We have Methane hydrates bubbling up off the coast of California. water off Florida has risen 2 degrees. in the past 100 years or so. CO2 levels are rising because of man. It is known that the Earth travels around the sun in an elliptical orbit that varies in shape, with time from nearly circular to distinctly elliptical. This, combined with the fact that the sun is not the center of the earth's orbit, causes the distance from the Earth to the sun to vary. For instance, the current annual variation of this distance is between 147 million kilometers and 152 million kilometers. The distances can be as much as 142 million kilometers for a minimum and 156 million kilometers for a maximum. The amount of solar energy received by the earth is greatest when the earth is nearest the sun. This phenomenon is called the eccentricity of the orbit and has a 100,000 year cycle. This factor, combined with the tilt of the earth's axis, is believed to cause seasonal climate changes which are out of phase in each hemisphere. For instance, northern hemisphere winters are currently milder and summers cooler than normal. The opposite situation, colder winters and hotter summers, is now occurring in the southern hemisphere.
We are should be in a cooling off cycle in Earth's history, but the CO2 levels are rising faster than the Earth can clear it up. Something will happen in this tug of war.