25 Years of CTBTO

The XXII Edoardo Amaldi Conference (Rome, April 2022).

I would like to thank the Accademia Nazionale dei Lincei for inviting me to speak at this XXII Edoardo Amaldi Conference on Nuclear Risks and Arms Control, Problems and Progress in the Time of Pandemics and War. The theme of this year’s conference is timely.

We are at a pivotal moment in history. The situation in Ukraine continues to be of grave concern. We have heard of nuclear weapons being put on high alert. Fears that the conflict will further escalate and expand are all too real. These events have put our efforts on nuclear non-proliferation and disarmament into a most sobering context and caused me to reflect on the poignant statement of The Elders, a group of world leaders of great renown. They said: “As long as nuclear weapons remain in existence, it is inevitable that they will someday be used, whether by design, accident or miscalculation.”

Today, this message is especially resonant, and it is one we should all heed. The road to nuclear disarmament may be long and winding, but I believe that there are simple steps that we can take now that will lead us to a world free from nuclear weapons. One essential step that will bring us ever closer to the world we all aspire to is the CTBT, which will provide a legally binding and verifiable prohibition on nuclear testing.

This keynote address is a journey of 25 years through the history of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO),¹ including the scientific and technical framework behind its verification regime, starting with an overview of the CTBT.

The CTBT is an important achievement as one can discern by looking at the number of nuclear tests conducted each year between 1945 and the actual signature date of the CTBT. Between 1945 and 1996 more than 2000 nuclear tests were carried out at over 60 locations throughout the world. These had a serious impact on human health and the environment. During this time, the average explosive yield of nuclear tests per year was equivalent to nearly 1,000 Hiroshima sized bombs. Since the CTBT opened for signature in 1996, less than a dozen tests have been conducted by only three States. Only one State has conducted several nuclear tests in this century. This proves to be a remarkable accomplishment that demonstrates the powerful contribution that the Treaty has made to international peace and security.

The journey towards the CTBT was not an easy path. More than four decades passed between the first call for a nuclear testing “standstill” agreement by Indian Prime Minister Jawaharlal Nehru in 1954 and the adoption of the Treaty in 1996. In the current international security context, I believe it useful to reflect upon the experience of the Cuban missile crisis of 1962. This event prompted world leaders to recognize the need to address the inherent risks of nuclear weapons. One such proposal was in fact a comprehensive ban on nuclear testing.

While a CTBT proved too difficult at that time, the Partial Test Ban Treaty (PTBT) was adopted in 1963 banning nuclear testing in the atmosphere, underwater, and in space. It did not, however, prohibit underground nuclear tests and did not include a verification mechanism. Concerns grew about the proliferation of nuclear weapons throughout the 1960’s, which resulted in the negotiation of the 1968 Treaty on the Non-Proliferation of Nuclear Weapons (NPT). While some States wanted to include a comprehensive ban on nuclear testing in the NPT, differing views prevented such an outcome. However, the determination to achieve the discontinuance of all nuclear tests is mentioned in its preamble.

There are three pillars of the NPT: Non-proliferation, Disarmament, and Peaceful use of nuclear energy. Article VI of the NPT obligates all States to take effective measures leading to the cessation of the nuclear arms race and disarmament. The duration of the NPT, which initially was prescribed for 25 years, was extended indefinitely by States Parties during the 1995 NPT Review and Extension Conference. One of the crucial elements in a package of agreements that led to the indefinite extension of the NPT was that a CTBT be negotiated no later than 1996.

Three intense years of negotiations took place at the Conference on Disarmament, which were preceded by a decades-long effort by a multilateral Group of Scientific Experts to lay the foundation of a verification regime. The CTBT was finally adopted by the General Assembly on 10 September 1996 and opened for signature on 24 September 1996. We should today be grateful for the result of this long process and efforts which put in place an effective, non-discriminatory verifiable measure of nuclear disarmament and non-proliferation. The CTBT has established a near universal global norm against nuclear testing, and its entry into force will constitute an essential step towards a world free of nuclear weapons. Summarizing the basic obligations of the CTBT (Article I, Paragraph I):

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.

There are now 186 States Signatories² to the CTBT, out of which 177 have ratified. However, the Treaty will enter into force only when all States listed in Annex 2 of the Treaty ratify it. States listed in Annex 2 are 44 States that possessed nuclear power or research reactors at the time of the final stage of negotiation of the Treaty at the Conference on Disarmament (CD) in 1996. As of today, there are eight remaining Annex 2 States that still must join the CTBT. China, Egypt, Iran, Israel and the US have already signed but not yet ratified the Treaty while the DPRK, India and Pakistan have neither signed nor ratified.

The success of the CTBT is in large part a reflection of the successful build-up of the Treaty’s verification regime. The CTBT verification regime has three pillars: the International Monitoring System (IMS), the International Data Centre (IDC) and On-Site Inspections (OSI).

