The Dalton Minimum 1790 to 1830 brought with it a period of lower-than-average global temperatures. The Oberlach Station in Germany, for example, experienced a 2C decline over 20 years, which devastated the country’s food production. The Year Without a Summer also occurred during the Dalton Minimum (in 1816). As did crop failures across Eurasia & the Americas, which led to food riots, famine and ultimately the deaths of millions upon millions of people.
That 40-year temperature decline (1790-1830) matches perfectly with a dip in solar activity.
And so do temperature plunges of the past — preceding the Dalton were the much deeper Maunder and Spörer GrandSolar Minimums.
Taking the Maunder Minimum1645 to 1715 (as we have far more data for it than theSpörer), we see it’s 70-or-so year spell of global cold, crop loss, and famine again correlates neatly with a sharp decline in solar output. During this Grand Solar Minimum, the Sun was all-but devoid of sunspots for not just years, but decades at a time.