Ireland has experienced an event unprecedented in recorded history: a category four extreme marine heatwave in our waters. Oceans play a crucial but often underappreciated role in regulating our climate, so how strong a warning signal is this? What could the impact be on marine life? And how does dust from the Sahara desert somehow factor in? We're joined by Lauren Boland, reporter with The Journal and author of our climate newsletter Temperature Check, and Dr Gerard McCarthy, oceanographer working with Maynooth University's ICARUS climate unit.The Explainer is brought to you by The Journal. Providing open access to valuable journalism in Ireland has been the aim of The Journal for a decade. You can contribute to ensure we can keep questioning, investigating, debunking, explaining and informing at www.thejournal.ie/contribute/