The Summary
- Global temperatures in the last two years have been even higher than climate scientists expected.
- A new study offers a possible reason why: Cloud cover has decreased.
- The research suggests that the reduction may be a consequence of global warming, which would mean the planet is heating up even faster than scientists thought.
Over the past two years, global temperatures have increased significantly more than experts had anticipated. The tendency has created a conundrum: Are the abrupt changes due to hidden climate change dynamics?
The hottest year on record was last year, and 2024 was expected to be even hotter during the summer. Researchers were unable to explain about 0.2 degrees Celsius (0.36 degrees Fahrenheit) of the warming that was seen in 2023, even after accounting for the anticipated impacts of greenhouse gas pollution and El Ni o, a natural phenomenon that usually raises temperatures.
A potential explanation is provided by a recent study: It discovered that for the last two years, there has been less cloud cover, which has allowed more light to reach and heat the Earth’s surface instead of being bounced back to space.
According to the study, which was published on Thursday in the journal Science, the temperature anomaly seen in 2023 is most likely the result of a general decrease in the planet’s albedo, as that dynamic is known.
According to Helge Goessling, a climate physicist at the Alfred Wegener Institute in Germany and one of the study’s authors, this essentially accounts for the most recent rise in solar radiation that has been recorded.
One of the most challenging parts of the climate system to examine and simulate has been the expected behavior of clouds in a warmer planet. By providing answers, scientists will be able to assess the planet’s sensitivity to greenhouse gas emissions.
Earth is probably warming significantly more quickly than scientists previously believed if the decreases in low cloud cover aren’t the product of chance.
According to Goessling, it’s still unclear how much of this might be fluctuation that disappears. It changes the chances in favor of a warming that is greater than anticipated.
The analysis of NASA satellite data regarding Earth’s reflectivity and climate models served as the foundation for the current study. It lists three potential explanations for why there are fewer low clouds forming, but it makes no judgments regarding the relative contributions of each.
One explanation for the decrease in cloud cover is that a natural process is momentarily deviating from its usual course. For instance, it’s plausible that natural variability is changing the mechanics of cloud formation by causing the ocean’s surface to warm more than anticipated.
A second alternative is modifications to the rules governing maritime commerce. In 2020, the International Maritime Organization set restrictions on the amount of sulfur that might be included in marine fuels. According to some experts, lowering the quantity of sulfur particles in the atmosphere may unintentionally slow the production of marine clouds.
According to Goessling, the sulfur particles can make clouds brighter and longer-lasting because they serve as condensation nuclei.
The third possibility is that clouds are decreasing as a result of global warming due to unknown feedback loops in the climate system.
If the latter two scenarios prove to be the main causes, the climate is more vulnerable to human pollution than many scientists had previously believed, and as a result, humanity is getting closer to surpassing the emission reduction goals established by world leaders. (Change sensitivity is the measure of how warm the earth would be if atmospheric concentrations of carbon dioxide and other greenhouse gases doubled.)
Zeke Hausfather, a research scientist at Berkeley Earth and the lead for climate science at the financial firm Stripe, said there are still a lot of unanswered concerns.
In an email, he stated, “We are still unsure whether these changes in cloud behavior are a new ongoing change to the climate system or are just short-term variability that would eventually return to more normal conditions.”
The average land and ocean surface temperatures in 2023 were 2.12 degrees Fahrenheit higher than those of the 20th century, according to the National Oceanic and Atmospheric Administration.
Global leaders are still not doing enough to cut greenhouse gas emissions. The Paris Agreement’s target of 1.5 degrees Celsius (2.7 degrees Fahrenheit) will be far exceeded by the average rise in global temperatures of more than 3 degrees Celsius (5.4 degrees Fahrenheit).
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