BRITISH Prime Minister Boris Johnson has called for wealthy countries to meet a pledge to spend $100 billion a year to tackle climate change as he prepares to host a United Nations summit starting at the end of October. Johnson and U.N. Secretary-General António Guterres will hold a roundtable of world leaders on Monday to get rich countries to deliver on the unmet pledge, made in 2009. "Richer nations have reaped the benefits of untrammelled pollution for generations, often at the expense of developing countries," Johnson said in a statement. "As those countries now try to grow their economies in…