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GLOBAL WARMING

French study ‘solves’ global warming riddle

French researchers this week claimed they have answered a riddle that has long perplexed scientists.

French study 'solves' global warming riddle
File photo of Antarctica: Photo: John "pathfinder" Lester

Levels of carbon dioxide rose hand-in-hand with warming at the end of the last Ice Age, according to a French study published on Thursday that will deal a blow to climate skeptics.

Their research centered the bubbles of atmospheric air, trapped in cores of ice drilled from Antarctica that date back to the last deglaciation, which ended some 10,000 years ago.

These tiny bubbles are closely scrutinised, for they contain carbon dioxide (CO2), the principal greenhouse gas behind global warming.

The higher or lower the CO2, according to the conventional benchmark, the greater or lower the atmospheric temperature.

The anomaly is this: the CO2 in the bubbles do not correspond to the level of warming indicated by the surrounding snowfall of that time.

Climate skeptics argued that this showed the CO2 rose after Earth's atmosphere warming.

It would thus imply that global warming today may come, at least in part, from natural means — not from carbon emissions from fossil fuels as the scientific consensus maintains.

Writing in the US journal Science, a team led by French glaciologist Frederic Parrenin looked at ice from five deep drilling expeditions in Antarctica.

By analysing the isotopic composition of the nitrogen gas in these samples, the researchers said they were able to filter out the confusing signal from the data.

During the last deglaciation, the temperature rose by 19 degrees Celsius (34.2 degrees Fahrenheit) while at the same time CO2 levels in the atmosphere rose by about 100 parts per million, they said.

The discrepancy comes from the physical process by which CO2 bubbles are formed in successive layers of snow.

"The gas bubbles are always more recent than the ice that surrounds them," France's National Centre for Scientific Research (CNRS) said in a statement.

Further work will be carried out on different ice samples taken from different eras to see whether this result holds.

The researchers said the study did not examine the reasons for the rise in temperature that ushered in today's deglaciation.

There are several natural factors for global warming, including volcanic eruption and rock weathering that releases heat-trapping greenhouse gases, as well as modifications in heat from the Sun and tiny changes in Earth's axis and orbit.

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CLIMATE CRISIS

Scorching summer was France’s second hottest on record

Three heatwaves since June produced France's second-hottest summer since records began in 1900, the Météo France weather service said on Tuesday, warning that scorching temperatures will be increasingly common as the climate crisis intensifies.

Scorching summer was France's second hottest on record

With 33 days of extreme heat overall, average temperatures for June, July and August were 2.3C above normal for the period of 1991-2020.

It was surpassed only by the 2003 heatwave that caught much of France unprepared for prolonged scorching conditions, leading to nearly 15,000 heat-related deaths, mainly among the elderly.

Data is not yet available for heat-related deaths this summer, but it is likely to be significantly lower than 15,000 thanks to preventative measures taken by local and national authorities. 

Most experts attribute the rising temperatures to the climate crisis, with Météo France noting that over the past eight summers in France, six have been among the 10-hottest ever.

By 2050, “we expect that around half of summer seasons will be at comparable temperatures, if not higher,” even if greenhouse gas emissions are contained, the agency’s research director Samuel Morin said at a press conference.

The heat helped drive a series of wildfires across France this summer, in particular a huge blaze in the southwest that burned for more than a month and blackened 20,000 hectares. 

Unusually, wildfires also broke out even in the normally cooler north of the country, and in total an area five times the size of Paris burned over the summer. 

Adding to the misery was a record drought that required widespread limits on water use, with July the driest month since 1961 – many areas still have water restrictions in place.

MAP: Where in France are there water restrictions and what do they mean?

Forecasters have also warned that autumn storms around the Mediterranean – a regular event as air temperatures cool – will be unusually intense this year because of the very high summer temperatures. A storm that hit the island of Corsica in mid August claimed six lives. 

“The summer we’ve just been through is a powerful call to order,” Prime Minister Elisabeth Borne said on Monday, laying out her priorities for an “ecological planning” programme to guide France’s efforts against climate change.

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