Dr Judith Hauck is a climate researcher at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). For the Global Carbon Project, she coordinates the estimates of how much CO2 is stored by the ocean. “This year was the first time that we not only used models to simulate the ocean sinks, but also included observation-based estimates.” The preliminary findings: in the course of 2021, the ocean will absorb ca. 10.6 billion metric tons of CO2. This will continue the trend of increasing CO2 absorption in the ocean, running parallel to rising concentrations of atmospheric CO2. Over the past decade (2011 to 2020), they rose to 10.3 billion metric tons of CO2 per year on average, amounting to 26 percent of total CO2emissions. “The development of the ocean carbon sink over the next few decades, in response to rising CO2concentrations and worsening climate change alike, will also affect the atmosphere. How exactly it will do so is something we’re currently investigating at the AWI.”
The natural land sink, which absorbed ca. 28 percent of anthropogenic emissions in the last decade, has increased its capacity over the past two decades. In the course of 2021, it will absorb an estimated 12.1 billion metric tons of CO2.
The remaining carbon budget is dwindling
Prolonged high emissions levels have further reduced the available carbon budget for limiting global warming to 1.5 degrees, 1.7 degrees or 2 degrees Celsius. As the Global Carbon Project reports, only 420 billion metric tons, 770 billion metric tons and 1,270 billion metric tons of CO2 remain for a 50-percent chance of achieving the 1.5-, 1.7- or 2-degree target, respectively. This equates to roughly 11, 20 or 32 years if emissions remain at the projected level for 2021. “The rebound in CO2 emissions to nearly the 2019 level shows that the countries’ plans still contain virtually no structurally effective solutions for a lasting reduction in emissions,” says Hauck. “The coronavirus lockdowns haven’t yet produced any lasting effect. Accordingly, we now need to find effective solutions and implement them globally in order to lastingly cut emissions.” After all, the goal of eliminating net greenhouse-gas emissions by 2050 (net-zero emissions) can only be reached if the total CO2 emissions are reduced by 1.4 billion metric tons on average every year. “In other words, we need to achieve the same kind of reduction that we saw in 2020, every year. That was a drop of 1.9 billion metric tons, mostly due to the lockdown-induced decline in mobility, but also in production.”
The Global Carbon Project is an international research project of Future Earth, a research initiative focusing on global sustainability. Its goal is to arrive at a comprehensive view of the carbon cycle, one that includes not only its bio-physical aspects, but also the human dimension and the interactions between them. Climate researchers from around the world contribute to the report. In Germany, experts from the Alfred Wegener Institute (Bremerhaven), Ludwig-Maximilians-Universität (Munich), Max Planck Institute for Meteorology (Hamburg), Max Planck Institute for Biogeochemistry (Jena), Karlsruhe Institute of Technology, GEOMAR Helmholtz Centre for Ocean Research (Kiel) and Leibniz Institute for Baltic Sea Research (Warnemünde) are participating.
The Global Carbon Budget 2021 is the 16th edition of the annual report. The numbers represent an update from 2020 which the IPCC used in the first part of its Sixth Assessment Report.