Why is Antarctic sea ice growing?

'This winter there was more sea ice than ever in Antarctica'-Guy Williams
‘This winter there was more sea ice than ever in Antarctica’-Guy Williams

Recently NASA reported that this year’s maximum wintertime extent of Antarctic sea ice was the largest on record, even greater than the previous year’s record.

This is understandably at odds with the public’s perception of how polar ice should respond to a warming climate, given the dramatic headlines of severe decline in Arctic summertime extent. But the “paradox of Antarctic sea ice” has been on climate scientists’ minds for some time.

Continental v. sea ice

First off, sea ice is different to the “continental ice” associated with polar ice caps, glaciers, ice shelves and icebergs. Continental ice is formed by the gradual deposition, build up and compaction of snow, resulting in ice that is hundreds to thousands of metres thick, storing and releasing freshwater that influences global sea-level over thousands of years.

Sea ice, though equally important to the climate system, is completely different. It is the thin layer (typically 1-2m) of ice that forms on the surface of the ocean when the latter is sufficiently cooled enough by the atmosphere.

From there sea ice can move with the winds and currents, continuing to grow both by freezing and through collisions (between the floes that make up the ice cover). When the atmosphere, and/or ocean is suitably warm again, such as in spring or if the sea ice has moved sufficiently towards the equator, then the sea ice melts again.

Antarctic v. Arctic

Secondly, we need to understand that the Arctic and Antarctic climate systems are very different, particularly in sea ice.

In the Arctic, sea ice forms in an ocean roughly centred on the North Pole that is surrounded by continents. A relatively large (though diminishing) proportion of the ice persists over multiple years before ultimately departing for warmer latitudes through exit points such as Fram Strait between Greenland and Svalbard.

In the south, on the other hand, sea ice forms outwards from the continental Antarctic Ice Sheet, where it is exposed to and strongly influenced by the winds and waters of the Southern Ocean. Here, there is a much stronger seasonal ebb and flow to sea ice coverage as over 80% of the sea ice area grows each autumn-winter and decays each spring-summer. This annual expansion-contraction from about 4 to 19 million square kms is one of the greatest seasonal changes on the Earth’s surface.

Area v. volume

Finally we need to remember that “extent” or “areal coverage” is only one way with which we monitor and study sea ice.

Sea ice turns out to be a very complex and variable medium that is very difficult to observe over large-scales. It is also constantly moving and restructuring. Until we achieve the “holy grail” of monitoring total sea ice volume from space and how it changes over time (and there are great steps towards this with European Space Agency’s environmental research satellite CryoSat-II), we are limited to interpreting its global behaviour through area.

What happened this winter?

This winter, the maximum total Antarctic sea ice extent was reported to be 19.47 million square kilometres, which is 3.6% above the winter average calculated from 1981 to 2010. This continues a trend that is weakly positive and remains in stark contrast to the decline in Arctic summer sea ice extent (2013 was 18% below the mean from 1981-2010).

To further complicate this picture, we find this net increase actually masks strong declines in particular regions around Antarctica, such as in the Bellingshausen Sea, which are on par or greater than those in the Arctic.

So while there is much greater attention given to the Arctic decline and the prediction of “ice-free summers” at the North Pole this century, Antarctic climate scientists still have their work cut out to understand the regional declines amidst the mild “net” expansion occurring in the southern hemisphere.

Here are some of the leading hypotheses currently being explored through a combination of satellite remote sensing, fieldwork in Antarctica and numerical model simulations – to help explain the increasing trend in overall Antarctic sea ice coverage:

  • Increased westerly winds around the Southern Ocean, linked to changes in the large-scale atmospheric circulation related to ozone depletion, will see greater northward movement of sea ice, and hence extent, of Antarctic sea ice.
  • Increased precipitation, in the form of either rain or snow, will increase the density stratification between the upper and middle layers of the Southern Ocean. This might reduce the oceanic heat transfer from relatively warm waters at below the surface layer, and therefore enhancing conditions at the surface for sea ice.
  • Similarly, a freshening of the surface layers from this precipitation would also increase the local freezing point of sea ice formation.
  • Another potential source of cooling and freshening in the upper ocean around Antarctica is increased melting of Antarctic continental ice, through ocean/ice shelf interaction and iceberg decay.
  • The observed changes in sea ice extent could be influenced by a combination of all these factors and still fall within the bounds of natural variability.

