How are greenhouse gas emissions monitored?

Tune in to our live debate on 21 October at 11am CET when our panellists will take us through the complex process of data collection and explain why monitoring is crucial for the EU’s net zero target. You can watch the video of the debate at the top of this article.

In this week’s Climate Now debate, we will delve into how greenhouse gas emissions are monitored and why it is important to measure sources in the push for net zero. 
Our panellists will also explain why the technology is still unable to give us accurate and comprehensive measurements for some sources and sinks of greenhouse gases and how improvements can be made.
Fill in this question form with your questions for our experts and they will be answered during the live broadcast:
Greenhouse gases (GHGs) have an important role for our planet. They trap heat close to the earth’s surface, ensuring that oceans don’t freeze and our world remains inhabitable. However, particularly since industrial times, human activity has rapidly increased the volume of emissions causing the planet to warm at an unprecedented rate. 
This has prompted an urgent need to curb emissions. To do so, nations, organisations and businesses need to better understand their capability to measure, monitor and model GHGs and therefore pinpoint the biggest emitters. 
To know if actions taken to reduce GHG levels are effective, technology has been developed to measure the concentrations of these gases in the atmosphere over time. It requires accurately detecting them in tiny amounts: carbon dioxide in the hundreds of parts per million, methane in thousands of parts per billion, nitrous oxide in the hundreds of parts per billion and fluorinated hydrocarbons at even lower levels.
The European Union and its member countries are required to report to the UN annually on their GHG emissions and regularly on their climate policies and measures and progress towards the targets. 
This involves measuring the emissions of GHGs including carbon dioxide, methane and nitrous oxide from all sectors including energy, industrial processes, land use, forestry, waste and agriculture. These are compiled to create the EU’s greenhouse gas inventory, which starts in 1990 and runs up until two years before the current year.  
GHG monitoring is also crucial to understanding the role of natural ecosystems as sources or sinks. The world’s natural carbon sinks absorb about half of all human emissions. But recent research by scientists found that in 2023, the hottest year on record, forests, plants and soil absorbed almost no carbon. 
In addition, this year the US nonprofit Amazon Conservation used satellite data to calculate how much carbon the Amazon forest stores. Researchers concluded that the effect of deforestation could mean the Amazon will start contributing more carbon than it absorbs from the atmosphere.
However, there are still significant gaps in our ability to accurately monitor greenhouse gas levels. Currently, a lot of reporting on GHG emissions is estimated using emissions factors, activity data and reporting data. 
Information gaps in this data result in inaccuracies, biases and omissions from emissions assessments. As such, real-world information and newly developed measurement technologies can help reduce reliance on estimations and provide more accurate emissions calculations.
Greenhouse gases come from myriad sources on our planet. Carbon dioxide is emitted when coal, oil and gas are burned for energy as well as wildfires and soil that is ploughed or disturbed for agriculture. Methane is emitted mainly from livestock, oil and gas wells and pipelines, landfills and wetlands while nitrous oxide comes from farm fields and factories and fluorinated gases leak from cooling equipment.
There are seven categories of GHG emissions in total: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3). These need to be measured at different scales, from smokestack level to a global level. 
This requires varying technologies to identify sources, sinks and fluxes which are then integrated for greater accuracy and consistency. These include analytical field devices and sensors, satellites, drones, balloons and ground-based equipment. 
The Copernicus Atmosphere Monitoring Service (CAMS) is one of the leading institutions monitoring levels of carbon dioxide and methane in the atmosphere. It does so by using instruments on the ground, in the air and onboard satellites. The service also uses computer systems to simulate concentrations of the two greenhouse gases based on its knowledge of the atmosphere, biosphere and reported emissions.
Copernicus is now working with the European Space Agency (ESA) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) to develop new CO2MVS satellites. These will measure concentrations of carbon dioxide and methane in the atmosphere with “unprecedented accuracy and detail” and be able to observe the entire globe in just a few days. It will also allow them to look at individual carbon dioxide and methane sources such as power plants and fossil fuel production sites.
