All the evidence indicates that most long-term climate change occurs in sudden jumps rather than incremental changes. Most of the labelled events are referred to in the text. (DIAGRAM ENCLOSED) Fig.2: The Intra-Eemian cold event, seen from various records that span the Eemian Interglacial.
Introduction Until a few decades ago it was generally thought that all large-scale global and regional climate changes occurred gradually over a timescale of many centuries or millennia, scarcely perceptible during a human lifetime.
The tendency of climate to change relatively suddenly has been one of the most suprising outcomes of the study of earth history, specifically the last 150,000 years (e.g., Taylor et al., 1993). M., 1992: Continuous 500,000-year climate record from vein calcite in Devil's Hole, Nevada, Science, 258, 255-260.
new redating testament - Dating climatic episodes of the holocene
Detailed analysis of terrestrial and marine records of climate change will, however, be necessary before we can say confidently on what timescale these events occurred; they almost certainly did not take longer than a few centuries.
Various mechanisms, involving changes in ocean circulation, changes in atmospheric concentrations of greenhouse gases or haze particles, and changes in snow and ice cover, have been invoked to explain these sudden regional and global transitions. 1997: Millenial-scale climatic oscillations during the last interglaciation in central China. Table 1 (Ages in calender years after Bond et al., 1997 for H0- H3; after Bond et al., 1993 for H4- H6).
We do not know whether such changes could occur in the near future as a result of human effects on climate. A., 1997: Paleoclimatic variability inferred from the spectral analysis of Greenland and Antarctic ice core data. Moseley, eds., Seel House Press, Liverpool, UK, 137-152 Zhisheng A. Timing of major Heinrich events during the last 130,000 years YD or H0 12.2 ka (calendar age) H1 16.8 H2 24.1 H3 30.1 H4 35.9 H5 50.0 H6 66.0 YD: Younger Dryas H: Heinrich event Table 2 .
Phenomena such as the Younger Dryas and Heinrich events might only occur in a 'glacial' world with much larger ice sheets and more extensive sea ice cover. Journal of Geophysical Research, 102, 26,441-26, 453. H., 1963: Pleistocene stratigraphy in the Netherlands, based on changes in vegetation and climate, Ned. Mijnbouwkundig Genootschap, Verhandelingen, Geologische Serie, 21-2, 173-196 Zagwijn, W. The time scale of the last 130,000 years since the start of the Eemian warm period. (1987) in the first column, after Imbrie et al 1984 in the second column.
However, a major sudden cold event did probably occur under global climate conditions similar to those of the present, during the Eemian interglacial, around 122,000 years ago. C., 1997: Duration and structure of the past four interglaciations. Woillard, G., 1978: Grande Pile peat bog: a continuous pollen record for the last 140,000 years. Woillard and Mook, 1982: REFERENCE Nature Wright H. jr 1993: Environmental determinism in Near Eastern Prehistory. H., 1975: Variations in climate as shown by pollen analysis, especially in the lower Pleistocene of Europe. [ ] Event Age (ka) last deglaciation (event 2.0), termination i: 12,050 yr  glacial maximim (event 2.2): 17,850 yr  boundary stage 2/3 (event 3.0): 24,110 yrs  boundary stage 3/4 (event 4.0): 58,960 yrs  boundary stage 4/5 (event 5.0): 73,910 years  event 5.1: 79,250 kyr  event 5.2: 90.950 kyr  event 5.3: 99,380 kyr  event 5.4: 110.790 kyr  event 5.5: 123,820 kyr .
Less intensive, but significant rapid climate changes also occurred during the present (Holocene) interglacial, with cold and dry phases occurring on a 1500-year cycle, and with climate transitions on a decade-to-century timescale. boundary stage 5/6 9event 6.0, termination ii): 129,840 yrs  Note: Stage 5 is defined as an interglacial stage that contains 3 negative events (i.e., warm), labeled 5.1, 5.3, and 5.5; and two positive events - cold - labeled 5.2 and 5.4. In the past few centuries, smaller transitions (such as the ending of the Little Ice Age at about 1650 AD) probably occurred over only a few decades at most. this numbering tends to supersede the 5a through 5 e names. Fig.1: A time course of events during the Quaternary and late Tertiary. by Jonathan Adams (1.), Mark Maslin (2.) & Ellen Thomas (3.) (1.) MS 6335, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA (2.) Environmental Change Research Centre, Department of Geography, University College London, 26 Bedford Way, London, WC1H 0AP, UK (3.) Center for the Study of Global Change, Department of Geology and Geophysics, Yale University, PO Box 208109, New Haven, Connecticut 06520-8109, USA and Department of Earth and Environmental Sciences, Wesleyan University, 265 Church Street, Middletown CT 06459-0139, USA.Abstract The time span of the past few million years has been punctuated by many rapid climate transitions, most of them on time scales of centuries to decades or even less.The most detailed information is available for the Younger Dryas-to-Holocene stepwise change around 11,500 years ago, which seems to have occurred over a few decades.The speed of this change is probably representative of similar but less well-studied climate transitions during the last few hundred thousand years.