Researchers have quantified the contributions of industrialized and developing nations' historical emissions to global surface temperature rise. Recent findings that nearly twothirds of total industrial CO 2 and CH 4 emissions can be traced to 90 major industrial carbon producers have drawn attention to their potential climate responsibilities. Here, we use a simple climate model to quantify the contribution of historical (1880-2010) and recent emissions traced to these producers to the historical rise in global atmospheric CO 2 , surface temperature, and sea level. Emissions traced to these 90 carbon producers contributed ∼57% of the observed rise in atmospheric CO 2 , ∼42-50% of the rise in global mean surface temperature (GMST), and ∼26-32% of global sea level (GSL) rise over the historical period and ∼43% (atmospheric CO 2 ), ∼29-35% (GMST), and ∼11-14% (GSL) since 1980 (based on bestestimate parameters and accounting for uncertainty arising from the lack of data on aerosol forcings traced to producers). Emissions traced to seven investor-owned and seven majority state-owned carbon producers were consistently among the top 20 largest individual company contributors to each global impact across both time periods. This study lays the groundwork for

Volunteers contributing idle computing time are helping to create an unprecedented combination of high-spatial and high-statistical resolution in simulations of climate in the C limate system modeling has made tremendous advancements in recent decades. Rapidly expanding computational capabilities and scientific research on fundamental processes have allowed simultaneous progress on a variety of fronts, such as expansion of the processes represented in climate models including interactive carbon cycles represented by biogeochemical models (e.g., Flato 2011), increases in spatial resolution (global models now providing century-long runs at grid spacing as low as ~50 km), and the number of simulations possible with a given model.One area of research currently at the crossroads of basic research and applications is the description of present and future climate at spatial scales that are meaningful both scientifically and for management applications (e.g., Means et al. 2010). Regional climate models (RCMs; e.g., Giorgi 1990) have been implemented over specific areas of interest with resolutions as high as 500 m (Wang et al. 2013) compared to 50-300 km for a GCM. Typically, such studies run the RCM one or at most a handful of times. The problem with having a very small number of simulations is that differences between past and future simulations can stem from several sources, not just the change in greenhouse gases: uncertainty is not well quantified. As O'Brien et al. (2011) note, some studies tacitly assume "that differences between model simulations are entirely due to a physical forcing" and show that internal variability can be larger than the signal in some instances; they

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The West African monsoon (WAM) is a vital source of rainfall for the African Sahel. In addition to the agricultural benefit of its rains, it benefits public health because bacterial meningitis outbreaks end with the monsoon onset. Outbreaks occur between December and May, a period of low humidity. Knowledge of the onset of high humidity could aid in predicting where the outbreaks will cease. Therefore, this study investigates the variability of atmospheric moisture during the spring over West Africa, characterizing the sources of moisture, as well as circulation patterns and relative influences of tropical and midlatitude systems. A conceptual model of the evolution of the premonsoon period is presented. The meridional and temporal variability of surface moisture during the spring is modulated by multiscale interactions, as illustrated for the period from mid-April to early May 2009. As westward-propagating, synoptic disturbances move across West Africa, a corresponding peak occurs in the surface relative humidity. With the passage of each disturbance a new and more humid regime is established. Filtered anomalies of outgoing longwave radiation (OLR) indicate that Kelvin waves, equatorial Rossby waves, and possibly the MJO contributed to the initiation and intensification of the synoptic disturbances. During the last of the disturbances, whose passage raised the relative humidity above 40%, a critical threshold for meningitis, an extratropical cyclone also contributed to moisture influx over the Sahel. Analysis of the period 2000–09 shows the relative influences of synoptic and subseasonal circulations on the onset of high relative humidity over the Sahel during the spring.