If another catastrophic caldera-forming Yellowstone eruption were to occur, it quite likely would alter global weather patterns and have enormous effects on human activity, especially agricultural production, for one-to-two decades.
Scientists studied three historical explosive eruptions of different sizes in Indonesia--Tambora (1815), Krakatau (1883), and Agung (1963). They noted that decreases in surface temperatures after the eruptions were of similar magnitude (0.18-1.3 °C). The amount of material injected into the stratosphere, however, differed greatly. By comparing the estimated amount of ash vs. sulfur injected into the stratosphere by each eruption, it was suggested that the longer residence time of sulfate aerosols, not the ash particles which fall out within a few months of an eruption, was the paramount controlling factor (Rampino and Self, 1982).
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If another catastrophic caldera-forming Yellowstone eruption were to occur, it quite likely would alter global weather patterns and have enormous effects on human activity, especially agricultural production, for one-to-two decades. In fact, the relatively small 1991 eruption of Mt. Pinatubo in the Philippines was shown to have temporarily, yet measurably, changed global temperatures. Scientists, however, at this time do not have the predictive ability to determine specific consequences or durations of possible global impacts from such large eruptions.