The take home messages is that while the increase in total Antarctic sea ice area is relatively minor compared to the Arctic, it masks the fact that some regions are in strong decline. Given the complex interactions of winds and currents driving patterns of sea ice variability and change in the Southern Ocean climate system, this is not unexpected.

But it is still fascinating to study.

Further Reading


Free Training Oppertunity for Students on Open Street mapping

Along with GFDRR (https://www.gfdrr.org/) as part of their OpenCities initiative (http://opencitiesproject.com/cities/dhaka/) we are hosting a half day hands-on training session on the crowd-sourced OpenStreetMap platform on Saturday 2nd November from 10 am to 2 pm at the World Bank Office (E-32 Agargaon, Sher-e-Bangla Nagar) covering the following:

  1. OSM Basics: How it works, it’s many uses & opportunities … as well as it’s limitations.
  2. OSM Excursion: An outdoor exercise to collect data using a clever tool designed to simplify geographic data collection.  
  3. OSM Editing: The process and the differences with traditional GIS editing.

Grateful for confirmation of your participation to Tahsina Akbar on tahsinabd88@gmail.com  . This will be a practical ‘hands-on’ session so we would request you to please bring your own laptop. 
Thanks kindly, Mark

PS – There is an excellent status report on OSM at http://www.mapbox.com/osm-data-report/


The Places Europeans Actually Discovered, Mapped

The tiny islands that European explorers really did discover.
In recent decades, respect for European explorers, such as Christopher Columbus, has waned, likely because these once-romanticized swashbuckling adventurers killed people, eradicated cultures, and “discovered” places that people (for example, the natives) already knew about. They did make some discoveries, though—lands never inhabited or where the inhabitants were already dead before Europeans made landfall.The map above, from historian and cartographer Bill Rankin, shows those places and the country that discovered each.

Its a Hard Choice: Nuclear over Coal ??

Most of the world’s electrical power is generated by utilizing non-renewable energy resources such as coal or uranium. While each material has a long and productive history of powering electrical plants, they also provide environmental challenges that defy easy comparison. Only by examining the total lifetime risks of the coal and uranium used in energy plants can it be determined which is better for the environment.

Greenhouse Gas Effect of Coal-Burning Plants
Coal-fired electric power plants emit massive amounts of greenhouse gases and other harmful pollutants to the atmosphere on a daily basis. Among the worst offenders are sulfur dioxide, which contributes to the formation of acid rain; nitrogen oxides, which combine with VOCs to form smog; and toxic compounds of mercury. That’s beyond the tonnage of carbon dioxide emissions that contribute directly to climate change. Burning coat releases over two pounds of carbon dioxide into the atmosphere for every kilowatt-hour of electricity it creates (See References 1, 2).

Greenhouse Gas Effect of Nuclear Power Plants

Nuclear power plants emit no carbon dioxide, sulfur dioxide, nitrogen oxides, mercury, or other toxic gases. A properly managed facility does not directly contribute to atmospheric climate change; the broad cooling towers characteristic of nuclear plants emit water vapor. Some coastal plants, however, discharge heated water back to lakes and seas, and this heat eventually radiates into surface warming. Raising water temperature in this way may also alter the way carbon dioxide is exchanged with the air by ocean bodies, leading to major shifts in weather patterns such as hurricanes (See references 1, 3, 4).

