Former US vice-president Al Gore has called upon Americans to abandon their dependence on fossil fuels.The Nobel laureate and author of climate change warning book An Inconvenient Truth has urged the US to switch completely to renewable energy by 2018 in order to tackle climate change and alleviate economic crises.Mr Gore claims that the aim is affordable and achievable, according to the BBC, and states that there is no sense in the US borrowing money from China in order to burn oil imported from the Middle East."The answer is to end our reliance on carbon-based fuels," he said in a speech in Washington."When you connect the dots, it turns out that the real solutions to the climate crisis are the very same measures needed to renew our economy and escape the trap of ever-rising energy prices."An Inconvenient Truth was made into a documentary in order to highlight the threat of global warming and to encourage governments across the world to act by presenting scientific evidence and a vision of the consequences of climate change.