Thursday, December 16, 2021

Extreme weather changes predicted by unprecedented model simulations

California fire. (Photo credit: Patrick Perkins via Unsplash)
There is growing public awareness that climate change will impact society not only through changes in mean temperatures and rainfall over the 21st century, but also in the occurrence of more pronounced extreme events, and more generally in natural variability in the Earth system. Such changes could also have large impacts on vulnerable ecosystems in both terrestrial and marine habitats.

A team of researchers including Malte Stuecker from the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST), explored projected future changes in climate and ecosystem variability and reported that the impact of climate change is apparent in nearly all aspects of climate variability. The study, led by the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea and published in Earth System Dynamics, emphasized that the impacts range from temperature and rainfall extremes over land to increased number of fires in California, to changes in bloom amplitude for phytoplankton in the North Atlantic Ocean.

Model simulations over 250 years

The team conducted a set of 100 global Earth system model simulations over 1850–2100, working with a “business-as-usual” scenario for relatively strong emissions of greenhouse gases over the 21st century. The runs were given different initial conditions, and, by virtue of the butterfly effect (a property of chaotic systems by which small changes in initial conditions can lead to large-scale and unpredictable variation in the future state of the system), they were able to represent a broad envelope of possible climate states over 1850-2100, enabling sophisticated analyses of changes in the variability of the Earth system over time.

Further, the relatively high resolution (~100 km) of the model, in conjunction with the 100 different realizations, represented an unprecedented set of technical challenges that needed to be met before advancing to the goal of assessing how climate variability is impacted by sustained anthropogenic changes to the climate system.

“We met these challenges by using the IBS/ICCP supercomputer Aleph, one of Korea’s fastest supercomputers,” said Sun-Seon Lee from the ICCP, a co-author of the study who ran the simulations together with her National Center for Atmospheric Research (NCAR) colleague Nan Rosenbloom. For the project, approximately 80 million hours of supercomputer time were used.

Widespread changes

Taken together, the computer simulations reveal that across our planet we can expect widespread changes in climate variability, ranging in timescales from storm events to decadal changes. Each of these changes has important impacts for sustainable resource management. For example, occurrences of extreme rainfall events over the 21st century indicate that extremes are expected to become more commonplace in many regions. These projected changes in rainfall extremes are in fact representative of changes in extremes in the future across a broad range of climate and ecosystem variables, which has important implications for future adaptation strategies.

“Without substantial mitigation of greenhouse gas emissions, together with sustained local adaptation efforts, these ubiquitous changes in climate volatility will extensively impact people and communities across the globe,” said Stuecker, an assistant professor of oceanography in SOEST.

In continuing NOAA funded projects, Stuecker, Brian Powell, Chris Sabine and other colleagues at UH Mānoa are currently utilizing these simulations for regional downscaling efforts to assess the impacts of future climate change and ocean acidification on regional fisheries and other coastal systems across the Hawaiian Archipelago.

This work resulted from a collaborative partnership between the ICCP and the Community Earth System Model project at the NCAR in the U.S. and also included researchers from the Korea Polar Research Institute, UH Mānoa, and the University of Colorado – Boulder. The NCAR is sponsored by the U.S. National Science Foundation and managed by the University Corporation for Atmospheric Research.

Source/Credit: University of Hawaiʻi


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