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The year 2020 is set to be the among the three warmest on record, according to the latest State of the Global Climate provisional report by World Meteorological Organization on December 1, 2020. Also, the decade 2011-2020 would be the warmest ever.
The global mean surface temperature for January-October was 1.2 degree Celsius higher than the pre-industrial baseline (1850-1900). For that period, 2020 is the second-warmest year on record.
The record heat in 2020 has been despite near-La Niña conditions prevailing in the equatorial Pacific Ocean since August and moderate La Niña conditions prevailing since October.
The La Niña phase of the El Niño Southern Oscillation (ENSO) phenomenon generally has a cooling effect on many parts of the world.
Scientific evidence indicates increasing temperatures are a direct result of human-led global warming — an impact of the emission of green house gases (GHG). After record GHG levels of 2019, there has been a slight dip this year due to measures taken by many countries to fight the ongoing novel coronavirus disease (COVID-19) pandemic, according to the report.
It. however, added that the reduction “will be practically indistinguishable from the natural inter-annual variability, driven largely by the terrestrial biosphere. Real-time data from specific locations, including Mauna Loa (Hawaii) and Cape Grim (Tasmania) indicate that levels of CO2, CH4 and N2O continued to increase in 2020.”
Temperatures over ocean surfaces were also high in 2020: 80 per cent of ocean areas experienced at least one marine heat wave (MHW) till date.
At such times, the average temperatures of the ocean surface (up to a depth of 300 feet or more) rise by 5-7°C above normal. MHWs can be caused by locally formed heat fluxes between the atmosphere and the ocean or due to large-scale drivers of the Earth’s climate like the ENSO. There were also much more strong MHWs (43 per cent) over the oceans in 2020 than moderate ones (28 per cent).
Global sea-level rise was also similar to 2019 values and the general decreasing trend has continued. This was mainly due to the increased melting of the ice sheets in Greenland and Antarctica, says the report.
In Greenland alone ice weighing 152 gigatonnes melted between September 2019 and August 2020, which was on the high end of the 40 year satellite records. Sea-level rise is an existential concern for the small island nations as a significant sea-level rise by the end of the century will mean that these countries will drown in the oceans and their respective populations will be homeless.
Extreme weather events such as tropical cyclones, floods, heavy rainfall and droughts which are also a well known and expensive consequence of global warming impacted many parts of the world.
The most dramatic was the record breaking Atlantic Hurricane Season which just concluded on November 30. The season witnessed 30 named storms from June 1 to November 30 which is the highest number ever recorded. A record number of these storms also made landfall along the United States coast.
There was heavy rainfall and flooding in many parts of Asia and Africa leading to loss of human lives, property and livelihoods. The most affected were the Sahel and Greater Horn regions of Africa and China, India, Korea and Japan regions of Asia.
South America on the other hand experienced severe droughts with northern Argentina, Paraguay and western areas of Brazil being some of the worst affected. Brazil alone recorded agricultural losses of $3 billion.
Further the report states that “climate and weather events have triggered significant population movements and have severely affected vulnerable people on the move, including in the Pacific region and Central America”. Climate induced human migration is one of the least understood impact of anthropogenic climate change.