Other causes, including
solar radiative output variations, are thought to be less important, but they are also far less certain.
He claimed that the Maunder Minimum coincided in time with an era of colder weather, and that by implication the absence of magnetic activity was accompanied by a net fall in the total
radiative output of the Sun.
An implicit corollary is that in the intervening period
the radiative output has been increasing, with a consequent warming of the Earth.
«Since irradiance variations are apparently minimal, changes in the Earth's climate that seem to be associated with changes in the level of solar activity — the Maunder Minimum and the Little Ice age for example — would then seem to be due to terrestrial responses to more subtle changes in the Sun's spectrum of
radiative output.
If someone asserts that we can not delay
the radiative output, this implies that (1) nothing can delay radiative output by its very nature, or (2) we have reached the limits of the reservoir.
In fact,
radiative output was low enough to suggest that all surface water on Earth should have been frozen solid during its early history, but evidence shows that it was not.