The IMS, when completed, will consist of 337 facilities worldwide to monitor the planet for any sign of a nuclear explosion. More than 90 percent of these 337 facilities are in place and sending data to the IDC. The IDC at the CTBTO headquarters in Vienna receives the data in near real-time from IMS stations. The data are processed and distributed to CTBT States Signatories in both raw and analysed form. The OSI pillar is being built up to be ready for when the CTBT enters into force. This will enable the dispatching of inspectors to an inspection area of a suspected nuclear explosion to conduct inspection activities and use inspection techniques. Thus, the sole purpose of an on-site inspection will be to clarify whether a nuclear weapons test explosion or any other nuclear explosion has been carried out in violation of the Treaty. Any decision to launch an OSI and decision whether any non-compliance with the Treaty has occurred will be made by the members of a future CTBTO Executive Council, which will serve as the executive organ of the CTBTO. The verification regime also encompasses a Consultation and Clarification process and Confidence-Building Measures.

The IMS employs four technologies—seismic, hydroacoustic, infrasound and radionuclide. Currently, 153 out of 170 seismic stations are certified (certified means a station was installed and meets specific technical requirements). All 11 hydroacoustic stations have been certified. 53 out of 60 infrasound stations are certified and 72 out of the 80 Radionuclide Particulate Monitoring Stations are certified. Of these 80 stations, 40 will have an additional capability for detection of Noble Gas Isotopes, which is an indicator particularly useful for detecting underground nuclear tests. 25 of the Noble Gas monitoring systems have already been certified. The IMS also comprises 16 Radionuclide Laboratories, of which 14 are certified. Italy hosts one seismic station in Valguarnera (Sicily) and Radionuclide Laboratory number 10 at the Italian National Inspectorate for Nuclear Safety and Radiation Protection (ISIN) in Rome.

The IMS collects data from each of the four types of monitoring stations and provides a near real-time picture of the entire globe. The data is processed at the IDC and goes through an automated analysis, after which alerts would be triggered with respective staff at all hours of the day and night should a suspicious event occur.

I continue to be amazed by how effective the CTBT verification regime is at detecting nuclear tests. All one must do is look at the response of the system during each of the six announced DPRK nuclear tests (Fig. 2.1). Within hours of the event occurring, the IDC processes the data and makes initial information available about the location, magnitude, and time of these Treaty-relevant events to Member States. Over the years, the number of stations detecting these events went from 22 to 134 as the IMS build-up progressed, and the body wave magnitude computed by the IDC increased from 4.08 to 6.07 for these events (Table 2.1). It’s noteworthy that the size of the area within which the event is located with 90% confidence, called the confidence ellipse, obtained with less than half of the IMS network in place at the time of the first DPRK nuclear test in 2006, which was estimated to be less than one kiloton, was only 880 km². The size of this area is well within the 1000 km² Treaty requirements for launching an OSI. In 2017, with the IMS nearly 90% complete, the confidence ellipse improved to 109 km² (Fig. 2.2). Numerous small seismic events, tectonic in nature, and known to have originated near the DPRK nuclear test site at Punggye-ri after the 2017 test have been detected and localized by the IMS and have continued until recently (as of June 2022).

Fig. 2.1

Vertical seismic motion produced by the six DPRK nuclear tests, recorded more than 5000 km from the test site by the IMS Auxiliary Seismic station in Aktyubinsk (Kazakhstan). The curves are all plotted on the same scale. The time axis indicates time relative to the origin in hours:minutes:seconds

Table 2.1 Dates, seismic body wave magnitude, number of IMS stations detecting and 90% confidence ellipse parameters for each of the six DPRK tests

Fig. 2.2

Graphical representation of the six DPRK test detection confidence ellipses

The extraordinary sensitivity of the sensors deployed at the more than 300 IMS stations strategically located all around the globe allows us to achieve a detection capability far better than expected from the original design. But what I find particularly exciting about the verification regime is the vast potential for the data to be used in civil and scientific applications. It is so encouraging that the CTBTO has agreements for providing reliable real-time IMS data to tsunami warning centres in 19 States Signatories. The tsunami related agreement with Italy was signed in 2019. I expect that more and more countries will take advantage of this opportunity to benefit from additional uses of our monitoring data.

Our seismic technology contributes to studies on earthquakes and volcanic eruptions, seismic hazard assessments, studies on the internal structure of the earth, the melting of glaciers, and tsunami warning systems.

