Global climate change driven by soot at the K-Pg boundary as the cause of the mass extinction

Abstract

The mass extinction of life 66 million years ago at the Cretaceous/Paleogene boundary, marked by the extinctions of dinosaurs and shallow marine organisms, is important because it led to the macroevolution of mammals and appearance of humans. The current hypothesis for the extinction is that an asteroid impact in present-day Mexico formed condensed aerosols in the stratosphere, which caused the cessation of photosynthesis and global near-freezing conditions. Here, we show that the stratospheric aerosols did not induce darkness that resulted in milder cooling than previously thought. We propose a new hypothesis that latitude-dependent climate changes caused by massive stratospheric soot explain the known mortality and survival on land and in oceans at the Cretaceous/Paleogene boundary. The stratospheric soot was ejected from the oil-rich area by the asteroid impact and was spread globally. The soot aerosols caused sufficiently colder climates at mid–high latitudes and drought with milder cooling at low latitudes on land, in addition to causing limited cessation of photosynthesis in global oceans within a few months to two years after the impact, followed by surface-water cooling in global oceans in a few years. The rapid climate change induced terrestrial extinctions followed by marine extinctions over several years.

Designing global climate and atmospheric chemistry simulations for 1 and 10 km diameter asteroid impacts using the properties of ejecta from the K-Pg impact

“…Soot was apparently lost by oxidation in aerobic deep-water sites in the 66 million years since emplacement. There is debate about whether these particles originated from global wildfires, or from the impact itself (Belcher et al, 2003(Belcher et al, , 2004(Belcher et al, , 2005Belcher, 2009;Harvey et al, 2008;Robertson et al, 2013a;Pierazzo and Artemieva, 2012;Premović, 2012;Morgan et al, 2013;Kaiho et al, 2016). Robertson et al (2013a), Pierazzo and Artemieva (2012), Premović (2012) and Morgan et al (2013) argue that it is implausible that there was enough carbon at the impact site to produce the amount of soot observed by Wolbach et al (1988).…”

“…We use these most likely values in Table 1. Kaiho et al (2016) argue that the soot came from burning hydrocarbons in the crater and that the total mass emitted was either 5 × 10 2 , 15 × 10 2 , or 26 × 10 2 Tg. If we reduce these values by the authors' factor of 2.6 to represent the stratospheric emissions, they are 0.4, 1.0, and 1.7 % of the globally distributed elemental carbon reported by Wolbach et al (1990b).…”

“…If we reduce these values by the authors' factor of 2.6 to represent the stratospheric emissions, they are 0.4, 1.0, and 1.7 % of the globally distributed elemental carbon reported by Wolbach et al (1990b). Kaiho et al (2016) measured several polycyclic aromatic hydrocarbons (PAHs) that are minor components of soot from one distal site in Caravaca de la Cruz, Spain, and another site at Beloc, Haiti, that is about 700 km from the crater. Since the PAHs measured are minor constituents of soot, Kaiho et al (2016) need to use a large correction factor to determine the amount of soot.…”

“…Kaiho et al (2016) measured several polycyclic aromatic hydrocarbons (PAHs) that are minor components of soot from one distal site in Caravaca de la Cruz, Spain, and another site at Beloc, Haiti, that is about 700 km from the crater. Since the PAHs measured are minor constituents of soot, Kaiho et al (2016) need to use a large correction factor to determine the amount of soot. They first multiply by factors of 2, 5.9, or 10 to account for possible loss of PAH concentrations over time.…”

“…In a series of papers, Belcher et al (2003Belcher et al ( , 2004Belcher et al ( , 2005Belcher et al ( , 2009) and Belcher (2009) argue from multiple points of view that there were no global forest fires. Harvey et al (2008) and Kaiho et al (2016) argue that the soot originated from oil, coal, and other organic deposits at the location of the impact. If correct, the soot might have been injected at high altitude along with the large spherules.…”