So, you're sitting in a car driving 100mph towards a wall. The car's safety system warns you, saying 'collision ahead, break NOW'. You're thinking "hey, no problem, no car since 1880 has driven into this wall, it must be a hallucination - I'm keeping my foot down baby".
Analogies used here:
The car - Energy policies
The safety system - Climate models
The warning - Result of these models
You driving into a wall - Laymen's opinions about why these models don't apply.
To put it differently:
1) There's a time delay of several decades between putting out the CO2 and temperature rise. What we're feeling now is the effects of energy policies in the 60ies and 70ies.
2) Since the 70ies our CO2 output has risen considerably, mainly due to emerging markets.
3) Most of this 0.8 degree warming you're talking about has occurred in the last 30 years.
Well - would you bet on the wall being an illusion, or would you rather brake just in case?