Andrew T. Wittenberg

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Since the mid-nineteenth century the Earth's surface has warmed, and models indicate that human activities have caused part of the warming by altering the radiative balance of the atmosphere. Simple theories suggest that global warming will reduce the strength of the mean tropical atmospheric circulation. An important aspect of this tropical circulation is(More)
Multicentury integrations from two global coupled ocean–atmosphere–land–ice models [Climate Model versions 2.0 (CM2.0) and 2.1 (CM2.1), developed at the Geophysical Fluid Dynamics Laboratory] are described in terms of their tropical Pacific climate and El Niño–Southern Oscillation (ENSO). The inte-grations are run without flux adjustments and provide(More)
Spatial variations in sea surface temperature (SST) and rainfall changes over the tropics are investigated based on ensemble simulations for the first half of the twenty-first century under the greenhouse gas (GHG) emission scenario A1B with coupled ocean–atmosphere general circulation models of the Geophysical Fluid Dynamics Laboratory (GFDL) and National(More)
The current generation of coupled climate models run at the Geophysical Fluid Dynamics Laboratory (GFDL) as part of the Climate Change Science Program contains ocean components that differ in almost every respect from those contained in previous generations of GFDL climate models. This paper summarizes the new physical features of the models and examines(More)
13 14 15 2 16 17 Abstract. 18 19 Regional surface temperature trends from the CMIP3 and CMIP5 20 th century runs are compared 20 with observations-at spatial scales ranging from global averages to individual grid points-21 using simulated intrinsic climate variability from pre-industrial control runs to assess whether 22 observed trends are detectable(More)
Recent studies report that two types of El Niñ o events have been observed. One is the cold tongue (CT) El Niñ o, which is characterized by relatively large sea surface temperature (SST) anomalies in the eastern Pacific, and the other is the warm pool (WP) El Niñ o, in which SST anomalies are confined to the central Pacific. Here, both types of El Niñ o(More)
Reduced levels of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are associated with deteriorated cognitive performance in senescence. Little work has been done on the effect of GH and IGF-1 on a crucial aspect of cognition, selective attention. This study investigated the effect of GH/IGF-1 on performance and brain potentials (EEG) during a(More)
El Niño and La Niña comprise the dominant mode of tropical climate variability: the El Niño and Southern Oscillation (ENSO) phenomenon. ENSO variations influence climate, ecosystems, and societies around the globe. It is, therefore, of great interest to understand the character of past and future ENSO variations. In this brief review, we explore our current(More)
Surface wind stresses are fundamental to understanding El Niño, yet most observational stress products are too short to permit multidecadal ENSO studies. Two exceptions are the Florida State University subjective analysis (FSU1) and the NCEP–NCAR reanalysis (NCEP1), which are widely used in climate research. Here, the focus is on the aspects of the stress(More)