computer simulations reveal that on our planet, we can expect widespread changes in climate variability, ranging from synoptic storms to seasons to El Niño to decades. Dr Gokhan Danabasoglu, co-author of the study and co-lead of the project, said that “an important step moving forward will be to more fully identify potential societal impacts and communicate the implications for coping strategies”. This wider study has already motivated a number of more specialized scientific investigations using the huge volume of results from the simulations, covering topics ranging from impacts on the marine ecosystem to hydrological changes that affect water supply.