ICOS Curve is an interactive data visualisation tool which shows the change in CO2 concentrations in the atmosphere above Europe over time. The Curve pulls in observation data from 38 ICOS Atmosphere stations in Europe.
Updated daily, the ICOS Curve provides an easy method of seeing greenhouse gas concentrations from across Europe in the same picture.
What can I use the ICOS Curve web application for?
- The ICOS Curve visualises the high-quality and accurate (comparable within 0.1 ppm for CO2) data from 38 ICOS Atmosphere stations in the Northern Hemisphere, showing the growing trend of CO2 concentrations in the atmosphere. You can use the visualisation – with none, one or several stations selected for comparison – in presentations, teaching, scientific and general texts and articles, etc.
- The web application allows you to select stations, the timeframe, and produce a graph that fits your interests.
- The application allows you to compare CO2 concentrations from stations geographically near you and compare with European and global averages or see how different parts of Europe differ from each other.
- You can browse more ICOS greenhouse gas measurement data at the ICOS Carbon Portal. You can freely download hourly data from every ICOS station: atmosphere, ecosystem and ocean measurements.
Where is the data from, who makes it?
ICOS provides standardised and open data from close to 180 measurement stations across Europe. The stations observe greenhouse gas concentrations in the atmosphere as well as carbon fluxes between the atmosphere, the land surface and the oceans. This ICOS curve visualises the daily median of the continuous observations from the 38 ICOS Atmosphere stations in the Northern Hemisphere. The measurements from the stations are standardised, following a rigorous protocol, and thus the data from different locations can be compared in a reliable way. The stations are hosted and run by top universities and research institutions in Europe. ICOS measurements are highly accurate and precise, and the data is openly available for anyone to use via ICOS Carbon Portal. The ICOS Curve data is updated daily using ICOS's Near Real Time data and Fast Track Data. The ICOS Atmosphere measurements comply with the World Meteorological Organisation (WMO) measurement guidelines and compatibility goals for greenhouse gases. ICOS is funded, at the moment, by 16 European member countries.
Why do we need European CO2 curve and data, when we already have global trends and data by NOAA and WMO?
The ICOS Curve complements the global carbon curves from, for example, the US National Ocean and Atmosphere Administration (NOAA), or the World Meteorological Organization (WMO). This redundancy of observations is crucial for informing the world about climate change and its underlying reasons. However, the ICOS curve also has some significant additional features due to the specific geographical and political landscape of Europe.
Europe is a densely populated and highly varied area, and the ICOS stations reach from the subtropics of the Canary Islands to Svalbard in the Arctic and from megacities like Paris and Rome to alpine heights and remote forested areas in Scandinavia. The type of the landscape, its capacity to uptake carbon, and the proximity of stations to populated areas producing emissions all affect the regional CO2 concentrations measured at a specific ICOS tower. Due to this variety, the European CO2 concentrations vary much more between measurement locations and at different times than at the more remote stations from the global network. The data from a dense network of atmospheric observations over Europe enables scientists to track valuable information on GHG sources and sinks from the differences between stations. The generated scientific knowledge can support and improve national inventories by providing additional scientific verification.
The ICOS Curve is an important addition to global efforts on informing about the atmospheric composition of GHG. Since it’s updated daily, it provides timely information relevant for climate action and decision making.
Moreover, ICOS station network and data increase the resilience of systematic observation of CO2 concentrations and their trends. The measurements are funded by 16 European countries being members of ICOS. For this reason, the network ensures continuity and transparency in climate monitoring.
ICOS has 47 Atmosphere stations – why are not all of them part of the Curve, only 38?
While the whole ICOS network contains 47 Atmosphere stations (as of 2025), some of them are not yet certified (labelled) according to the ICOS standards. The ICOS Curve only uses data from the stations in the Northern Hemisphere which have been certified as ICOS Atmosphere stations. The non-certified stations cannot yet present multi-annual time-series. The ICOS certification process is rigorous and requires months of work from the station crew, supported by the ICOS Thematic Centres.
Many stations have been operational before being integrated into ICOS. During the pre-ICOS period they were not using ICOS standards because those were taken into use when ICOS came into life 10 years ago. However, these pre-ICOS data are very valuable for the historical assessment of the current situation. Therefore, they were reanalysed (“as close to ICOS as possible”) and added to the ICOS Curve data set. For this reason, the ICOS curve reaches back to the 1970s and can be well connected to the Mauna Loa observations, the Keeling Curve.