Earth more sensitive still to effects of climate change

TAMPA, Nov 24 (AFP): The world's oceans have absorbed more heat than previously thought over the last quarter of a century, scientists said on Thursday, leaving Earth more sensitive still to the effects of climate change.
Oceans cover more than two thirds of the planet's surface and play a vital role in sustaining life on Earth.
According to their most recent assessment this month, scientists from the Intergovernmental Panel on Climate Change (IPCC) say the world's oceans have absorbed 90 per cent of the temperature rise caused by man-made carbon emissions.
But new research published in the journal Nature used a novel method of measuring ocean temperature.
It found that for each of the last 25 years, oceans may have absorbed heat energy equivalent to as much as 150 times the amount of electricity mankind produces annually.
That is between 10-70 per cent higher than previous studies showed.
Whereas those studies relied on tallying the excess heat produced by known man-made greenhouse gas emissions, a team of US-based scientists focused on two gases found naturally in the atmosphere: oxygen and carbon dioxide.
Both gases are soluble in water, but the rate at which water absorbs them decreases as it warms.
By measuring atmospheric oxygen and CO2 for each year, scientists were able to estimate how much heat oceans had absorbed on a global scale.
The authors initially calculated that oceans had warmed 60 percent more than previously thought.
However, after some controversy, they acknowledged mistakes in the margin-of-error calculations, and subsequently settled on a range of 10-70 per cent.
"Our error margins are too big now to really weigh in on the precise amount of warming that's going on in the ocean," said author Ralph Keeling, of the UC San Diego's Scripps Institution of Oceanography, after being made aware of the error.
"We really muffed the error margins," he told the San Diego Tribune.
The IPCC warns that drastic measures need taking in order to limit global warming to 1.5 Celsius by the end of the century but the world produced a record amount of carbon emissions in 2017.
Meanwhile, scientists are proposing an ingenious but as-yet-unproven way to tackle climate change: spraying sun-dimming chemicals into the Earth's atmosphere.
The research by scientists at Harvard and Yale universities, published in the journal Environmental Research Letters, proposes using a technique known as stratospheric aerosol injection, which they say could cut the rate of global warming in half.
The technique would involve spraying large amounts of sulfate particles into the Earth's lower stratosphere at altitudes as high as 12 miles.
The scientists propose delivering the sulfates with specially designed high-altitude aircraft, balloons or large naval-style guns.
Stratospheric aerosol injection would involve spraying sulfate particles into the Earth's stratosphere at altitudes as high as 12 miles.
Despite the technology being undeveloped and with no existing aircraft suitable for adaptation, the researchers say that "developing a new, purpose-built tanker with substantial payload capabilities would neither be technologically difficult nor prohibitively expensive."
They estimate the total cost of launching a hypothetical system in 15 years' time at around $3.5 billion, with running costs of $2.25 billion a year over a 15-year period.