Lord Stern, the climate economist, yesterday urged governments to raise their spending on green energy in economic stimulus packages and to combat carbon dioxide emissions, saying the decision could save billions of dollars in coming years. Governments have been wary of taking measures, such as emissions trading or carbon taxes, that would combat climate change but increase the price of energy when the economy was descending into gloom. "My view is that when hydrocarbon prices are falling, that makes it easier to do this," he said. He and three co-authors of the Stern review of climate change - a landmark 2006 publication that found that to tackle global warming would cost less than inaction - published a paper yesterday arguing governments must ensure a "green" focus to attempts to put the global economy back on track. They said the economic stimulus packages in preparation worldwide would only lead to a greater economic crisis if they failed to concentrate funds and investment on low-carbon growth. A global investment of $400bn (