Understanding Climate Change #3

I may have fallen behind on the blogging I said I would do for Climate Change: Challenges & Solutions. I guess the good thing about these online courses is that you can take them at your own pace. To be fair I’ve had this post on my computer for weeks but never got round to uploading it. Better late than never though am I right? I’ve skipped writing about week 3, but if you’re interested it was all about the signs of climate change and the global carbon cycle. Here’s some links if you want to know more:

On to week 4!

Projecting the future

An in-depth look at climate modelling was the subject of the first section this week. Climate predictions are made using climate models. These are huge simulations run by supercomputers and take account of all the components affecting the climate system – ocean currents, carbon storage in vegetation etc. They also include human factors like the burning of fossil fuels and deforestation.

More evidence that human behaviour is influencing the climate comes from these models. When they are devoid of human factors, the models provide an accurate reproduction of the actual climate up to about 1970. Past this, the model diverges from reality, instead showing rapid warming when in fact it should be cooling. This allows the IPCC to say this:

There is a 90% chance that the global warming we’ve seen today is due to man-made greenhouse gasses.

There are variations in the outcome of the models when different assumptions are made about our involvement. Obviously nobody knows for sure how the population will grow or how much longer we will be burning those fossil fuels at the current rate, so different values are inputted to the model and the outcome calculated. The prediction for a ‘business as usual’ approach where fossil fuels are burned at the same rate leads to warming of about 6 degrees.

Six degrees of warming would spell disaster for millions of people the world over. Just one of the results would be the collapse of the Greenland ice sheet; which could raise sea levels by more than 10 metres. Not to mention the fact that those predictions were made using an outdated rate of fossil fuel burring. Currently fossil fuels are being burned at rate faster than those models predicted so we are on track for warming in excess of 6 degrees unless we do something about it very soon.

Geoengineering the climate

If you remember, the target for warming that was set during COP21 was 1.5 degrees. If we stopped all fossil fuel burning today, the global average temperature would still increase as a result of the carbon dioxide we have already released. To actually keep to that target, we would need some form of geoengineering – using technology to control the climate. There are many proposals with varying degrees of usefulness.

Carbon capture

Carbon capture is one of the main branches of geoengineering. For example, carbon dioxide in the atmosphere can be dissolved in water and reacted with calcium hydroxide to form solid calcium carbonate. Hence carbon dioxide has been transferred from the atmosphere to a solid and can then be stored.

The reaction to form calcium carbonate is an example of a chemical process. Biological process can also be utilised. Algae in the ocean may be stimulated to increase their uptake of carbon dioxide. The algae would eventually sink to the ocean floor, taking with it the captured carbon dioxide.

The problem with carbon capture is that it cannot be used to reverse climate change. It can only reduce the amount of warming since it is unrealistic to assume any of these strategies could take out more carbon dioxide from the atmosphere than the total we emit.

Solar radiation management

Management of incoming solar radiation is the second major branch of geoengineering. One example of this would be to release large amounts of sulphur dioxide into the upper atmosphere. There it would form droplets of sulphuric acid that reflect incoming radiation and cool the planet. A similar technique would be to inject aerosols into susceptible clouds making them brighter and more reflective.

There are other more expensive ways to manage solar radiation. Huge space reflectors could be placed around the Earth, or the albedo effect could be utilised using reflectors at the surface (in the same way the roofs of buildings are painted white to reflect more sunlight).

Which one is best?

There is good and bad in every geoengineering method – no single one is the cure-all that some might be hoping for. The use of atmospheric aerosols is less expensive and can be effective, could cause ozone depletion and warming of the stratosphere. The removal of carbon dioxide by algae stimulation relies on the correct species getting the correct nutrients.

Managing solar radiation could also lead to a much bigger problem in the future if deployed while we continue to increase carbon dioxide levels. If one of the methods had a wide roll out, but then there were to be a failure in the technology, the result would be a catastrophic sharp rise in global temperatures. There is also evidence that managing solar radiation could lead to a drought over the Amazon rainforest.

Should we geoengineer our climate?

There is obviously no correct answer here and the question divides the opinions of many scientists. On one hand the likelihood that our fossil fuel-burning habits are not going to be changing enough to completely rule out the use of these technologies. Then again many of them are either extremely expensive or pose a high risk to ecosystems and other areas of the climate.

If it were me making the decisions, I would drastically scale-back the use of fossil fuels and other sources of emissions before any of these technologies actually get the go ahead, since the risks are too high. If it were possible to solve the problem by doing this alone it would have already been done, or we would at least be closer to a solution. I believe we should advance the geoengineering technologies we have, develop new ones and test them to make sure we have them available as a last resort.

What do you think? Could geoengineering be the solution? Should we be putting more money and effort into these technologies? It would be great to hear more people’s views on this.

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Jack Nokes Written by:

Environmentalist and engineering student.