Here's the situation

We burn a lot of fossil fuel

Global fossil carbon emission by fuel type, 1800–2007

Which is increasing the amount of CO2 in the atmosphere

CO2 is a greenhouse gas, so the increase is raising the global average temperature

Meanwhile the global population is increasing

The demand for oil is rising

Oil is becoming more expensive at the moment

Causing investment in more difficult to reach oil and alternative energy like biofuels

U.S. energy legislation requires that 4.9 billion bushels of corn [4]--46% of a projected harvest of 10.8 billion bushels [1]--be used to produce ethanol for fuel. This mandate diverts corn from food and feed production, driving up prices faster and further than they might have otherwise. Despite claims that ethanol as a "renewable fuel" might help with energy independence, the total amount of energy obtained from ethanol is only 1% of American energy consumption [5], and the amount of fossil fuel energy needed to grow the corn and convert it to ethanol is at least 3/4 of the ethanol energy yield [6].

http://necsi.edu/research/social/foodprices/briefing/

The grain diverted to produce ethanol means less food, which raises global food prices.

The rising cost of oil increases food prices, since it is required to produce and transport food.

Global warming increases the likelihood of droughts, reducing the amount of grain produced and further increasing global food prices.

Rising food prices increase social unrest

Food prices (black line) and food riots and the Arab Spring (red lines).

Global warming is causing Arctic ice to melt faster than worst case scenarios modelled by sceintists

As the Arctic melts and more open ocean is exposed, it becomes easier to drill for oil there, allowing us to increase global oil production. Interesting times ahead.