THE world seems incapable of taking decisive action on climate change but we may soon have to consider some bizarre options to stop global warming if we fail to act.

The Paris Agreement sets a target of well under 2 degrees celsius warming and researchers decided to look at how much it would cost to achieve this target, and the more ambitious target of 1.5C, as well as what the potential benefits were.

The report warns that if the world doesn’t act now, it won’t be able to stay under the 1.5C target unless it turns to some risky or expensive measures.

The paper The Economics of 1.5˚C Climate Change, published in the journal Annual Review of Environment and Resources, warned that some models had found a global carbon price of $100 per tonne of emitted carbon dioxide would need to be introduced by 2020 to stay under 1.5C. This is three times higher than the price to keep warming under 2C.

For comparison, the carbon price introduced in Australia by the Gillard Government in 2012 started at $23.

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But researchers found limiting warning to 1.5C, compared to 2C, would have significant benefits for human and natural systems.

In particular, the effects would be significant for water resources, agriculture, and human health and are particularly large in poorer regions. Small Island Developing States like those in the Pacific, parts of Southeast Asia, and the Mediterranean are among the regions that would benefit most.

It would also preserve Arctic summer sea ice, protect two million kilometre square of permafrost, allow some coral reefs to survive, and prevent some of the increase in extreme weather events such as heatwaves, floods, and droughts.

Lead author Professor Simon Dietz warned that if the world wanted to keep the 1.5C option open it would have to act now, or face having to implement risky methods of blocking out sunlight.

Prof Dietz of the ESRC Centre for Climate Change Economics and Policy, hosted by the London School of Economics and Political Science and the University of Leeds, warned that keeping global warning to 1.5C could soon become too expensive to justify, despite the benefits.

“Any further delay likely renders the 1.5C target unattainable by conventional means,” the report states.

In order to meet the target, there would need to be a huge drop in energy demand across the whole economy and things like bio-energy with carbon capture and storage (BECCS) would probably have to be introduced.

BECCS involves growing trees and crops, then burning them to generate energy and then capturing and storing the emissions.

Unfortunately there was no clear answer about whether the benefits of keeping warning to 1.5C exceeded the costs, partly because there is uncertainty about what the costs and benefits actually are.

“The evidence we have simply does not give us a clear answer on whether the benefits of limiting warming to 1.5C exceed the costs,” Prof Dietz said.

The fast-disappearing window for action and the high cost of reducing emissions has led to a lot of interest lately in other new “climate engineering” technology.

This could include expensive large-scale carbon dioxide removal or risky “solar radiation management”.

AEROSOL INJECTIONS AND CLOUD BRIGHTENING

Radiation management literally aims to reduce warming of the planet by deflecting sunlight.

Methods include stratospheric aerosol injections, marine cloud brightening, space mirrors and painting roofs white.

Aerosol injections involve spraying aerosols into the stratosphere so that the particles block and reflect the sun’s rays, to bring temperatures down.

Marine cloud brightening works in a similar way and involves seeding clouds with a fine spray of saltwater to encourage micro-droplets to form. These micro-droplets scatter incoming radiation and make clouds last longer.

These measures are relatively cheap, some estimates suggest they would only cost between $3 billion and $30 billion a year, which is very affordable compared to global GDP of $75 trillion.

But the report warns that because these techniques are inexpensive, some countries may make individual decisions to use them to respond to real or perceived climate emergencies. Or they may simply want to set the “global thermostat” to their preferred temperature.

This makes it very difficult to control the use of these techniques.

The measures also do not do much to address other problems like ocean acidification, greater ozone depletion and could also make solar power less productive.

They also throw up new risks as their effectiveness in controlling temperatures has not been tested in field experiments. Any small-scale tests would be unlikely to predict the exact outcomes.

There’s also the risk that if the measures had to be stopped suddenly, the rapid warming of the planet afterwards could be devastating.

Other more expensive options include removing carbon dioxide by planting more vegetation or by directly capturing carbon dioxide from the atmosphere and storing it.

However, these methods of large-scale carbon dioxide removal tend to be slow-acting, costly and could be challenging for agriculture, sustainability and biodiversity.

THE WAY FORWARD

The report noted that the case for carbon pricing was stronger than ever but given the urgency of the problem and the politics around it, there could be a place for more interventionist policies.

It acknowledged carbon pricing had not been that effective in stimulating private research and development and more direct approaches could be more helpful, such as the Apollo Program, which aims to get countries to fund research on how to make carbon-free electricity cheaper than coal by 2025.

“Some researchers have found that setting standards is more effective in reducing emissions and more acceptable to public opinion, despite its costs,” the report noted.

Co-author of the paper, Dr Ajay Gambhir, of the Grantham Research Institute on Climate Change and the Environment, said the benefits of keeping global warming below 1.5C, compared to 2C, were striking.

“Even though it will be significantly more challenging to achieve the lower temperature goal … we must not close the door on it,” Dr Gambhir said.

“This means we need to step up the immediacy and pace of action.”