"The Mauna Loa record shows a 19.4% increase in the mean annual concentration, from 315.98 parts
per million by volume (ppmv) of dry air in 1959 to 377.38 ppmv in 2004.
The 1997-1998 increase in the annual growth rate of 2.87 ppmv represets the largest single yearly
jump since the Mauna Loa record began in 1958."
http://cdiac.ornl.gov/trends/co2/sio-mlo.htm

These measurements indicate a rise in annual average atmospheric CO2 concentration from 356.66 parts per million by volume (ppmv) in 1992 to 371.12 ppmv in 2001, or an increase of about 1.61 ppmv/year, on average. These data, from flask samples, may be compared with continuous measurements made by Scripps Institution of Oceanography and by the National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostics Laboratory (CMDL). Both of these data sets are available in TRENDS. The Scripps data show an increase from 356.37 ppmv in 1992 to 370.89 ppmv in 2001, or an increase of 1.61 ppmv/year. The NOAA/CMDL data are available in TRENDS only through 1998. For 1992-1998, these (CSIRO) data show an increase from 356.66 ppmv to 366.44 ppmv, or an average annual increase of 1.63 ppmv/year; the NOAA/CMDL data show an increase from 356.28 ppmv in 1992 to 366.49 ppmv in 1998, or an average increase of 1.70 ppmv/year during the same period. Differences are partly due to different sampling methods; the CSIRO (flask) data are taken at particular times, while the Scripps and NOAA/CMDL data represent continuous measurements. There are also differences in statistical treatment of the data (e.g., acceptance criteria, smoothing techniques), as well as instrument differences which are discussed by Masarie et al. (2001).
http://cdiac.ornl.gov/trends/co2/csiro/csiro-mlo.html

A recently issued report by the US National Oceanic and Atmospheric Administration (NOAA) of an unexpectedly large increase in carbon dioxide levels from 2002 to 2003 has raised concerns that the earth may already be entering a time of rapid and abrupt climate change. The measurements taken at NOAA's Mauna Loa Observatory showed CO2 levels had jumped 2.5 ppm from 2002 to 2003 to a level of 376 ppm.
http://www.climate.org/topics/climate/co2jump.shtml

Sunday, April 10, 2005:
"By the time Mauna Loa took its first measurements in 1958, it was up to 315.6 parts per million. The CO2 level has increased each year since then. Through the 1960s, the rate of increase was less than 1 ppm per year. During the past couple of decades, it has averaged 1.5 ppm.

But occasionally, it jumps higher than that. In 1998 there was a spike. And during another spike in 2002 and 2003, the rate was 2.6 and 2.3 ppm, respectively.

Preliminary indications are that the increase for 2004 will be about 1.5, Tans said.

Last month, the overall CO2 level surpassed 380 ppm — by far the highest it has been in thousands of years. While it's increasing regularly, the rise isn't always steady, as indicated by the recent spike.
http://the.honoluluadvertiser.com/article/2005/Apr/10/ln/ln27p.html

"Sir David told BBC News the 2 ppm rise of the last two years is "likely to be an anomaly, which would not be unprecedented, and not the start of a trend, unless it is proved otherwise".
...
Dr David Hofmann, of Noaa, told the Guardian newspaper on Monday: "I don't think an increase of 2 ppm for two years in a row is highly significant - there are climatic perturbations that can make this occur."
http://news.bbc.co.uk/1/hi/sci/tech/3732274.stm