Hydroacoustic technology contributes to the monitoring and location of underwater volcanic events and undersea earthquakes, some of which trigger tsunamis. Another exciting area where hydroacoustic technology can be useful is monitoring changes in sea temperature and signs of global warming through variation in acoustic signal travel time (ocean acoustic thermometry studies). There is also extensive research being undertaken on ocean processes and marine life.³ I was particularly intrigued by the discovery of a new population of pygmy blue whales by researchers studying the acoustic signals collected by our hydroacoustic network.,^{4 5}

Hydroacoustic data from IMS Hydrophone stations were also used to assist the Argentine Authorities when the submarine ARA San Juan was lost on 15th November 2017.⁶ Tragically, all crew members lost their lives. Upon request from the Argentine Authorities, the CTBTO provided assistance, analysing its data in search of any signal which could be potentially related to the disappearance of the submarine. An impulsive hydroacoustic signal was detected by two IMS hydrophone stations, the location calculated for this event was not far from where the submarine had its last contact with the base. The time of the event determined from the acoustic signal travel time was also not long after the submarine had its last known communication. The two stations which detected this signal were located about 6,000 km and 7,700 km from the event, respectively. After a long search operation, on 17th November 2018, Argentine Authorities confirmed that the San Juan was found on the seafloor at 900 m depth, at less than 20 km distance from the event location estimated from CTBTO hydroacoustic data.

Infrasound technology contributes to the detection of volcanic eruptions which can have significant effects on civil aviation. It can also be used to support atmospheric and meteorological studies, tracking of storms, detection of meteors disintegrating in the atmosphere, and studies of signals generated by avalanches, among others.

Many of you will recall in January this year the explosive eruption of the Hunga Tonga-Hunga Ha’apai volcano in Tonga. This catastrophic explosive eruption and tsunami generated infrasound, seismic and hydroacoustic signals that were recorded by the IMS.⁷ What you might not be aware of, is that this eruption was the largest event ever detected by the IMS infrasound network. As the pressure waves created by this violent interaction of magma and seawater spread throughout the atmosphere, our infrasound stations, all around the world, began to light up one by one. Before long, every one of the 53 certified infrasound stations recorded signals from the event. But this is not the most impressive part. The IMS infrasound stations recorded pressure waves generated by this event that propagated around the globe for at least the first four days after the eruption. This breath-taking example of the sensitivity of the system testifies to both its incredible nuclear test detection capability, as well as its enormous value for civil and scientific applications.

The CTBTO Radionuclide network is also an incredible resource. The CTBTO is a member of the Inter-Agency Committee on Radiological and Nuclear Emergencies (IACRNE), a network that facilitates and coordinates cooperation between relevant international organizations to respond effectively in the event of an emergency such as a nuclear accident in which radioactive materials are released⁸, our radionuclide network is always ready to support in the response to radiological emergencies, such as was the case in the aftermath of the Fukushima (Japan) nuclear accident in 2011. Furthermore, data from radionuclide stations can help to increase understanding of the long-range exchange of pollutants, monitoring the stratosphere/troposphere exchange and validating global climate models, and determining the quantity of dust and pollens present over a certain period of time.

One aspect of Radionuclide technology-related scientific applications that I find especially noteworthy is the study of the Beryllium-7 (⁷Be) Isotope in relation to meteorological phenomena.⁹ This research has contributed to understanding long-term global change in the atmosphere, and even predicting the onset of monsoons with a lead-time of about 30 days.¹⁰ To briefly explain this latter example: this isotope is generated in the upper layer of the atmosphere, and “seeps” through adjacent atmospheric circulation cells to reach the earth’s surface where it can be measured. When the circulation of these large atmospheric cells changes, this causes the ⁷Be concentration measured at two IMS Radionuclide Particulate Stations in Russia & Australia to change. Detection of these changes makes it possible to predict the onset of the monsoon in India with about 30 days lead-time ahead of meteorological forecasts.

To conclude this technical part of the keynote, let me give you a quick impression of the data flow: data collected from stations are transferred by satellite to Vienna. From there, the information is also passed on to all authorized users in the National Data Centres. In Vienna, the data are analysed by the IDC processing data-stream and reviewed by teams of human analysts. Automatically generated and human-reviewed event bulletins are produced and distributed to Member States. Italy has a National Data Centre (NDC) for waveforms located in a facility of the Italian Institute of Geophysics and Volcanology (INGV) in Rome, and one NDC for Radionuclide data at the National Agency for New Technologies, Energy and Sustainable Development (ENEA) in Bologna. There are currently more than 1700 authorized users in 143 countries. Data from our sensors are also available free of charge for scientific research to scientists and researchers via the virtual Data Exploitation Centre (vDEC).¹¹

The examples provided here highlight the additional value of the verification regime beyond the core mission of nuclear test monitoring. Be it tsunami early warning, contributing to earthquake detection or climate change research, the range of applications of these data is astonishing. I believe we are only scratching the surface on how these data can be utilized for the benefit of humanity.

To conclude on a high-note: let us have a look at where the CTBT is at after 25 years. There is near-universal adherence to the CTBT’s prohibition on nuclear explosions. The norm against nuclear testing established by the CTBT is strong, but until the Treaty enters into force and is universal, the risks of nuclear testing will persist. Every ratification counts and I believe that everyone has a role to play. The 25th anniversary year of the Treaty is a time for us to engage and create momentum towards universalization to put an end to nuclear testing by anyone, anywhere, for all time. We are undertaking strategic and multi-tracked outreach to advance the goal of universalization and I have set a target for us to achieve at least five additional ratifications by the end of the anniversary year this September.

Thank you.