Thank you for pointing this out.
Here is the source where I found this figure: http://247wallst.com/2013/01/25/super-bowl-xlvii-major-money-stats-and-factoids/
Toward the bottom of the article, under the "Local Stats for New Orleans" section, the aurthor states, "Energy usage at the Superdome and at supporting facilities was listed as roughly 4,600 MW of electricity. The generation of this electricity will result in approximately 3.8 million pounds of CO2 emissions. Entergy Corp. said that it will donate carbon credits to offset or neutralize the impact of these emissions."