The Sun and Global Warming
We find good correspondence between global temperature and solar induced temperature curves during the pre-industrial period such as the cooling periods occurring during the Maunder Minimum (1645–1715) and the Dalton Minimum (1795–1825). The sun might have contributed approximately 50% of the observed global warming since 1900
They do not use a climate model. It is hard for me to tell, but I think that what they are doing is what econometricians would call “reduced-form” estimation rather than structural estimation.