It is work that requires both acute scientific knowledge and great diplomatic skill: monitoring the global environment for evidence of nuclear weapons tests, and working to persuade a last few nations to ratify a treaty that would ban such tests.

At a time of geopolitical tension between many of the world's nuclear powers, the work might lend itself to pessimism. But for Lassina Zerbo, the executive secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), optimism is essential to the role ­– optimism, tempered by realism.

"We cannot decide just by words that we want to get nuclear weapons off the planet," Zerbo told an audience in Trieste, Italy, at the annual TWAS Paolo Budinich Science Diplomacy Lecture. "In the context of arms control and non-proliferation and nuclear disarmament, what is the easiest common denominator that we can achieve today, that we can grasp...and create the conditions of trust needed to build a world without nuclear weapons?"

The answer, he said, is the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which would prohibit all nuclear explosions worldwide. In his lecture, and in a filmed interview with TWAS, Zerbo said that the Treaty, though not legally binding, has nonetheless had a powerful impact through its system that monitors the globe for evidence of nuclear explosions. It is now a topic of global attention, and it plays a more visible role in formal and informal non-proliferation meetings. With the technology and diplomatic framework largely in place, he added, the current obstacles to final entry into force are now only political.

The Treaty was first adopted by the United Nations General Assembly in 1996. Since then, 184 nations have signed it and 168 have ratified it. For final approval, the treaty must be ratified by 44 nations that were included in Treaty negotiations between 1994 and 1996; at the time, all had nuclear power reactors or research reactors. Today, eight of those countries have not given final approval to the Treaty: India, Pakistan and the Democratic People's Republic of Korea (North Korea), all of which have nuclear weapons, have not signed the CTBT; China, Egypt, Iran, Israel and the United States have signed it, but not ratified it.

"So you have 90% to 95% percent of the planet saying 'no' and 'never' to nuclear testing, and only eight states remain to join the overall majority," Zerbo said. "Our job is to build trust and confidence for the others to be comfortable with the signature and ratification of the CTBT."

Zerbo delivered the Budinich Lecture 14 June at the Abdus Salam International Centre for Theoretical Physics (ICTP) in Trieste, Italy. The event was moderated by TWAS Executive Director Romain Murenzi.

A remarkable journey

Zerbo's professional journey has been remarkable: He grew up in Bobo-Dioulasso, the second largest city in Burkina Faso, one of the world's 47 Least Developed Countries; it has no nuclear research or power facilities. As a youth Zerbo wanted to be a lawyer, but he was directed by the government to study science, and he became a geophysicist. After working in the mining industry at locations across the world, he wanted to shift his focus to science for healthy communities in Africa, and to law and policy. 

That led him to the CTBTO. In 2004 he was selected to head the Organisation's International Data Centre, which processes and analyses monitoring data on possible nuclear tests. The centre is a core component of the International Monitoring System, a network of 337 facilities in 92 countries with unparalleled sensitivity to evidence of nuclear test explosions through seismological, infrasound and hydro-acoustic analysis, as well as by detecting the presence of radionuclides and noble gases in the atmosphere, even at minuscule levels. Data are shared with all countries that have signed the Treaty.

Over 2,000 nuclear test explosions were conducted globally between 1945 and 1996 – but only ten since 1996. In the 21st century, only North Korea has conducted nuclear test explosions.

Zerbo was elected as executive secretary of the Vienna-based Treaty organisation in 2013. The American Association for the Advancement of Science (AAAS), which works closely with TWAS in the field of science diplomacy, honoured him with its 2018 Award for Science Diplomacy for “using his scientific expertise and leadership ability to tackle difficult challenges and promote world peace”.

In his TWAS lecture, Zerbo described the technological power of the monitoring system: About 80% of the CTBTO's USD130 million annual budget goes toward verification and related science. But that's also an investment in diplomacy. For example, he acknowledged that some countries might consider pulling out of the Treaty, but remain because they want access to data from the monitoring system. Not only is the data useful for detecting nuclear explosions, but also for events such as volcanic eruptions, earthquakes, tsunamis and nuclear accidents.

In 2014, then-US Secretary of State John Kerry called the CBTBO's International Monitoring System "'one of the great accomplishments of the modern world'," Zerbo recalled. "Kerry said that not because of the science, but because there is hardly a better place than this where science can serve policy and meet the aspirations of diplomacy in a multilateral setting."