Waste Disposal
A typical coal-burning power plant creates over 300,000 tons of waste ash and sludge each year. That residue forms a toxic mess with pollutants such as arsenic, cadmium, chromium and mercury (See Reference 5). A typical nuclear power plant generates 20 metric tons of radioactive waste annually. This material must be isolated, transported and stored in remote locations for hundreds of years. Exposure to high levels of radiation is deadly to people and animals (See Reference 6).
Hard Choices
While a nuclear power plant is completely safe under ideal conditions, the failure of a poorly designed facility in Chernobyl led to the world’s largest single eco-disaster. The failure of the Fukushima nuclear power plants following a series of earthquakes and tsunamis demonstrated that even well designed nuclear energy systems are not risk-free. Frightening as those episodes may seem, however, the danger of climate change caused by greenhouse gas emissions may be more urgent — and thus make nuclear a better choice than coal for the environment.

Which will Give the Signal Green: Coal or Nuclear ??

Human-caused climate change and air pollution remain major global-scale problems and are both due mostly to fossil fuel burning. Mitigation efforts for both of these problems should be undertaken concurrently in order to maximize effectiveness. Such efforts can be accomplished largely with currently available low-carbon and carbon-free alternative energy sources like nuclear power and renewables, as well as energy efficiency improvements.

Figure 1. Cumulative net deaths prevented assuming nuclear power replaces fossil fuels. The top panel (a) shows results for the historical period in our study (1971-2009), with mean values (labeled) and ranges for the baseline historical scenario. The middle (b) and bottom (c) panels show results for the high-end and low-end projections, respectively, of nuclear power supply estimated by the IAEA (ref. 4) for the period 2010-2050. Error bars reflect the ranges for the fossil fuel mortality factors listed in Table 1 of our paper. The larger columns in panels (b) and (c) reflect the all-coal case and are labeled with their mean values, while the smaller columns reflect the all-gas case; values for the latter are not shown because they are all simply a factor of about 10 lower (reflecting the order-of-magnitude difference between the mortality factors for coal and gas). Countries/regions are arranged in descending order of CO2 emissions in recent years. FSU15=15 countries of the Former Soviet Union and OECD=Organization for Economic Cooperation and Development.


In a recently published paper (ref. 1), we provide an objective, long-term, quantitative analysis of the effects of nuclear power on human health (mortality) and the environment (climate). Several previous scientific papers have quantified global-scale greenhouse gas (GHG) emissions avoided by nuclear power, but to our knowledge, ours is the first to quantify avoided human deaths as well as avoided GHG emissions on global, regional, and national scales.

The paper demonstrates that without nuclear power, it will be even harder to mitigate human-caused climate change and air pollution. This is fundamentally because historical energy production data reveal that if nuclear power never existed, the energy it supplied almost certainly would have been supplied by fossil fuels instead (overwhelmingly coal), which cause much higher air pollution-related mortality and GHG emissions per unit energy produced (ref. 2).

Figure 2. Mean net deaths prevented annually by nuclear power between 1971-2009 for various countries/regions. Ranges not shown but are a factor of ~4 higher and lower than the mean values.

Using historical electricity production data and mortality and emission factors from the peer-reviewed scientific literature, we found that despite the three major nuclear accidents the world has experienced, nuclear power prevented an average of over 1.8 million net deaths worldwide between 1971-2009 (see Fig. 1). This amounts to at least hundreds and more likely thousands of times more deaths than it caused. An average of 76,000 deaths per year were avoided annually between 2000-2009 (see Fig. 2), with a range of 19,000-300,000 per year.

Likewise, we calculated that nuclear power prevented an average of 64 gigatonnes of CO2-equivalent (GtCO2-eq) net GHG emissions globally between 1971-2009 (see Fig. 3). This is about 15 times more emissions than it caused. It is equivalent to the past 35 years of CO2 emissions from coal burning in the U.S. or 17 years in China (ref. 3) — i.e., historical nuclear energy production has prevented the building of hundreds of large coal-fired power plants.

