Peak Carbon Dioxide Emissions and Peak Carbon Dioxide Concentration

David P. Turner / December 2, 2020

Updated November 23, 2022 based on the 2022  Global Carbon Budget Report and the 2022 International Energy Agency World Energy Outlook Report.

In 2020, a remarkable speculation circulated in the cybersphere to the effect that global emissions of carbon dioxide (CO2) from fossil fuel combustion may have peaked in 2019.  Considering that recent formal projections generally indicated increasing emissions through 2030 or longer, this assertion was striking.  It matters because CO2 emissions determine the growth in the atmospheric CO2 concentration, which in turn influences the magnitude of global warming.

The atmospheric CO2 concentration is currently around 420 ppm (up from a preindustrial value of around 280 ppm) and is rising at a rate of 2-3 ppm per year.  The consensus among climate scientists is that rapid greenhouse-gas-driven climate change will be harmful to the human enterprise on Earth.  It would be good news indeed if CO2 emissions were on the way down.

Estimates for annual global CO2 emissions are produced by assembling data on consumption of coal, oil, and natural gas, as well as data on production of cement, which also releases CO2 (the sum is termed Fossil Fuel & Industry emissions).  Two independent emissions estimates (GCP and IEA) differ slightly. Deforestation is another significant anthropogenic source of CO2, but it is not considered in this blog post except to say that reducing deforestation will further reduce total CO2 emissions.

The suggestion that peak fossil fuel emissions occurred in 2019 held true in 2020 and 2021, but 2022 saw about a  1% increase over 2019.  However, there is significant uncertainty about these emissions estimates, especially of late considering how volatile the global energy market has become in 2022 because of the war in Ukraine.  It will thus be interesting to see the Global Carbon Project update of its 2022 emissions estimates (available in April 2023).  The input data set then will reflect observations over the complete year.

Despite the possible increase in emissions, the new IEA report calls 2022 a global turning point in the transition to a renewable energy future, an assertion based on the step-change in available financing (led by the Inflation Reduction Act in the U.S.).  The IEA also suggests that the 2020s will be the turning point decade in CO2 emissions, i.e. decadal emissions in the 2030s will be lower.

Several specific observations points towards lower emissions in the near-term future.

1.  The rate of increase in global emissions has been low in recent years (before the 2021 recovery from the Covid-19 pandemic), averaging less than 1% per year for 2010-2019.

2.  Global coal emissions in 2022 are about the same as in 2012.  Aging coal powered electricity plants in the U.S. are being replaced with plants powered by natural gas (more efficient that coal) or renewable energy.  Some coal plants have been prematurely retired.  A gradual phase out in global coal consumption is being driven by the price advantage of renewable energy, impacts of coal emissions on human health, and the reluctance of insurance companies to cover new coal power plant construction.  China has agreed to stop financing the construction of coal power plants in developing nations.

3.  Peak oil use may have occurred in 2019.  Global demand in 2020 fell 7.6% because of Covid-19, recovered by 4.4% in 2021, and increased an additional 2.2% in 2022.  Structural changes such as reduced commuting and business-related flying mean that some of the demand reductions associated with Covid-19 will be persistent.  Vehicles powered by electricity and hydrogen rather than gasoline are on the ascendancy, sparked in part by governmental mandates to phase in zero emissions vehicles.

4.  Even a near-term peak in natural gas consumption is being discussed.  The GCP budget for 2022 shows a 0.2% decline in gas emissions.  Again, the price advantage of renewable sources will increasingly weigh against fossil-fuel-based power plants.  The growing importance of energy security at the national level also argues against dependence on imported fossil fuels.  Ramped up production of renewable natural gas could substitute for fossil natural gas in some applications.

Surprisingly, it appears likely that a near-term decline in total fossil fuel use will be driven more by lack of demand than lack of supply.

Emissions from cement manufacturing fell slightly (1.6%) in 2022.  A recent study suggests that the COuptake from slow weathering of aging cement around the world is providing a large offset (more than half) to current cement manufacturing emissions.  Innovative uses of wood and geopolymers can potentially replace cement in many construction applications.

The Biden administration has returned the U.S. (largest cumulative CO2 emissions on the planet) to the international fold with respect to climate change mitigation.  President Xi Jinping of China (largest CO2 emitter on the planet) has also displayed leadership on the climate change issue.  A revitalized collaboration between the U.S. and China on climate change mitigation could push the needle on global emissions reduction.

A critical missing piece in the global struggle to reduce CO2 emissions is the soaring use of coal in India (up 14.8% in 2021 and 5% in 2022).  Offers of climate finance from the more developed world could go a long way towards funding the needed renewable energy revolution there.

Currently about half of fossil fuel COemissions remain in the atmosphere, with the remainder sequestered on the land (e.g. in vegetation and soil) and in the ocean.  Once fossil fuel emissions begin decreasing and fall by half − and assuming the net effect of increasing CO2 and climate warming is still substantial carbon uptake by the land and ocean − the atmospheric CO2 concentration will peak and begin to decrease.  The year of peak CO2 concentration could be as early as 2040 (see carbon cycle projection tool below).

There is of course plenty that might go wrong.  The net effect on the land and ocean sequestration just referred to could be a decline in carbon uptake.  On land, carbon sources such as permafrost melting and forest fires will be stimulated by climate warming.  In the ocean, warming will intensify stratification, thereby reducing carbon removal to the ocean interior.  The steady increase in the ocean carbon sink since around 2000 has stalled in recent years, for poorly understood reasons.

On the other hand, land sequestration is increasing now and could continue to do so in response to CO2 enhancement of photosynthesis and plant water use efficiency.  Policy driven increases in the land carbon sink (e.g. more reforestation and afforestation) are also possible.

Whatever specific years do turn out to be peak CO2 emissions and peak CO2 concentration, they will be remembered as historic hallmarks in humanity’s effort to address an existential threat of its own making.

Recommended:  Interactive CO2 Emissions and Concentration Projection Tool.

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2 thoughts on “Peak Carbon Dioxide Emissions and Peak Carbon Dioxide Concentration

  1. 2021 surely represents an increase in global CO2 emissions… but will it be greater than 2019? Our new EBI Q2 2021 forecast model estimates peak CO2 emissions in the year 2024… so things are moving fast since last model we 2029.
    And… global GHG emissions are separate? So mostly methane and mostly from oil & gas and ag and landfills.
    D Turner we’d like to do an email Q&A for the next edition of CCBJ.
    Grant Ferrier
    Editor, Environmental Business Journal
    Editor, Climate Change Business Journal

    • Grant,
      Yes, it will be interesting to see how fast global fossil fuel consumption recovers from the pandemic!
      I would do an email Q&A.

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