New Delhi: Leaders at the G-20 Summit, which took place in Rome on October 30-31, affirmed their commitment to the 2015 Paris Agreement goal wherein it had been decided to keep the rise in average global temperatures to 1.5 degrees Celsius, compared to pre-industrial times. Beyond this point, scientists say, the dangers of global warming grow immensely.
“We remain committed to the Paris Agreement goal to hold the global average temperature increase well below 2°C and to pursue efforts to limit it to 1.5°C above pre-industrial levels, also as a means to enable the achievement of the 2030 Agenda,” the G20 leaders said in a joint statement.
The much-awaited COP26 climate conference has also begun in Glasgow, Scotland, where representatives of nearly 200 countries are meeting from October 31 to November 12 to strengthen action under the 2015 Paris Agreement.
COP26 President Alok Sharma warned that the window to keep within the 1.5 degree warming target is closing.
"We know our shared planet is changing for the worse, and we can only address that together," he said, according to media reports.
"Where Paris promised, Glasgow delivers," he said.
Signed in 2015, the Paris Agreement aims to limit global warming to below 2 degrees Celsius, preferably to 1.5 degrees Celsius.
Scientists say keeping global warming below 1.5 degrees will avoid the worst climate impacts.
The 196 countries that adopted the Paris Agreement at COP21 in Paris have the 'long-term temperature goal' of limiting the global temperature increase to 1.5 degrees Celsius.
The Intergovernmental Panel on Climate Change (IPCC), in a 2019 special report titled, 'Global warming of 1.5°C', mentioned the impacts of global warming of 1.5 degrees Celsius above pre-industrial levels on our planet.
The IPCC report highlights that a warming of more than 1.5°C would increase climate-related risks for natural and human systems.
For instance, small island regions are more prone to climate-related risks, due to their geographic location.
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Why Target Was Brought Down To 1.5 Degrees From 2 Degrees
When countries across the world first started discussing how to tackle the challenges posed by climate change together, their objective was to limit the rising global average temperatures to within 2°C since the pre-industrial levels.
The pre-industrial times refer to the period between 1850 and 1900, which roughly coincided with the so-called Second Industrial Revolution. These five decades saw massive advances in technology and the resultant expansion of infrastructure around the world.
However, with the predicted impact, if the world got warmer by 2°C, showing that it could potentially threaten the existence of many of the least developed nations, the latter asked for the goal to be lowered to within 1.5°C.
The target of 1.5°C demanded much deeper emission cuts, requiring deployment of financial, technological and other resources to a huge extent.
While the highest emitters could not dismiss altogether the threats these smaller countries and island nations faced, they were reluctant to commit to the 1.5 degree warming target.
Trying to strike a balance, the 2015 Paris Agreement then decided to “hold” the rise in average global temperature to “well below” 2°C, and also promised to pursue efforts to get to the 1.5°C target.
The global average has already risen by over 1°C from pre-industrial times, and at this rate, the 1.5°C limit could be crossed by 2040, according to reports.
A key finding of the 2019 IPCC special report is that there is no region in the world that has achieved the long-term temperature goal of limiting warming to 1.5 degrees Celsius.
The Arctic region exhibits the strongest warming during its cool seasons, while the mid-latitude regions of the Earth show the strongest warming during the warm seasons.
There are many regions in which warming has surpassed 1.5 degrees Celsius above pre-industrial levels.
More than one-fifth of all humans live in regions where there has been warming greater than 1.5 degrees Celsius in at least one season.
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What Will Limiting Global Warming To 1.5 Degrees Achieve?
About 14 per cent of Earth's population will be exposed to severe heatwaves at least once every five years, when there is warming of 1.5 degrees Celsius. This figure will go up to 37 per cent at 2 degrees warming.
Limiting warming to 1.5 degrees Celsius would reduce the number of people frequently exposed to extreme heatwaves by about 420 million. Also, around 65 million fewer people would be exposed to extreme heatwaves, the IPCC report says.
