CO2e Increases By 4 ppm For The Second Year In A Row

In 2016 the combined effect of all greenhouse gases (CO2e which includes the effects of such gases as methane and nitrous oxide) increased by the equivalent of 4ppm of CO2, to 489ppm, according to NOAA[i]. This is the second year in a row that CO2e has increased by 4ppm, and this decade the yearly increase has not been below 3ppm. The average increase is close to 3.5ppm CO2e, well above the rate of increase in CO2 alone. At this rate, the level of CO2e will hit 500ppm by 2020. In prehistoric times, such a level has been associated with temperatures 30C above preindustrial levels. The only thing counter-balancing these high levels of greenhouse gases are the atmospheric sulfate aerosols, produced by such things as burning coal, that help reflect back the Sun’s energy. Without those, the Earth would already be on a rapid path to catastrophic climate change.

The Montreal Accord policies to reduce CFC’s, together with reduction in methane emissions during the first decade of the twenty first century, offset the increases in carbon dioxide concentrations. Due to this, the CO2e increase in greenhouse gases was relatively stable from 1990 to 2010. Since then, the rate of CO2e increases has jumped significantly, from an average of 2.6ppm per year to 3.43ppm per year. This is an increase of nearly a third in less than a decade.

With policy actions to reduce sulfate aerosols, due to their negative public health effects, the dimming counter-balance will be reduced while concentrations of greenhouse gases continue to increase. Acceleration in the rise in global temperatures can be expected, even if countries keep to their Paris commitments. With the albedo of the Arctic being reduced as the sea ice melts at an increasing rate, the climate system is being set up to provide some very bad surprises for the optimists.

[i] NOAA (2017), The NOAA Annual Greenhouse Gas Index (AGGI), NOAA. Accessible at

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2 Responses to CO2e Increases By 4 ppm For The Second Year In A Row

  1. Joe says:

    Even though anthropogenic carbon emissions have supposedly been flat for the last couple of years, the rate of increase in atmospheric CO2 ppm has been accelerating. Does this mean that CO2 increases from natural positive feedbacks are starting to overwhelm human control over emissions? Or perhaps the reports about human emissions leveling off are just wrong?

    • rboyd says:

      The periods of El Nino tend to correlate with higher levels of increase in atmospheric CO2, as the warmer surface waters tend to take in less CO2. So some of the acceleration may be a short-term El Nino effect.

      Some possibility that the Pacific Decadal Oscillation (PDO) has reversed, which will tend to produce warmer Pacific surface waters - again reducing the uptake of CO2 (cooler waters take in more CO2).

      All of the headlines about carbon emissions ignore methane, nitrous oxide etc., so miss any acceleration in these emissions. The benefits of the Montreal Accords on the CFCs are also becoming less each year, so less offset to other greenhouse gases.

      So, a little early to state that the sinks are reducing. Given the risks involved policy should be based on the precautionary principal. If so, we would be rapidly cutting emissions now. By the time we will know what is happening with the sinks a good few more years will have passed us by.


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