 "Climate change, global warming")
July 2023 was in turn 0.28°C warmer than the previous record-hot July in 2019. Photo: Bloomberg
July 2023 was in turn 0.28°C warmer than the previous record-hot July in 2019, so the remarkable jump in temperature during the past year has yet to ease off completely. The warmest global air temperature recorded was in December 2023, at 1.78°C above the pre-industrial average temperature for December – and 0.31°C warmer than the previous record.
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. The end of this streak does not diminish the mounting threat of climate change.
So what caused these record temperatures? Several factors came together, but the biggest and most important is climate change, largely caused by burning fossil fuels.
What caused the heat streak
Temperatures typical of Earth 150 years ago are used for comparison to measure modern global warming. The reference period, 1850–1900, was before most greenhouse gases associated with global industrialisation – which increase the heat present in Earth’s ocean and atmosphere – had been emitted.
But global warming doesn’t happen in a smooth progression. Like UK house prices, the general trend is up, but there are ups and downs along the way.
The warm El Niño phase of this cycle began to kick in a year ago, reached its peak around the end of 2023 and is now trending neutral, which is why the record-breaking streak has ended.
The 2023/2024 El Niño was strong, but it wasn’t super-strong. It doesn’t fully explain the remarkable degree to which the past year broke temperature records. The exact influence of other factors has yet to be fully untangled.
We know there is a small positive contribution from the Sun, which is in a phase of its 11-year sunspot cycle in which it radiates fractionally more energy to the Earth.
Methane (also a byproduct of the fossil fuel industry, alongside cattle and wetlands) is another important greenhouse gas and its concentration in the air has risen more rapidly in the past decade than over the previous decade.
Scientists are also assessing how much measures to clean up air pollution might be adding to warming, since certain particulate air pollutants can reflect sunlight and influence the formation of clouds.
A temperature ratchet
As the Pacific Ocean is now likely to revert towards La Niña conditions, global temperatures will continue to ease back, but probably not to the levels seen prior to 2023/24.
El Niño acts a bit like a ratchet on global warming. A big El Niño event breaks new records and establishes a new, higher norm for global temperatures. That new normal reflects the underlying global warming trend.
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.
The Paris agreement on climate change committed the world to make every effort to limit global warming to 1.5°C, because the impacts of climate change are expected to accelerate beyond that level.
The good news is that the shift away from fossil fuels has started in sectors such as electricity generation, where renewable energy meets a growing share of rising demand. But the transition is not happening fast enough, by a large margin. Meeting climate targets is not compatible with fully exploiting existing fossil-fuel infrastructure, yet new investment in oil rigs and gas fields continues.
Headlines about record breaking global temperatures will probably return. But they need not do so forever. There are many options for accelerating the transition to a decarbonised economy, and it is increasingly urgent that these are pursued.
First Published: Aug 18 2024 | 11:20 AM IST
