We use this page to report the carbon dioxide measurements from the Mauna Loa site in the Pacific. The graph will include some previous years' results and the current year up to the last month. The last month's results are usually published around the 8th day of the next month.


Apologies for the absence of this feature, it won't happen again.

The El Nino effect lingers on leading to a higher concentration than might be expected. Oh My! Oh My! as the Mole would have said, seeing the February figure. The Jan-Jan  increase of ~3.5 ppmv is exceptional and we shall await further results with great interest.

Ralph Keeling reports: 

In recent years, CO2 has been increasing by around 2.2 ppm, per year. Barring anything unusual, we would therefore expect next year's September [2016] value to be around 399.3 ppm, just barely below 400 ppm, and we'd expect the lowest daily minima to be around 398 ppm or so. But we seem now to be on the verge of the largest El Niño event since 1997. This is significant because CO2 tends to rise much faster during and just following El Niño events. From September 1997 to September 1998, for example, CO2 rose by a whopping 3.7 ppm. If this El Niño is comparable, the rise from September 2015 to September 2016 could easily be 4.4 ppm, allowing for an El Niño boost and allowing that fossil-fuel emissions rates globally are larger now than in 1998. Taking these factors into account, a reasonable forecast for next year's September minimum is around 402 ppm, with the lowest daily minima also over 400 ppm.

The El Niño growth spurt in atmospheric CO2 is mostly caused by drought in the tropics. Rainfall that normally falls over tropical landmasses shifts to the oceans during El Niño events. This slows the normal growth of tropical forests and increases forest fires. Indonesia suffered severe fires during the 1997 event and, from recent news, is already being hit hard this year.

The loss of carbon from tropical forests in El Niño years is temporary as the forests tend to regrow in normal years, building back their biomass and sucking CO2 out of the air in the process. But the eventual recovery from this El Niño won't bring us back below 400 ppm, because its impact will be dwarfed by the global consumption of fossil fuels, pushing CO2 levels ever higher.

The graph shows the annual increases in atmospheric CO2 conentration since 1959. There are two aspects of the graph; the generally increasing trend and the maxima and minima superposed upon it. There is a general increase in atmospheric CO2concentration because of our burning of fossil fuels that is also rising. The differences in the annual increases are affected by the surface temperature of the ocean. Higher temperatures lead to lower CO2 solubility and in consequence to a greater than average increase, the reverse being the case for cooler ocean. The relatively higher value for 2015 shows the El Nino effect which is smaller than the major value of 1998.