The two-year increase in global temperature is causing concern among scientists

As the year 2023 drew to a close, scientists had hoped that a global stretch of record heat might finally start to fade this year. Temporary conditions, such as the El Niño climate pattern, which has long been known to raise average global temperatures, were likely to give way and allow Earth to cool.

That did not occur.

On the contrary, global temperatures are still close to record highs. 2024 is most likely to be even warmer than 2023, which was by far the warmest year in recorded human history. However, some scientists believe this may suggest that the global climate is undergoing fundamental changes that are causing temperatures to rise more quickly than expected.

According to climate physicist Helge Goessling of the Alfred Wegener Institute in Germany, “this shifts the odds towards probably more warming in the pipeline.”.

Even if the heat is exceptional, one or two years of it does not necessarily indicate that the warming trend is accelerating. Scientists are exploring a number of theories for why the heat is been so persistent.

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They concur that the primary cause is that the world’s oceans continue to be abnormally warm, well above normal, which raises the temperature on land as well. This might just be an unlucky two years and turn out to be a transient phenomenon.

In the coming months, temperatures may begin to drop, and we would attribute this to internal variability. Zeke Hausfather, a climate scientist at Berkeley Earth, stated, “I don’t think we can rule that out just yet.”. However, he went on, “I believe there are indications that the warmth will be fairly persistent.”. “”.

However, some scientists fear that because the oceans have gotten so warm, they won’t cool down as much as they used to, which could speed up climate change by creating a feedback loop.

According to Kevin Trenberth, a distinguished scholar with the National Center for Atmospheric Research, “the best single indicator that the planet is warming is the global ocean, which is warming relentlessly year after year.”.

Even if other factors make the world a little hotter, they are only temporary. One important one, scientists say, is that years of efforts to clean up air pollutants are having an unintended consequence — removing a layer in the atmosphere that was reflecting some of the sun’s heat back into space.

Scientists say the lack of a clear explanation reduces their confidence that climate change will follow the established pattern predicted by models, regardless of the combination of factors or how long they last.

Hausfather remarked, “We can’t rule out much bigger changes in the future.”. As we learn more about climate change, we realize that uncertainty is not on our side. “.”.

Experts had been hoping that the trend could be reversed with the end of El Niño. Last winter marked the peak of the regular global climate pattern, which is fueled by a pool of warmer-than-normal waters across the Pacific. Typically, the global average temperature begins to decrease approximately five months after El Niño peaks.

This is frequently due to the fact that La Niña quickly replaces El Niño. The same strip of Pacific waters gets colder than usual under this pattern, which causes the planet to cool more broadly. Additionally, La Niña hasn’t shown up as scientists had anticipated.

The world is now waiting for help as it faces what is expected to be its first year above the long-feared threshold of planetary warming: average global temperatures that are 1 to 5 degrees Celsius warmer than they were two centuries ago, before people began burning enormous amounts of fossil fuels. At least a few years above this threshold are necessary to formally cross it. ().

With temperatures 1 point 48 degrees Celsius higher than the preindustrial average, 2023 is currently the warmest year on record. But 2024 is predicted to break the previous record with temperatures of at least 1 degree 55. By a margin of more than three tenths of a degree, last year’s record was more above the predicted trajectory of global warming than scientists had ever observed. It is anticipated that the margin will be even higher this year.

According to Trenberth, even seemingly insignificant temperature changes of one degree or less can have significant consequences.

He compared it to “the straw that breaks the camel’s back.”.

This includes melting glaciers whose freshwater resources are essential for energy generation, rising extremes of heat and humidity that are potentially fatal, and shifting ocean heat patterns that may affect important fisheries. Additionally, scientists predict that if temperature benchmarks are exceeded for several years in a row, storms, floods, and droughts will all become more intense, with a variety of cascading effects.

Record-warm waters are causing problems.

The current conditions are unlike anything that has been observed in previous years when El Niño has subsided.

According to an analysis of sea surface temperatures after three significant El Niño years (2024, 1998, and 1983), a La Niña-like pattern was visible in each of the three years, with an area of cooler-than-normal conditions forming in the equatorial Pacific Ocean.

In 2024, however, the patch was small, unimpressive, and dwarfed by the warmer-than-normal seas that encircle most of the world, including portions of all ocean basins.

