Sky & Telescope - March 2025 - 18

Science & Society
Polar cell
Ferrel cell
Hadley cell
60º
" That's enough to move an observatory away from a
preferable zone to a less preferable zone, " Graham says. Also,
these cells now have more energy in them, and their air currents
are moving faster. " What goes up more quickly should
go down more quickly, too, and that has the potential to
affect stability in the atmosphere, " Graham adds.
It's not like Mauna Kea or Paranal are going to turn into
30º
a place like Scotland, he says, " but the precision required in
astronomy today could easily be affected by the relatively
minor perturbations that we expect from climate change. "
30º
60º
pATMOSPHERIC CIRCULATION Due to the complex interplay of
Earth's rotation and heat transport, the lower atmosphere in each hemisphere
divides into three distinct wind cells. Each cell is essentially a
closed circuit of circulating winds that redistributes heat. Several of the
world's professional observatories lie near where cool air in the Hadley
cells sinks toward the surface (see map on facing page).
ocean. They also do a poor job at dealing with variables like
cloud cover and changes in astronomical seeing.
" Clouds are very hard to model, " Haslebacher said. Maybe
the next generation of climate models could help with that,
she adds. " You would need higher-resolution climate models
to really be able to simulate clouds. "
More importantly, climate projections rely on historical
data, limiting their ability to predict unprecedented extreme
events or novel climate scenarios. " Climate as we measured it
is no longer a guide to what we might expect in the future -
we're in a no man's land, " says Edward Graham (University
of the Highlands and Islands, United Kingdom). Computer
simulations, especially those based on artificial intelligence
and machine learning " cannot foresee extreme events that
have not occurred before. "
Graham has conducted a thorough analysis of the plausible
evolution of the Hadley cells, the giant overturning
circulation patterns powered by hot air that rises at the equator.
That air cools as it travels poleward and sinks at roughly
30° latitude. Not by chance, some of the most prominent
observatories of the world are in the sinking branches of the
Hadley cells: The sinking air moves very slowly and has lost
almost all its humidity during the trip from the equator, creating
stable, dry atmospheres optimal for astronomers.
Graham found that the Hadley cells, powered by extra heat
in the atmosphere, are expanding. The Pacific Hadley cell is
growing fastest, moving at a rate of between half a degree to
two degrees in latitude per decade. That's a shift of hundreds
of kilometers over 50 years.
18 MARCH 2025 * SKY & TELESCOPE
More than Clear Skies
Astronomical observatories in remote locations require a
careful balance of scientific and logistical factors. Practical
considerations such as energy, water, food, safety, and healthcare
for staff are as important as scientific requirements. The
human element, however, is often overlooked. " It's not only
an observatory running by itself, there are people there, "
Cantalloube says. As demonstrated by events like the Chilean
protests of 2019 and the COVID-19 pandemic, political and
social stability are as essential as clear skies. Otherwise, " we
could go to North Korea, it's a good site, " Cantalloube says.
" But we don't go to North Korea, right? "
Climate change exacerbates these challenges. Extreme
weather events not only disrupt operations but put people in
harm's way. The 2023 Lahaina fire in Hawai'i, for example,
destroyed more than 2,200 homes and killed nearly 100
people - a far graver outcome than losing observing time.
The broader societal impacts of climate change, including
economic instability and resource scarcity, can also indirectly
affect astronomical research through funding cuts and
reduced public support. " I would say those are the things that
astronomers might feel first, " Graham says.
Some are already noticing. Van Kooten says that since the
pandemic, fewer astronomers are traveling to observatories
to observe, relying even more on local telescope operators
instead. This trend may be reinforced as individuals avoid airplane
travel due to concerns about its environmental impact.
Institutions and governments might eventually discourage
travel. This push to stay home could lead to the loss of handson
experience for astronomers, particularly younger generations,
hindering their understanding of telescope systems and
overall development. " I've just met people who have chosen
not to fly to observe, and that's already [one way] climate
change is affecting astronomers right now, " van Kooten says.
Skywatchers worldwide are also losing opportunities to
enjoy their hobby. " Smoke makes it impossible to get good
deep-sky images, " says S&T Contributing Editor Alan Dyer, an
astrophotographer based in southern Alberta, Canada. He has
canceled several observing trips due to smoke and fire risks.
Astronomical organizations and institutions need to proactively
address the evolving climate to narrow the uncertainty,
mitigate risks, and ensure the future of their operations,
Graham says. " Not nearly enough work has been done
in this particular area. "
HADLEY CELLS: BEATRIZ INGLESSIS / S&T
Sky & Telescope - March 2025

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