In this capacity, he was responsible for writing reports on including aviation within the European Union Emission Trading Scheme (2007)[1][2] and an ETS reform (2021).

[4] Between 2000 and 2001, he served on the European Parliament’s Temporary Committee on Human Genetics and Other New Technologies in Modern Medicine.

[12] From 2012 until 2018, Liese was a member of the CDU leadership under the party’s successive chairwomen Angela Merkel (2012-2018) and Annegret Kramp-Karrenbauer (2018).

In similar negotiations following the 2017 federal elections, he was part of the working group on energy, climate protection and the environment, led by Armin Laschet, Georg Nüßlein and Barbara Hendricks.

[17] Ahead of the Christian Democrats’ leadership election in 2018, Liese publicly endorsed Friedrich Merz to succeed Angela Merkel as the party's chair.