Methane hydrates: enough to meet all energy needs and last a thousand years or whatever. Not much effort being applied to extract it.
Methane is a much greater greenhouse gas than CO2 and could be dangerous to the planet if a large release were to happen. Here are a few articles explaining the pros and cons of Methane Hydrates as fuel. http://science.howstuffworks.com/environmental/green-tech/energy-production/frozen-fuel.htm
"Recent data suggest that just 1 percent of Earth's methane hydrate deposits could yield enough natural gas to meet America's energy needs for 170,000 years" Let's get some! "...Holocene epoch, about 8,000 years ago. Known as the Storegga Submarine Landslide, the event caused massive amounts of sediments to slide about 497 miles (800 kilometers) down the continental slope...." That's why they call it the Holocene Climate Optimum!
Holocene means 'completely current' or the current warm period after the last glacial period. And Epoch means the 'start'. So that's when the last ice age ended and the current interglacial warm period began. This methane hydrate sounds like the solution to our energy needs for the next century or longer. At least until solar or some other passive method of energy is sufficiently developed. I'm not sure what biproducts burning it produces but I'm sure the environmental nuts will find something seriously wrong with it besides the risk of accidental release.