CO2 emissions are rising more slowly – but are still higher than last year
What amount of greenhouse gases, especially carbon dioxide (CO2), is released into the atmosphere year after year, and how much can be absorbed by the land and oceans? The Global Carbon Project (GCP), a worldwide consortium of climate researchers, has published annual reports since 2006. According to the GCP’s latest report, global carbon emissions continued to rise in 2019, although more slowly than in previous years. While less coal was burnt on a global scale, the growing use of natural gas and increased emissions from land use more than made up for this decline.
CO2 emissions have to be dramatically reduced worldwide,
The concentration of carbon dioxide in the atmosphere continues to rise, and will most likely reach an annual mean value of 410 ppm (parts per million); that amounts to a 47 percent rise in comparison to preindustrial levels.
With an estimated value of nearly 37 billion metric tons of CO2 (GtCO2), emissions from the burning of fossil fuels will likely be more than four percent higher than in 2015, the year in which the Paris Agreement was signed. According to AWI biogeoscientist Judith Hauck, “CO2 emissions have to be dramatically reduced worldwide, in order to avoid exceeding the 1.5°C limit established in the Paris Agreement.”
That being said, the speed at which the emissions from burning fossil fuels are rising has declined, and at 0.6 percent (-0.2 to +1.5 percent uncertainty range) for 2019, lies well below the rates for 2017 (1.5 percent) and 2018 (2.1 percent). If we look at the average for the past decade, half of all fossil CO2 emissions came from the energy sector, with industry and transportation accounting for another quarter each.
Gas can only provide a short-term alternative
In Europe, a higher CO2 price helped to drive down emissions, especially because less electricity was produced using coal. But despite this drop, coal remained the main source of anthropogenic CO2 emissions for the past decade, accounting for 42 percent of all fossil emissions. Further, even if burning natural gas produces 40 percent less CO2 per energy unit than coal, gas can only provide a short-term alternative for energy production at best, the experts at the Global Carbon Project claim, because it does not help to achieve the goal of reducing overall emissions to net zero.
Emissions from changes in land use are characterised by considerable uncertainty, and amounted to an average of ca. 5.5 GtCO2 per year in the last decade. Initial estimates of the emissions from changes in land use for 2019 indicate an increase of ca. 0.8 GtCO2 over the previous year, chiefly due to intensified slash-and-burn agriculture in the Amazon. Data from the Brazilian Space Agency show that deforestation has steadily increased in the Brazilian sector of the Amazon rainforest since 2008. At the same time, there was an unusually high level of fire activity in the deforestation regions of Indonesia.
Oceans are the most important CO2 sinks
But in terms of the global carbon balance, the experts consider not only the emissions, but also the absorption of carbon by vegetation and the oceans: the CO2 sinks. Every year, only ca. 45% of CO2 emissions remain in the atmosphere. “In 2018 the world’s oceans absorbed 23% of the carbon dioxide emissions released by human activities, performing an invaluable service for human beings. Without them, the carbon dioxide concentration in the atmosphere would rise even more quickly, accelerating climate change in the process,” says Judith Hauck, explaining the oceans’ role in the global carbon balance. In this regard, the positive effects of land-based sinks since the beginning of industrialisation are roughly balanced out by the emissions from land use. Accordingly, the oceans are the most important CO2 sinks in the long term.
However, Judith Hauck warns that this ‘service’ might not always be so readily available: “In 2018 the oceans’ absorption of CO2 climbed to 9.6 +/- 2.2 GtCO2. There aren’t yet any signs of the carbon sinks’ absorption capacity stagnating. But we know that eventually, when the oceans’ buffering capacity has been exhausted, we will reach a saturation point. Moreover, the warming of the oceans reduces their CO2 absorption.”
The original publication: Pierre Friedlingstein et al.: Global Carbon Budget 2019