People are running "the dumbest experiment in history" by continuing to burn fossil fuels, Elon Musk said in an interview earlier this year with Wait But Why's Tim Urban.

As Musk explained:

"The greater the change to the chemical composition of the physical, chemical makeup of the oceans and atmosphere [due to increased carbon emissions], the greater the long-term effect will be.

"Given that at some point they'll run out anyway, why run this crazy experiment to see how bad it'll be? We know it's at least some bad, and the overwhelming scientific consensus is that it'll be really bad."

Musk, a renewables entreprenuer who serves as CEO of Tesla and SpaceX and chairman of SolarCity, has clear reasons for saying this, yet it's hard to deny his logic.

Use of fossil fuels like coal, oil, and gas will end either when we run out of them or when we do enough damage to the earth that we have to stop.

If you use data from oil and gas giant BP, at present rates of extraction we'll be out of oil by 2067, natural gas by 2069, and coal by 2121. It's possible that we'll discover more oil trapped in tar sands or deep under the ocean, but it just gets more expensive and riskier to extract. And we'll still run out.

What's more we don't even want to use all the fossil fuels we have. Burning nonrenewable fuels makes the atmosphere warmer, and burning coal is worse than using other energy sources.

If we get to that point, the limiting factor won't be how many years of fossil fuels we have left, it will be how much more atmospheric change the planet can take. Some researchers already think we've reached the point where there's enough carbon in the atmosphere to cause catastrophic impacts to humanity.

That's why video game designer/Iron Man-protagonist Musk (and yes, genius tech entrepreneur) got involved with and became the CEO of the electric car company that became Tesla. Tesla's official mission is "to accelerate the advent of sustainable transport by bringing compelling mass-market electric cars to market as soon as possible."

If Tesla can convince the world that cars can run without oil, that would make a huge difference, as burning oil is responsible for about a third of greenhouse gas emissions, and getting electricity from a power plant through an electrical grid is more efficient than burning gas.

Tesla Model S BlueTeslaAn electric Tesla on the move.

Even in places in the US where coal provides a good proportion of electrical power, electric vehicles are still cleaner than gas-powered cars. But for true sustainability, electricity production needs to change too. In particular, countries need to stop using coal as soon as possible.

Sustainable alternatives include renewables like hydroelectric, wind, solar, and geothermal power. Nuclear power is also far cleaner than any sort of fossil fuel energy source.

Musk's comment about a dangerous experiment echos what scientists have been saying for decades.

In the 1950s, seminal global warming scientist Roger Revelle wrote about our industrial fuel consumption that "Human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future." That line that would go on to be the most quoted statement in history of global warming, according to Daniel Yergin's "The Quest."

It's just that now we're that much further along in that geophysical experiment, and if we don't put the brakes on it soon, we won't know how bad it'll be.

Here's a Wait But Why chart that explains where we are:

fossil fuels timelineWait But Why

Right now, we're just going along using fossil fuels, despite the fact that we know this is a bad idea and it has an endpoint. The sooner we get past that point and move to the next era in energy, the better.