At the beginning of this year Bulgaria, considered as one of the poorest countries in the European Union, became the latest to officially join the eurozone. Bulgaria’s legal tender since 1881 had been the lev, but since the mid-1990s it had been pegged to other European currencies, first to the German deutschmark and now to the euro. But it remains to be seen if the country’s economic policy can take advantage of the opportunities that joining the single currency can afford, in terms of trade and economic development.

Monetary unions are not a new concept, some like the Scandinavian monetary union date back to the 19th Century, involving Denmark, Sweden and Norway. It established a fixed exchange rate system based on the gold standard, whilst member countries still had their own currencies before it was gradually dissolved from the outbreak of World War One onwards.

Today, the biggest monetary union is the eurozone, used by around 358 million people across 21 European Union countries. It has one monetary authority for all the members and a standardised currency and coinage.

And now the Economic Community of West African States, known as ECOWAS is actively planning a monetary union with a common currency called the eco and pegged to the euro. The ambition is for greater economic sovereignty and regional economic integration.

But with the US dollar as the world’s dominant global reserve currency, even though it’s not part of a global monetary union, is there an argument for one currency across all borders and if so, what should it be?

So, on The Inquiry this week we’re asking, ‘What’s the future for monetary unions?’

Contributors: Assoc Prof Ralitsa Simeonova-Ganeva, Sofia University St Kliment Ohridski, Bulgaria Prof Barry Eichengreen, University of California, Berkeley, USA Prof Mohamed Ben Omar Ndiaye, Cheikh Anta Diop University, Senegal Dr Judy Shelton, Senior Fellow, The Independent Institute, California, USA

Presenter: Charmaine Cozier Producers: Daniel Rosney and Jill Collins Researcher: Evie Yabsley Editor: Tom Bigwood Technical producer: Toby James Production management: Phoebe Lomas and Liam Morrey

(Photo: Euro and US dollar banknotes. Credit: BBC/Corbis Royalty Free)

The Himalayan glaciers are melting more rapidly as global temperatures rise, raising concerns about the future of ecosystems and communities across the Himalayan mountain range. Glaciers store more than two thirds of the world’s freshwater and help regulate global temperatures by reflecting the sun’s rays.

Across South Asia, melting ice is contributing to the formation of unstable glacial lakes and increasing the risks of floods, droughts and avalanches. The Himalayas are a vital source of water for millions of people, supporting agriculture, energy production and livelihoods from tourism.

Experts warn that continued glacier loss could have significant consequences for people living in the region and the mountainous ecosystem, but what can be done to respond to these changes?

Contributors: Pasang Yangjee Sherpa, assistant professor at the University of British Columbia, Canada Pam Pearson, director and founder of the International Cryosphere Climate Initiative, US Matthias Huss, glaciologist and senior scientist at the Swiss Federal Institute of Technology Zurich, Switzerland Alton Byers, faculty research scientist at the Institute of Arctic and Alpine Research at the University of Colorado, US

Presenter: Tanya Beckett Producer: Matt Toulson Researchers: Evie Yabsley and Amelia Cox Editor: Tom Bigwood Technical Producer: Mitch Goodall Production Management: Phoebe Lomas and Liam Morrey

(Photo: Trekkers walk to Everest Base Camp in Nepal. Credit: Kriangkrai Thitimakorn/Getty Images)

The recent election result in Hungary has been seen as a welcome relief within the European Union.

The bloc of 27 nations has, at times, felt frustrated with the country for blocking what the other 26 members have agreed to do, especially regarding financial support for Ukraine.

Now the EU has been able to push through a loan to Ukraine of more than US$100bn, and some observers believe the union’s turbulent years are behind it.

As it marks 10 years since the United Kingdom voted to leave, and with Montenegro expected to soon join, this week, what is the future of the European Union?’

Contributors: Dr Monika Sus, professor at the Polish Academy of Sciences and at the Robert Schuman Centre of the European University Institute in Florence, Italy Michael Geary, professor of European history at the Norwegian University of Science and Technology, Norway Catherine E. de Vries, author How Europe Survives: The Adaptability and Resilience of a Continent in Peril, vice dean of the school for politics, economics and global affairs at IE University of Madrid, Spain Dr Andi Hoxhaj, lecturer in law and director of the European law and LLM programme at King's College, London, UK

Presenter: Daniel Rosney Producer: Jill Collins Researcher: Evie Yabsley Editor: Tom Bigwood Technical Producer: James Bradshaw Production Management: Phoebe Lomas and Liam Morrey

(Photo: European Union flags. Credit: Reuters)

Global oil markets have been affected by the US Israel war with Iran, leading to higher jet fuel prices and increased attention on supply risks.

But how serious is the situation? While some experts point to tightening supply chains and regional bottlenecks, others say there is no clear evidence so far of immediate shortages.

Even so, the refining and distribution of jet fuel remains a potential vulnerability, as disruption can have notable impacts even when crude oil itself is available. With air travel crucial to trade and tourism, the resilience of fuel supply is a growing concern for economies and travellers. Can alternative suppliers and fuel sources help limit the impact of future disruption?

Contributors: Zach Aman, professor of chemical engineering, the University of Western Australia Ahmed Mehdi, senior fellow at the Oxford Institute for Energy Studies and managing director at Renaissance Energy Advisors, UK Dumebi Oluwole, lead economist at Stears, Nigeria Li Qiao, professor of aeronautics and astronautics, Purdue University, US

Presenter: Rajan Datar Producer: Matt Toulson Researcher: Evie Yabsley Editor: Tom Bigwood Technical producer: Mitch Goodall

(Photo: Airline worker attaching fuel pipe to plane to refuel. Credit: Justin Sullivan/Getty Images)