Daily Archives: June 20, 2017

Warmer Temperatures Might Actually Enhance Predator Control of Parasites

Spencer R. Hall, Alan J. Tessier, Meghan A. Duffy, Marianne Huebner, and Carla E. Cceres. Warmer Does Not Have to Mean Sicker: Temperature and Predators can Jointly Drive Timing of Epidemics. Ecology, 87(7), 2006, pp. 1684-1695

Ecologists and epidemiologists worry that global warming will increase disease prevalence. These fears arise because several direct and indirect mechanisms link warming to disease, and because parasite outbreaks are increasing in many taxa. However, this outcome is not a foregone conclusion, as physiological and community-interaction-based mechanisms may inhibit epidemics at warmer temperatures. Here, we explore this thermal-community ecology-based mechanism, centering on fish predators that selectively prey upon Daphnia infected with a fungal parasite. We used an interplay between a simple model built around this system’s biology and laboratory experiments designed to parameterize the model. Through this data-model interaction, we found that a given density of predators can inhibit epidemics as temperatures rise when thermal physiology of the predator scales more steeply than that of the host. This case is met in our nsh-Daphnia-iungus system. Furthermore, the combination of steeply scaling parasite physiology and predation-induced mortality can inhibit epidemics at lower temperatures. This effect may terminate fungal epidemics of Daphnia as lakes cool in autumn. Thus, predation and physiology could constrain epidemics to intermediate temperatures (a pattern that we see in our system). More generally, these results accentuate the possibility that warmer temperatures might actually enhance predator control of parasites.

Global Satellite Temperature Products, Methods and Results

Roy W. Spencer, John R. Christy, and William D. Braswell. UAH Version 6 Global Satellite Temperature Products: Methodology and Results. Asia-Pac. J. Atmos. Sci., 53(1), 121-130, 2017  DOI:10.1007/s13143-017-0010-y

Version 6 of the UAH MSU/AMSU global satellite temperature dataset represents an extensive revision of the procedures employed in previous versions of the UAH datasets. The two most significant results from an end-user perspective are (1) a decrease in the global-average lower tropospheric temperature (LT) trend from +0.14o C decade−1 to +0.11o C decade−1 (Jan. 1979 through Dec. 2015); and (2) the geographic distribution of the LT trends, including higher spatial resolution, owing to a new method for computing LT. We describe the major changes in processing strategy, including a new method for monthly gridpoint averaging which uses all of the footprint data yet eliminates the need for limb correction; a new multi-channel (rather than multi-angle) method for computing the lower tropospheric (LT) temperature product which requires an additional tropopause (TP) channel to be used; and a new empirical method for diurnal drift correction. We show results for LT, the midtroposphere (MT, from MSU2/AMSU5), and lower stratosphere (LS, from MSU4/AMSU9). A 0.03o C decade−1 reduction in the global LT trend from the Version 5.6 product is partly due to lesser sensitivity of the new LT to land surface skin temperature (est. 0.01o C decade−1 ), with the remainder of the reduction (0.02o C decade−1 ) due to the new diurnal drift adjustment, the more robust method of LT calculation, and other changes in processing procedures.