This local law mandates that preliminary budget accounting and executive budget accounting include an accounting of the carbon emissions, carbon offsets, carbon mitigation and net carbon impact that would be generated by each unit of appropriation in the preliminary budget, by each agency, and by the entire city government and include, where appropriate, the changes from the adopted budget for previous year to the carbon emissions, carbon offsets, carbon mitigation and net carbon impact that would be generated by each unit of appropriation in the preliminary budget, by each agency, and by the entire city government with an explanation of the cause of such changes.