Overview - Solar Climate Forcing

Ultimately all of the energy driving the earth's climate and ecosystems originates with the sun. Variations in solar output can have significant impacts on climate changes, and are known to have done so at various times during history. There are direct effects from absorption if solar radiation in the atmosphere and at the earth's surface (which is then re-radiated upward to the atmosphere once again), and indirect mechanisms by which solar radiation may induce atmospheric chemistry changes that could affect atmospheric responses to other forcings, though this is less certain. These effects also tend to follow cycles, many of which correlate reasonably well with cycles in sunspot activity, and can be tracked to some extent. A variety of direct and proxy measures of solar forcing reveals that it is likely to have been an important, if not primary contributor to early 20th century warming, but much less of a factor since the middle 20th century. Many climate change skeptics have attempted unsuccessfully to argue otherwise, but these arguments have not withstood scrutiny and are not widely accepted today.