"Evolution of the Southern Annular Mode during the past millennium," by N. J. Abram et al., Nature Clim. Change (2014); doi:10.1038/nclimate2235

Nature Climate Change (11 May 2014); doi:10.1038/nclimate2235

Evolution of the Southern Annular Mode during the past millennium

• Nerilie J. Abram,
• Robert Mulvaney,
• Françoise Vimeux,
• Steven J. Phipps,
• John Turner and 
• Matthew H. England

Abstract

The Southern Annular Mode (SAM) is the primary pattern of climate variability in the Southern Hemisphere^1,2, influencing latitudinal rainfall distribution and temperatures from the subtropics to Antarctica. The positive summer trend in the SAM over recent decades is widely attributed to stratospheric ozone depletion²; however, the brevity of observational records from Antarctica¹—one of the core zones that defines SAM variability—limits our understanding of long-term SAM behaviour. Here we reconstruct annual mean changes in the SAM since AD 1000 using, for the first time, proxy records that encompass the full mid-latitude to polar domain across the Drake Passage sector. We find that the SAM has undergone a progressive shift towards its positive phase since the 15th century, causing cooling of the main Antarctic continent at the same time that the Antarctic Peninsula has warmed. The positive trend in the SAM since ~AD 1940 is reproduced by multimodel climate simulations forced with rising greenhouse gas levels and later ozone depletion, and the long-term average SAM index is now at its highest level for at least the past 1,000 years. Reconstructed SAM trends before the 20th century are more prominent than those in radiative-forcing climate experiments and may be associated with a teleconnected response to tropical Pacific climate. Our findings imply that predictions of further greenhouse-driven increases in the SAM over the coming century³ also need to account for the possibility of opposing effects from tropical Pacific climate changes.

At a glance

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Link:  http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2235.html

Awesome cool! Michael Ashley at the South Pole! Week 5 of the Antarctic Diaries!

This stuff is so cool!  Who knew?


The Antarctic Diaries. Week Five

It’s hard to ignore Antarctica’s natural beauty, especially when ice halos come out to play. Michael Ashley

Professor Michael Ashley is currently in Antarctica to deploy a telescope to one of the most remote locations on Earth – a place known as Ridge A, some 850 km from the South Pole.

This is the fifth instalment in Professor Ashley’s Antarctica Diaries. To read the previous instalments, follow the links at the bottom of this article.

January 9 – Airdrop, or not

An “airdrop” is where an aircraft flies over and, rather than landing, drops cargo using parachutes. This isn’t all that useful during summertime, where it is easier just to land an LC-130 on the ice. But during winter (when it’s not possible to land due to low ground temperatures which freeze the aircraft’s hydraulics) an airdrop can be the only way of getting urgent cargo such as medical supplies to the Pole.

For the past week, a C-17 aircraft has been waiting at Christchurch for the weather to be good enough for an airdrop. The C-17 will fly non-stop to the Pole, drop its cargo, and then head back to Christchurch.

Early this morning, after several false starts, the C-17 started its long journey south, and just after breakfast a group of 50 of us waited about 500 metres from the station to witness the airdrop. By all accounts it can be quite spectacular.

Much, much more at this link, and it just keeps getting more and more interesting as you keep reading, no kidding!  Do you know what the SPUD experiment is, for example?  The Holy Grail of cosmology...!

http://theconversation.edu.au/the-antarctica-diaries-week-five-5002

Andrew Glikson: Antarctic blues and the Australian drought

This is a repeat -- but it is such a nice one!

Antarctic blues and the Australian drought

Andrew GliksonEarth and paleo-climate scientist
Australian National University

The Antarctic ice sheet has not always been there.

The ice began to form about 34 million years ago, by the late Eocene, when the Antarctic continent (Fig. 1) became isolated through the opening of the Drake Passage between the Antarctic peninsula and southern tip of South America, restricting access of warm currents, and when global carbon dioxide levels decreased to below 450 parts per million CO2, decreasing the mean temperature of Earth by near -6 °C [1].



Fig. 1. The Antarctic continent from space

The current global rise in atmospheric CO2 levels to 387 ppm (over 400 ppm-e radiative equivalent of CO2 + CH4 + N2O) ensues in warming of the Antarctic ice, in particular of western Antarctica, and of the Antarctic peninsula (Fig. 2). It further reduces concentration of circum-Antarctic sea ice (Fig. 3). Another expression of warming is the accelerating movement of glaciers, where the mass of the ice sheet decreased significantly at a rate of 152 ± 80 cubic kilometers of ice per year [2].

