The Partial Test Ban Treaty from 1963, which banned nuclear tests in the atmosphere, underwater and in space, and the Threshold Test Ban Treaty from 1974, which limited the yield of underground tests to 150 kilotons, represented significant steps towards achievement of the CTBT.

Since World War 2, more than 2000 nuclear tests have been carried out at different locations all over the world.

The Partial Test Ban Treaty from 1963, which banned nuclear tests in the atmosphere, underwater and in space, and the Threshold Test Ban Treaty from 1974, which limited the yield of underground tests to 150 kilotons, represented significant steps towards achievement of the CTBT.

The CTBT was negotiated in the Conference on Disarmament in Geneva during 1994-1996 and adopted by the UN General Assembly on 10 September 1996. As of July 2016, the CTBT has been signed by 183 states and ratified by 164 of these. The CTBT will enter into force when it has been ratified by 44 states named in the Treaty. Of these 44 states, 36 have ratified the Treaty.

The CTBT bans all nuclear explosions in all environments. The treaty's verification regime consists of the following elements:

  • An International Monitoring System (IMS) with an International Data Centre (IDC)
  • Provisions for consultation and clarification
  • On-site inspections
  • Confidence-building measures

The IMS comprises altogether 321 stations for seismological monitoring, hydroacoustic monitoring, infrasound monitoring and radionuclide monitoring. The radionuclide stations are supported by 16 radionuclide laboratories in the analysis of samples. The global distribution of these 337 facilities is shown in the map.

Data from IMS stations are transmitted to the IDC using a purpose-built global communications infrastructure. The IDC provides States Signatories with results from its analysis of data from the IMS stations.

A process of consultation and clarification

If a situation occurs in which concern is expressed as to the nature of an event (e. g., a suspicion of a nuclear test), a process of consultation and clarification should be entered into to clarify and resolve any matter that caused the concern. If the concern persists after this process, a decision can be made to conduct an inspection at the site of the event that caused the concern. Such on-site inspections will be very intrusive, as they will apply a range of measurements using a variety of geophysical and other technologies to clarify what might have happened.

The CTBTO

The verification regime of the CTBT is being established by the Preparatory Commission for the Comprehensive Test-Ban-Treaty Organization (CTBTO). The CTBTO took up work in Vienna, Austria in 1997, and is composed of policy-making organs for representatives of the States Signatories, and a Provisional Technical Secretariat (PTS) with approximately 260 employees. The budget of the CTBTO for 2016 is approximately $ 130 million. Activities of the CTBTO are funded through annual dues paid by the States Signatories.

As of 2016, the IMS is nearing 90 % completion. The IMS and the IDC are being operated largely in line with operational procedures that will apply after entry into force (EIF) of the CTBT. On-site inspections can only be conducted after EIF of the Treaty.

The map at the top of this article, shows a world map of the International Monitoring System of the CTBT.