The CTBT is a multilateral treaty that bans nuclear weapons test explosions, for either civilian or military purposes. Adopted by the United Nations General Assembly in 1996, the CTBT seeks to halt the development of nuclear weapons and foster global disarmament. The Treaty sets up a global monitoring system to detect nuclear tests and provides a framework for on-site inspections.

The CTBT traces its origins to the Partial Nuclear Test Ban Treaty (PTBT), signed in 1963. The PTBT emerged from growing concerns about hydrogen bombs and nuclear fallout. Although the PTBT was initially intended as a comprehensive test ban, many states, including the USSR, objected to its proposed verification methods. Despite these objections, the PTBT’s implementation led to a significant decrease in atmospheric radioactive particles and set the stage for the CTBT years later. The PTBT was also cited in the formation of the NPT.

Towards the end of the Cold War, several states began to reevaluate the prospect of a comprehensive test ban. After an amendment conference for the PTBT, negotiations for the CTBT began in 1993. The CTBT was then adopted by over two-thirds of the United Nations General Assembly. While 185 states have signed and 174 have ratified the CTBT, it has not yet entered into force because eight specific states have not ratified it. The CTBT represents a crucial step towards achieving a nuclear-free world.

Obligations

The CTBT contains two obligations as specified under Article 1. Those include:

1. Each State Party undertakes not to carry out any nuclear weapon test explosion or any other nuclear explosion, and to prohibit and prevent any such nuclear explosion at any place under its jurisdiction or control.
2. Each State Party undertakes, furthermore, to refrain from causing, encouraging, or in any way participating in the carrying out of any nuclear weapon test explosion or any other nuclear explosion.

Verification

Essentially, states have a duty to respect the prohibition of nuclear weapons test explosions, and seek out methods of preventing further incidents. As such, the CTBT is often seen as a corollary to other disarmament-adjacent efforts, including the TPNW or general fissile-material restriction treaties.

A core pillar of the CTBT are its verification and monitoring measures. These measures include a global network of seismic, hydroacoustic, infrasound, and radionuclide stations to detect nuclear explosions. Additionally, the treaty provides for on-site inspections to investigate suspicious events and mandates the use of satellite and other remote sensing technologies. This robust verification regime aims to detect and deter any nuclear testing by member states.

The Preparatory Commission for the CTBT, headquartered in Vienna, strives to advance the adoption of the CTBT and prepare a global verification regime for when the treaty enters into force. As it is an interim organization, the preparatory commission will form into the CTBTO, contingent on eight key states ratifying the treaty. Those states include China, North Korea, Egypt, India, Israel, Iran, Pakistan, Russia, and the United States. Upon these states’ ratification of the CTBT, the treaty will enter into force.

Since the CTBT opened for signature in 1996, three countries–India, Pakistan, and North Korea– have carried out nuclear weapons tests. The CTBTO Preparatory Commission had successfully detected all of those test explosions. While the CTBT has not yet entered into force, it has successfully advanced the cause of nuclear disarmament.