How climate change is accelerating sea level rise

New York, Sep 24: The worst fears about Global climate change have come true. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner.

Effects that scientists had predicted in the past would result from global climate change are now occurring: loss of sea ice, accelerated sea level rise and longer, more intense heat waves.

The data, compiled by the World Meteorological Organization (WMO), says climate change is accelerating, with sea levels rising, carbon dioxide levels increasing and ice sheets melting faster than ever before.

Sea level rise

The five-year-period saw an increase of 5 mm per year, compared to 4 mm per year in the decade from 2007-16. The WMO noted that the contribution of land ice melt from the world glaciers and the ice sheets has increased over time and now dominate the sea level budget, rather than thermal expansion.

Shrinking ice

From 2015-18, the average Arctic's average September minimum (summer) sea-ice was found to be well below the 1980-2010 average, as was the "as was the average winter sea-ice extent," the WMO noted, adding that the four lowest records for winter occurred during this period.

A similar situation unfolded at the Antarctic, with summer and winter sea-ice values being found to be reaching its lowest and second lowest extent in 2017-18. "The amount of ice lost annually from the Antarctic ice sheet increased at least six-fold, from 40 Gt per year in 1979-1990 to 252 Gt per year in 2009-2017," it added adding that the Greenland ice sheet has also been losing rapidly.

Future effects

Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 4 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.

In the next several decades, storm surges and high tides could combine with sea level rise and land subsidence to further increase flooding in many regions, according to NASA.

Sea level rise will continue past 2100 because the oceans take a very long time to respond to warmer conditions at the Earth's surface. Ocean waters will therefore continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than those of the current century, NASA added.

Coastal flooding

Driven mostly by rising sea levels, the frequency of coastal 100-year floods (a severe flood with a 1% likelihood of occurring in a given year) is expected to increase greatly throughout the coming century. By mid- to late-century, floods of this severity could plausibly occur almost once per year, a change driven mostly by rising sea levels, a report from Mass Audubon.

In future scenarios for some coastal locations, it is possible that what is now called a 100-year flood could occur as frequently as high tide. Not only does this pose extraordinary challenges for coastal communities, it also has potentially devastating consequences for wildlife that rely on coastal habitat, the report added.

The 2015 Paris Agreement saw countries lay out national targets to reduce their emissions to limit long-term temperature rise by either 2 degrees Celsius or 1.5C.