Halldór Thorgeirsson is Senior Director for Intergovernmental Affairs at the UN Climate Change Secretariat in Bonn, Germany. There he oversees substantive, procedural and logistic support by the secretariat to negotiation processes and governance arrangements under the Climate Change Convention, the Kyoto Protocol and the Paris Agreement.

Oversaw the substantive support to the negotiations of the Paris Agreement adopted in December 2015 starting with the adoption of the Durban Platform for Enhanced Action in 2011. This included chairing internal UNFCCC Implementation Coordination Committee and managing a negotiation support and coordination team (the Implementation Strategy Unit). Provided strategic advice to the Executive Office of the UN Secretary General in 2016 on the alignment of the implementation of the Paris Agreement and the 2030 Agenda for Sustainable Development and served as Director of the SG's Climate Change Support Team October-December of 2016.

Directed a programme responsible for the support to the two Kyoto Carbon Market mechanisms (Clean Development Mechanism and Joint Implementation) and to their governing boards and panels.

Lead one of three clusters of programmes within the secretariat consisting of three programmes on 1) adaptation, technology and science; 2) carbon market mechanisms; and 3) compliance under the Kyoto Protocol. Each programme was lead by a coordinator responsible for programme management. Oversaw the support to the Subsidiary Body for Scientific and Technological Advice (SBSTA) and the 2006-2007 “Dialogue on long-term cooperative action to address climate change by enhancing implementation of the Convention”, which lead to the adoption of the Bali Action Plan in 2007.

Directed a programme that maintains the science-policy interface; oversees support to the Subsidiary Body for Scientific and Technological Advice (SBSTA); analyses and synthesizes information on methods relating to greenhouse gas (GHG) inventories, land use, impacts, vulnerability and adaptation; receives GHG inventories from Parties and coordinates annual review of these inventories; maintains information on GHG emissions and removals and trends.

Directed the Office of Sustainable Development and International Affairs responsible for sustainable development policy formulation and international environmental cooperation reporting directly to the Secretary General of the Ministry.Responsibilities included:• Chair of the Subsidiary Body for Scientific Advice under the UNFCCC and Co-chair of negotiations of the land use component of the UNFCCC Marrakech Accords;• Chair of negotiations on the consideration of the IPCC Third Assessment Report in 2001 and of two UNFCCC workshops on the findings of the report;• Alternate member of the Board of the Nordic Environmental Finance Corporation; • Active participation in the negotiation of the Stockholm Convention on Persistent Organic Pollutant;chaired negotiations on chemicals at the UNEP Governing Council in 2002 and 2003 and resident of the first UNEP Preparatory Committee for the Development of a Strategic Approach to International Chemicals Management (SAICM).• Coordination of the development of the National Strategy for Sustainable Development and the National Climate Change Policy both adopted by the Government in 2002;• Representing Iceland at meetings of UNFCCC, UNEP, IPCC, CSD, OSPAR, OECD, Nordic Council of Ministers and the Arctic Council;

Lead the Division of Environmental Sciences including the management of participation in three Nordic research projects (on nitrogen cycling, the impact of elevated carbon dioxide on the carbon balance of trees in situ and on the fluxes of carbon dioxide and water over barley fields in Sweden (NOPEX) and two European projects (on fluxes of carbon and water over forest canopies (EUROFLUX) and on fluxes of methane from Arctic wetlands (CONGAS)). Developed a forest ecology research site in the south of Iceland, advised two Ph.D. students and taught plant physiology at the University of Iceland. Served as a member of the Icelandic Research Council for two three-year terms and represented Iceland in the Management Committee for Environment Research in the third, fourth and fifth European Framework Programmes and in the International Group of Funding Agencies for Global Change Research.