Injecting Particles into the Atmosphere Can Temporarily Cool Down the Climate

May 20, 2016 | Joanne Kennell

climate change
Photo credit: Day Donaldson/flickr (CC by SA 2.0)

Intentionally manipulating the global climate.

Climate engineering, also known as geoengineering, is a highly controversial, and still mostly hypothetical, topic that deals with techniques and technologies for intentionally manipulating the global climate in order to abate or stall the most extreme effects of climate change.

According to a new study from the University of Eastern Finland, it may be possible to slow down and even temporarily stop the runaway-train of global warming by increasing atmospheric aerosol concentrations. However, the authors note that this form of climate engineering does not remove the need to reduce greenhouse gas emissions.

Focusing on methods of climate engineering, the researchers used global climate models to analyze the ability of atmospheric aerosols — tiny particles suspended in the atmosphere — to cool down the climate, as well as the consequences of their use.

Aerosol particles injected into the stratosphere — the second major layer of Earth’s atmosphere — are extremely efficient in cooling down the climate. This is a process that mimics massive volcanic eruptions that release aerosol particles into the stratosphere, where they reflect solar radiation back into space, which can cool the climate — even for years.

On the other hand, aerosols injected into the troposphere — the lowest layer of Earth’s atmosphere — can impact the climate by increasing the number of cloud droplets in clouds, making them whiter and more effective in reflecting solar radiation back into space.

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Some current traffic and industry-induced aerosol emissions cool down the climate, but their cooling effect on the global temperature is much smaller compared to the warming effect of present greenhouse gas emissions. It could be possible to use global airline and ship traffic for atmospheric temperature regulation by increasing the sulphuric concentrations of fuels. This would not only increase stratospheric aerosol concentrations, but also promote greater cloud reflectivity.

However, sulphuric concentrations of fuels would have to surpass the levels defined in international agreements and it would mainly be targeted to the northern hemisphere, which is responsible for most of the global traffic.

According to the study, even the most promising methods of climate engineering won't cool down the climate unless the growth of greenhouse gas emissions are reined in.

If greenhouse gas emissions continue to grow, reversing the effects would require the injection of increasingly large amounts of aerosols into the atmosphere. As a consequence, the aerosols relative particle sizes increase, resulting in a smaller cooling influence, thus reducing the effectiveness of climate engineering.

What’s more, climate engineering can’t reverse all the consequences of increased carbon dioxide concentrations, such as changes in rainfall.

This means that climate engineering is unable, even in theory, to reverse global warming caused by growing greenhouse emissions, especially if they continue to increase at current rates. According to the authors, climate change should be mitigated by reducing greenhouse gases, while climate engineering, even at its best, could only provide a temporary relief in extreme situations.

The findings were published in the journal Atmospheric Chemistry and Physics.


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