It’s the sun, dammit!
I’ve just finished watching The Great Global Warming Swindle - a Channel 4 documentary that basically states that something we’ve begun taking for granted, is really resting on shaky scientific grounds.
Key arguments: CO2 in the atmosphere lags behind temperature changes by about 800 years. It’s the old "correlation does not equal causation" again - there might indeed be causation between CO2 and temperature, it’s just the other way around.
The sun, that gigantic energetic nuclear furnace in the sky, is what’s driving Earth’s atmosphere: 
Thus, it’s really not surprising that we’re seeing the temperature and CO2 rise at the moment, since it’s about 800 years since the Medieval Maximum. (They have actually been rising since the late 18th century) "The sun is driving climate change, CO2 is irrelevant" - Dr Piers Corbyn