Based on a combination of ground stations and satellite observations, NASA/GISS reports a mean temperature increase of +0.12 °C per decade for the entire continent of Antarctica, and +0.17 °C per decade for western Antarctica, during 1957-2006 (NASA, 21.1.2009) (Fig. 2). Manifestations of warming include reduced concentration of sea ice around parts of Antarctica (Fig. 3) and the disintegration of ice shelves (Fig. 4) due to the effect of warming seas. In particular, the part of western Antarctica which overlies sub-sea level basement is vulnerable to sea water-induced melting. While most of the peripheral near-coastal zones of west and east Antarctica display various degrees of warming and glacier melt, a small area in east Antarctica have been cooling, a likely result of ozone depletion above Antarctica, ozone being a greenhouse gas, as well as acceleration and wind-chill effect of the Antarctic wind vortex (Fig. 5).



Fig. 2. NASA Goddard Institute of Space Science, 21.1.2009. Satellite and ground station data confirm 50 years of west Antarctica warming. Values in °C over 50 years.



Fig. 3. Sea ice per cent concentration trends in the Arctic Sea and around Antarctica for October 2008 relative to 1979-2000 October monthly average. National Snow and Ice Data Center.

Regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming inWestern Antarctica [3]. Breakup of ice shelves is exemplified by the Wilkins ice shelf (Fig. 4), which for the first time continued to breakdown during winter (June-July) 2008 [4].



Fig. 4. Satellite images shows the Wilkins Ice Shelf as it began to break up. The large image is from March 6; the images at right, from top to bottom, are from February 28, February 29, and March 8. NSIDC processed these images from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, which flies on NASA’s Earth Observing System Aqua and Terra satellites.

The southward migration of climate zones by nearly 400 km and the retreat of the Antarctic wind vortex (Fig. 5) have combined to increase drought conditions in southern Australia. In the last thirty years, a 20% loss of the average rainfall along Australia's southern fringe occurred, marked by sudden drops in rainfall in southwestern Australia in the 1970s, and in Victoria in the 1990s, affecting agriculture and reservoir supplies for more than six million people [5]. The consequences in terms of maximum temperature rise (Fig. 6A), rainfall variations (Fig. 6B), and extreme heat wave conditions (Fig. 6C) are evident.


Figure 5. The Antarctic wind vortex viewed from the Galileo spacecraft. As climate zones migrate toward the poles, the southward contraction of the swirling cold moist fronts results in reduced rainfall over southern Australia.

Loss of Antarctic ice shelves and ice sheets, indicated by time variable gravity show mass loss [2] threatens to raise sea levels on the scale of many metres, leading to inundation of coastal regions, deltas, and low river valleys around the world (Fig. 7). Melting of western Antarctic ice would raise sea levels by nearly 7 metres, whereas melting of the entire Antarctic ice sheet would raise sea levels by some 70 metres, returning the Earth to pre-late Eocene conditions (Fig. 6).


Figure 6A. Australia maximum temperature variations in °C per 10 years, 1970-2008 (Australian Bureau of Meteorology).


Figure 6B. Australia annual total rainfall variations in mm per 10 years, 1970-2008 (Australian Bureau of Meteorology).


Figure 6C. Maximum temperatures for Australia, 7 February 2009. Australian Bureau of Meteorology.


Fig. 7. Projected sea level rise (Hansen, 2007). The color bars represent topographic elevations in metres. Sea level rise by up to 25 metres (Greenlandand western Antarctic ice melt) is represented in blues, and up to 75 metres (total Antarctic melt) in yellow.

Until recently, whenever climate research organizations reported increases in Arctic Sea ice melt rates [6], advocates of global “cooling” have been making references to the Antarctic continent as a supposed counter argument [7]. Referring to small, stable or slightly cooling parts of east Anarctica (Fig 2), a plethora of bogus climate websites claims Antarctic warming is not a part of global warming [8].

Presumably regarding Antarctica as part of another planet?

Nor do “climate skeptics” shed too many tears about Emperor penguins, the magnificent birds which have to migrate from their inland colonies across ice shelves and sea ice (Fig. 8), where the females lay just one egg that is tended by the male. The ice plays a major role in their overall breeding success. Further, the extent of sea ice cover influences the abundance of krill and the fish species that eat them – both food sources for the penguins.

