Die Sonne? Die habe doch gar keinen Einfluss auf das Klima. Daran wird zumindest in Klimaalarmistenkreisen stark geglaubt. Eine neue Studie vom 28. April 2016 aus den Geophysical Research Letters bringt das Weltbild nun endgültig ins Wanken. Forscher konnten zeigen, dass Änderungen der solaren UV-Strahlung im Monatsmaßstab einen deutlichen Einfluss auf die Temperaturen in den unteren Wetterstockwerken in den Tropen haben. Hier der Abstract der Arbeit von L. L. Hood von der Univeristy of Arizona in Tucson:
Lagged response of tropical tropospheric temperature to solar ultraviolet variations on intraseasonal time scales
Correlative and regression analyses of daily ERA-Interim reanalysis data for three separate solar maximum periods confirm the existence of a temperature response to short-term (mainly ∼27 day) solar ultraviolet variations at tropical latitudes in both the lower stratosphere and troposphere. The response, which occurs at a phase lag of 6–10 days after the solar forcing peak, consists of a warming in the lower stratosphere, consistent with relative downwelling and a slowing of the mean meridional (Brewer-Dobson) circulation, and a cooling in the troposphere. The midtropospheric cooling response is most significant in the tropical Pacific, especially under positive El Niño–Southern Oscillation conditions and may be related to a reduction in the number of Madden-Julian oscillation events that propagate eastward into the central Pacific following peaks in short-term solar forcing.
Thomas et al. fanden solar-gesteuerte Tempersaturveränderungen in der Mesosphäre, die sie im November 2015 im Journal of Atmospheric and Solar-Terrestrial Physics beschrieben:
Solar-induced 27-day variations of mesospheric temperature and water vapor from the AIM SOFIE experiment: Drivers of polar mesospheric cloud variability
Polar Mesospheric Clouds (PMCs) are known to be influenced by changes in water vapor and temperature in the cold summertime mesopause. Solar variability of these constituents has been held responsible for 11-year and 27-day variability of PMC activity, although the detailed mechanisms are not yet understood. It is also known that the solar influence on PMC variability is a minor contributor to the overall day-to-day variability, which is dominated by effects of gravity waves, planetary waves, and inter-hemispheric coupling. To address this issue, we have analyzed 15 seasons of data taken from the Solar Occultation for Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite. The SOFIE data contain precise measurements of water vapor, temperature and ice water content (among other quantities). These high-latitude measurements are made during the PMC season at the terminator, and therefore directly relate to the simultaneous measurements of mesospheric ice. Using a composite data set of Lyman-α irradiance, we correlated the time variation of the atmospheric variables with the 27-day variability of solar ultraviolet irradiance. We used a combination of time-lagged linear regression and Superposed Epoch Analysis to extract the solar contribution as sensitivity values (response/forcing) vs. height. We compare these results to previously published results, and show that the temperature sensitivity is somewhat higher, whereas the water sensitivity is nearly the same as published values. The time lags are shorter than that expected from direct solar heating and photodissociation, suggesting that the responses are due to 27-day variations of vertical winds. An analytic solution for temperature changes forced by solar irradiance variations suggests that if the response is due purely to Lyman-α heating and Newtonian cooling, the response should vary throughout the summertime season and depend primarily upon the height-dependent column density of molecular oxygen.
Einen spürbaren Klimaeinfluss von solaren UV-Schwankungen berichteten auch Ball et al. in einer Studie, die am 25. Januar 2016 in Nature Geoscience erschien. Interessantes Resultat: Die Modelle können die Realität nicht reproduzieren. Hier der Abstract:
High solar cycle spectral variations inconsistent with stratospheric ozone observations
Solar variability can influence surface climate, for example by affecting the mid-to-high-latitude surface pressure gradient associated with the North Atlantic Oscillation1. One key mechanism behind such an influence is the absorption of solar ultraviolet (UV) radiation by ozone in the tropical stratosphere, a process that modifies temperature and wind patterns and hence wave propagation and atmospheric circulation2, 3, 4, 5. The amplitude of UV variability is uncertain, yet it directly affects the magnitude of the climate response6: observations from the SOlar Radiation and Climate Experiment (SORCE) satellite7 show broadband changes up to three times larger than previous measurements8, 9. Here we present estimates of the stratospheric ozone variability during the solar cycle. Specifically, we estimate the photolytic response of stratospheric ozone to changes in spectral solar irradiance by calculating the difference between a reference chemistry–climate model simulation of ozone variability driven only by transport (with no changes in solar irradiance) and observations of ozone concentrations. Subtracting the reference from simulations with time-varying irradiance, we can evaluate different data sets of measured and modelled spectral irradiance. We find that at altitudes above pressure levels of 5 hPa, the ozone response to solar variability simulated using the SORCE spectral solar irradiance data are inconsistent with the observations.
Die lange vernachlässigte Verknüpfung zwischen der Schwankungen der Sonnenaktivität und klimatischen Veränderungen an der Meeresoberfläche, Troposphäre und Stratosphäre beschrieben auch Yamakawa et al. im März 2016 im Fachblatt Quaternary International:
Relationships between solar activity and variations in SST and atmospheric circulation in the stratosphere and troposphere
Relationships between solar activity and variations in both sea surface temperature (SST) and atmospheric circulation at the time of the solar maximum are presented. The global distribution of correlation coefficients between annual relative sunspot numbers (SSN) and SST from July to December was examined over a 111-year period from 1901 to 2011. Areas with a significant positive correlation accounted for 11.7% of the global sea surface in December, mainly over three regions in the Pacific. The influence of solar activity on global atmospheric pressure variations and circulation in the maximum years was also analyzed from 1979 to 2011. The results indicated that higher geopotential height anomalies tended to appear in the stratosphere and troposphere in the northern hemisphere, centering on around the Hawaiian Islands from November to December, in the second year of the solar maximum. The SST distribution in the Pacific with strong north and south Pacific Highs produced a pattern that resembled teleconnection patterns such as the Pacific Decadal Oscillation (PDO) and the Central-Pacific (CP) El Niño, or El Niño Modoki (ENM). It is suggested that the solar activity had an influence on the troposphere via not only the stratosphere but also the sea surface.