Daily Archives: July 21, 2014

Radiative forcing and temperature change: Potsdam, Germany

Gerald Stanhill and Ori Ahiman. Radiative forcing and temperature change at Potsdam between 1893 and 2012. Journal of Geophysical Research: Atmospheres. DOI: 10.1002/2014JD021877

Radiative forcing in both the short and long-wave lengths reaching the Earth’s surface accounted for more than 80% of the inter-annual variations in the mean yearly temperatures measured at Potsdam, Germany during the last 120 years. Three-quarters of the increase in the long-wave flux was due to changes in the water content of the lower atmosphere; the remainder was attributed to increases in CO2 and other anthropogenic, radiatively active gases. Over the period radiative forcing in the short-wave flux slightly exceeded that in the long-wave but its effect on air temperature was much less as the climate sensitivity to atmospheric radiation, 0.187 °C per Wm−2, was three times greater than to short-wave global radiation. This anomalous finding, similar to that previously reported at two coastal sites, awaits explanation as does the complex interaction existing between radiative forcing and advection in determining temperature change.

Click here for full paper (fee).

National Children’s Study household testing does not reflect drinking water exposures in rural areas

This particular paper evaluated the applicability of household water sampling in rural NCS study areas. But in general, measurement of tap water concentrations do not directly measure human exposures regardless of how tight the statistics turn out. Tap water measurements can only serve as a surrogate measure used to estimate actual human exposure if other data (e.g. actual tap water intake) are known or are estimated (the common practice). This is true even in large metropolitan water systems.

Binkley TL, Thiex NW, Specker BL. Validation of drinking water disinfection by-product exposure assessment for rural areas in the National Children’s Study. Journal of Exposure Science and Environmental Epidemiology. 2014 Jul 16. doi: 10.1038/jes.2014.51.

The objective of this study was to provide evidence to evaluate the proposed National Children’s Study (NCS) protocol for household water sampling in rural study areas. Day-to-day variability in total trihalomethane (TTHM) concentrations in community water supplies (CWS) in rural areas was determined, and the correlation between TTHM concentrations from household taps and CWS monitoring reports was evaluated. Daily water samples were collected from 7 households serviced by 7 different CWS for 15 days. Coefficients of variation for TTHM concentration over 15 days ranged from 8% to 20% depending on the household. Correlations were tested between TTHM household concentrations and the closest date- and location-matched CWS monitoring reports for the 15-day mean (R=0.85, P50 μg/l corresponded to measured NCS household concentrations ranging from 2 to 60 μg/l. TTHM concentrations were higher in CWS than NCS samples (11.2±3.2 μg/l, mean difference±SE, P<0.01). These results show that in rural areas there is high variability within households and poor correlation at higher concentrations, suggesting that TTHM concentrations from CWS monitoring reports are not an accurate measure of exposure in the household.

Click here for full paper (fee).