Misreadings of climate science by “climate skeptics” have delayed efforts at climate mitigation by at least 20 years. In the words of Clive Hamilton [9]: “If scientific advances cause scientists to reject the conclusions of past IPCC reports … not much harm will be done. … but if … fellow skeptics were successful in stopping policies to cut emissions and the IPCC projections turn out to be correct, then environmental catastrophe will follow and millions of people will die. Do they lose sleep over this? Do they worry about how their grandchildren will see them? Or are they so consumed by the crusade that they know they will never be proven wrong?”


Fig. 8. Melting Antarctic iceberg.

References

Link to this article: http://webdiary.com.au/cms/?q=node/2725

S.-W. Son, N. F. Tandon, L. M. Polvani, D. W. Waugh, Geophys. Res. Lett., 36 (2009): Ozone hole and Southern Hemisphere climate change

Geophysical Research Letters, 36 (2009) L15705; doi: 10.1029/2009GL038671.

Ozone hole and Southern Hemisphere climate change

Ozone hole and Southern Hemisphere climate change

Seok-Woo Son (Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada), Neil F. Tandon (Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, U.S.A.), Lorenzo M. Polvani (Department of Applied Physics and Applied Mathematics and Department of Earth and Environmental Sciences, Columbia University, New York, NY, U.S.A.), and Darryn W. Waugh (Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, U.S.A.)

Abstract

Climate change in the Southern Hemisphere (SH) has been robustly documented in the last several years. It has altered the atmospheric circulation in a surprising number of ways: a rising global tropopause, a poleward intensification of the westerly jet, a poleward shift in storm tracks, a poleward expansion of the Hadley cell, and many others. While these changes have been extensively related with anthropogenic warming resulting from the increase in greenhouse gases, their potential link to stratospheric cooling resulting from ozone depletion has only recently been examined and a comprehensive picture is still lacking. Examining model output from the coupled climate models participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (AR4), and grouping them depending on the stratospheric ozone forcing used, we here show that stratospheric ozone affects the entire atmospheric circulation in the SH, from the polar regions to the subtropics, and from the stratosphere to the surface. Furthermore, model projections suggest that the anticipated ozone recovery, resulting from the implementation of the Montreal Protocol, will likely decelerate future climate change resulting from increased greenhouse gases, although it might accelerate surface warming over Antarctica.

(Received 16 April 2009, accepted 13 July 2009, published 11 August 2009.)

Son, S.-W., N. F. Tandon, L. M. Polvani, & D. W. Waugh (2009), Ozone hole and Southern Hemisphere climate change, Geophys. Res. Lett., 36, L15705; doi: 10.1029/2009GL038671.

Link to abstract: http://www.agu.org/pubs/crossref/2009/2009GL038671.shtml

Andrew Glikson: Global warming toward 2 degrees centigrade

According to the IPCC AR4-2007 report [1], a total anthropogenic greenhouse factor of 3.06 Watt/m², equivalent to about +2.3 °C, is masked by a compensating aerosol albedo effect of -1.25 Watt/m² (mainly sulphur from industrial emissions), equivalent to about -0.9 °C (without land clearing albedo gain and ice melt albedo loss) (Table 1). Once the short-lived aerosols dissipate, adding the reflectance loss of melting polar ice (where maximum warming of up to 4 °C occurs), mean global temperatures track toward +2 °C, considered by the European Union to be the maximum permissible level.

From Table 1, subtracting the aerosol masking effect, the magnitude of the 1750-2005 mean forcing at ~3 Watt/m² is approaching 50% of the total last glaciation termination of 6.5 +/-1.5 Watt, not accounting for developments since 2005. This includes the reduction in albedo due to melting of Arctic Sea ice and other parts of the cryosphere. Since the mid-1990s the mean global temperature trend has become increasingly irregular, representing an increase in climate variability with global warming, as reflected by variations in the ENSO cycle and oscillating ice melt and re-freeze cycles.

The solar sunspot cycle effect is at about +/-0.1 °C, an order of magnitude less than greenhouse forcing. Sharp peaks include the 1998 El-Nino peak (near +0.55 °C) and the 2007 La Nina trough (near -0.7 °C) [2]. Mean global temperature continued to rise during 1999-2005 by about 0.2 °C. The effects of this warming on the cryosphere include:

(A) Reduction in the Arctic Sea multi-year ice cover from about 4.2 to 2.5 million km² during 2000-2009 [3].

