Paris:

Last year’s northern hemisphere summer was the hottest in 2,000 years, according to a new study published on Tuesday.

Scientists say 2023 was the hottest year globally since records began in 1850, but the study in the journal Nature indicates human-caused climate change pushed northern summer highs well beyond anything seen in two millennia.

“We shouldn’t be surprised,” the study’s lead author Jan Esper told AFP. 

“For me it’s just the continuation of what we started by releasing greenhouse gases” that cause global warming, said Esper, a professor of climatology at Germany’s Johannes Gutenberg University.  

Scientists used tree-ring data from sites across the northern hemisphere to estimate global temperatures between the first century AD and 1850, before the advent of modern observational instruments. 

The conservative estimate found that 2023 was at least 0.5 degrees Celsius hotter than the warmest northern hemisphere summer of that period in AD246.

Otherwise, it was 1.19 degrees warmer.  

Study co-author Max Torbenson told reporters that 25 of the last 28 years exceeded the summer highs of AD246 — the hottest year before modern temperature records began. 

By contrast the coolest summer of that 2,000-year period was nearly four degrees below 2023 summer temperatures in the northern hemisphere due to a major volcanic eruption.

Scientists say volcanic activity could bring about cooler conditions in future as they did in the past, but that ultimately humanity’s release of greenhouse gases would keep trapping heat in the atmosphere.

In 1992, an eruption the previous year helped soften the impact of the El Nino weather system, which warms the Pacific Ocean and can bring hotter global conditions. 

After the effect subsided, temperatures soared in 1998, which the study noted was one of the warmest summers after 2023 and 2016 respectively — both also El Nino years.

Esper said the only way to curb rising temperatures was to immediately start cutting emissions and “the longer we wait, the more difficult and expensive it will be”. 

– Health risks – 

A separate study published on Tuesday warned that higher temperatures and ageing populations would see tens of millions of older people being exposed to dangerous heat extremes by 2050.

Already 14 percent of elderly people are exposed to days exceeding 37.5 degrees, which can aggravate health conditions and even lead to death, said the study in the journal Nature Communications. 

That number is expected to climb to 23 percent by the middle of the century, the study said.

“Different countries in the world are facing similar issues… but the level of preparedness, the adaptive capacity of people and of society is different,” the study’s lead author Giacomo Falchetta told AFP.

Europe has systems in place to support people during heatwaves but faces considerable change as one of the fastest warming regions on Earth, said Falchetta of the Euro-Mediterranean Center on Climate Change. 

The share of elderly people in Africa and Asia is set to grow dramatically though populations in poorer regions lack access to sufficient clean water or healthcare to cope with heat extremes, Falchetta said. 

“It raises questions of inequality around the world in terms of how governments and regions are equipped to cope with this,” he said. 

While 2050 appears far off, Falchetta said people as young as 40 today would be among those vulnerable to future heatwaves.

Ageing populations cannot be avoided but “reducing emissions can really reduce to some extent the heat exposure that will be felt”, he said. 

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

The Earth experienced the warmest June-August period on record this year, according to American space agency NASA and the National Oceanic and Atmospheric Administration (NOAA). It was the hottest summer in the Northern Hemisphere and the warmest winter in the Southern Hemisphere.

The months of June, July, and August were 0.23 degrees Celsius warmer than any previous summer in NASA’s record and 1.2 degrees Celsius warmer than the average summer between 1951 and 1980. Additionally, August temperature was 1.2 degrees Celsius higher than usual. It is to be noted that in the Northern Hemisphere, meteorological summer lasts from June to August.

This new record comes as a global heat wave intensified wildfires in Canada and Hawaii and fueled intense heat in South America, Japan, Europe, and the US, as per NASA.

NASA Administrator Bill Nelson said in a statement, “Summer 2023’s record-setting temperatures aren’t just a set of numbers – they result in dire real-world consequences. From sweltering temperatures in Arizona and across the country, to wildfires across Canada, and extreme flooding in Europe and Asia, extreme weather is threatening lives and livelihoods around the world.”

Greenhouse gas emissions have been identified as a major driver behind climate change and the worldwide warming trend that resulted in such a sweltering summer. NOAA chief scientist Sarah Kapnick said, “Not only was last month the warmest August on record by quite a lot, it was also the globe’s 45th-consecutive August and the 534th-consecutive month with temperatures above the 20th-century average. Global marine heat waves and a growing El Nino are driving additional warming this year, but as long as emissions continue driving a steady march of background warming, we expect further records to be broken in the years to come.”

The tropical Pacific Ocean experiences El Nino, a natural climate trend characterised by higher-than-normal sea surface temperatures. The phenomenon may have wide-ranging consequences, frequently bringing colder, wetter weather to the Southwest of the US and drought to nations in the western Pacific, such as Australia and Indonesia, according to NASA.

“Unfortunately, climate change is happening. Things that we said would come to pass are coming to pass. And it will get worse if we continue to emit carbon dioxide and other greenhouse gases into our atmosphere,” Gavin Schmidt, a climate scientist with the space agency stated.