Although the sun is the driver of Earth's climate, demonstrating a direct connection between solar variability and climate change has proved difficult. One of the problems is that while solar particle emissions and short wave radiation change by large amounts in a solar cycle, total irradiance varies minimally and accurate measurements have only been available in the satellite era. Some associations however have been observed between historical records of solar activity and climate change and also between variability in cosmogenic proxies for solar variability and millennial scale variability in paleoclimate records from moraine sequences, Greenland ice cores, and lake sediments by Climate Change Institute researchers (Denton and Karlen, 1973; O'Brien et al., 1995; Mayewski et al., 1993, 1997, 2004; Stager et al., 2004).
Although considerable attention has been paid to the record of temperature change over the last few centuries, the range and rate of change of atmospheric circulation and hydrology remain elusive. Examination of globally distributed (pole-equator-pole), high resolution, climate proxy records by Climate Change Institute researchers demonstrates major changes in these variables over the last 10,000 years (see summaries by Mayewski et al., 2004; Maasch et al., in press). Further this work reveals a first-order relationship between a variable Sun and changes in atmospheric circulation and hydrology (Figure 1) that is not as apparent with other climate forcing agents (Figures 2).
Annually dated, instrumentally calibrated, proxies for atmospheric circulation from several Antarctic ice cores (ITASE, Siple Dome, Law Dome) reveal decadal-scale associations with a South Pole ice core 10 Be proxy (from Bard et al., 2000) for solar variability over the last 600 years (Figure 3) and annual scale associations with solar variability since AD 1720. Increased (decreased) solar irradiance is associated with increased (decreased) zonal wind strength near the edge of the Antarctic polar vortex. The association is particularly strong in both the Indian and Pacific Oceans and as such may contribute to understanding climate forcing that controls drought in Australia and other Southern Hemisphere climate events. The mechanism for the association between solar variability and atmospheric circulation suggested by Mayewski et al. (in press 2005) may be found through previous empirical and modeling studies whereby increased solar ultra-violet (UV) radiation leads to increased production of stratospheric ozone, resulting in increased (decreased) temperatures in the lower stratosphere (troposphere) (McCormack and Hood, 1996; Chandra and others, 1996; Randel and Cobb, 1999), and consequently an increase in the thermal gradient from high to low latitudes attended by an increase in lower tropospheric zonal wind speeds over the Northern Hemisphere (Shindell and others, 1999).
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