Source:  Bill Collins and Dan Hawkes


CASCADE is investigating whether and how current hurricanes are affected by global climate change and how these effects will be amplified by future climate change. At the top is a satellite image of Superstorm Sandy while at the bottom is a simulation of a typical Atlantic hurricane.

Changes in the risk of extreme weather events may pose some of the
greatest hazards to our society and environment, as the climate changes
due to anthropogenic (i.e., human-caused) warming. Extreme weather has
recently focused public attention on the dramatic consequences that
follow from such events. In 2011, unusually high precipitation, combined
with high snowpack, caused extensive flooding throughout the central
United States. In 2012, a heat wave across the same region produced the
country’s hottest year on record, and Superstorm Sandy caused severe
storm surges along the Eastern seaboard. The year 2013 brought intense
downpours and subsequent flooding across Colorado’s front range, causing
equally unprecedented damage.

Clearly, we need to get a handle on these extreme events–to predict
such events with greater reliability, to predict how such extreme
events might change in the future, and to determine whether the nature
of extreme events has already changed, and why.

Last month (October 2013) in response to this challenge, DOE
initiated the development of a comprehensive climate model that would
simulate extreme events, as part of the Calibrated and Systematic
Characterization, Attribution and Detection of Extremes (CASCADE)
Scientific Focus Area (SFA)—to advance scientific capabilities in
studying climate extremes and in conducting extreme climate analysis.
The CASCADE SFA, awarded by DOE’s Regional and Global Climate Modeling
Program, will be a three-year ($2.25 M per year) multi-organizational
project centered at LBNL, with ESD Climate Sciences Department Head Bill
serving as principal investigator. ESD climate scientists Travis O'Brien, Soyoung Jeon, and Karthik Kashinath will also be working on this project.

The program has a number of different aims. It will (1) advance
understanding of the connections among scales, intensities, causative
factors, and impacts of extremes; (2) develop new frameworks by which to
identify the fidelity of simulated extremes using multimodel
hindcasts, near-term forecasts, and perturbed-physics ensembles; and
(3) apply this information to determine uncertainties in simulated
future trends in extremes from the Community Earth System Model (CESM)
system.  Finally, the CASCADE team will advise developers on how best
to improve the fidelity of climate extremes simulated by DOE’s
state-of-the-science climate models.

One key aspect of the team's approach to meeting its aims will be to
develop and apply new methods for extreme event detection and
characterization. These methods will utilize advanced statistical
techniques and uncertainty quantification and analysis, realized as
software capable of processing extreme amounts of simulation and
observational data on the world's largest computational platforms. This
software will be architected and deployed in a way to leverage
community support and to be extendable and usable by the broader
climate community.

This work is anticipated to produce several significant new
capabilities for climate science. These capabilities include development
of high-throughput pipelines to determine various uncertainties in
model simulation, creation of flexible and extendable linkages among
widely used statistical and analytic tools for end-to-end workflows, and
extension of uncertainty quantification tools to treat a wide variety
of extreme phenomena.

The CASCADE SFA will draw upon the expertise of a diverse team of
climate scientists, computational scientists, and statisticians—from
LBNL’s Computational Research Division as well as from ESD–along with
scientists from U.C. Berkeley and U.C. Davis. The work will be
coordinated with other related projects already under way at LBNL,
including large-scale simulations of climate extremes in the recent past
and near-term future, and the wide-ranging, collaborative
investigation of multiscale processes in the climate system. The
resulting connections and related projects will ensure tight
integration of observations, experiments, and modeling of extreme
climate phenomena.

Collins and other members of the project's leadership have
contributed to a number of international climate assessment
reports—including the last two Intergovernmental Panel on Climate Change
reports–that have shaped the public dialogue about climate change.
Members of the CASCADE team have also developed new statistical methods
for understanding extreme weather phenomena, have published
high-performance software tools for climate data analysis, and have led
the development of the next generation of Earth system models.