Himalayan glaciers lost 28% of ice in last 40 years

Change in ice loss in Himalayan glaciers — Ice thickness change (meters per year) at different elevations for 1975-2000 (blue) and 2000-2016 (red)

A new study of ice mass loss in 650 Himalayan glaciers over the past 40 years has revealed accelerating ice loss. The study recent extracted digital elevation models from declassified spy films which were compared with recent ASTER stereo imagery to quantify ice loss for the periods 1975–2000 and 2000–2016. The glaciers included in the study comprising approximately 34% of the total glacierized area in the region, or roughly 55% of the total glacial ice volume. The observed annual mass losses suggest that of the total ice mass present in 1975, about 87% remained in 2000 and 72% remained in 2016. The results also indicate that the average rate of ice loss was twice as rapid in 2000-2016 compared to 1975-2000.

Acceleration of ice loss across the Himalayas over the past 40 years, J. M. Maurer, J. M. Schaefer, S. Rupper and A. Corley, Science Advances 19 Jun 2019: Vol. 5, no. 6, eaav7266 DOI: 10.1126/sciadv.aav7266

From Our Files

Milankovitch cycles Nature December 8 2016

Link between Milankovitch’s theory of orbital forcing and ice ages remains an open question

A seminal book by Milankovitch in 1941 proposed that the sequence of ice ages that has characterized long term changes in the Earth’s climate over the past hundreds of thousands of years was due to changes in the amount of solar radiation reaching the Earth as a result of small variations in the Earth’s orientation and orbit with respect to the sun. Since then research has shown that Milankovitch cycles by themselves do not determine the timing of glacial and interglacial cycles and that we still lack a unified mechanism that links changes in Earth’s orbit to ice ages.

Greenland ice core records reveal periods of rapid warming across globe during last deglaciation

Air bubbles in Greenland ice cores are analyzed to compare changes in Greenland surface temperature and atmospheric methane concentration during a rapid warming event lasting 200 years during the last deglaciation. It is found that changes in Greenland surface temperature and atmospheric methane emissions occurred essentially synchronously indicating that this warming event included the tropics.

Did global warming stop from 1998 to 2012 ?

In 2009 a widely used dataset indicated that the average temperature of the Earth’s surface may have stopped warming, or that it was warming at a lower rate than the long term average. A new analysis shows that the trend for 1998–2012 is indistinguishable from the best estimate of the long trend for 1951–2012.

Evidence of CO2 outgassing from the Southern Ocean early in the last deglaciation

During the last deglaciation atmosphere CO2 concentration rose by about 80 ppm amplifying climate warming. This study of radiocarbon in deep sea corals found that Southern ocean deep water was radiocarbon-depleted throughout the last ice age, but this depletion disappeared between 16,600 and 14,600 years ago consistent with Southern Ocean CO2 outgassing that corresponded to the first pulse of increased atmospheric CO2 early in the deglaciation.