Facts about global warming

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  • Global Land-Ocean Temperature Index. Credit of the picture: NASA.

    Mean annual mass balance for reference glaciers since 1980. Credit of the picture: World Glacier Monitoring Service.

    Cumulative mean annual mass balance for reference glaciers since 1980 . Credit of the picture: World Glacier Monitoring Service.

    Antarctica and Greenland mass variation since 2002. Credit of the picture: NASA

    Sea level rise since 1870 and rate of change. Credit of the picture: NASA

  • Facts about global warming
    05.12.2015 16:17

    The 2015 Climate Conference is currently taking place among 190 countries, with the goal of reaching an agreement to keep global mean temperatures below 2°C.  Which are the scientific facts behind this aim? Let´s try to explain them.

    Current state of climate change

    Since the industrial revolution, the burning of fossil fuels and the loss of forests have increased the atmospheric concentrations of CO2 from 280 part per million (ppm) in 1850 to the current concentration of 401.58 ppm, measured in October.

    The rise in global temperatures since industrial revolution has been 0.75°C. This global temperature is the difference between the 1951-1980 average temperature and the current global temperatures. According to NASA, the 10 warmest years in the 134-year record have all occurred since 2000, with the exception of 1998. The year 2014 ranks as the warmest on record with this year likely to overcome it due to the influence of El Niño.

    Arctic sea ice reaches its minimum each September. September Arctic sea ice is now declining at a rate of 13.3 percent per decade, relative to the 1981 to 2010 average.

    Data from NASA satellites show that the land ice sheets in both Antarctica and Greenland are losing mass. The continent of Antarctica has been losing about 134 billion metric tons of ice per year since 2002, while the Greenland ice sheet has been losing an estimated 287 billion metric tons per year.

    Sea level is also rising at the rate of 3.24 mm per year with an increase since 1870 of 178 mm since 1870 so far. Sea level rise is caused primarily by two factors related to global warming: the added water from melting land ice and the expansion of sea water as it warms.

    According to the World Glacier Monitoring Service, globally the trend for glaciers worldwide over the past few decades is for a strong ice loss with a cumulative average thickness loss of the reference glaciers since 1980 at 17.5 meters of water equivalent (mwe).  MWE  represents the average thickness gained (positive balance) or lost (negative balance) from the glacier during that particular year.

    Projections

    Recently the MetOffice released a research saying that for the first time since industrial revolution global temperature will reach 1°C this year, paving the way to be the common temperatures as long as we do not stop emitting carbon dioxide. There is a general consensus that below 2°C we will be able to keep climate change sort of under control. With more than 2°C these  events below are more likely to occur.

    There will be changes in precipitation patterns with some wet areas becoming wetter whilst droughts will become regular in already dry places such as southern Spain and northern Africa.  Heatwaves will become normal across much of Europe and the United States.

    Sea level will continue to rise to reach 0.3 to 1.2 m ( 1 to 4 feet), higher by 2100, which may cause many coastal cities to flood. Especially in danger will be Bangladesh, the Netherlands and Polynesian islands.

    More intense hurricanes are expected, although there is ongoing research to find out if global warming will increase the number of this extreme weather events. El Niño may also become more regular.

    Many glaciers are likely to disappear across the globe and the Arctic Ocean is expected to become essentially ice free in summer before mid-century.

    There is a high risk of the permafrost melting, releasing a powerful  greenhouse gas called methane that may increase global temperatures to levels that nature and human beings are incapable to cope with. This is known to some as “runaway climate change”.

    More research is needed,  concerning the consequences and the range of uncertainty of some changes but the basic science behind climate change is understood and settled.

    By: Mario Cuellar