Lack of financing is one of the biggest barriers to moving away from fossil fuels, officials and experts said at a global conference Monday in Colombia aimed at speeding up the shift from fossil fuels to cleaner energy. The gathering in the Caribbean city of Santa Marta comes as governments face mounting pressure to move beyond climate pledges and begin outlining how to phase out oil, gas and coal, the main drivers of global warming. While U.N. climate talks have acknowledged the need for a transition, they have produced few concrete mechanisms, leaving countries and regions to grapple with the economic challenges largely on their own.