Diplomatic tensions over global warming are expected to be a major focus at the G20 summit in Brazil this week, as negotiators at U.N. talks in Azerbaijan struggle to reach an agreement on climate finance. The G20 leaders, who hold the purse strings for climate finance, are being urged to take the lead in addressing the issue. However, discussions at the G20 summit have been snagged on the issue of expanding the base of contributors to include richer developing nations. The success of the ongoing COP29 summit and the next U.N. climate summit, COP30, hosted in Brazil next year, depends on a breakthrough on climate finance.