Changes

A contrasting study to that done by Rutledge is a 2008 study by Pushker Kharecha and James Hansen, "Implications of 'peak oil' for atmospheric CO2 and climate."<ref>[http://pubs.giss.nasa.gov/docs/2008/2008_Kharecha_Hansen.pdf "Implications of 'peak oil' for atmospheric CO2 and climate,"] Pushker A. Kharecha and James E. Hansen, Global Biochemical Cycles, August 5, 2008</ref> Kharecha and Hansen modeled a coal phase-out scenario in which developed countries leveled out their coal usage from 2012 to 2022, then reduced it at a straightline pace until zeroing it out in 2050. Developing countries would level their usage out in 2022 and would also zero out their usage by 2050. This coalphase-phaseout out scenario, which would release 110 Gt of carbon from coal into the atmosphere from 2007 through 2050, was then analyzed in connection with a variety of assumptions about oil and gas depletion. The peak carbon dioxide level connected to the various scenarios ranged from 428 to 446 parts per million (ppm). A "business as usual" scenario in which coal usage was not limited produced a peak carbon dioxide level of 563 ppm.