Three of the world’s top five miners will need to step up asset sales in the second half of this year to meet a $14-billion full-year target as they race to cut debt, with a recent rally in commodities prices seen as short-lived. The world’s biggest miners predicted doom and gloom for 2016 six months ago when they booked their worst earnings in more than a decade, slashed dividends and put an array of copper, coal, iron ore and other assets on the block.