1816 was The Year Without a Summer, as the 1815 eruption of Tambora sent detritus into the atmosphere, wreaking havoc on temperatures and, by extension, agriculture. The U.S. and Western Europe did not escape its wrath - famines occurred in both places.
What with how farming has evolved, would another eruption of Tambora still produce the same effects? Assume for this thought experiment that we’re talking about in the industrialized world.
I read Gillen D’Arcy-Wood’s book on the Tambora eruption, which I really loved. It traces a whole swag of environmental impacts - some of which were in places very remote from the then European world.
The effect of the eruption of that Icelandic volcano whose name I could never pronouce shows what effect modern air travel would suffer. It would probably be potentially be a multi-week shut-down across a big chunk of the globe.
At least the global economy is more integrated with, theoretically, more potential for shortfalls in agriculture in one area to be made up from elsewhere. But would this work if total production dropped dramatically, with the wealthier countries more able to secure available food for their own security? Refugee flows would likely increase, with the usual rise in zealous policing and xenophobic political rhetoric. Dont know if you could ‘super-charge’ existing agricultural production to take effect immediately to make a difference in the 0-5 years after the eruption.