> the sudden ignition of underground oil at the Yucatán impact site could have jetted into the upper atmosphere a mass of fine black carbon, also known as soot

> the sudden ignition of underground oil at the Yucatán impact site could have jetted into the upper atmosphere a mass of fine black carbon, also known as soot ... black carbon injected into the stratosphere would ... [act] as a long-lived sunshade that could abruptly cool Earth and inhibit photosynthesis over a period of years