Welcome to Episode 6 of the Positive Tipping Points Special! A 7-episode special series on the road to COP30 in Belem, with guest host Liz Courtney.

Sea level isn’t creeping up by accident; it’s obeying physics we’ve understood for a long time. We sit down with Professor Benjamin Horton—one of the world’s leading sea level scientists—to translate complex mechanisms into plain English, connect polar ice to equatorial risk, and show how today’s choices shape tomorrow’s coastlines. From ocean heat swelling the seas to the accelerating melt of Greenland and Antarctica, we walk through the drivers, the uncertainties that matter, and the signals we can already measure from space and on the ground.

The conversation travels from the Vostok ice core—800,000 years of atmosphere trapped in bubbles—to geological snapshots 2.8 million years ago, when CO2 sat near today’s levels, global temperatures ran 3 to 5 degrees warmer, and sea level rose 10 to 20 metres. That deep history frames the present: it tells us what Earth is capable of and why peaking emissions by 2030 is not a slogan but a lifeline. We also get granular about regional and local realities. Gravity changes as ice sheets shrink, pushing more water toward the tropics. Currents stack seas unevenly. Cities on sinking deltas face a double hit from subsidence and storm surge. Risk is layered, and so are the solutions.

Ben lays out three priorities for the next five years: invest in science and monitoring from pole to postcode, accelerate renewables instead of leaning on unproven carbon capture, and build genuine community engagement so warnings turn into action. There’s grounded optimism here too. We spotlight new cooling materials inspired by desert ants that reflect over 90% of sunlight, practical research that helped trigger timely evacuations in Vietnam, and the steady engine of education driving new ideas. We close with a cultural challenge: bring influencers into the fight and pull climate scientists into the rooms where the biggest decisions are made.

Your Hosts:
Dan Leverington
Loreto Gutierrez

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