The Sun’s activity follows a regular cycle, driven by changes in its magnetic field. Scientists typically measure solar activity by counting sunspots – dark areas on the Sun’s surface that form where magnetic fields are strongest. These ebb and flow in a repeating cycle averaging 11 years.
In the first half of the solar cycle, magnetic activity progressively ramps up until the ‘solar maximum’, when the number of sunspots can reach over 200. This is accompanied by an increase in the Sun’s energy output. Over the second half of the cycle, solar activity wanes, dipping to the ‘solar minimum’ before a new cycle begins.
We are currently at a solar minimum, and will therefore see an increase in solar activity between now and 2025. However, even at solar maximum, the energy that the Earth receives from the Sun is only around 0.1 per cent higher than average. This has only a tiny impact on our global temperatures, which pales in comparison with the effect of human-emitted greenhouse gases such as carbon dioxide.
The last three solar cycles have all been weaker than their predecessor, leading some scientists to speculate that we could be about to enter a prolonged period of lower solar activity. But at best this would offset global temperature rise by just 0.3°C, and it would only be a temporary effect until the Sun’s activity ramped up again.
- What would happen if the Earth became tidally locked to the Sun?
- If global warming increases rainfall, could the extra clouds block sunlight and help cool the Earth?
- How much closer to the Sun could Earth’s orbit get and still be habitable?
- Do we really know what climate change will do to our planet?