CLOUDS AGHHHHHHHHH YAYAYAYYA!!!! Part 3

Hello fellow readers! This post is the “Big One”, the one that clarifies clouds’ role in climate change and, interestingly enough, the role climate change plays on clouds. Without further ado, let’s get right into it.

Climate Change Affecting Clouds

According to an article from Nature, experts have “observed and simulated cloud change patterns [that] are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes.” This is a lot to take in so I am going to break it down into:

1. Storms (and cloud cover) moving poleward and the expansion of subtropical dry zones
2. The increasing vertical growth of clouds

Before I go deeper into this topic, I want to preface that experts don’t really know what is causing these global shifts due to the “disagreement among climate models and observational datasets over what cloud changes have occurred in recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes” (Nature). Therefore, I don’t really know what is happening either. A lot of the material in this blog is a mix of data-supported facts, scientific assumptions from experts, and my own thoughts sprinkled in.

1. Storms Moving Poleward & Subtropical Dry Zones Expanding

From what I’ve gathered, the main reason for both of these global shifts is the excess greenhouse gas emissions which is causing global warming which is causing the Hadley cells to grow (Environmental Defense Fund). This is HUGE! Hadley cells, one of the factors driving prevailing wind patterns, are convection cells in the atmosphere where warm air from the Equator rises ⬆️, flows poleward ➡️, cools, sinks at middle latitudes ⬇️, flows toward the Equator ⬅️, etc.. With the Hadley cells expanding, this means the cool air is sinking at higher latitudes. The reason the Hadley cells are expanding is because, with global warming, the air has to move farther poleward to cool enough to sink.

According to a study done by experts at NOAA, MIT, and Princeton, “Hurricanes are drifting toward the poles most likely due to an expansion of the Hadley Cell” (EDF). These storms “have been shifting pole-ward at a rate of 30 to 40 miles per decade over the last 30 years” (ibid) and are also getting stronger. The hurricanes are just the storms experts have tracked. Along with these storms, cloud coverage is also moving poleward which will cause a whole host of problems that I will get to later in this post. I am not quite sure what the correlation is between the Hadley Cells expanding and clouds/storms shifting poleward so if you know anything about this, please enlighten me!

As for the subtropic expansion, I am in a similar predicament; I am pretty sure that the subtropic expansion has to do with Hadley cell expansion in some way but I am not exactly sure how. I do know that Hadley cells have their downward turn at the mid-latitudes where the subtropics are and that this means the subtropics experience higher pressure. I also know that high pressure means storms cannot grow which causes the subtropics to be really dry, hence the deserts found in these latitudes (Sharan, the Arabian Peninsula, most of Australia, etc.). If the Hadley cells are expanding, does this mean the high pressure areas are expanding or just moving poleward? Respectively, does this mean the subtropics are expanding or just moving poleward? Is it only the subtropics expanding or are other climate zones as well? Anyways, these are questions my research could not fill in so, yet again, if you know anything about this please email me at 25fay@da.org.

2. Increasing Vertical Growth of Clouds

Alrighty. That was a very hard section to write and wrap my head around because there are so many conflicting pieces of research😮‍💨. To say the least, I would take most of what I wrote in the previous section with a grain of salt. Luckily, we are now onto a topic I feel more confident talking about: the increasing vertical growth of clouds😌.

The growth of clouds gets blocked when it reaches the top of the troposphere AKA the tropopause. This is why cumulonimbus clouds have the anvil shape on top: it grows vertically, hits the top of the troposphere, and then expands horizontally.

The tropopause is the atmospheric boundary between the troposphere and the stratosphere that coincides with an abrupt change in the Environmental Lapse Rate AKA how quickly the temperature changes based on the altitude (e.g., -10 deg C/km). Clouds stop growing vertically at the tropopause because, “water vapor is condensed out of the air that is entering the stratosphere” (Wikipedia). This is known as an atmospheric cold trap “because it traps [condenses] ascending gases with high boiling points [like water vapor], forcing them to drop back into Earth” (Wikipedia). Pretty much, it gets too cold for the clouds to continue growing upwards.

But, due to global warming, the troposphere is expanding upwards and thus, the tropopause is at a higher altitude. Also, the tropopause “cold-trap” is weakening, allowing more water vapor to enter the stratosphere. (By more water vapor I mean more than the usual 4 ppm found in the stratosphere.) If the world is heating up, this means the bottom of the troposphere starts at a warmer temperature. This means you will have to go higher up in the atmosphere to reach the point at which the air is at the temperature in which the tropopause starts. This is a bunch of word garble so I drew some lines on a diagram and called it a day:

But what does this have to do with clouds? If the tropopause and its cold trap are higher up in the atmosphere, this means clouds can grow taller.

I found very little online about the implications of taller clouds but, I think it is a reasonable assumption that storms would get more intense and rainfalls would get heavier. This is because the cloud can grow more and thus hold more precipitation. These taller clouds could also affect plane travel as planes tend to fly just over the anvils; if the anvils get higher, the planes will have to take a new route.

Although all of the before mentioned global shifts are caused by climate change, they also have an effect on climate change. So let’s get into it 🥳.

Clouds Affecting Climate Change

I found some really good diagrams about this that don’t need much explanation, and this post is already getting really long, so I am going to let you read them through without much additional explanation. Firstly, the diagrams immediately below illustrate when clouds reflect versus trap sunlight.

Building off of these diagrams, if clouds form higher in the atmosphere as the troposphere expands, these clouds are more likely to trap heat than reflect it (see the diagram to the right). As more clouds trap heat and less reflect back into space, a positive feedback loop occurs: Earth heats up even quicker, causing the troposphere to expand more, which causes clouds to develop higher in the atmosphere exacerbating the problem.

As clouds/storms move poleward, this leaves the Equator with out as much cloud coverage and middle latitudes with more clouds. Also, the poles receive less sunlight. If the clouds are shifting towards areas with less sunlight hitting them, this means they don’t reflect as much sunlight because they aren’t receiving as much. On the other hand, the areas near the Equator are hit by more sunlight and are calculated to have less cloud coverage. So, even more sunlight is getting absorbed, heating up the Earth a bit more (EDF). Yay, more climate change🥲.

But, right now, clouds are overall helping the Earth stay cool with about two-thirds of Earth covered by clouds at any given time (wired.com). However, as time goes on, this is projected to change (ibid).

Here is some good news though: the tipping point for cloud disappearance is when the atmosphere reaches a concentration of 1,200 ppm of CO2 (ibid). As of April 19, 2024, the atmosphere is at 429.97 ppm of CO2 (CO2-Earth). We still have a good amount of time before this starts to happens.

All in all, clouds are a significant unknown factor in climate change and scientists are only now shifting their focus to them. I enjoyed looking past the aesthetic of clouds and instead to the impact of them. I hope you leave this post with a new appreciation for the influence those white puffballs in the sky.

See you next time for the last Cloud post Final Investigations🔎 where I go through all the extra questions I wasn’t able to address yet like: Why/How do clouds form in different layers? What is the tipping point that causes a cloud to release precipitation? Why are some clouds darker than others?

If you have any other cloud questions, or any question really, feel free to reach out so I can include them in my next post!

¡Adiós!