The Atlantic current is already dropped 20% in the last 50 years. If you look at the currents the water will be taken up to the arctic to kill the already struggling life up there...
The methane reduces the density of the water, it would hold more heat and thus resist sinking into the cold water undercurrents that circulate down to the equator again. This may indeed stop the Atlantic conveyor and cause an ice age...probably a mini one, perhaps 1500 years, like the Younger Dryas.
The black death may get over to the Caribbean and kill the coral which will leave the islands undefended by tsunamis and hurricanes.
If the vegetation kill gets to the point of forest die off then we get fires, increased CO2 released, erosion, dropped water tables and disruption of the entire water cycle towards rapid desertification. Lakes and rives will fail and silt up, massive floods will occur.
With the nutrient and water cycles destroyed and massive carcinogenic pollution everywhere...disease will run rampant and birth rates will fall. I think we are seeing a nice little cull unfolding in slow motion...of the little people mind you.
The next stupid thing we humans could do would be to surgically removed Iran's nuke facilities.