(B) Increase in Greenland September ice melt area from 350,000 to 550,000 km² during 1997-2007 [4].

(C) Warming of the entire Antarctic continent by 0.6 °C and of west Antarctic by 0.85 °C during 1957-2006 [5], reflected by collapse of west Antarctic ice shelves [6].

Variations in temperature and sea ice cover around Antarctica are effected by the shrinking polar wind vortex and tropospheric and stratospheric ozone layer conditions, resulting in geographic and temporal variability in sea and land ice cover (http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice_south.php?src=eoa-ann).

Ongoing global warming may lead to the release of methane from permafrost, collapse of the North Atlantic Thermohaline current, high-energy weather events, and yet little-specified shifts in atmospheric states (tipping points) [7].

Table 1. Comparisons between anthropocene (1750-2005), last glacial termination (20-11.7 kyr) and Pliocene (~3 Ma) CO2 levels, climate forcings, mean global temperatures, and sea levels. Sources: [1, 19].

Period	CO2 ppm	Forcings (Watt/m²)	Temperature oC (1 oC ~ ¾ W/m2)	Sea level (m)
1750-2005	260-387	Greenhouse: +3.06 Albedo: -1.25* Current balance: +1.81 Ice albedo loss (? W/m2)	~ +2.3 ~-0.9?T oC	Tracking toward Pliocene levels
Last glacial termination (20-11.7 kyr)	180-280	Greenhouse gases: +3.0 +/-0.5 Ice sheets and vegetation albedo loss: +3.5 +/-1.0.	~ +5.0 +/-1.0	+120
Pliocene (3 Ma)	400		+2 to 3	+25 +/-12

*Not including land clearing.

This experiment by Homo "sapiens" is a novel one. Developments may include periods of cooling, as may be indicated by the current slow-down of Greenland glaciers. In a recent paper by Dakos et al. (2008), abrupt climate changes in the past are shown to have been preceded by quiet periods [8].

"Skeptics" use such short-term variability, for example slowing down of Greenland glaciers, to argue "global cooling" -- and thereby a "justification" -- for further carbon emissions [9-11].

The implication s of climate change for ecosystems are illustrated in the new book Heatstroke: Nature in an Age of Global Warming" by Anthony Barnosky, of Yale University, who states: "I think probably the biggest cause for worry is we really are seeing the disappearance of whole ecological niches, which means extinctions" [12].

Despite intensified warnings from the Copenhagen climate conference [13], as a self-fulfilling prophecy the "great moral issue of our time" [14] is being relegated to secondary priority [15].

Given that warnings by scientists have proven mostly correct, as contrasted with watered-down reports percolating upward through bureaucracies, there is little evidence the authorities are listening to the recent dire warnings by climate scientists [16].

The decline by CSIRO to report directly to the recent Senate climate inquiry [17], reminiscent of the Howard era [18], has only been saved by the courage of individual scientists, one of whom compared current targets to 'Russian roulette with the climate system with most of the chambers loaded'.

[1] http://www.ipcc.ch/ ; SPM.2.

[2] http://data.giss.nasa.gov/gistemp/graphs/Fig.C.lrg.gif

[3] http://www.nasa.gov/topics/earth/features/arctic_thinice.html

[4] http://nsidc.org/data/virtual_globes/

[5] http://www.giss.nasa.gov/research/news/20090121/

[6] http://nsidc.org/news/press/20080325_Wilkins.html

[7] http://climatechangepsychology.blogspot.com/2009/02/timothy-m-lenton-et-al-pnas-105-6.html ; http://researchpages.net/ESMG/people/tim-lenton/tipping-points/.

