Access
This article is part of Nature's premium content.
Published online 16 April 2008 |
452,
798-802
(2008)
| doi:10.1038/452798a
Corrected online: 16 April 2008
News Feature
Climate change: Losing Greenland
Is the Arctic's biggest ice sheet in irreversible meltdown? And would we know if it were? Alexandra Witze reports.
When people talk about catastrophic climate change, there's a fair chance that Greenland is on their mind. If they use the term 'tipping point', then it is pretty much a sure thing.
To read this story in full you will need to login or make a payment (see right).
Comments
Reader comments are usually moderated after posting. If you find something offensive or inappropriate, you can speed this process by clicking 'Report this comment' (or, if that doesn't work for you, email webadmin@nature.com). For more controversial topics, we reserve the right to moderate before comments are published.
Why does Nature publish emotion-laden headlines like these - "Climate change: Losing Greenland" and "Is the Arctic's biggest ice sheet in irreversible meltdown?" Of course, Earth's climate is changing. It has always been changing. Interactions between the Sun and the ever-changing orbital positions of the planets cause the Sun to be jerked, like a yo-yo on a string, about the center of mass of the solar system. This action produces solar cycles and continuous changes in Earth's climate. - Oliver K. Manuel REFERENCES: 1. P. D. Jose, "Sun's motion and sunspots", Astronomy Journal 70 (1965) 193-200; 2. R. W. Fairbridge and J. H. Shirley, "Prolonged minima and the 179 year cycle of the solar inertial motion," Solar Physics 110 (1987) 191-220; 3. J. Shirley, "Axial rotation, orbital revolution, and solar spin-orbit coupling," Monthly Notices of the Royal Astronomical Society 368 (2006) 280-282.
Readers without access to a technical library may want to use the following links to a few of many studies which show that changes in solar activity and in Earth's climate are caused by interactions between the Sun and the orbital positions of the planets, especially the more massive planets. - Oliver K. Manuel http://www.griffith.edu.au/conference/ics2007/pdf/ICS176.pdf http://www.lavoisier.com.au/papers/Conf2007/Alexander-etal-2007.pdf http://bourabai.narod.ru/landscheidt/publications.htm
I thing all scientist working on climate change are aware of the implications of solar activity and astronomical orbit changes. It is nothing new and in many studies the effect are also considered (mostly for the longer term changes). But as for studies like this the effect, compared to other factors, are small there are not explicetly mentioned.
What I didn't see in the article is what happened to the Greenland ice cap in the period 1935-1950. The retraction of the breakup point of the largest glacier at Ilulisat (Jacobshavn) was much faster in that period than recently. See the NASA web site at: http://www.nasa.gov/vision/earth/lookingatearth/jakobshavn.html and specifically the long-term retreat (1850-2003): http://www.nasa.gov/101948main_calvingstill_1850_2003.tiff (7 MB .tiff file!). The retreat in the period 1929-1953 (24 years) is as fast as in the period 1953-2003 (50 years). Moreover, summer temperatures around Greenland still are higher in the 1935-1950 period than recently, see: http://www.ferdinand-engelbeen.be/klimaat/greenland_temp.html Even in the 1950's there was a rapid thinning of the glacier of about 70 meters, comparable to today, see the last paragraph of: http://www.agu.org/meetings/fm05/fm05-sessions/fm05_C41A.html As most of the CO2 increase was after 1945, this points to natural causes of regional temperature and ice retreat variations, not directly related to greenhouse gases. If the regional climate changes again, this may lead to a reversal of the ice melting...
Interesting to note that a map dating to the pre-1400s shows Greenland as an island completely surrounded by water. This was at the peak of the "medieval warm period" - undoubtedly caused by the carbon dioxide expelled by the visit of Eric The Red. I could never understand why he called it "Greenland"... unless melting had somehow happened before and today's decline is simply a cyclical continuation of a perfectly normal process.
I have one comment on the Eemian sea level. You stated: "Temperatures in Greenland were roughly 5 °C higher during the Eemian than they are today. Yet sea level was only one or two metres higher, and every ice core that has ever been drilled deep enough on the island has included some ice from the Eemian." As far as I know most peer viewed articles about the global sea level during Eemian conclude with at least three meters, and probably more than five meters, higher than at present.
After reading this article I was very surprised there was no mention, not even a passing statement, of the recent finding of the huge geothermal component to melting found in the NE sector of Greenland, especially with so many of the interviews from scientist at the University which made this discovery. A wealth of information continues to stream in confirming the importance of a natural driver of global warming. Some other examples are: volcanic activity under the active melt regions of Antarctica; inner core jerks associated with the “Great Pacific Climate Change� in the early 1970’s; seismic links to El Nino established in the late 1980’s; CO2 lagging the heat peaks in ice core data by over 600 years and lagging five years in modern geophysical proxies; many known climatic links to sun spot activity and orbital parameters which have not been explained by solar light intensity variations; CO2 liquid bubbles the size of basketballs ascending from deep ocean trenches documented by Pacific Marine Environmental Labs, earthquake swarms in the Mediterranean associated with sea surface temperature (SST) anomalies and ocean circulation reversals during the 2003 European heat wave which caused over a thousand deaths; earthquake swarms Nov. 2002 in Alaska preceding huge snow melts causing the Iditarod dog sled race to move further north in 2003; melting of the Artic ice cap directly over the underlying mid-ocean ridge warming confirmed by deep ocean profiles; SST anomalies reflecting the underlying ridge configurations in the eastern Pacific and the Guaymas basin rift during 1998 El Nino; deep double layered thermoclines associated with warm sterile (hydrothermal) waters off the coast of Peru found in deep ocean profiles during the 1982 El Nino; simultaneous worldwide squid and marine mammal deaths and beachings in the late summer 2002. Just to name a few. The greenhouses gasers seem to be barking up the wrong proverbial tree.
As programme manager of the long-term Danish governmental "Programme for Monitoring of the Greenland Ice Sheet (PROMICE)" I have to object to the statement in the article that [...there is no systematic, long-term, broadly based monitoring of the sort needed to produce a truly comprehensive account of what is happening with the ice sheet.] The Danish government initiated this rather comprehensive programme in 2006 deploying automatic stations in every region of the Greenland ice sheet margin to measure melt rates directly. The programme also aims at determining the ice lost by iceberg calving through a combination of satellite analysis and airborne laser and radar surveys. Additionally, the local ice caps and glaciers surrounding the ice sheet are being inventoried and changes recorded, starting with aerial photos from the 1980s. We collaborate or coordinate with a number of the researchers mentioned in the above article (and many more) in order to maximize the efforts. In other words, we are conducting a long-term, systematic monitoring effort to provide a comprehensive account of what is happening with the Greenland ice sheet.