Stories tagged CMMAP

Sep
20
2011

There’s been some buzz about the relationship between clouds and climate recently, prompting Andrew Revkin of the New York Times’ Dot Earth blog to get his panties in a twist about the “…over-interpretation of a couple of [scientific] papers…”

What gives? I wanted to know too, so I’ve done a bit – ok, a lot – of research and this is what I can tell you: The heart of the discussion is not whether there is a cloud-climate connection (that’s clear), but rather over what that relationship behaves like. There are at least three possible theories, but before we get to those, let’s review some important background concepts.

Gimme the Basics First

Cloud Formation

First, scientists think of air as units of volume called air masses. Each air mass is identified by its temperature and moisture content. Clouds are basically wet air masses that form when rising air masses expand and cool, causing the moisture in the air to condense. You can see the process in action yourself just by exhaling outside on a cool morning. The Center for Multiscale Modeling of Atmospheric Processes has a webpage to answer your other questions about clouds.

Earth’s Energy Budget
Earth's energy budget: Incoming solar energy is either absorbed (orange) or reflected (yellow).  Outgoing energy is radiated (red).  The arrows show the direction and magnitude of movement where thick arrows signify bigger movements.
Earth's energy budget: Incoming solar energy is either absorbed (orange) or reflected (yellow). Outgoing energy is radiated (red). The arrows show the direction and magnitude of movement where thick arrows signify bigger movements.Courtesy NASA

Energy from the Sun is essential for life on Earth. Let’s pretend the Earth has an “energy budget” where solar energy is like money, absorption is like a deposit, reflection is like a transfer, and radiation is like a withdrawal. It’s not a perfect analogy, but it’ll work for starters: Most of the incoming solar energy (money) is absorbed by (deposited into) the ocean and earth surface, but some is absorbed or reflected (transferred) by the atmosphere and clouds. Most of the outgoing energy is radiated (withdrawn) to space from the atmosphere and clouds. The figure to the right illustrates this process.

The Greenhouse Effect

Thanks to the greenhouse effect, our planet is warm enough to live on. The greenhouse effect occurs within the earth’s energy budget when some of the heat radiating (withdrawing… remember our budget analogy from above?) from the ocean and earth surface is reflected (transferred) back to Earth by greenhouse gases in the atmosphere. Greenhouse gases include carbon dioxide, methane, and water vapor. This National Geographic interactive website entertains the concept.

Climate Change

Climate change is occurring largely because humans are adding more greenhouse gases to the atmosphere. More greenhouse gases in the atmosphere means more heat reflected back to earth and warmer temperatures. Warmer temperatures might sound pretty good to your right now (especially if you live in Minnesota and could see your breath this morning as you walked to school or work), but it’s not. Why? Check out NASA’s really great website on the effects of climate change.

Alright, already. What’s the climate-cloud relationship?

From what I can tell, there are three possible theories about the climate-cloud relationship:

  • Clouds actively drive climate change. This is a linear process where clouds reflect too much heat back to Earth, which increases the average global temperature and causes climate change.
  • Clouds passively blunt climate change. This is a cyclical process where more climate change includes increasing average global temperature, which increases average global evaporation, which creates more clouds. More clouds absorb more heat, keeping the average global temperature from rising even faster and lessening climate change. This slows down (note: it does not stop) the rate of climate change.
  • Clouds passively amplify climate change. This is a cyclical process where more climate change includes increasing the average global temperature, which increases average global evaporation, which creates more clouds. More clouds reflect more heat back to Earth, which raises the average global temperatures and worsens climate change. This speeds up the rate of climate change.
  • So which is it? Probably NOT Theory #1. Maybe Theory #2… or maybe it’s Theory #3? Scientists aren’t quite sure yet, so neither am I, but the evidence is stacking against Theory #1 leaving two possible options. The next big question seems to be surrounding the size of the effects of Theory #2 and Theory #3.

    Using what you just read about cloud formation, the earth’s energy budget, greenhouse gases, and climate change (Woah. You just learned a lot!), what do you think? What’s the climate-cloud relationship?

    If you want, you can read more about what scientists are saying about the climate-cloud relationship here:

Sep
03
2010

WHY?: Clouds are hard to model, so let's show them who's boss.
WHY?: Clouds are hard to model, so let's show them who's boss.Courtesy Paige Shoemaker

Next time you look at the clouds, shake your fist and yell at those jerks for making our lives difficult. You might look crazy, but somebody needs to tell those fools.

