No record in May (but close)

This is the second post in what will be a series tracking monthly year-over-year changes in atmospheric CO2. Last month set a record but May merely came close, with the 3rd-highest year-over-year increase for the month since initiation of the Muana Loa data series.

The following chart plots minimum and maximum annual changes in CO2 occurring in May, from 1960 to 2010, measuring minimum and maximum values on a rolling 12-month basis. The color area is the spread between minimum and maximum change. Long plateaus indicate periods in which no new records were being set. Choppy areas indicate shorter time intervals between new maximum or minimum values. The white line is 10-year moving average.

Click image to view full-size

Here are the top-3 year-over-year CO2 increases which have occurred in May:

1. May, 2003  +2.96 ppm

2. May, 1998  +2.86 ppm

3. May, 2010  +2.76 ppm