Abdelrahman
Recently, scientists have engaged in an intriguing debate: Could the lunar surface temperatures have decreased as a result of global Covid-19 lockdowns?
Last year, two researchers suggested that the cessation of activities during the lockdown resulted in noticeable effects even on the moon, leading to a minor drop in temperatures on its surface. However, a new study challenges this claim, asserting that it is impossible to directly link the drop in temperature to the decline in global emissions that accompanied the lockdown.
Following several studies that highlighted a significant impact on air quality worldwide, two Indian researchers set out to explore if these atmospheric variations might have influenced the moon.
Durga Prasad, a scientist at the Physical Research Laboratory (PRL) in Ahmedabad and the lead author of the study, shared with Space.com that they viewed this as a unique opportunity to examine Covid’s effects on lunar conditions.
Prasad and co-author G. Ambily, also from PRL, analyzed data collected by NASA’s Lunar Reconnaissance Orbiter (LRO) from various locations near the lunar equator. They found that, between April and May 2020, surface temperatures dropped by 8 to 10 degrees Kelvin in the evenings, which they attributed to the pandemic-related global shutdown.
However, as is common in scientific inquiry, not all experts agree with their interpretation.
Shirin Haque, from the University of the West Indies in Trinidad, expressed skepticism through an email to Space.com, stating, “The situation is quite complex, and I believe not all factors have been taken into account.” Haque, alongside her colleague, questioned the original data’s interpretations that led to the initial conclusions.
Related: Coronavirus lockdowns have led to dramatic changes in pollution levels observed from space
Effects of Reduced Activity
As the Covid-19 pandemic began in early 2020, China was the first nation to impose lockdowns on its cities. Gradually, other countries followed suit, leading to a global shutdown after the World Health Organization declared a pandemic in March. By June, nations started to ease restrictions as life shifted into what many described as “the new normal.”
Multiple independent studies revealed that the lockdown had a remarkable impact on Earth’s atmosphere, a finding supported by anecdotal evidence. Images of major cities like Los Angeles showcased unusually clear skies in the spring of 2020. As people remained indoors, emissions from vehicles and planes drastically decreased.
When sunlight reaches Earth, part of it is absorbed while the rest is reflected as radiation. The planet also emits its own radiation, with both processes influenced by greenhouse gases in the atmosphere. This interplay produces what is known as terrestrial radiation or Earthshine.
During the lunar daytime, the moon receives energy from both the sun and Earth. At night, with its back to the sun facing a daylight Earth, the moon’s near side experiences warmth solely from our planet. Previous studies have indicated that Earthshine can influence lunar nighttime temperatures, a phenomenon first proposed by Leonardo da Vinci.
“When aerosol levels decrease, less solar radiation escapes back into space,” remarked Prasad.
The researchers utilized LRO’s Diviner Lunar Radiometer Experiment, a tool designed for measuring lunar surface temperatures. They identified six locations on the moon’s near side, all near the equator and with similar roughness and brightness values, to limit direct radiation impact. Data collection occurred between 10 p.m. and 4 a.m. local lunar time, minimizing the influence of daytime heat. The temperatures gathered spanned from 2017 to 2022, focusing particularly on the months surrounding the April to May 2020 lockdown peak.
“A six-month timeframe provides a robust data set for analysis,” Prasad explained. The findings were presented in September’s edition of the journal Monthly Notices of the Royal Astronomical Society (MNRAS).
Related: Stunning time-lapse photos capture the moon glowing with Earthshine
Differing Perspectives on Data
Yet, the issue remains complex.
Haque initially received the article from a colleague who questioned its validity. “I was surprised and assumed it might be a questionable publication, yet it appeared in a reputable astronomy journal,” she reflected.
Upon discussing the results with fellow astronomers, she noted, “A sense of disbelief and skepticism prevailed.” This led her and collaborator William Schonberg from the Missouri University of Science and Technology to investigate the findings, as they thought the claims were too remarkable to accept at face value.
Their conclusions appeared in MNRAS in January 2025.
While the impact of Earthshine on lunar temperatures is established, Haque and Schonberg express concerns regarding the extent to which the global lockdown influenced the observed cooling.
They noted a correlation between the temperature drop and its timing. Whereas Prasad and Ambily focused on measurements between April and May 2020, Haque pointed out that temperature declines had begun in 2019, prior to the lockdown, and were gradual, rather than abrupt.
Prasad counters this perspective, asserting that “Schonberg and Haque’s claims of prior temperature drops are based solely on visual analysis of a trendline.” He indicated that this trendline serves a visual purpose and averages observations, emphasizing that the specific data clusters from April and May are crucial.
Haque and Schonberg also lamented the study’s lack of clarity on the trendline’s creation, labeling this omission “unfortunate.” They suggested that if the trendline was misleading, it should not have been included.
Moreover, they highlighted another notable temperature decrease in 2018 that Prasad and Ambily had also noted, arguing that this drop could hold significance independent of the Covid shutdown.
Prasad maintained that their analysis concentrated solely on the lockdown period, stating, “Our research specifically examined the data from April to May, as it corresponds with the peak lockdown timeframe in 2020.”
Schonberg added, “It is premature to assert that the temperature drop observed was linked to reduced human activity during Covid-19 lockdowns. We think it’s essential to differentiate correlation from causation.”
Related: Experts predict air pollution levels will rebound as Covid-19 restrictions ease
Despite the contention, Prasad and Ambily remain confident in their conclusions.
“We have not claimed that the temperature drop is exclusively due to the Covid lockdown,” he clarified. “However, finding no alternative explanation, it appears that the lockdown is the most plausible factor.”
Haque and Schonberg conveyed their appreciation for their colleagues’ openness to different explanations, yet criticized the original article’s title, “Effects of Covid-19 global lockdown on our moon,” for seemingly dismissing the ambiguity surrounding the findings.
“It seems the title conveys a certainty that contradicts the uncertainty the authors would like readers to derive from their research,” they stated, noting that the conclusion suggests the temperature dip is undeniably connected to the global lockdown.
Prasad urged for further research to clarify the implications of their findings, concluding, “Without a concrete alternative explanation for the observed temperature anomaly coinciding with the strict lockdown period, it stands to reason that the Covid-19 lockdown is the likely cause.”
