Acceleration of global warming divides scientists – 12/23/2023 – Environment

The abnormally high temperatures that hit the world in 2023, in addition to all their harmful effects on human beings and ecosystems, also caused some uproar in the community of scientists studying the climate crisis.

Does this year’s uncontrolled heat show that the effects of climate change have changed levels for good? Or is it more correct to see them as an extension of what was already foreseen, boosted by natural cycles?

“There is a certain rift within the community, and we will only be able to be sure of what is happening after some time, or with more studies”, summarizes geographer Karina Bruno Lima, a doctoral student in climatology at UFRGS (Federal University of Rio Grande southern). Everyone, of course, agrees that human action is the key to explaining the deterioration of the climate system.

Doubts about what is happening to the climate place two research heavyweights in the area on opposing sides, the Americans James Hansen, from the Earth Institute at Columbia University, and Michael Mann, from the University of Pennsylvania.

“There are two more crystallized positions”, says Alexandre Araújo Costa, climatologist at the State University of Ceará. Both, of course, agree that human action is the key to explaining the deterioration of the climate system.

“Hansen has pointed out the risk of feedbacks, feedbacks that can make the situation much more dangerous than we imagined until recently. Mann says: look, things are bad enough without thinking about it. It’s not that he denies the seriousness of what is happening, it’s just that he sees it as something that has been sung for a long time.”

Both Lima and Costa point out that, in the list of possible culprits for the apparent acceleration of the climate crisis in recent times, there must be a prominent role for so-called aerosols. Roughly speaking, the term designates small particles suspended in the atmosphere whose effect on the climate tends to be multifaceted.

Various human activities, such as the burning of biomass (incinerating a forest, for example), the use of fuels such as diesel in vehicles or certain types of industry can release large quantities and forms of aerosols into the air.

Some of them can absorb solar radiation and heat the atmosphere even more. Others, by interfering with the details of cloud formation, help to reflect sunlight and end up having a cooling effect.

Ironically, everything indicates that “dirtier” industries and fuels, widely used in the 20th century, may have contained part of the effects of global warming for a few decades thanks to the aerosols they emitted, avoiding an extra increase of up to 0.4°C in temperature of the planet.

The gradual replacement of aerosol-generating technologies with cleaner alternatives has reduced air pollution, which is good news for the population’s lungs, but may also explain the “rebound effect” of recently rising temperatures.

“It’s an abstinence crisis”, compares Araújo Costa. “As I usually say to my students, it will get worse before it gets better, especially because we haven’t even started the decarbonization process in earnest.”

Other factors may also be favoring a greater than expected increase in temperature. One of them has to do with changes in albedo, which corresponds to the ability of the Earth’s surface to reflect or absorb solar radiation. When the Arctic used to spend most of its time covered in snow and ice, for example, the whiteness of the polar regions reflected sunlight.

The melting of ice, however, exposing more and more, and for longer, the ocean areas in these regions, causes the absorption of sunlight — and, therefore, heat — to increase, since the sea water is much darker than snow.

On the other hand, the El Niño phenomenon, powerful this year, could be an element of natural variability in the climate system that injected an extra dose of drama into a situation that was already not at all favorable.

“Particularly, I think there is growing evidence [de uma aceleração]”, ponders Karina Lima. She cites a study led by Zeke Hausfather, from the non-governmental institution Berkeley Earth, in which computer models that simulate the evolution of the climate showed warming 40% faster in the 2015-2030 period than in the period between 1970 and 2014.

“I see a little reason on both sides”, says Araújo Costa. “Yes, 2023 was something extraordinary, and we will have to see what 2024 will be like. One point on which Hansen is right has to do directly with us: if all these buttons continue to be pressed, causing successive droughts in the Amazon, we run the risk of losing it even without cutting down a single tree.”

Politically, recalls the researcher, this should make it clear that a “quick and fair” transition away from fossil fuels is needed, instead of the confusing signals sent by the Brazilian government in favor of continued investments in oil.

Another key point, says Lima, is that the impacts associated with extreme weather events should not be underestimated, even if average warming does not change levels anytime soon. “They are not a distant threat, we are all susceptible to them, and everything can change very quickly.”