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Although differences exist between seasonal- and decadal-scale climate variability, predictability, and prediction, investment in observations, prediction systems, and decision systems for either time scale can benefit both. Fil: Goddard, Lisa. Columbia University; Estados Unidos Fil: Hurrell, James W.. National Center for Atmospheric Research; Estados Unidos Fil: Kirtman, Benjamin P.. University of Miami; Estados Unidos Fil: Murphy, James. Hadley Centre for Climate Prediction and Research; Reino Unido Fil: Stockdale, Timothy. European Centre for Medium-Range Weather Forecasts; Reino Unido Fil: Vera, Carolina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina

There is a new perspective of a continuum of prediction problems, with a blurring of the distinction between short-term predictions and long-term climate projections. At the heart of this new persp...

he potential relationships between tropical cyclones and global climate change are scientifically and socially complex, with great implications for society. The exceptional nature of the 2005 North Atlantic hurricane season alone provides great incentives for better understanding the full range of interactions and causes and effects thereof. The 2005 season saw the largest number (27) of named storms (sustained winds over 17 m s–1) and the largest number (14) of hurricanes (sustained winds over 33 m s–1), and it was the only year with three category 5 storms (maximum sustained winds over 67 m s–1). Also recorded was the most intense storm on record (Wilma, minimum pressure 882 hPa), the most intense storm ever in the Gulf of Mexico (Rita, 897 hPa), and the most costly storm on record (Katrina; some estimates put the cost of Katrina at as high as $200 billion; see information online at www.rms.com/Publications/ KatrinaReport_LessonsandImplications.pdf). (Please see www.ncdc.noaa.gov/oa/climate/research/2005/ hurricanes05.html for additional details.) The climate is in the process of a rapid warming, caused in part by human activities, including emission of greenhouse gases (GHGs) and aerosols, and changes in land use (Houghton et al. 2001; Karl and Trenberth 2003). These climate changes may well be changing the properties of tropical cyclones, yet the potential relationships between climate change and tropical cyclones and the consequences for humans have been downplayed or dismissed by a number of recent articles, testimonies, and press releases (e.g., Michaels et al. 2005;1 Pielke et al. 2005; Mayfield 2005). For example, the recent article with the allencompassing title “Hurricanes and global warming” by Pielke et al. (2005) raises several important points, yet it is incomplete and misleading because it 1) omits any mention of several of the most important aspects of the potential relationships between hurricanes and global warming, including rainfall, sea level, and storm surge; 2) leaves the impression that there is no significant connection between recent climate change caused by human activities and hurricane characteristics and impacts; and 3) does not take full account of the significance of recently identified trends and variations in tropical storms in causing impacts as compared to increasing societal vulnerability. In a similar vein, public statements and testimonies by prominent hurricane forecasters have denied or minimized important connections between global warming and tropical cyclones, attributing interannual variations in tropical cyclones only to natural variability (e.g., Mayfield 2005). It is true that society’s vulnerability to hurricane damage is increasing rapidly, predominantly because of the rise in population and property values near

A comprehensive comparison is made between two tropospheric temperature datasets over the period 1979–98: the most recent and substantially revised (version d) microwave sounding unit (MSU) channel 2 data retrievals, and a gridded radiosonde analysis provided by the Hadley Centre of the U.K. Meteorological Office. The latter is vertically weighted to approximate the deep layer temperatures measured by the satellite data. At individual grid points, there is good overall agreement among monthly anomalies, especially over the Northern Hemisphere continents where the climate signal is large, although monthly root-mean-square (rms) differences typically exceed 0.6°C. Over the Tropics, correlations are lower and rms differences can be as large as the standard deviations of monthly anomalies. Differences in the gridpoint variances are significant at many locations, which presumably reflects sources of noise in one or both measurement systems. It is often argued for climate purposes that temperature anomalies are...

A comprehensive comparison is made among four sea surface temperature (SST) datasets: the optimum interpolation (OI) and the empirical orthogonal function reconstructed SST analyses from the National Centers for Environmental Prediction (NCEP), the Global Sea-Ice and SST dataset (GISST, version 2.3b) from the United Kingdom Meteorological Office, and the optimal smoothing SST analysis from the Lamont-Doherty Earth Observatory (LDEO). Significant differences exist between the GISST and NCEP 1961–90 SST climatologies, especially in the marginal sea-ice zones and in regions of important small-scale features, such as the Gulf Stream, which are better resolved by the NCEP product. Significant differences also exist in the SST anomalies that relate strongly to the number of in situ observations available. In recent years, correlations between monthly anomalies are less than 0.75 south of about 10°N and are lower still over the southern oceans and parts of the tropical Pacific where root-mean-square differences ...

The Community Earth System Model (CESM) is a flexible and extensible community tool used to investigate a diverse set of Earth system interactions across multiple time and space scales. This global coupled model significantly extends its predecessor, the Community Climate System Model, by incorporating new Earth system simulation capabilities. These comprise the ability to simulate biogeochemical cycles, including those of carbon and nitrogen, a variety of atmospheric chemistry options, the Greenland Ice Sheet, and an atmosphere that extends to the lower thermosphere. These and other new model capabilities are enabling investigations into a wide range of pressing scientific questions, providing new foresight into possible future climates and increasing our collective knowledge about the behavior and interactions of the Earth system. Simulations with numerous configurations of the CESM have been provided to phase 5 of the Coupled Model Intercomparison Project (CMIP5) and are being analyzed by the broad com...