[3] Likewise, since that year she served as a negotiator for the Spanish delegation in the United Nations Framework Convention on Climate Change and is part of the Intergovernmental Panel on Climate Change (IPCC).

In June 2018, she was appointed Special Advisor to the Cabinet of the Minister of Ecological Transition, Teresa Ribera, where she directed, coordinated and defined the National Integrated Energy and Climate Plan 2021-2030 and the Long-Term Decarbonization Strategy 2050.

[4] The following year, in 2019, Aagesen represented Spain at the 2019 United Nations Climate Change Conference (COP25) held in Madrid.

[5] On 17 January 2020, she was appointed Secretary of State for Energy,[6] the second most important position in Ribera's department.

[7][8][9] In November 2024 Aagesen was announced to become the Third Deputy Prime Minister and Minister for the Ecological Transition and the Demographic Challenge, replacing Teresa Ribera,[10] something already expected by the press and the energy sector who considered her the "natural candidate.