Climate Diagnostics Center Accomplishments FY 2010
Publications
In 2009-2010, CDC published 26 peer-reviewed papers on topics that included:
- Techniques for removing El Niño-Southern Oscillation (ENSO) related variations from the historical climate record to better isolate climate change signals
- A demonstration using the newly developed CDC/ NOAA 20th Century Reanalysis (20CR) dataset that the 1918/19 El Niño event, which coincided with the “Great Influenza Epidemic,” may have been much stronger than previously thought
- Global air-sea thermal coupling and related non-Gaussian sea-surface temperature (SST) variability
- The importance of air-sea coupling in the evolution of ENSO and the tropical Madden-Julian Oscillation (MJO)
- Interannual ENSO variability forced through coupled atmosphere-ocean feedback loops
- The changing hydrology of the Colorado River Basin and the American Southwest
- Representation of regional trends in the climate models used in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4)
- Summer precipitation variability over South America as simulated by the IPCC AR4 models
- The simulation of cloud, precipitation, and radiation in climate models
- Reconciling non-Gaussian climate statistics with linear predictable dynamics
- Oceanic influences on recent continental warming
Data and Forecast Products
Additionally, CDC continued the development of several observational and atmospheric circulation datasets and forecast products, and provided scientific input to international programs, including:
- Providing leadership in the international Global Climate Observing System Surface-Pressure Working Group, to promote the development of long-term, high-quality surface-pressure datasets
- Completing production of a global atmospheric circulation dataset for 1891-2008, using only daily surface pressure observations and an ensemble-Kalman-filter-based data assimilation system, and making the dataset widely available through a web interface. Read more...
- Starting production of version two of the global atmospheric circulation dataset, extending it back to 1871 using a longer and improved surface-pressure database and an CIRES Annual Report 2010 67 improved model for assimilating those data. The improved model included better specifications of time-varying CO2 and aerosol radiative forcings over the assimilation period. This effort will extend our ability to quantify climate variability over the historical record, provide uncertainty estimates for climate change detection, and aid attribution efforts to inform climate policy decisions.
- Developing and releasing a new experimental forecast product (jointly with NOAA ESRL’s Physical Sciences Division) for subseasonal tropical forecasts based on a coupled linear inverse model of weekly tropical SSTs and outgoing longwave radiation variations. Read more...
Discoveries
CDC researchers recently reached some surprising
conclusions concerning the contributions of ENSO-related
variations to observed 20th century climate trends. In
a study published recently in the Journal of Climate, we
stressed that isolating such contributions is challenging
for several reasons, including ambiguities arising from
how ENSO itself is defined. In particular, we argued that
defining ENSO in terms of any single index and ENSO-related
variations in terms of regressions on that index, as
done in most previous studies, can lead to wrong conclusions.
We believe ENSO is best viewed not as a number but as an evolving dynamical process for this purpose. Specifically, we identified ENSO with the four dynamical eigenvectors of tropical SST evolution that are most important in the observed evolution of ENSO events over several months, and used this definition to isolate the ENSO-related component of global SST variations on a month-by-month basis in a 136-yr (1871-2006) global SST dataset.
The analysis showed that ENSO-related trends have contributed substantially to the 136-yr SST trends in all ocean basins, and accounted for nearly 40 percent of the trend in globally averaged SSTs. The ENSO-unrelated component of the SST trends, obtained by removing the ENSO-related component, shows a particularly striking strong cooling trend in the eastern equatorial Pacific region of largest ENSO-related SST variability.
These results have large implications for our understanding of how the global climate system in general, and the tropical climate system in particular, may be responding to anthropogenic and other climate forcing.