[8] http://www.indiana.edu/~halllab/L577/Topic3/Dakosetal_2008_PNAS.pdf

[9] http://www.worldclimatereport.com/index.php/2009/01/23/glacier-slowdown-in-greenland-how-inconvenient/

[10] http://www.connorcourt.com/catalog1/index.php?main_page=product_info&cPath=7&products_id=103 ; http://scienceblogs.com/deltoid/2009/05/ian_enting_is_checking_plimers.php http://bravenewclimate.com/2009/04/23/ian-plimer-heaven-and-earth/ ; http://www.theaustralian.news.com.au/story/0,,25433059-5003900,00.htmlhttp://www.crikey.com.au/2009/05/05/plimer-wants-to-talk-science-ok-here-goes/

[11] http://australianconservative.com/main-site/category/policy/environment/page/2/

[12] http://www.e360.yale.edu/content/feature.msp?id=2154

[13] http://climatecongress.ku.dk/newsroom/congress_key_messages/

[14] http://www.theaustralian.news.com.au/story/0,,25037352-7583,00.html?from=public_rss

[15] http://johnquiggin.com/index.php/archives/2009/04/24/doolittle-and-delay/

[16] http://www.thewest.com.au/default.aspx?MenuID=28&ContentID=139318 http://wotnews.com.au/like/7_australian_climate_scientists_forecast_an_end_to_coal/3359286/.

[17] http://www.abc.net.au/worldtoday/content/2008/s2543405.htm

[18] http://www.safecom.org.au/csiro-silence.htm

[19] http://pubs.giss.nasa.gov/abstracts/2008/Hansen_etal.html

Link to article: http://www.opednews.com/articles/GLOBE-WARMING-TOWARD-TWO-D-by-Andrew-Glikson-090531-738.html

J Turner et al. GRL 36; Non‐annular atmospheric circulation change induced by stratospheric ozone depletion: Antarctic sea ice extent increase role

Geophysical Research Letters, 36, L08502; doi:10.1029/2009GL037524.

Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent

Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent

John Turner (British Antarctic Survey, National Environment Research Council, Cambridge, U.K.), Josefino C. Comiso (NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.), Gareth J. Marshall, Tom A. Lachlan‐Cope, Tom Bracegirdle, Ted Maksym, Michael P. Meredith, Zhaomin Wang, and Andrew Orr (British Antarctic Survey, National Environment Research Council, Cambridge, U.K.)

Abstract

Based on a new analysis of passive microwave satellite data, we demonstrate that the annual mean extent of Antarctic sea ice has increased at a statistically significant rate of 0.97% dec⁻¹ since the late 1970s. The largest increase has been in autumn when there has been a dipole of significant positive and negative trends in the Ross and Amundsen‐Bellingshausen Seas respectively. The autumn increase in the Ross Sea sector is primarily a result of stronger cyclonic atmospheric flow over the Amundsen Sea. Model experiments suggest that the trend towards stronger cyclonic circulation is mainly a result of stratospheric ozone depletion, which has strengthened autumn wind speeds around the continent, deepening the Amundsen Sea Low through flow separation around the high coastal orography. However, statistics derived from a climate model control run suggest that the observed sea ice increase might still be within the range of natural climate variability.

(Received 29 January 2009, accepted 25 March 2009, published 23 April 2009.)

Turner, J., J. C. Comiso, G. J. Marshall, T. A. Lachlan‐Cope, T. Bracegirdle, T. Maksym, M. P. Meredith, Z. Wang, & A. Orr (2009), Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent, Geophysical Research Letters, 36, L08502; doi:10.1029/2009GL037524.

Link to abstract: http://www.agu.org/pubs/crossref/2009/2009GL037524.shtml

Antarctic polar vortex sends Australian drought spiralling

Antarctic vortex sends drought spiralling

Mark Horstman, ABC Science Online

Thursday, 18 September 2003

The weather systems driven by the strong westerly winds of the Antarctic polar vortex curl over the southern continents in this satellite view of Antarctica (NASA, Galileo)

An alarming interaction between ozone depletion and global warming may explain why Australia's southern cities and farms have lost 20% of their rainfall in the last 30 years.

The claims are aired tonight on ABC-TV's Catalyst program tonight.

"It really is a revolution in the climate sciences," said Dr David Jones, chief analyst of the National Climate Centre at Australia's Bureau of Meteorology in Melbourne. "We can't just look at natural variability or greenhouse climate change in isolation -- we also have to factor in ozone."

Across many future climate projections, Australia in winter shows the largest reductions of rainfall of any region in the world. However, rainfall in south-western Australia has already decreased faster than predicted, suggesting factors other than those already identified are at work. According to Jones and colleagues, the clues lie 20 km high above Antarctica.