While it's relatively easy to model temperature changes over the last century thanks to detailed records, clouds are more tricky to understand because we don't have a similar history of cloud observations, and also because they are ornery. So in order to understand how clouds work, scientists are building a body of evidence to model cloud behavior and help show how clouds will impact our weather as well as our climate in the future. I believe they also plan to show those clouds who is the boss of them.

Hurricane help!
Like a child running loose in a toy store, hurricanes have always been difficult to predict because they can unexpectedly change direction. This confounds plans for evacuation, leading some people to leave areas that are never hit, leading others to stay put and potentially face nasty weather because they don't trust the meteorologist, and leading meteorologists to keep Advil in business. But since the 90s, our ability to predict where hurricanes will make landfall has become twice as accurate. This new prescience is due to the development and use of more accurate models of how clouds work, which is in turn due to better understanding of cloud dynamics and faster computers. How about that, punk clouds?

Intensity, however, remains elusive to model. (Shh, don't let them know we have a weakness!)

Go home, son: If wily Earl thought he could outsmart the meteorologists, then he's in for a schoolin'.
Go home, son: If wily Earl thought he could outsmart the meteorologists, then he's in for a schoolin'.Courtesy NASA

"While we pride ourselves that the track forecast is getting better and better, we remain humbled by the uncertainties of the science we don't yet understand," Schott said. "This is not an algebra question where there's only one right answer."

-Timothy Schott, tropical cyclone program leader for the National Weather Service in Silver Spring, Md.

Hurricane Earl
Despite being a "forecasting nightmare," Earl ended up hitting about where it was predicted to go. This means that the right people have been evacuated to avoid injury and fatality. That's right, stick your tail between your legs, Earl.

Connecting to climate
Short-term events such as hurricanes and other storms are difficult to predict, but climate change is a whole other world of uncertainty--again, thanks to those uncouth clouds. Climate scientists are developing new tools, such as satellite technologies that show how much light different cloud types reflect and models that demonstrate localized cloud processes. These approaches look specifically at certain groups of clouds and their patterns of change to add detail to older, larger models that look at climate over larger scales.

Booyah!: Climate computer nerds prevail.
Booyah!: Climate computer nerds prevail.Courtesy Nic McPhee

The problem with the older models is that they have a low resolution that doesn't accurately represent clouds because the clouds are smaller than they can show. Think of it like Google maps--at the beginning, you're looking at the entire planet, or a whole continent--this is similar to older, low-res climate models. The new models are like zooming in on a city--you can see bus stops, restaurants, and highways. But you have to zoom out to see how these small pieces relate to the larger surroundings. In a similar way, the new high-res models are helping to inform older models--this type of work is called multiscale modeling.

Researchers at the Center for Multiscale Modeling of Atmospheric Processes (CMMAP) are developing this exact type of model. You can read about their advances here. This work is important because it brings insight into questions about whether clouds will reflect or trap more sunlight, which can have a big impact on the rate of global warming. It also helps us understand whether geoengineering projects that alter clouds will really have the intended effect. Plus it's just one more way we can pwn clouds.

Jul
07
2010

Questions in the Clouds
A recent article in Scientific American described a study in which a few scientists interviewed 14 of their colleagues specializing in climate change to make predictions about three possible future scenarios: low, medium, and high degrees of global warming. The climate scientists were also asked to predict when Earth's climate might reach a tipping point and change so drastically that humans find it difficult to survive. As part of their response, they drew attention to factors that added caveats to their predictions. One of the biggest questions: what will the clouds do?

Low-level clouds are tricksy: Studies show that these low-level clouds, called stratocumulus, cause climate researchers to squeeze their stress balls.
Low-level clouds are tricksy: Studies show that these low-level clouds, called stratocumulus, cause climate researchers to squeeze their stress balls.Courtesy Benutzer:LivingShadow, Wikimedia Commons

As the climate changes, the atmosphere's behavior changes, too--making predictions difficult. Clouds are interesting characters because they both reflect sunlight and absorb it. Different types of clouds both reflect and absorb in different proportions, but their behavior also changes with the temperature, making them difficult to model. CMMAP is one organization working to improve cloud representations in models of Earth's climate. (And their website is loaded with great information about clouds!)

