Most of us learned all about clouds in grade school -- from the different types of clouds there are in the sky to how they form. But for climate scientists, there is much more to learn about clouds -- especially when it comes to the role clouds play in climate change.
Clouds can trap heat in Earth's atmosphere, causing warmer temperatures on the planet's surface. But they also reflect solar radiation, resulting in lower temperatures. This dual role has made it tricky to build reliable models of our changing climate -- and even led some scientists, who are far outside the mainstream, to push back against the large body of evidence showing that climate change is a real problem.
So, what exactly is the overall influence of clouds on climate change and our planet's future? To cut through the fog, I spoke with Dr. Greg Holland, senior scientist at the National Center for Atmospheric Research, for answers.
Watch the video above, and/or click the link below for a transcript. Don't forget to sound off in the comments section at the bottom of the page. Talk nerdy to me!
JACQUELINE HOWARD: Hey everyone. Jacqueline Howard here. All around the world, sophisticated supercomputers are crunching huge amounts of data to create climate models, or simulations, that help us understand how our world is changing. Now, this data includes global temperatures, extreme weather events, rainfall, sea levels, and even wind patterns. Sounds crazy cool, right? But there remains some doubt around one critical component: Clouds. And because of this, some people question the very validity of climate models. As a 2012 article in The New York Times puts it, “clouds’ effect on climate change is last bastion for dissenters.” So, what does that mean? What do mainstream scientists say about clouds and the role they play in climate change? Can we harness clouds to save the planet? For answers, I reached out to the prominent climate expert Dr. Greg Holland. He’s a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado.
DR. GREG HOLLAND: The really important thing about clouds is understanding this very fine interaction between the warming part, and the cooling part, and how that may actually impact future climate. Right now, the scientific consensus is that the warming, in other words the net effect of redistribution of water vapor and the re-radiation of heat back down to the surface, dominates. And unfortunately that’s bad news because if that is true, that accelerates global change rather than helping us mitigate it.
JH: Did you get that? Clouds both heat and cool our planet. That's why some say it’s difficult to predict cloud behavior and the net effect they have on our global climate. But a recent report from the Intergovernmental Panel on Climate Change, or IPCC, hints at a more certain relationship between clouds and our climate.
GH: The current consensus on this from the IPCC is that the clouds are in the net warming. Not real sure. There is a possibility that the other effects are dominating and they could be cooling. So this is one of those areas that we need to know a lot more.
JH: The cooling component is what fuels some of the criticism current climate models receive. See, low-level thick clouds, like stratus clouds, keep us cool by reflecting solar radiation, or they may absorb heat emitted from our planet’s surface and then radiate that heat out into space. But high, thin clouds, like cirrus clouds, primarily keep us warm by absorbing heat emitted from our planet’s surface and then re-radiating that heat back down to us. Another way clouds may warm our planet is by distributing water vapor.
GH: That last one is a critical one because water vapor is the biggest greenhouse gas we have. It’s about 70 to 80 percent of all of the greenhouse warming on the Earth is due to water vapor.
JH: What if we actually controlled cloud behavior to mitigate global climate change ourselves? Think about it. If low-level clouds cool the planet, what if we artificially whip some up to keep human-induced warming in check?
GH: There are actually very good scientific studies that have looked at this using complex computer models and some fairly advanced theory. If we can increase the size of that bank of cloud, then we can cool the locality, but also, we can increase it enough, and the models have shown this and the theories have shown this, we could increase it enough to be able to have a net cooling effect on the world at large. So there’s one possibility where we could, what is called geoengineering, the climate to use clouds to our advantage.
JH: Clouds for the win! But geoengineering can be risky business. For instance, one proposal is to amp up production of these cooling clouds by what's called cloud brightening. Now, that's when you blast salty mist into the air to speed up formation of water droplets in clouds. But do you think we should be looking up at clouds to combat human-induced climate change here on Earth? Let me know in the comments. Leave your thoughts in the cloud. Talk nerdy to me!
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