Since 1896, scientists have been puzzling about how much of a
temperature increase on Earth would occur if carbon dioxide in the
atmosphere doubled. This "climate sensitivity number", based on the
doubling of CO2, is predicted to be as low as 3 degrees F. by the few
optimists and as high as 8 degrees F. by the pessimists. Most believe
that the increase will be about 5 degrees F. overall.
As an'overall' average for the entire planet's surface, five degrees may not
seem like much; but, if you account that the ocean covers 70% of the
surface and yields less than a five degree increase, it highlights the
fact that the land temperatures will increase proportionately more (and
the poles will increase the most).
All this long term climate change is based on a doubling of CO2. Note that temperature lags behind
CO2 increases. At the present rate of CO2 increases
and the laggardly human response to correct this, we're looking at
eventual tripling or quadrupling of CO2. No computer model can predict
what will happen then.
http://www.google.com/search?q=co2+increase+temperature+change&source=lnms&tbm=isch&sa=X&ei=GeqjUaCxD8TeqQHw2YDABQ&ved=0CAgQ_AUoAQ&biw=320&bih=416#biv=i%7C2%3Bd%7COeFYHz0vSs0XHM%3A
Chart:
http://www.nytimes.com/2013/05/14/science/what-will-a-doubling-of-carbon-dioxide-mean-for-climate.html
