Do Clouds Affect Climate Change?
Clouds play an important role in warming and cooling the planet – two thirds of the planet are covered by clouds at any given time – allowing us to benefit from a cooler Earth. But can clouds affect, or help fight, climate change?
A Short Intro to Clouds
Water evaporates from the Earth’s surface and condenses in the atmosphere, making clouds. There are many different types of clouds, and each one has a different impact on the climate and the world that we live in. For example, trade cumulus clouds are small, fluffy clouds that are commonly found in the tropics – should there be a reduction of these types of clouds, temperatures would rise, causing a higher intensity of global warming.1
Less clouds imply a high-pressure system with little precipitation, whereas high-level cirrus clouds or low-level stratus clouds imply a low-pressure system. Clouds act as an “Atmospheric Blanket”,2 as they can cool the surface by reflecting harmful rays from the sun.
Water Cycle
Clouds absorb water from seas and oceans via evaporation, they then move around the globe providing rain to other areas of the world, which ends up back on the ground or large in bodies of water. Most of the clouds responsible for storing rain and ice are mixed-phase clouds.
Cloud Climate Feedback
Clouds affect the climate, and the climate affects the clouds, resulting in cloud-climate feedback.
Clouds and Climate Change – the Good
Clouds can help to cool the Earth’s surface by blocking harmful light rays from the sun. This helps to keep the Earth cooler. Additionally, the more water that these clouds contain, rather than ice, the more reflective they are of the sun’s rays. Reflecting the sun’s radiation cools the Earth’s atmosphere.
Clouds and Climate Change – the Bad
However, clouds have a negative side – they can trap heat in the atmosphere. This happens during the night, when warm air rises from the Earth’s surface. If a thick cloud is present, it will trap the warm air and reflect it back to the Earth’s surface, thus warming it up.
Additionally, cirrus clouds contain only ice crystals, allowing the sun’s rays to filter through them and hit Earth. Again, this results in a higher temperature on the surface. If Earth’s temperatures continue to rise, clouds could become thinner, or even burn off entirely, leaving clearer skies which could increase the Earth’s temperature by degrees with global warming. Less clouds mean that darker surfaces, such as land, will absorb solar energy, heating the air further.
Cloud Climate Change Predictions
By knowing what clouds do and what they’re capable of, scientists can use this information to reduce the uncertainty in global warming forecasts and predicting how the Earth’s climate will continue to warm.
However, as clouds are extremely unpredictable, it makes it a challenging component of the climate system. Previous studies have shown that clouds may transform from cool to warm – changing from holding a mixture of rain and ice, to liquid only – which affects the cooling properties of clouds. As water droplets are smaller than ice, they reflect sunlight more easily, helping to reflect harmful rays from the sun, thus helping to keep the Earth cooler.
Scientists have stated that older climate models contain far more ice than current satellite observations indicate,3 meaning cloud predicting models were underestimating the amount of liquid contained in clouds. This means that the models were overestimating the thickness of future clouds and how much liquid they would have in warmer weather, thus giving a more positive outlook. Many scientists have been updating their models to be more accurate.
Outlook
Overall, more clouds could help to reflect the sun’s harmful rays and help to keep the Earth cooler, but it will only help marginally – scientists are still calculating by how much. In comparison, if the Earth continues to warm, there may be fewer clouds to cool it down, so we can’t rely on clouds to always help the climate crisis.
In the meantime, climate change needs to be tackled by a reduction in greenhouse gases and offsetting unavoidable carbon emissions.
1 EUREC4A
3 Study