Since scientists began modeling climate change, there have been many ideas about how clouds will impact global warming. But they faced difficulties because many of the same questions asked about clouds in the 1950s remain unanswered today. Some researchers thought that low-level clouds would reflect more sunlight on warm days, thereby slowing global warming in its tracks.

Cumulonimbus: Vertical growth ain't no joke.
Cumulonimbus: Vertical growth ain't no joke.Courtesy Simon Eugster, Wikimedia Commons

Cloudy Answers
But research at NASA has shown that in general, low-level clouds reflect more sunlight on cold days and less sunlight on warm days. Further, as the oceans warm, low-level clouds dissipate. This had led scientists to predict that warming would initiate a positive-feedback cycle, whereby as the climate warmed, low-level clouds would dissipate and spur on further warming.

However, the low-level clouds are thought to be balanced out by clouds with vertical growth, which may expand and reflect more sun on warm days. Researchers think that these vertical clouds could mitigate some or all of the effects of clouds' behavior on global warming. Of course, it's important to keep in mind that scientists are still only beginning to unravel the mysteries of clouds and further research will be essential to create accurate models of their behavior.

Noctilucent: "Why you gotta be all up in my grill with your carbon, yo?"
Noctilucent: "Why you gotta be all up in my grill with your carbon, yo?"Courtesy Hrald, Wikimedia Commons

Signs from Above
Another type of cloud is important in climate change discussions as an indicator of global warming rather than an influence on climate: noctilucent clouds. These clouds occur higher in the atmosphere than any other. They used to be visible only from latitudes near the poles, but began appearing closer to the equator in recent years. Because noctilucent clouds can only form in very cold temperatures, their presence at lower latitudes indicates cooler temperatures high in the atmosphere than before. Researchers think that these cooler temperatures are caused by global warming--that phenomenon creates warmer temperatures near the surface by reflecting heat emitted by the surface back toward the surface. Before global warming, this heat would have escaped to higher areas of the atmosphere to warm them, making the formation of noctilucent clouds impossible at lower latitudes.

Of course, global warming isn't the only way we impact clouds…

Contrails: Not only do they give off greenhouse gases, jets mess with the clouds. Jerks.
Contrails: Not only do they give off greenhouse gases, jets mess with the clouds. Jerks.Courtesy NASA, Wikimedia Commons

Jets and Clouds
As if natural clouds weren't enough of a question mark, jets throw a monkey wrench in climate models, too. The contrails they leave behind can create pseudo clouds that alter temperatures by lowering daytime highs and decreasing nighttime lows because of the ways they reflect and absorb radiation. Jets also punch holes in natural clouds and cause immediate impacts on the weather.

And just 'cause I can't get enough, here's more cloud info.

Jun
07
2009

The King of All Clouds: ... here to rule the skies
The King of All Clouds: ... here to rule the skiesCourtesy akakumo
Did you know that mathematical equations can calculate the temperature, wind speed, and humidity of clouds? Well, the Center for Multiscale Modeling of Atmospheric Processes (CMMAP, pronounced “see-map”) is using these equations and developing a revolutionary approach to climate modeling that will help us understand the roles of clouds today and in the future.

So what is climate modeling exactly? Good question. Think of a giant grid that covers the globe, with cells the size of Delaware. Within each grid, the mathematical equations that I mentioned above are used to predict weather forecasts and climate simulations. But there’s a problem with this grid system: the clouds are much smaller than the cells used in the global models, thus creating a large source of uncertainty in today’s climate models.

CMMAP has come up with a solution to this problem called multi-scale modeling framework (MMF). Their radical new approach will simulate realistic cloud processes in a tiny-fraction of each Delaware-sized cell, greatly improving the climate model. In order to represent each small-scale process, scientists have invented equations that define the temperature and moisture content in a cloud based on the atmospheric conditions in the entire grid cell. Though this is quite an advancement from the technologies of the past, there is still work to be done to accurately represent clouds in the climate model. As developments in MMF continue, CMMAP could potentially hold the key that is necessary in unlocking the mystery to understanding the weather and climate.

If you’d like to learn more about the formation of clouds or more research that CMMAP is conducting, check out the links!