Scientists wonder if, beyond climate change and the El Niño phenomenon, there are additional reasons that explain the runaway warming of the Earth this year. The EU's Copernicus climate change service confirmed the day before yesterday that July broke all records and exceeded by 0.33ºC the hottest month in recorded history so far, July 2019.
Scientists agree that the main cause of this record-breaking July has been warming, the result of activities involving the burning of coal, oil or gas. But other factors appear, such as the 165 million tons of water vapor ejected into the atmosphere in January 2022 by the Hunga Tonga-Hunga Ha'apai submarine volcano, in the Pacific, or certain improvements in the quality of cleaner air, especially in maritime transport, which would increase solar radiation.
“What is behind all this is global warming. Every year the probability that there are extreme temperatures and that the thresholds are exceeded, is greater. The trend is very clear, that is the pattern”, says Carlo Buontempo, director of the Copernicus climate change service. "We are in a phase of the year in which the warming caused by El Niño is already playing a prominent role, and it is not only a warming of the Pacific, but also of the Atlantic and other oceans," he adds.
One of the agents suspected of this aggravated warming is the eruption of Hunga Tonga, which registered a strong explosion on January 15, 2022. It is estimated that the eruption injected 165 million tons of water vapor into the stratosphere, a powerful gas of greenhouse effect that traps heat as 500,000 tons of sulfur dioxide (SO2).
Scientists are trying to find out how all that volume of hot water could affect the Earth's surface in the coming years. "It was a unique event," Holger Voemel, a scientist at the National Center for Atmospheric Research in Colorado, has been reiterating.
Rubén del Campo, spokesman for Aemet, alludes to the publication at the beginning of the year of a new study that analyzed the amount of steam produced and its distribution, and in which it was pointed out that the global average temperature could increase due to this effect in a few hundredths of a degree (between 3 and 4 hundredths). "It is a small increase, but, together with climate change and El Niño, they are factors that are adding up," he says.
Normally, large volcanic eruptions tend to cool the Earth because they produce a lot of SO2 emissions, aerosols and other particles, which have a cooling effect on the planet. These aerosols act as an "awning" and bounce solar radiation, as occurred in the case of the Pinatubo volcano in 1991. However, in the case of Hunga Tonga, it is a volcano that emerged from under water, which I am spewing unprecedented amounts of vapor into the stratosphere and where it will take years to dissipate.
On the other hand, a preliminary modalization study, which has not yet been submitted to scientific review, suggests that its maximum climatic effect could be felt in the middle of the decade and lead to warming in some areas, especially in the northern hemisphere, of up to 1.5ºC in winter, while in others it could cause a cooling of 1ºC, especially in the southern hemisphere.
The volcano, so far, “may have made a relatively small contribution; but it can be said that it can play an important role” in the future, adds Carlo Buontempo.
Michael Diamond, a climatologist at Florida State University, says shipping, now somewhat cleaner, may be another factor. For decades, shipping has used very dirty, high sulfur dioxide fuel, which emits particles that reflect sunlight in a process that cools the atmosphere and masks some of the global warming (although it pollutes the air we breathe).
However, the new regulations for the merchant marine (of the World Maritime Organization) have been reducing the presence of sulfur, especially in the North Atlantic, where a large part of the maritime traffic occurs. That decrease has been estimated at 10%. Less sulfur in the atmosphere means fewer aerosols blocking solar radiation, and therefore may lead to more land and sea surface heating. And another side effect. Aerosol particles serve as nuclei for clouds to form; and if there are fewer condensation nuclei, there will be fewer clouds and therefore more sun will also reach Earth, says the Aemet spokesman.
Diamond estimates that there will be a warming of 0.1ºC by mid-century from shipping regulations, although warming could be 5 to 10 times stronger in heavily trafficked areas in the North Atlantic.
The reduction of these air polluting elements has been able to clean the atmosphere, but Carlo Buontempo does not believe that "it played a determining role" in the high temperatures in July.
In this search for "suspicious elements" of aggravating global warming, the lower volume of circulation of African dust from the Sahara to the Atlantic is also pointed out, which also means less presence of aerosols and less cooling capacity. Rubén del Campo explains that this has been a clearly natural phenomenon, produced at the beginning of summer, in a context of anomalous atmospheric circulation and a high pressure system concentrated in the North Atlantic and less so in the Azores.
"The news that July has been the warmest month on record should perhaps not come as a surprise," Chris Hewitt, director of climate services at the World Meteorological Organization, said during the UN press briefing on August 8.
The latest WMO Annual State of the Climate Report indicated that 2015 to 2022 were the eight warmest years on record, and this is due to clear decade-over-decade warming.
"As we continue to see continued increases in greenhouse gas concentrations in the atmosphere, this long-term warming will continue and temperature records will continue to be broken," he said.
While the race is open to find out if this will be the hottest year in history. 2020 remains the hottest year of all so far, tied with 2016.
Comparing the averages for this year to date, from January to July, the average world temperature in 2023 is the third highest on record, with an increase of 0.43°C compared to the period 1991-2020, while that comparative increase was 0.49°C in 2016 and 0.48°C in 2020.
On the other hand, the gap between 2023 and 2016 is expected to narrow in the coming months, since the last months of 2016 were relatively cold (reducing the annual average at the end of the year by 0.44 °C), while it is expected that the rest of 2023 will be relatively warm since this year there is an episode of El Niño warming.
