Future prospects - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 318

11

Future prospects

11.1 THE NEXT ICE AGE (OR LACK THEREOF )

11.1.1 Introduction

The last ice age began to wane about 18,000 years ago. Path E in Figure 10.1
shows that there was a moderate increase in solar input to high northern latitudes
starting about 18 kybp which could be interpreted as contributing to the end of
the last ice age, although this increase in solar input was not as great as it was in
several previous cycles, and these previous increases in solar input did not result in
an interglacial. Solar input to high northern latitudes has been decreasing since
about 11 kybp , but as yet there is no sign of any cooling effect. It remains far
from clear whether and how much changes in solar input to high northern
latitudes induce ice ages and interglacials. However, Stott et al. (2007) found
evidence that the terminations of recent ice ages appear to have originated in the
Southern Hemisphere. Ice age termination is discussed in Section 10.2.3.
Looked at simplistically, Figure 7.1 , for example, might suggest that warm
interglacial periods with temperatures corresponding to the Holocene typically do
not last exceptionally long—perhaps 5,000 to 20,000 years. Since the Holocene has
now been in effect for more than 10,000 years, one may wonder when the next ice
age may begin. The answer may lie in the plethora of conjectures on this topic,
both pro and con. 1
One school of thought is that there is a natural periodicity to the Earth
that goes beyond human influence and, when its time arrives, the next ice age
will occur. Had there not been a significant impact on the Earth's heat balance
and climate by anthropogenic activity (greenhouse gas emissions, production of
atmospheric aerosols, changes in land use, deforestation, water use, urban heat

1 If you insert ''the next ice age'' into Google, you obtain over 100,000 responses.