The great retreat

Editor's Notes

1. Ice margins are now receding all over the world. The Little Ice Age was a period from about 1550 to 1850 when the world experienced relatively cooler temperatures compared to the present. Subsequently, until about 1940, glaciers around the world retreated as the climate warmed substantially. Glacial retreat slowed and even reversed temporarily, in many cases, between 1950 and 1980 as a slight global cooling occurred. Since 1980, a significant global warming has led to glacier retreat becoming increasingly rapid and ubiquitous, so much so that some glaciers have disappeared altogether, and the existence of a great number of the remaining glaciers of the world is threatened. This recent period of glacial budget deficits is often referred to as the great retreat.
2. As you fly over Greenland or Antarctica it is difficult to recognize any ablation or wastage at all. But on the margins of these ice caps and, even more so, in Alpine glaciers, the evidence of excessive ice wastage is all too obvious.
3. Fluctuations in the mass of ice on our planet is the norm. It is the acceleration in this recent ice wastage which is causing scientists some concern. The retreat of glaciers since 1850 affects the availability of fresh water for irrigation and domestic use, mountain recreation, animals and plants that depend on glacier-melt, and in the longer term, the level of the oceans.
4. Only 20,000 years ago Scotland was covered by the Devensian ice sheet. This ice wasted back, probably completely, before ice again occupied the western Highlands and reached into the lowlands in what was called the Loch Lomond Readvance which reached its maximum extent around 10,800 years ago.
5. The ice margins retreated to the mountains of Europe, Iceland and Greenland.
6. Arctic sea ice was at a new record low on September 16, 2012 at 3.41 million square kilometers (1.32 million square miles). The new record low was thus 760,000 square kilometers (293,000 square miles) below the previous record minimum extent, which occurred on September 18, 2007. The 2012 value is only half (51%) of the 1979–2000 average extent of arctic sea ice at the September minimum. The six lowest seasonal minimum ice extents in the satellite record have all occurred between 2007 and 2012.