Science and diplomacy: the long view

For Zerbo, that reflects a central challenge for science diplomacy: Use all means to maintain dialogue with the eight holdout nations, and through patient diplomacy encourage them toward final ratification. And in the process, discourage further nuclear testing worldwide.

Zerbo has used his science diplomacy skills to promote the Treaty, even while the current international security context is not always conducive to that goal. He has established constructive relations with the US government and with China, which for the first time certified several of the International Monitoring System stations on their territory and started sending data to the CTBTO. He established relations with Iran, Egypt and Israel and resolved many challenges related to the Treaty in those regions. 

After almost two decades working in leading positions in the field of disarmament and non-proliferation, he knows that all stakeholders should be involved in the process. Challenges are inevitable, of course, and they require him to balance optimism, pragmatism and innovation. And he emphasised that the challenges are often not scientific or diplomatic, but political.

North Korea has tested six nuclear devices, but as its programme emerged there was a collective international disbelief that the small, isolated country had this capacity, Zerbo explained. Data from the CTBTO's nuclear-test-monitoring system was crucial in proving each successive advance in country's capacity ­– and in alerting the world to potential risk.

However, it seemed essential for the CTBTO to have channels of communication to North Korea. In advance of a 2016 meeting to mark the 20th anniversary of the Treaty's first signatures, he proposed to invite the North Koreans. Then, before a separate conference in Russia, he proposed to speak informally with North Koreans who would be there. Some advised against it, citing the political risks of news photos that might come from such a meeting.

"I said, 'Ok, but look: What is our job? Our job is to get them on board. Let's try it!' So of course I talked to them," he recalled. "This is the kind of challenge we're dealing with."

Or consider the longstanding tension between Pakistan and India, both nuclear states. Zerbo sent a CTBTO delegation to Islamabad in May 2018 for unprecedented meetings with high-level Pakistani government leaders. Pakistan has demonstrated support for the Treaty, and even though it hasn't signed, it has observer status in the Treaty's governing body. Further, it has proposed to join with India in a bi-lateral moratorium on nuclear testing.

Pakistan’s approach towards the strengthening of a regional non-prolif & disarmament includes a bilateral moratorium w/ India. Pakistan observership to #CTBT is a constructive step– Confidence building in South-East Asia while reiterating commitment 2 #nuclearTestFree world.”

— Lassina Zerbo (@SinaZerbo) June 21, 2018

India, however, opposes the moratorium. While that may suggest inflexibility or overconfidence on the part of its negotiators, Zerbo said, politics is the real obstacle, and he believes that any solution should address the concerns of both parties altogether and at the same time. But the necessary condition is an open dialogue for confidence-building, otherwise any unilateral proposal from one party will continue to be received with suspicion by the other one.

A role for young scientists

In Zerbo's view, these political divides may reflect a generational orientation: the conflicts of the late 20th century are difficult to escape for the generation shaped by those conflicts. Therefore he imagines that young people may be well-equipped to work from the middle to bring all sides together.

He has been inspired by young Pakistanis and young Indians at CTBTO events. "They sit together, they do simulations," he said. "They're into talking and into working... The Pakistan and India that they want are not the ones they are given today. They are the ones making a difference. It's the next generation – they will make the difference for all of us."

To take advantage of the passion of students and early-career scientists, he has formed the CTBTO Youth Group for those who are focusing their work on peace and security and who want to promote the aims of the Treaty.

Zerbo also praised the work of TWAS and ICTP, both of which work to educate and train early-career scientists from the developing world. "I'm certainly looking forward to working more closely with you," he told the audience. "We can search together for opportunities for cooperation, and in this way improve the things that you do and improve what we do. I'll come back to Trieste – I know we can do great things together."

The annual TWAS lecture is named for Paolo Budinich, an influential Italian physicist and a scientific partner of Abdus Salam, the Pakistani Nobel laureate. The two developed and launched ICTP in 1964, in Trieste, Italy. Budinich also played a significant role in Salam's work to found TWAS and he helped to develop other national and international scientific institutions in Trieste. He died in 2013.

Edward W. Lempinen