Atmosphere Contents

4. Energy Budgets

The sun's solar cycle and energy output

Solar activity is modulated by the approximate 11 year solar cycle. During more active cycles, more intense output of radiation and solar winds, phenomenon such as sun spots (magnetic storms), flares and faculae (bright convective hot spots) are more prominent/frequent on the sun's surface. A long term change/trend in the solar cycle could have significant affects on the Earth's climate.

Irradiance

The figure above shows the recording of the solar irradiance from satellites since the late 1970s. The solar cycle can be clearly seen in this timeseries. According to IPCC Assessment (2007), there are no significant trends found in the satellite datasets showing either an increase or decrease in the sun's overall activity. However, climate model simulations and solar irradiance reconstructions (as far back as 1600) do show slight increases in solar irradiance and activity. The general consensus in the science community though, is that anthropogenic activity is the dominant force driving climate change.

What effect could a change in solar output of 1% per century have on the Earth's climate?