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Has the loss from Greenland’s vast ice sheet reached a tipping point? According to glaciologist Michalea King, the rate at which its ice flows into the sea stepped up about 15 years ago. The process of glacial retreat is outpacing the accumulation snow and ice in Greenland’s interior and the loss of Greenland’s ice to the Ocean is set to continue for many years to come.

An international study of past climate changes during the last ice age reveals how fast changes to weather patterns and climate states can reverberate around the world. During the last ice age, when temperatures rose suddenly in Greenland a series of changes to the climate in Europe and the monsoons in Asia and South America occurred almost simultaneously - within decades of each other. Climate scientists Eric Wolff and Ellen Corrick have discovered this through studies of stalagmites from caves around the world. It’s a demonstration of how rapidly and dramatically the Earth’s atmospheric system can change when it’s perturbed.

Was the hottest temperature ever on Earth recorded last weekend? A weather station in Death Valley in California recorded a temperature of 54.4 degrees C. Roland Pease discusses the controversy with extreme weather historian Christopher Burt.

Andrea Dupree of Harvard-Smithsonian Center for Astrophysics reveals the latest on the giant star Betelgeuse which to everyone’s amazement dimmed dramatically at the beginning of the year. At the time some people wondered whether it was about to explode as a supernova but Andrea’s new findings suggest an event at the star which is almost as extraordinary.

If you’re one of the millions of people who used lockdown to try something new like baking sourdough bread, you may well be wondering what’s happening chemically inside your loaf, especially if the end result keeps changing. Well, you’re not alone. Listeners Soheil and Sean are both keen bakers but want to know more about the thing that makes bread rise: yeast. What is yeast? Where does it come from and can you catch it? And how hard is it to ‘make’ yourself? Soon after lockdown took effect, commercial supplies of the stuff disappeared from supermarket shelves across the globe.

The shortage also affected brewers the world over. A big fan of yeast in most of its forms, Marnie Chesterton took on the challenge of creating her own. She talks to the brewers who hunt rare strains to create the perfect beer, and hears from the biologist who says these amazing microbes, used for thousands of years, could be used to make food production more sustainable. And she discovers how this simple ingredient could be instrumental in the fight against climate change.

(Image: Masses of ice break off from the edge of a glacier. Credit: Press Association)