Quaternary Glaciation - Next Glacial Period

Next Glacial Period

In popular culture, there is often reference to "the next ice age". Technically, since the Earth is already in an ice age at present, this usually refers to the next glacial period (because the Earth is currently in an interglacial period).

The next glacial seemed to be rapidly approaching, when paleoclimatologists met in 1972 to discuss this issue (a period of so-called global cooling). The previous interglacial periods seemed to have lasted about 10,000 years each. Assuming that the present interglacial period would be just as long, they concluded, "it is likely that the present-day warm epoch will terminate relatively soon if man does not intervene." Since 1972, our understanding of the climate system has improved. It is known that not all interglacial periods are of the same length and that solar heating varies in a non-linear fashion forced by the Milankovitch orbital cycles (see Causes section above). At the same time, it is also known that greenhouse gases are increasing in concentration with each passing year. Based on the variations in solar heating and on the amount of CO₂ in the atmosphere, some calculations of future temperatures have been made. According to these estimates, the interglacial period the Earth is in now may persist for another 50,000 years if CO₂ levels increase to 750 parts per million (ppm) (the present atmospheric concentration of CO₂ is about 393 ppm by volume, but is rising rapidly as humans continue to burn fossil fuels.) If CO₂ drops instead to 210 ppm, then the next glacial period may only be 15,000 years away.

Moreover, studies of seafloor sediments and ice cores from glaciers around the world, namely Greenland, indicate that climatic change is not smooth. Studies of isotopic composition of the ice cores indicate the change from warm to frigid temperatures can occur in a decade or two. In addition, the ice cores show that an ice age is not uniformly cold, nor are interglacial periods uniformly warm (see also stadial). Analysis of ice cores of the entire thickness of the Greenland glacier shows that climate over the last 250,000 years has changed frequently and abruptly. The present interglacial period (the last 10,000 to 15,000 years) has been fairly stable and warm, but the previous one was interrupted by numerous frigid spells lasting hundreds of years. If the previous period was more typical than the present one, the period of stable climate in which humans flourished—inventing agriculture and thus civilization—may have been possible only because of a highly unusual period of stable temperature.