2° C no longer seen as global warming guard rail
AWORLD THAT HEATS UP BY 20C COULD SEE MASS DISPLACEMENT, A DROP IN PER CAPITA INCOME, SHORTAGES OF FOOD AND FRESHWATER, AND THE LOSS OF ANIMAL AND PLANT SPECIES
Limiting global warming to two degrees Celsius will not prevent destructive and deadly climate impacts, as once hoped, dozens of experts concluded in a score of scientific studies released on Monday.
A world that heats up by 2⁰C — long regarded as the temperature ceiling for a climate safe planet — could see mass displacement due to rising seas, a drop in per capita income, regional shortages of food and fresh water, and the loss of animal and plant species at an accelerated speed.
Poor and emerging countries of Asia, Africa and Latin America will get hit hardest, according to the studies in the British Royal Society’s Philosophical Transactions A.
“We are detecting large changes in climate impacts for a 2⁰C world, and so should take steps to avoid this,” said lead editor Dann Mitchell, an assistant professor at the University of Bristol.
The 197- nation Paris climate treaty, inked in 2015, vows to halt warming at “well under” 2⁰C compared to mid- 19th century levels, and “pursue efforts” to cap the rise at 1.5⁰C. UN Secretary- General Antonio Guterres last Thursday said climate change was “the most systemic threat to humankind”.
Time to adapt
With only one degree of warming so far, Earth has seen a crescendo of droughts, heatwaves, and storms ramped up by rising seas.
Voluntary national pledges made under the Paris pact to cut CO2 emissions, if fulfilled, would yield a 3⁰C world at best.
The treaty also requires that — by the end of the century — humanity stop adding more greenhouse gases to the atmosphere than oceans and forests can absorb, a threshold known as “net zero emissions”.
“How fast we get to a 2⁰C world” is critical, Mitchell said.
“If it only takes a couple of decades, we will be in trouble because we won’t have time to adapt to the climate.”
Among the conclusions found in the new studies:
Economic growth: Researchers led by Felix Pretis, an economist at the University of Oxford, predict that two degrees of global warming will see GDP per person drop, on average, 13 per cent by 2100, once costly climate change impacts are factored in.
A 2⁰C world will also “show significant negative impact on the rates of economic growth,” Pretis said. Under a 1.5⁰C scenario, he added, growth projections “are near indistinguishable from current conditions”.
Rising seas: Under a 2⁰C scenario, oceans rise about half a metre over the course of the 21st century, but well over a metre by 2300, another study found.
“When the planet warms, it takes the ocean hundreds, if not thousands, of years to fully respond,” lead author Rober Nicholls, a professor of coastal engineering at the University of Southampton, said.
That’s bad news for 500 million people living in “highly vulnerable” low- lying deltas, mainly in Asia, alongwith some 400 million people in coastal cities, many of which are already sinking due to over- construction or collapsing water tables.
Even in a 2⁰C world, the number of people affected by flooding could approach 200 million by 2300, the study calculated.
Food, water stress: Two degrees of warming would spare humanity much misery compared to our current trajectory, but would still lead to increased drought, flooding, heatwaves and the disruption of weather patterns.
Some regions will be hit worse than others, as will countries with rainfall- dependent agriculture, a team by Richard Betts, head of climate impacts research at the University of Exeter found.
The countries that show “the greatest increase in vulnerability to food insecurity when moving from the present- day climate to 2⁰C global warming are Oman, India, Bangladesh, Saudi Arabia and Brazil,” he said.
1.5⁰C vs. 2⁰C: A draft “special report” by the UN climate science panel to be unveiled in October, obtained by AFP, concludes that “holding warming at 1.5⁰C by the end of the 21st century [ is] extremely unlikely.”
At current rates, the greenhouse gas emissions putting that goal out of reach will have been released within 10 to 15 years.
Meanwhile, CO2 emissions — after remaining stable for three years, raising hopes that they had peaked — rose by 1.4 per cent in 2017, the International Energy Agency said this week.
But every tenth- of- a- degree counts, said Mitchell. “Even if we can’t limit global temperature increase to 1.5⁰C, but can limit it to 1.7⁰C or 1.8⁰C, this is still hugely more beneficial than just giving up,” he said.
“We can still keep temperatures well below 2 degrees,” said Myles Allen, a professor of geosystem science at the University of Oxford a co- author on several of the studies.
But doing so requires that “we start now and reduce emissions steadily to zero in the second half of the century,” he said.