here is an image of a chart al gore used in the video, 'an inconvenient truth'. it shows 650,000 years of temperature and co2 concentrations as determined from the antartic ice cores.
on the left the scale shows the co2 concetration. in 650,000 years it has never been over 300.
on the right the lowest yellow dot is the current levels of co2 concentration. although the scale does not repeat onto the right side i have added a green line to show the 300 mark. as you can see the current level is well over that historic limit at about 450.
the higher yellow dot is the projected, according to generally accepted scientific data, of the co2 concentrations in less than 50 years from now. it is literally off the chart and there is no precedent for anything remotely like it in 650,000 years. that period of time spans, as i recall, 5 or 6 complete ice ages. and you thought there only been one...
additionally, for those who think scientists are making all this up, or who just don't trust anybody...
a scientist is a specialist in a particular field. he will have a 'doctorate' from a university.
a physician, that you might go to for diagnosis and treatment of cancer, will also be known as a doctor. his specialty is the human body. while doctors do make mistakes, i would prefer to get my second opinion from a physician trained and practicing in san francisco than one trained and practicing in tijuana. especially if the one in tijuana says he can cure me with herbs, spices, and a special brew stirred with the blackend feathers of a chicken born under the full moon.
if all the doctors i go to in the states say i have cancer, then at some point i am simply going to have to believe them. or place my trust in herbal enemas in tijuana.