To compute potential future effects, we started with the projected nuclear energy supply for 2010-2050 from an assessment made by the UN International Atomic Energy Agency that takes into account the effects of the Fukushima accident (ref. 4). We assume that the projected nuclear energy is canceled and replaced entirely by energy from either coal or natural gas. We calculate that this nuclear phaseout scenario leads to an average of 420,000-7 million deaths and 80-240 GtCO2-eq emissions globally (the high-end values reflect the all coal case; see Figs. 1 and 3). This emissions range corresponds to 16-48% of the “allowable” cumulative CO2 emissions between 2012-2050 if the world chooses to aim for a target atmospheric CO2 concentration of 350 ppm by around the end of this century (ref. 5). In other words, projected nuclear power could reduce the CO2 mitigation burden for meeting this target by as much as 16-48%.

Figure 3. Cumulative net GHG emissions prevented assuming nuclear power replaces fossil fuels. The three panels are ordered the same as in Fig. 1, except that mean values for both the all coal and all gas cases are labeled. Error bars reflect the ranges for the fossil fuel emission factors listed in Table 1 of our paper.

The largest uncertainties and limitations of our analysis stem from the assumed values for impacts per unit electric energy produced. However, we emphasize that our results for both prevented mortality and prevented GHG emissions could be substantial underestimates. This is because (among other reasons) our mortality and emission factors are based on analysis of Europe and the US (respectively), and thus neglect the fact that fatal air pollution and GHG emissions from power plants in developing countries are on average substantially higher per unit energy produced than in developed countries.

Our findings also have important implications for large-scale “fuel switching” to natural gas from coal or from nuclear. Although natural gas burning emits less fatal pollutants and GHGs than coal burning, it is far deadlier than nuclear power, causing about 40 times more deaths per unit electric energy produced (ref. 2).

Also, such fuel switching is practically guaranteed to worsen the climate problem for several reasons. First, carbon capture and storage is an immature technology and is therefore unlikely to constrain the resulting GHG emissions in the necessary time frame. Second, electricity infrastructure generally has a long lifetime (e.g., fossil fuel power plants typically operate for up to ~50 years). Third, potentially usable natural gas resources (especially unconventional ones like shale gas) are enormous, containing many hundreds to thousands of gigatonnes of carbon (based on ref. 6). For perspective, the atmosphere currently contains ~830 GtC, of which ~200 GtC are from industrial-era fossil fuel burning.

We conclude that nuclear energy — despite posing several challenges, as do all energy sources (ref. 7) — needs to be retained and significantly expanded in order to avoid or minimize the devastating impacts of unabated climate change and air pollution caused by fossil fuel burning.


1. Kharecha, P.A., and J.E. Hansen, 2013: Prevented mortality and greenhouse gas emissions from historical and projected nuclear powerEnviron. Sci. Technol., in press, doi:10.1021/es3051197.

2. Markandya, A., and P. Wilkinson, 2007: Electricity generation and health. Lancet, 370, 979-990, doi: 10.1016/S0140-6736(07)61253-7.

3. Boden, T. A., G. Marland, R.J. Andres, 2012: Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A., doi:10.3334/CDIAC/00001_V2012.

4. International Atomic Energy Agency, 2011: Energy, Electricity and Nuclear Power Estimates for the Period up to 2050: 2011 Edition. IAEA Reference Data Series 1/31. Available at http://www-pub.iaea.org/MTCD/Publications/PDF/RDS1_31.pdf

5. Hansen, J., P. Kharecha, Mki. Sato, V. Masson-Delmotte, et al., 2013: Scientific prescription to avoid dangerous climate change to protect young people, future generations, and naturePLOS One, submitted.

6. GEA, 2012: Global Energy Assessment — Toward a Sustainable Future. Cambridge University Press, Cambridge, UK and New York, NY, USA and the International Institute for Applied Systems Analysis, Laxenburg, Austria. Available at http://www.globalenergyassessment.org.

7. Kharecha, P.A., C.F. Kutscher, J.E. Hansen, and E. Mazria, 2010: Options for near-term phaseout of CO2 emissions from coal use in the United StatesEnviron. Sci. Technol., 44, 4050-4062, doi:10.1021/es903884a.


Food Security Risk Index Map 2013



This is a map created by risk analysis experts Maplecroft using the key elements of food security set by FAO. The Food Security Risk Index (FSRI) is calculated based on assessing 12 components of food security. The indicators include the accessibility and availability of food and the stability of food supplies across all countries. Additionally, the index takes into consideration the nutritional and health elements of populations.

