What Happens If Earth Loses Its Clouds?


Um, sorry to be the bearer of startling news,
but…the clouds are disappearing? Like we could be edging closer and closer
to a world with no clouds, which could contribute a significant 8 degrees to the already predicted
global temperature rise. (looking up at the sky) “No come bacccckkkk!” We all know climate change is already radically
changing our world and will continue to do so. But an unexpected byproduct of high atmospheric
carbon dioxide levels is a loss of clouds. I know it sounds insane, but it may have happened
before. Around 56 million years ago, the geologic
record indicates that the world was essentially ice free. In other words, it was SUPER hot, with an
average annual temperature of around 30 degrees celsius—a hot flash in the earth’s history
we now refer to as the Paleocene-Eocene Thermal Maximum. In trying to figure out how the heck earth
could have gotten that toasty, today’s scientists estimate that it could be due to a loss of
cloud cover—particularly stratocumulus clouds. To help us unravel this theory, we spoke to
journalist Nathalie Wolchover, who spent over a year researching this topic. Nathalie: The question of how stratocumulus
clouds will change is kind of the most important question in knowing how bad kind of global
warming is going to be going forward. Stratocumulus clouds are the most common cloud
type and more of earth’s surface is covered by them than any other kind of cloud. They keep Earth and its oceans cool by shading
all of us underneath them and bouncing sunlight back into space, away from us. A lot of them also produce a nice drizzle. They’re dependent on convective instability,
and they form a distinctive, relatively thin layer because their growth upwards is limited
by a zone of dry stable air above them, even while they draw moisture from whatever’s
underneath them. Their structure is totally dependent on their
ability to release and absorb heat and moisture in a very particular way. A way that cannot be disturbed. Now, we do have very high-fidelity simulations
and computer models that help us understand the possible effects of climate change. From sea ice melt to sea level rise to temperature
changes, we can understand how fluctuating factors like levels of atmospheric CO2 may
affect the earth’s natural systems. These kinds of models are run on supercomputers
because they have so many intricate moving parts that the calculations would just be
impossible on any other kind of computer. But cloud dynamics, like what’s happening
inside stratocumulus clouds, actually take place on too small a scale to be included
in these larger models. They’re also just so complex that they’re
very difficult to predict, so they get left out of big climate simulations that tell us
a lot about what could happen to our world as it warms. A joint research team from CalTech and the
Pacific Northwest National Laboratory tackled this gap in our climate models. They created a novel application of the same
kind of simulations we use for larger climate phenomena: a large-eddy simulation. Applying this on a smaller scale allowed them
to study cloud behavior in response to several factors—one of them being atmospheric CO2
concentration. And it turns out—as the CO2 levels rise,
the stratocumulus clouds can’t achieve as much longwave cooling, or the release of heat
from the top of the cloud. This disturbs the convection that keeps the
cloud together, and they just break apart. Nathalie Wolchever: So they found that this
breakup of stratocumulus clouds could actually add eight degrees Celsius of additional warming
to the Earth’s system in the future. And a big question is at what point will that
tipping point occur. But based on some Simple simple assumptions
this tipping point would occur when the CO2 in the atmosphere reaches twelve hundred parts
per million. And that’s actually CO2 equivalent. So that would include other greenhouse gases
Kind of yeah. So that level is three times the current level
of CO2 in the atmosphere. This work confirms that high historic CO2
levels may have caused the lack of cloud cover that led to a sweltering PETM back in the
day. But it also presents the alarming prospect
that rising atmospheric CO2 today not only raises global temperatures, but could lead
to loss of cloud cover. This results in even hotter global temperatures
than we’d previously anticipated—just because our climate models didn’t include
cloud dynamics. Nathalie: And it’s also important to remember
that this tipping point is far enough away that we can avoid it. And that’s been interesting to talk to these
scientists and kind of understand that they are more optimistic than you might expect
because I mean maybe that’s the nature of the people who study climate change. You have to be optimistic or you just wouldn’t
be able to stand dealing day in and day out with this prospect. This research makes an essential contribution
to our understanding of atmospheric science in an era of changing climate. But this simulation only looked at one particular
area of the globe that’s prone to cloud loss, and we may not be able to extrapolate
that behavior to the whole world, at least not without further work on the subject. It’s a crucial example of why continuing
to understand how all these complex unknowns work together is SO important, and needs to
be supported. So we can keep preparing for our new reality,
and hopefully, if we detect these issues early enough, take action that could keep them from
happening in the first place. Now that we have your attention, it’s Earth
DayAnd let’s not forget about Earth Day, . Ever wonder what would happen if the earth
just get a liiiiittle bit hotter? Found out in this episode and if you like
climate science updates like these subscribe! Thanks so much for watching and we’ll see
you next time on Seeker.

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