* Offsets slowing energy efficiency and renewables investment. : LONDON, May 14 (Reuters) - Global energy investment steadied at nearly $1.85 trillion last year after three years of decline, with slowing energy efficiency and renewables spending offset by increases in oil, gas and coal, the International Energy Agency said. Upstream oil and gas spending in 2018 rose by nearly 4% year on year to $477 billion because of a rise in oil prices and a shift to shale gas and projects with shorter construction periods, according to the IEA’s 2019 World Energy Investment report.