Global crops failures. Photosynthesis stops for months. Decades for plants to recover. Major regional extinctions. Hundreds of years.
Most values are very approximate - within an order of magnitude.
Crater diameters were derived from Jay Melosh's Crater Calculator , using dense rock impactor and target surface and a 45 degree impact angle. The transient crater is important for calculating environmental effects since it is associated with ejected material. It is possible that the Indo-China event involved a very low impact angle. Fireball ignition radius and ballistic ejecta ignition radius from Toon Figure 16. 4 psi Blast radius from Toon Figure 5.