When looking at the map covering 197 countries you will notice that the food security of Somalia and the Democratic Republic of Congo as lowest, whilst countries in the drought stricken Horn of Africa are also at extreme risk.

Hunger Map 2013

The FAO Hunger Map 2013 has been published . This map displays nutritional information for developing countries. The data are based on the latest edition of FAO’s annual publication “The State of Food Insecurity in the World”.

FAO_Hunger Map 2013

Most of the world’s hungry live in developing countries. According to the latest Food and Agriculture Organization (FAO) statistics, there are 870 million hungry people in the world and 98 percent of them are in developing countries.  They are distributed like this (WFP, 2013):

578 million in Asia and the Pacific
239 million in Sub-Saharan Africa
53 million in Latin America and the Caribbean
37 million in the Near East and North Africa

19 million in developed countries

Rural risk

Three-quarters of all hungry people live in rural areas, mainly in the villages of Asia and Africa. Overwhelmingly dependent on agriculture for their food, these populations have no alternative source of income or employment. As a result, they are vulnerable to crises. Many migrate to cities in their search for employment, swelling the ever-expanding populations of shanty towns in developing countries.

Hungry farmers

FAO calculates that around half of the world’s hungry people are from smallholder farming communities,  surviving off marginal lands prone to natural disasters like drought or flood. Another 20 percent belong to landless families dependent on farming and about 10 percent live in communities whose livelihoods depend on herding, fishing or forest resources.

The remaining 20 percent live in shanty towns on the periphery of the biggest cities in developing countries. The numbers of poor and hungry city dwellers are rising rapidly along with the world’s total urban population.


An estimated 146 million children in developing countries are underweight – the result of acute or chronic hunger (Source: The State of the World’s Children, UNICEF, 2009).  All too often, child hunger is inherited: up to 17 million children are born underweight annually, the result of inadequate nutrition before and during pregnancy.


Women are the world’s primary food producers, yet cultural traditions and social structures often mean women are much more affected by hunger and poverty than men. A mother who is stunted or underweight due to an inadequate diet often give birth to low birthweight children.

Around 50 per cent of pregnant women in developing countries are iron deficient (source: Unicef). Lack of iron means 315,000 women die annually from hemorrhage at childbirth. As a result, women, and in particular expectant and nursing mothers, often need special or increased intake of food.

Some Basic Definition (FAO)

  • Undernutrition

The outcome of undernourishment, and/or poor absorption and/or poor biological use of nutrients consumed as a result of repeated infectious disease. It includes being underweight for one’s age, too short for one’s age (stunted), dangerously thin for one’s height (wasted) and deficient in vitamins and minerals (micronutrient malnutrition).

  • Undernourishment or Chronic Hunger

A state, lasting for at least one year, of inability to acquire enough food, defined as a level of food intake insufficient to meet dietary energy requirements. For the purposes of this report, hunger was defined as being synonymous with chronic undernourishment.

Number and percentage of undernourished persons
1990-1992 1015 million (19%)
2000-2002 957 million (15%)
2005-2007 907 million (14%)
2008-2010 878 million (13%)
2011-2013 842 million (12%)
  • Malnutrition

An abnormal physiological condition caused by inadequate, unbalanced or excessive consumption of macronutrients and/or micronutrients. Malnutrition includes undernutrition and overnutrition as well as micronutrient deficiencies.

  • Food security

A situation that exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life. Based on this definition, four food security dimensions can be identified: food availability, economic and physical access to food, food utilization and stability over time.

  • Food insecurity

A situation that exists when people lack secure access to sufficient amounts of safe and nutritious food for normal growth and development and an active and healthy life. It may be caused by the unavailability of food, insufficient purchasing power, inappropriate distribution or inadequate use of food at the household level. Food insecurity, poor conditions of health and sanitation and inappropriate care and feeding practices are the major causes of poor nutritional status. Food insecurity may be chronic, seasonal or transitory.