U.S. carbon dioxide emissions for January-May are down six
percent from 2011 to 2012. Headlines have highlighted the fact
that emissions from January-March hit a twenty year low. What
explains the shift? That question has been the subject of
intense debate. John Hanger argues that 77 percent of that
decline can be attributed to the shift from coal to gas. The
folks over at CO2Scorecard, looking at January-March data, put
that number at a more modest 21 percent. These are drastically
different figures. What number should we believe? Part of the
discrepancy comes from looking at different time periods.
January-March emissions were affected more by the warm winter
than April-May ones were. That makes sense because January-March
is part of the winter. April-May emissions were affected more by
rock bottom natural gas prices than January-March ones were.
That makes sense because it was April-May when rock bottom (i.e.
sub-two-dollars wellhead) natural gas prices prevailed. Let’s
focus on the full January-May span,