Climate-relevant Trace Gases

Various short-lived and long-lived trace gases play a central role for the Earth's climate. The long-lived greenhouse gas methane (CH4), on which a special focus is placed in this matrix group, is in second place with regard to the anthropogenic greenhouse effect. Particularly critical with regard to CH4 are the not well understood changes of its growth rate in recent decades. The sources of the third most important anthropogenic greenhouse gas, nitrous oxide (N2O), are also discussed in the matrix group.

In addition, there are many trace gases with much shorter lifetimes that are also on the agenda of this matrix group. Examples of these are ozone, nitrogen oxides, carbon monoxide, sulphur dioxide and non-methane hydrocarbons. These have lifetimes of between hours, days and several weeks.

Both CH4 and short-lived trace gases influence the distribution and concentration of the hydroxyl radical (OH), which determines the oxidising capacity of the atmosphere. The oxidation capacity is in turn decisive for the degradation of CH4 and other trace substances and in this way influences both the air quality at ground level and the chemical formation of water vapour in the stratosphere.

Molecular hydrogen (H2) has no direct radiative effect. However, it has the potential to influence other climate-relevant trace gases through its influence on OH and is therefore also considered in this matrix group.

The aim of this matrix group is to bundle the various methodical capacities of the institute and use the synergies to deepen our understanding on the topic of climate-relevant trace substances. Embedded in the DLR programmes Space, Aeronautics and Transportation, the focus is on the following scientific questions:

  • How do these properties and processes change in a changing climate and what feedbacks exist with regard to climate-relevant trace gases?
  • What role do CH4, short-lived trace gases and H2 play in the oxidising capacity of the atmosphere?
  • How large are the sources and sinks and how large is the variability of the mixing ratio of atmospheric methane and nitrous oxide?
  • What are the direct and indirect climate effects of short-lived trace gases such as nitrogen oxides and ozone?
  • What are promising mitigation options when dealing with air quality and climate mitigation targets simultaneously?

These research questions are tackled with a broad spectrum of methods. The following research tools are available for this purpose:

  • Aircraft-based active remote sensing with the CHARM-F LIDAR
  • Airborne in-situ measurements of methane and other trace gases
  • Global and regional numerical modelling to describe atmospheric processes
  • Inverse modelling to estimate emissions from observational data
  • Utilisation of remote sensing data (e.g. satellite missions Sentinel-5P, GOSAT, or from ground-based stations such as TCCON)
Spectrum of methods including measurements and modelling of short-lived trace gases
The broad spectrum of methods includes measurements and modelling on different temporal and spatial scales. This allows a comprehensive analysis of the influence of short-lived trace gases on the atmosphere. The blue arrows indicate the transition from the currently used models to the next generation model ICON/MESSy.
DLR Cessna Caravan during CoMet campaign
View into the DLR Cessna Caravan targeting on the quantification of methane emissions with CHARM-F and in-situ methods in the Upper Silesian coal mining region during the CoMet mission.