These vast blobs of unusual oceanic heat are called marine heat waves, and they are usually characterized by seas that are significantly warmer than normal for an extended period of time, in the top 10% of historical observations. There are strong to severe marine heat waves in the Mediterranean Sea, the western and eastern Indian Oceans, the Atlantic, and a large portion of the Pacific.

Over one-third of the world’s oceans were at that high threshold in October. Conversely, ocean temperatures on less than 1% of the planet were within the lowest 10% of historical values.

The extremes of warm and cold ocean temperatures ought to balance each other out more precisely. However, what is occurring is a glaring example of how the majority of Earth’s energy imbalance is being absorbed by the oceans, where heat builds up the fastest. There are far more warm extremes than cold ones.

That’s a problem because what happens in the ocean doesn’t stay in the ocean.

Over 70% of the Earth is covered by ocean water, so conditions there have a significant impact on land temperatures and humidity, with coastal heat waves occasionally causing terrestrial ones to rise. Weather systems can occasionally linger, bringing with them the perfect conditions for the development of marine heat waves and long, sunny, wind-free days. Occasionally, these systems can cross both the ocean and the land, causing a linked heat wave and transferring humidity.

According to Trenberth, one of the main causes of the unrelenting rise in global average surface temperatures is the growing heat in the oceans, especially in the upper 1,000 feet.

Furthermore, variations in ocean heat content can impact not only air temperatures but also sea ice, storm energy, and global water cycles.

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Researchers are starting to investigate other potential causes of these variations in global temperature.

According to a recent study, 20 to 30 percent of the warming observed over the North Atlantic and North Pacific may have been caused by a decrease in air pollution over the world’s oceans, according to lead author Andrew Gettelman, a scientist at the Pacific Northwest National Laboratory.

Sulfur dioxide particle concentrations, which tend to promote cloud formation, have significantly decreased since 2020 when shipping liners were subject to restrictions on the amount of sulfur in their fuels. Even though there will be fewer clouds and less pollution, the oceans will warm as more solar radiation strikes them.

According to a study published Tuesday, a decrease in cloud cover probably played a role in the planet’s previously unexplained warming that occurred last year, which may have been between 0 and 2 degrees Celsius. Goessling and associates believe that resulted from both cleaner shipping emissions and a positive feedback loop whereby warming near the Earth’s surface causes less cloud cover, which in turn causes even more warming.

According to the study, the amount of sunlight reflected back into space by light-colored surfaces like clouds, snow, and ice cover, known as planetary albedo, may have been at its lowest level since at least 1940 in 2023.

Other factors, like an increase in water vapor in the stratosphere following a volcanic eruption in 2022, have also been questioned.

But Earth’s systems are so complex that it’s been impossible to parse what exactly is happening to allow the surge in global temperatures to persist for so long.

Gettelman asked, “Is this a passing trend or is this a real acceleration of the warming?”. “Everyone is currently attempting to comprehend that. “.”.

What is the next step?

It is generally predicted that this year will be the warmest on record, primarily due to the massive ocean heat reserves.

And as far as widespread warmer-than-average seas are concerned, seasonal model guidance keeps the accelerator running until early 2025.

The planet’s storm tracks, jet streams, and atmospheric circulation patterns will all alter due to record ocean heat and global temperatures. We’ll keep setting temperature records.

The extent of these changes is partially determined by the amount of warming that takes place in the upcoming year. That remains uncertain, though, as the cooling that typically follows El Niño has yet to materialize.

Hausfather, who also works for the payments company Stripe, suggests that temperatures may soon start to decline and that natural planetary variations may be more significant than scientists initially thought.

According to him, a period of neutral weather—one that is neither La Niña nor El Niño—should result in a cooling effect on global average temperatures even in the absence of a La Niña.

However, there would be nothing to stop the next El Niño from sending global temperatures skyrocketing if this year’s unusual planetary warmth doesn’t slow down into 2025. The starting point for the next El Niño would be that much higher. It is unclear if that will occur later in 2025.

According to Hausfather, the lack of clarity is concerning because some of the most tenable explanations permit the most drastic scenarios of global warming.

“We may not find it consoling that we don’t know the answer in this case,” he stated.