At 2 degrees Celsius warming, the hottest days at Earth's mid-latitudes will be up to 4 degrees Celsius, while at 1.5 degrees Celsius, the warming will be up to 3 degrees Celsius.
Twice as many megacities as today are likely to become heat stressed at warming above 1.5 degrees Celsius.
This may cause 350 million more people to become heat stressed by 2050.
The deadly heatwaves experienced by India and Pakistan in 2015 may occur annually if there is 2 degrees Celsius warming. At 1.5 degrees Celsius warming or less, arctic land regions will see cold extremes warm by 5.5 degrees Celsius. However, a warming of 1.5 degrees to 2 degrees Celsius will cause cold extremes to be up to 8 degrees Celsius warmer.
Limiting warming to 1.5 degrees Celsius is expected to significantly reduce the probability of drought and risks related to water-availability in some regions, such as the Mediterranean, South Africa, South America, and Australia, finds the IPCC report.
Comparing 2-degree warming to 1.5 degrees, around 61 million more people in Earth's urban areas will be exposed to severe drought.
Limiting global warming to 1.5 degrees Celsius will cause a 50 per cent decrease in the number of people experiencing climate change-induced water stress, depending on future socioeconomic conditions.
People in river basins will be most vulnerable.
Some regions on Earth, especially in the Northern Hemisphere high latitudes, will see an increase in heavy rainfall events at 2 degrees Celsius warming compared to 1.5 degrees Celsius warming.
Impact Of 1.5 Degrees Warming On Biodiversity And Ecosystems
Loss of species and extinction: The IPCC report mentions studies conducted on 105,000 species of insects, plants and vertebrates, and says the climatically determined geographic regions of 6 per cent of insects, 8 per cent of plants, and 4 per cent of vertebrates will be reduced by more than half at 1.5 degrees Celsius warming.
Fires, extreme weather, invasive species: 1.5 degrees warming will reduce the risks from forest fires, extreme weather events, and invasive species, compared with 2 degrees Celsius warming.
Biome shifts: Around 50 per cent less area will be affected by biome shifts at 1.5 degrees Celsius warming compared to 2 degrees Celsius warming. 2 degrees Celsius warming will cause around 13 per cent of land areas to see their ecosystems shift from one type of biome to another.
Rainforests and boreal forests: Warming of 1.5 to 2 degrees Celsius will result in reduction of rainforest biomass, and an increase in deforestation and wildfires.
Impact Of 1.5 Degrees Of Warming On Oceans
Sea level: Even at 1.5 degrees Celsius temperature increase, sea levels will continue to rise, due to the heat stored in the oceans from human-produced warming, the authors of the IPCC report explain.
Polar ice sheets: The instabilities in the Antarctic ice sheet, and the irreversible loss of the Greenland ice sheet could cause the sea level to rise to more than 6 feet, over hundreds to thousands of years, at a warming between 1.5 and 2 degrees Celsius.
Ocean temperatures, acidity, oxygen levels: Limiting warming to 1.5 degrees Celsius would reduce increases in ocean temperature and associated increases in ocean acidity, compared to 2 degrees Celsius warming. However, 1.5 degrees warming will still cause oceans to become more acidic due to higher concentrations of carbon-dioxide. Also, ocean oxygen levels will decrease, leading to more "dead zones".
Sea ice: The Arctic Ocean will become free of sea ice during only one summer per century, at 1.5 degrees Celsius warming. However, 2 degrees Celsius warming will result in at least one ice-free summer every decade, due to more melting. At 1.5 degrees Celsius warming, loss of sea ice will impact the habitats of phytoplanktons, and marine mammals like polar bears and whales.
Marine ecosystems: The geographic ranges of many marine species will shift to higher latitudes, and new ecosystems will appear, at 1.5 degrees Celsius warming. Fisheries and aquaculture will be less productive. However, the risks are higher at 2 degrees Celsius.