The Antarctic polar vortex is a natural, continent-wide 'tornado' of 200 km/h, super-cold winds surrounding the ozone 'hole' from the stratosphere to the surface. It is created by the movement of the globe interacting with temperature differences between the pole and the rest of the Earth's surface. The vortex delivers the winter rain-bearing westerly winds called the 'Roaring Forties,' which southern Australia relies on for its water supplies.

However, Jones and team have found that global warming and ozone depletion are interacting to shrink and accelerate the vortex, dragging crucial rainfall towards the South Pole, away from Australia's landmass.

The 'reliable' rainfall regions most affected by the loss of winter rains are coloured dark blue and purple (Bureau of Meteorology)

The researchers relied on three decades of data from Antarctica, U.S. and Australian research to show the operation of a vicious cycle. On the one hand, ozone depletion leads to cooler temperatures and lower pressures above Antarctica. On the other, greenhouse warming leads to higher temperatures and pressures over other parts of the globe. This steepens the temperature-pressure gradient between Antarctica and the rest of the Southern Hemisphere, resulting in the stronger and faster-spinning polar vortex which 'pulls' the rain-bearing westerlies southwards.

The last thirty years have recorded a dramatic 20% loss of the average rainfall along Australia's southern fringe, marked by sudden drops in southwestern Australia in the 1970s, and Victoria in the 1990s. Apart from providing much needed water to farmers, winter rains are crucial for topping up the reservoir supplies for more than six million people living in our southern capitals. The reservoirs of Melbourne, Adelaide, and Perth are all currently at low levels -- Perth has been at 18% capacity this year (2003).

Dramatic declines in winter rainfall over the last thirty years have resulted in even sharper falls in the streamflows that recharge city reservoirs (Mark Horstman)

Dr James Risbey, at Monash University in Melbourne, believes the 2002 drought [pdf report] was the worst in recorded history -- and the first in Australia with a global warming 'signature' -- because the temperatures were higher than in other drought years.

The mid-range prediction for temperature increase in Australia by the end of this century is 4 °C. This has a direct impact on the water balance because as warming continues the amount of evaporation increases.

Risbey fears a climatic 'double whammy': where the combination of less rainfall from a contracting vortex and less available moisture from increasing evaporation rates drags southern Australia into a state of permanent drought.

"With four degrees of warming across Australia, we'd need to see an increase in rainfall of some 30 odd percent to keep pace with that. This is most unlikely to happen, and so we're going into increasing water deficit across the continent."

"The worst case scenario is that we start to run out of water around the cities," he told Catalyst. "In that case we'd have to think seriously about moving some of the water out of agriculture and into urban uses."

Link to article: http://www.abc.net.au/science/news/enviro/EnviroRepublish_946924.htm

Andrew Glikson: Antarctic blues and the Australian drought

Antarctic blues and the Australian drought

Antarctic blues and the Australian drought
Andrew Glikson
Earth and paleo-climate scientist
Australian National University

The Antarctic ice sheet has not always been there.

The ice began to form about 34 million years ago, by the late Eocene, when the Antarctic continent (Fig. 1) became isolated through the opening of the Drake Passage between the Antarctic peninsula and southern tip of South America, restricting access of warm currents, and when global carbon dioxide levels decreased to below 450 parts per million CO2, decreasing the mean temperature of Earth by near -6 °C [1].

Fig. 1. The Antarctic continent from space

The current global rise in atmospheric CO2 levels to 387 ppm (over 400 ppm-e radiative equivalent of CO2 + CH4 + N2O) ensues in warming of the Antarctic ice, in particular of western Antarctica, and of the Antarctic peninsula (Fig. 2). It further reduces concentration of circum-Antarctic sea ice (Fig. 3). Another expression of warming is the accelerating movement of glaciers, where the mass of the ice sheet decreased significantly at a rate of 152 ± 80 cubic kilometers of ice per year [2].

Based on a combination of ground stations and satellite observations, NASA/GISS reports a mean temperature increase of +0.12 °C per decade for the entire continent of Antarctica, and +0.17 °C per decade for western Antarctica, during 1957-2006 (NASA, 21.1.2009) (Fig. 2). Manifestations of warming include reduced concentration of sea ice around parts of Antarctica (Fig. 3) and the disintegration of ice shelves (Fig. 4) due to the effect of warming seas. In particular, the part of western Antarctica which overlies sub-sea level basement is vulnerable to sea water-induced melting. While most of the peripheral near-coastal zones of west and east Antarctica display various degrees of warming and glacier melt, a small area in east Antarctica have been cooling, a likely result of ozone depletion above Antarctica, ozone being a greenhouse gas, as well as acceleration and wind-chill effect of the Antarctic wind vortex (Fig. 5).

