Oceans will transition to unprecedented conditions soon, flags IPCC in report
Extreme sea level events that are historically rare, occurring once per century, are projected to occur at least once a year in many locations, particularly the tropical region, by 2050.Updated: Sep 26, 2019 10:55 IST
In a wake-up call to world leaders, the Intergovernmental Panel on Climate Change (IPCC) has warned that oceans are projected to transition to “unprecedented” conditions, marked by an increase in temperatures, higher acidification and a decline in the oxygen levels over the rest of the 21st century,
Marine heat waves and extreme El Nino and La Nina phenomena will become frequent, IPCC said in a report released on Wednesday. Extreme sea level events that are historically rare, occurring once per century, are projected to occur at least once a year in many locations, particularly the tropical region, by 2050.
El Nino is a climate pattern characterised by sea surface temperatures in the tropical Pacific Ocean rising to above normal levels. La Nina is marked by sea surface temperatures in the central Pacific Ocean dropping to below normal levels.
In India, parts of the West Bengal and Odisha coasts are likely to experience such events annually by 2075, according to a map referred to by IPCC, while the Americas, Australia and others will experience such event even earlier, by 2040.
The report states that the global mean surface temperature is projected to rise by around 1.6 degree over pre-industrial levels by as early as 2031-2050 and this projection is used in the report to assess future scenarios.
An IPCC report last year on global warming of 1.5 degrees had said the consequences of a 1.5 degree rise includes warming of extreme temperatures in many regions, increases in frequency, intensity, and amount of heavy precipitation in several regions. A UN Science Advisory Committee said last week that average global temperature is already 1.1°C above pre-industrial times.
Underlining the urgency for action, the “Special Report on the Ocean and Cryosphere in a Changing Climate” by IPCC, which has assessed research on the state of glaciers, oceans and marine ecosystems. has projected that global glacier mass loss in the next few decades till 2050 will increase river runoff and related hazards like landslides, avalanches and floods, which will have serious consequences for India’s Himalayan region, according to experts.
In all emissions scenarios, average annual and summer runoff from glaciers are projected to peak before the end of the 21st century, for example in High Mountain Asia, which includes the Hindu Kush Himalayas, glacier run-off will peak around mid-century followed by a decline.
While making dire projections about the future, the report also sums up how climate change impacts have aleady intensified to dangerous proportions. Since 1993 the rate of ocean warming has more than doubled, intense marine heat waves have also doubled in frequency since 1982, receding glaciers and ice sheets have increased the rate of sea level rise—rising twice as fast compared to the 20th century.
Till now, the oceans have absorbed about 20 to 30% of human induced carbon dioxide (CO2) emissions and 90% of excess heat in the climate system since the 1980s, causing ocean acidification. Ocean heat and acidification has led to shifts in the distribution of fish populations and has already reduced the global catch potential. Communities that depend highly on seafood may face risks to nutritional health and food security, the report has warned.
The extent of Arctic sea ice is declining every month of the year. If global warming is stabilised at 1.5 degrees C above pre-industrial levels, the Arctic Ocean would only be ice-free in September once in every 100 years. For global warming of 2 degrees C, this would occur up to one year in three, the report warns.
About 670 million people in high mountain regions, 680 million people in low-lying coastal areas, four million people in the Arctic region and 65 million people in small islands are exposed to these extreme events. Without major investments in adaptation, they would be further exposed to escalating flood risks, the report says. Some island nations are likely to become uninhabitable due to climate change but habitability thresholds remain extremely difficult to assess, say the report’s authors.
“Sea level is rising in Indian Ocean also. In north Tamil Nadu, Puducherry, Vishakapatnam coastal erosion is happening; one of the reasons for it is sea level rise. We have 36 tide gauges which are measuring sea level rise over the years. It will give us an indication of how we are impacted,” said M Rajeevan, secretary, ministry of earth sciences.
Data presented in the Lok Sabha recently showed Diamond Harbour in West Bengal had recorded a sea level rise rate of 5.16 mm per year between 1948 and 2005; Kandla in Gujarat saw a sea level rise rate of 2.89 mm/year. The global mean sea level rise was 3.6 mm per year in the 2006-2015 period compared to 0.16 mm/year between 1902 and 2015.
“Our studies also show that in the 2030 to 2050 period glacier mass loss in the Himalayas will be accelerated and become even more serious after that. This will mean higher discharge in rivers which will also be accentuated by extreme precipitation events,” said AL Ramanathan, glaciologist from Jawaharlal Nehru University.
The IPCC special report was approved on September 24 by 195 IPCC member governments. It will be a crucial scientific input at the 25th Conference of Parties at the United Nations Framework Convention on Climate Change (UNFCCC) in Chile in December.