For 13 consecutive months, global average air and ocean temperatures were probably the hottest they have been in human history.
This streak of extraordinary heat ended last month, the EU’s Copernicus Climate Change Service reported, as July 2024 was only the second hottest ever recorded – 0.04°C cooler than a record set the previous July.
In its wake are thousands of heat-related deaths, ailing ecosystems, and a planet firmly on the precipice of a profoundly altered climate.
“Global warming has consistently toppled records for warm global average temperatures in recent decades, but breaking them by as much as a quarter of a degree for several months is not common,” says Christopher Merchant, a professor of ocean and Earth observation at the University of Reading.
Air temperatures peaked in December 2023, when the Earth was 1.78°C hotter than the pre-industrial average for that time of year. Buoy-based sensors confirmed that the ocean was also record-warm at the time.
So what caused this stretch of unusually high temperatures on land and at sea?
“Several factors came together,” Merchant says. “But the biggest and most important is climate change, largely caused by burning fossil fuels.”
Big Oil and the little boy
When scientists refer to Earth’s pre-industrial temperature, they typically mean a global average taken between 1850 and 1900. Factories and power plants still existed in the second half of the 19th century, especially in Europe and North America, but the vast majority of greenhouse gas emissions generated by human activity had yet to be emitted. What’s more, meteorologists have a fairly good temperature record for this period with which to compare modern warming.
What this comparison tells us is that July 2024 was 1.48°C warmer than a typical July before the mass burning of coal, oil and gas, Merchant says. Roughly 1.3°C of that is directly attributable to global heating caused by these fossil emissions and land-use changes (deforestation, livestock farming) over the intervening decades.
The remainder, which caused the sudden temperature spike beginning in June 2023, was largely the result of a natural cycle in the climate known as El Niño.
“An El Niño event is a reorganisation of the water across the vast reaches of the Pacific Ocean. El Niño is so important to the workings of worldwide weather as it increases the temperature of the air on average across all of Earth’s surface, not only over the Pacific,” Merchant explains.
El Niño has ended, and with it, the run of record global average temperatures. Merchant expects temperatures to ease back slightly, but says there is no going back to the pre-2023 norm.
“A plausible scenario is that global temperatures will fluctuate near the 1.4°C level for several years, until the next big El Niño event pushes the world above 1.5°C of warming, perhaps in the early 2030s,” he says.
Over? Shoot!
Since the 2015 Paris agreement, the political consensus on climate change has been to strive to limit warming to 1.5°C. A slew of catastrophic and potentially irreversible changes to the systems that keep Earth habitable are more likely to occur once this long-term average has been crossed.
It’s possible that this process has already started for one system in particular: tropical coral reefs. Earth’s largest, the Great Barrier Reef off Australia, has suffered five mass bleaching events in the past nine summers and recently endured its worst heat in at least 400 years.
The new plan, if one exists among the world’s governments (approving new oil and gas production is still a normal feature of governing), would seem to accept the 1.5°C target being breached at least temporarily.
“The question is, how do we manage this period of ‘overshoot’ and bring temperatures back down?” asks Jonathan Symons, a lecturer in international relations at Macquarie University.
In autumn last year, a commission mainly composed of former government ministers from several countries published a report on the implications of overshooting 1.5°C. The report argued that high-emitters like Australia should now aim for “net-negative emissions” and begin urgently removing carbon from the air – by restoring habitats and deploying carbon capture and storage technology.
Symons summed up their reservations with both :“The commission worries many carbon removal approaches are phoney, impermanent or have adverse social and environmental impacts.”
One drastic option the Climate Overshoot Commission ruled out was “solar radiation management”: reflecting some of the Sun’s heat and light back to space by injecting reflective particles into the atmosphere, among other techniques. Academics continue to debate whether this is now an unpleasant necessity or more reckless vandalism of the atmosphere.
In lieu of a radical change of course, present global climate policy could breach the 1.5°C target by a degree Celsius or more according to an analysis published in Nature Climate Change on Monday.
The world seems to be delaying the end of fossil fuels, gambling that nature will hold its breath. Research has so far condemned this wishful thinking: computer models predict “waves of extinctions” and ecological damage spanning centuries from even a brief sojourn at 2°C.
Jack Marley is Environment + Energy Editor, The Conversation UK. This article is republished from The Conversation.
Published - August 20, 2024 08:07 am IST
