The biggest carbon emissions come from fossil fuel burning and cement manufacture. But without knowing how much fuel is burnt and how much cement is made every day, it is tough to gauge the extent of the problem.
This lack of knowledge also affects important efforts to reduce emissions. Without an immediate way to assess their effectiveness, it is hard for climate scientists, industrialists, governments and policy makers to decide how best to act.
Which is why the work of Zhu Liu at Tsinghau University in Beijing and colleagues around the world, is so significant. This group has begun to track global emissions of carbon dioxide on a daily basis and begun to publish this data in near-real time on an online dashboard. Their website — the Carbon Monitor — displays the daily carbon emissions across the entire planet at: www.carbonmonitor.org.cn/
The team’s ambitious goal is to inform research, to better understand the impact of emissions and to help policy makers make better decisions about how to reduce carbon emissions. The importance of these are hard to understate.
First some background. Most countries calculate their own carbon emissions and release them on an annual basis, usually a year or more after the fact. So global figures, calculated by adding all the national-level numbers, usually lag the actual emission levels by at two years or more.
By contrast, Liu and colleagues derive their figures by calculating fuel use and cement production on a near daily basis. However, the task is huge.
The researchers’ approach is to calculate the carbon emissions from every major country and for each sector of the economy that produces it, every day.
That calculation is simple in theory. The amount of carbon produced in a given industry depends on the amount of activity in that industry and the fuel type used to power it. The calculation can be further refined using the amount of energy that the fuel type produces.
The team calibrate this calculation by looking at the actual emissions from the past in official published figures–the most recent are from 2018. The team have teased apart these figures to reveal the daily emissions in 2018 for each industry sector in each country. They then use these figures as a kind of gold standard.
The next step is to calculate the current emissions by working out how activity has changed in each sector relative to 2018. But as well as activity levels, the team must also take into account any changes in fuel types — whether more renewables are used for example — and also how fuel-burning efficiencies have improved too, for example by how much vehicles have become more fuel efficient over that time.
These changes then give them a way to estimate the current carbon dioxide emissions levels.
These estimates are possible on a daily level for many industries because it has become much easier to monitor daily changes in activity levels. For example, most countries publish the amount of electrical power they produce on a daily basis. And carbon emissions from road transport can be calculated simply by measuring traffic levels in over 400 of the world’s biggest cities. The way traffic levels change over time is a good proxy for the way fuel consumption changed too.
The Devil in the Detail
Liu and colleagues do this for all the industrial sectors that produce emissions. So in addition to the power industry and road transport sector, this includes shipping and aviation, cement production as well as heating for residential and commercial buildings, which can be gauged by measuring local temperature variations.
Of course, the devil is in the detail. A big part of the team’s work is in taking disparate sources of data and making it comparable, as well as taking into account the various sources of error.
But the results are impressive. The Carbon Monitor website shows the daily emissions on a global basis but also on a regional or national level and by industrial sector.
The dashboard has come into its own in the first half of 2020 by revealing exactly by how much global carbon emissions have fallen during the COVID-19 epidemic. “The Carbon Monitor near-real-time CO2 emission dataset shows a 7.8% decline of CO2 emission globally from Jan 1st to Apr 30th in 2020 when compared with the same period in 2019,” say Liu and colleagues.
However, emissions have already begun to grow again, largely because of the increase in economic activities in China as lockdown lifts. Indeed, emissions from China are now approaching 2019 levels.
Of course, the Carbon Monitor does not include all sources of carbon emissions. For example, it does not monitor changes in the use of land use — such as cutting down forests — which Is responsible for about 10 per cent of global carbon dioxide emissions.
Nevertheless, this is important work. It has the potential to show the immediate impact of policies or changes in behavior designed to reduce emissions. That could be crucial for galvanizing public support and giving policy makers the data they need to justify their actions and propose new measures.
Ultimately, accurate measurements provide the foundations for any good plan. And as far as climate change goes, the world desperately needs better, more far-sighted planning.
Ref: Carbon Monitor, a Near-Real-Time Daily Dataset of Global CO2 Emission From Fossil Fuel and Cement Production. arxiv.org/abs/2006.07690