Fig. 2. NASA Goddard Institute of Space Science, 21.1.2009. Satellite and ground station data confirm 50 years of west Antarctica warming. Values in °C over 50 years

Fig. 3. Sea ice per cent concentration trends in the Arctic Sea and around Antarctica for October 2008 relative to 1979-2000 October monthly average. National Snow and Ice Data Center.

Regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming in Western Antarctica [3]. Breakup of ice shelves is exemplified by the Wilkins ice shelf (Fig. 4), which for the first time continued to breakdown during winter (June-July) 2008 [4].

Fig. 4. Satellite images shows the Wilkins Ice Shelf as it began to break up. The large image is from March 6; the images at right, from top to bottom, are from February 28, February 29, and March 8. NSIDC processed these images from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, which flies on NASA’s Earth Observing System Aqua and Terra satellites.

The southward migration of climate zones by nearly 400 km and the retreat of the Antarctic wind vortex (Fig. 5) have combined to increase drought conditions in southern Australia. In the last thirty years, a 20% loss of the average rainfall along Australia's southern fringe occurred, marked by sudden drops in rainfall in southwestern Australia in the 1970s, and in Victoria in the 1990s, affecting agriculture and reservoir supplies for more than six million people [5]. The consequences in terms of maximum temperature rise (Fig. 6A), rainfall variations (Fig. 6B), and extreme heat wave conditions (Fig. 6C) are evident.

Figure 5. The Antarctic wind vortex viewed from the Galileo spacecraft. As climate zones migrate toward the poles, the southward contraction of the swirling cold moist fronts results in reduced rainfall over southern Australia.

Loss of Antarctic ice shelves and ice sheets, indicated by time variable gravity show mass loss [2] threatens to raise sea levels on the scale of many metres, leading to inundation of coastal regions, deltas, and low river valleys around the world (Fig. 7). Melting of western Antarctic ice would raise sea levels by nearly 7 metres, whereas melting of the entire Antarctic ice sheet would raise sea levels by some 70 metres, returning the Earth to pre-late Eocene conditions (Fig. 6).

Figure 6A. Australia maximum temperature variations in °C per 10 years, 1970-2008 (Australian Bureau of Meteorology).

Figure 6B. Australia annual total rainfall variations in mm per 10 years, 1970-2008 (Australian Bureau of Meteorology).

Figure 6C. Maximum temperatures for Australia, 7 February 2009. Australian Bureau of Meteorology.

Fig. 7. Projected sea level rise (Hansen, 2007). The color bars represent topographic elevations in metres. Sea level rise by up to 25 metres (Greenland and western Antarctic ice melt) is represented in blues, and up to 75 metres (total Antarctic melt) in yellow.

Until recently, whenever climate research organizations reported increases in Arctic Sea ice melt rates [6], advocates of global “cooling” have been making references to the Antarctic continent as a supposed counter argument [7]. Referring to small, stable or slightly cooling parts of east Anarctica (Fig 2), a plethora of bogus climate websites claims Antarctic warming is not a part of global warming [8].

Presumably regarding Antarctica as part of another planet?

Nor do “climate skeptics” shed too many tears about Emperor penguins, the magnificent birds which have to migrate from their inland colonies across ice shelves and sea ice (Fig. 8), where the females lay just one egg that is tended by the male. The ice plays a major role in their overall breeding success. Further, the extent of sea ice cover influences the abundance of krill and the fish species that eat them – both food sources for the penguins.

Misreadings of climate science by “climate skeptics” have delayed efforts at climate mitigation by at least 20 years. In the words of Clive Hamilton [9]: “If scientific advances cause scientists to reject the conclusions of past IPCC reports … not much harm will be done. … but if … fellow skeptics were successful in stopping policies to cut emissions and the IPCC projections turn out to be correct, then environmental catastrophe will follow and millions of people will die. Do they lose sleep over this? Do they worry about how their grandchildren will see them? Or are they so consumed by the crusade that they know they will never be proven wrong?”

Fig. 8. Melting Antarctic iceberg.

References

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