Earth was even cooler than previously thought 6,000 years ago

The problem comes in reconciling data which suggest an early warm period during the Holocene era 12,000 years ago followed by global cooling with climate models strongly suggest a steady rise in global average temperatures throughout the past.

Skeptics have pointed to the mystery as evidence of a period of a warmer climate before human influences.

“Our reconstruction shows that the first half of the Holocene was colder than in industrial times due to the cooling effects of remnant ice sheets from the previous glacial period – contrary to previous reconstructions of global temperatures,” explained Dr. Samantha Bova, a paleoclimate researcher at Rutgers University.

Bova and her team based their findings on core samples taken from the ocean floor. Using fossils of tiny single-celled organisms that lived at the ocean surface, scientists are able to reconstruct temperature histories going back 128 centuries.

“Late Holocene warming was indeed caused by the increase in greenhouse gases, as predicted by climate models, and that eliminates any doubts about the key role of carbon dioxide in global warming.” added Bova.

The new data also suggests a different explanation for melting ice during the early Holocene period.

Clues found in the ocean floor from the early Holocene era line up with a period when Earth's orbit was much more oval-shaped. This along with increased tilt in the Earth's axis made for warmer summers and colder winters, but not necessarily an increase in annual temperatures.

The bottom line says Bova, "we can see that humans are really having an impact on the world that we live in. We know from the geologic record that the rate of warming today is faster than any point in at least the last 800,000 years"