There are also newer satellites that have been developed such as the GHGSat, CarbonMapper, and MethaneSAT with higher resolutions which can monitor emissions plumes from smaller scale sources. Panellist Bram Maasakkers will be talking about the TROPOspheric Monitoring Instrument (TROPOMI) on board the Copernicus Sentinel-5 Precursor satellite which creates daily global maps of atmospheric gases including methane, nitrogen dioxide and sulphur dioxide. 
When countries and companies use a bottom-up approach, it involves measuring two key variables: the rate at which an activity tends to produce GHG emissions and the duration of the activity. 
The problem with this system is that unexpected leaks and other irregular releases of GHGs from things like appliances or pipelines are not accounted for. These so-called fugitive emissions made up 5.3 per cent of global GHG emissions in 2013, according to one study. 
A ‘typical’ amount of leakage is now usually factored into emissions inventories but scientists have found that they are still a considerable underestimation of the problem.
The bottom-up approach has also shown to be far less accurate in developing countries where national statistics for the underlying data are not readily available. 
Furthermore, this system does not typically take into account natural sources and sinks of GHGs, which also drive climate change. This results in uncertainty over how significant different factors are in the increasing levels of GHGs and the effectiveness of mitigation actions. 
The top-down approach, on the other hand, starts with measurements of total atmospheric GHGs in an area and then works backwards to pinpoint the sources and their contribution. This means fugitive emissions are included in the data and their sources can be more easily identified.
However, with this approach, it can be difficult to accurately quantify the contributions of individual sources from total GHG measurements. In addition, variations in pressure, temperature and relative humidity can reduce the accuracy of top-down measurements when sensors are not properly calibrated for the conditions.  
Sample bias is another problem. When top-down measurements are taken at one time and in one location, they may not be representative of emissions occurring at other times and in other parts of an area.  
Tune into our debate on 21 October to hear what our panellists say is the future of accurate global greenhouse gas monitoring. 
Richard Engelen is a member of the Senior Management Team of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Deputy Director of the Copernicus Atmosphere Monitoring Service, which ECMWF operates on behalf of the European Union.
Engelen is a scientific expert in remote sensing and data assimilation of atmospheric composition with a special focus on the carbon cycle. He is (co-)author of around 50 international peer-reviewed publications in the scientific literature as well as many contributions to conference and workshop proceedings.
He is or has been a member of the Science Advisory Boards of several European projects and a member of expert panels for the European Commission as well as of various proposal review committees in the USA and in the Netherlands.
J.D. (Bram) Maasakkers is a scientist at SRON Netherlands Institute for Space Research. His work focuses on better understanding anthropogenic methane and carbon monoxide emissions using observations of atmospheric concentrations from satellites.
Maasakkers was a summer intern at Harvard as part of the Atmospheric Chemistry Modeling Group, which uses advanced atmospheric chemistry models to understand the atmosphere’s chemical composition, how it is changed by human activity, and what that means for life on Earth. He then joined the research group full-time as a PhD candidate in environmental science and engineering in 2013. 
Dr Oksana Tarasova has worked at the World Meteorological Organisation since 2009. She has been a Senior Scientific Officer in the Infrastructure Department since August 2022 working on the development of the Global Greenhouse Gas Monitoring Infrastructure. 
She was the Head of the Atmospheric Environment Research Division in the Science and Innovation Department from 2014 to 2022 and has a background in Physics and a PhD in Atmosphere Physics.  
The main focus of Tarasova’s activities is international cooperation in observations and analysis of atmospheric composition, with specific expertise in the areas of greenhouse gases. She is currently a member of multiple advisory boards and research projects. She is an author and co-author of over 100 publications.
Amir Sokolowski is the Global Director of the Climate Change Team at CDP, a not-for-profit charity that runs the global disclosure system for investors, companies, cities, states and regions to manage their environmental impacts.
His team provides the strategic direction, helping ensure that CDP incentivises ambition and is in line with the latest knowledge and developments on the subject. Sokolowski has 16 years of experience working on the ground, with governments and as part of international negotiations enhancing every element of climate governance. 
He has worked across many countries drafting legislation, verifying REDD+ (Reducing Emissions from Deforestation and Forest Degradation) projects, negotiating institutions around carbon markets and contributing to the Paris Rule Book.  
Sokolowski has an MPhil from the University of Oxford, specialising in environmental law, and a BA in Medieval History from Tel Aviv University.