Sea ice can be described as frozen seawater floating on the surface of the polar oceans. It does not include icebergs or ice shelves, as these are originating from glaciers, rather than sea water. Sea ice becomes thickest and most widespread over the respective winter months in each hemisphere, covering the oceans around the Arctic and Antarctic with millions of square kilometres of ice. It melts when the seasons change, but in the Arctic large areas remain covered all year around, while Antarctic sea ice melts away over the summer in the southern hemisphere.
Housing has always been a decisive and sometimes divisive political issue. Home ownership has of course long been an aspiration for many people, and in the post-war period between 1953 and 1971 the number of households renting and owning reached an equal level, as documented in official census statistics for England and Wales. Ownership then surpassed renting, reaching its peak in 2001 at 69%. In the decade that followed, this number went down to 64%. The following two maps show the ownership rate in the UK in a conventional and an equal population projection:
Nuclear power contributes only a small share to the global energy production. According to the World Energy Statistics 2015 published by the International Energy Agency (IEA) nuclear power accounts for 4.8% of the total primary energy supply worldwide, far behind oil (31.1%), coal (28.9%), natural gas (21.4%) and even behind biofuels and waste (10.2%).
Of the producers of nuclear power, the United States are by far the largest with 33.2% of the world’s total, followed by France (17.1%) and Russia (7.0%). The United Kingdom’s production accounts for 2.9%. In contrast, France generates the largest share of its domestic electricity generation from nuclear power (74.4%). It is followed by Sweden (43.4%), Ukraine (43.0%) and South Korea (25.8%), while the United Kingdom comes fifth with 19.2%.
It took a long time for humankind to move out of Africa and inhabit the rest of the planet. Archaeological research and genetic studies based on fossils found in plains of east Africa suggest that modern humans evolved nearly 200,000 years ago. Palaeontological findings and genetic footprints are also the basis for current theories of how modern humans (Homo sapiens) started spreading around the globe. Such models and timings keep changing, with new discoveries being made on a fairly regular basis.
The below map illustrates the migration of humanity across the Earth with all movement originating in Africa and with the estimated dates of arrival shown at key directions and locations. The dates are based on a number of scientifically validated estimates. They build upon the ‘Out of Africa’ model that assumes the spread of modern humans from their African origins across the globe, superseding any other human species that had lived in parts of the planet before (and sometimes as) Homo sapiens arrived.
Renewable energy is defined as ‘energy from a source that is not depleted’. Main sources include biomass, hydropower, wind, biofuels, solar, heat pumps, biogas, geothermal, and marine (such as tidal power). Data by the International Energy Agency sees the share of renewable energy in global power generation at 22 per cent in 2013, with an estimated increase to 26 per cent by 2020 as a result of supportive policies by a large number of governments.
Tropical cyclonic systems are generally referred to as tropical storms. They are better known by their regional names, such as hurricanes in the Caribbean and North America, or typhoons in parts of Asia. They form near the equator over larger bodies of warm waters that evaporate from the ocean surface and fuel these emerging storm systems. Their strong winds and heavy rainfalls frequently become part of our news as they often put large numbers of human livelihoods at risk.
Recent studies show that the number of tropical cyclones (as well as tropical cyclone intensity) over the past decades has increased. Tracks of tropical storms collected over a longer period can indicate where such storms occur most frequently. The records used in this issue’s visualisation covers data from 1945 to 2008.