In cooperation with solar physicists at the Swedish Institute of Space Physics in Lund and climate physicists at the Space and Atmospherics Department, Imperial College, London, the sun-climate group at DTU Space carried out a comprehensive study of the Sun-climate link. The tasks carried out included a literary survey on previously obtained results, identification of relevant solar and climate data, and analysis of correlations between these data.
The emphasis was on direct measurements, i.e., incuding only limited amounts of proxy data, and thus limiting the analysis mainly to the last 50 years and with a strong emphasis on the last 30 years where satellite data have become available both for solar output and for global measurements of Earth's climate.
Correlations between solar output and Earth's climate are evident, but the physical links between these are still unresolved. One obstacle in pin-pointing the physical sun-climate link through analysis of solar-climate correlations is that the different forms of solar output, e.g., radiated energy, ultraviolet radiation, high energy particles, solar wind, and magnetic energy, all vary simultaneously in tune with the solar activity. In the ISAC project multi-regression analysis was employed in order to overcome this obstacle.
The conclusion is that ultraviolet radiation and magnetic energy carried by the solar wind are the most likely candidates for solar influence on Earth's climate. Ultraviolet radiation through influence in the stratosphere, the solar wind through its effect on the amount of cosmic rays received by the Earth and their role on Earth's cloud cover.
The ISAC project was commisioned by The European Space Agency under the Earth Observation Programmes in order to study the link between fluctuations in solar activity and the climate on Earth.
The project is at its final stages, and the final presentation was held at ESA, ESTEC in Holland on 12 April 2007.
The following PDF-reports have been made public:
WP 100 Technical Note
WP 101 Solar Variability
WP 102 Influences of Solar Variability on Earth
WP 103 Climate Variability Correlated with Solar Activity
WP 104 Modelling of Sun-induced Climate Variability
WP 200 Technical Note
WP 201 Solar Output
WP 202 Possible Interactions and Modifications
WP 203 Earth’s Climate
WP 301,302,401,402 Data analysis and correlations
WP 403 Stratosphere
WP 304 Data Interprtation - Solar - Technical Note
WP 501a Role of TSI
WP 502 Solar wind interaction with magnetosphere and ionosphere
WP 501b Role of UV and energetic particles
WP503 Role of Ionisation
WP 601 External Forcing
ISAC final report