The Courier & Advertiser (Angus and Dundee)
Scots researchers help reveal biggest CO2 rise
The amount of carbon dioxide in the atmosphere is increasing 10 times faster than at any point in the past 50,000 years, research in Scotland and the US has shown.
A team of researchers led by Oregon State University and St Andrews University did a detailed chemical analysis of ancient Antarctic ice.
Their findings, published in the Proceedings of the National Academy of Sciences, provide important understanding of abrupt climate change periods in Earth’s past.
They branded the rate of carbon dioxide (CO2) increase “unprecedented”, and said it was driven by human emissions.
When CO2 enters the atmosphere, it contributes to warming of the climate due to the greenhouse effect. In the past, the levels have fluctuated due to ice age cycles and other natural causes, but today they are rising because of human emissions, according to scientists.
Dr Kathleen Wendt, an assistant professor in Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences and the study’s lead author, said: “The rate of CO2 change today really is unprecedented.
“Our research identified the fastest rates of past natural CO2 rise ever observed, and the rate occurring today – largely driven by human emissions – is 10 times higher.”
Ice that built up in the Antarctic over hundreds of thousands of years includes ancient atmospheric gases trapped in air bubbles.
Scientists used samples of ice from up to two miles deep to analyse the trace chemicals.
Previous research showed that during the last ice age, which ended about 10,000 years ago, there were several periods where carbon dioxide levels appeared to jump much higher than the average. But the measurements were not detailed enough to reveal the full nature of the rapid changes.
Dr Wendt said: “You probably wouldn’t expect to see that in the dead of the last ice age.
“But our interest was piqued, and we wanted to go back to those periods and conduct measurements at greater detail to find out what was happening.”
They identified a pattern that showed the jumps in carbon dioxide occurred alongside North Atlantic cold intervals known as Heinrich Events, associated with abrupt climate shifts around the world.
Study co-author Dr James Rae, from the School of Earth and Environmental Sciences at St Andrews University, said: “These Heinrich Events kick off an astonishing sequence of rapid shifts in climate around the world.
“They start with a weakening of the North Atlantic’s circulation system, which causes rapid cooling in north-western Europe, sea ice expansion from Scotland to New York, and disruption to tropical monsoons. Our paper shows they also change winds and circulation in the ocean round Antarctica, which belches out CO2.”
During the largest of the natural rises, carbon dioxide increased by about 14 parts per million in 55 years, and the jumps occurred about once every 7,000 years or so. At current rates, that magnitude of increase takes only five to six years.
Evidence suggests that during past periods of natural carbon dioxide rise, the westerly winds that play an important role in the circulation of the deep ocean were also strengthening, leading to a rapid release of CO2 from the Southern Ocean.
Other research has suggested these westerlies will strengthen over the next century due to climate change. The researchers said their findings suggest if that occurs, it will reduce the Southern Ocean’s capacity to absorb humangenerated carbon dioxide.
Dr Wendt said: “We rely on the Southern Ocean to take up part of the carbon dioxide we emit, but rapidly increasing southerly winds weaken its ability to do so.”