Extreme measures to block the sun

The Paris Agreement sets a warming target well below 2 degrees Celsius and researchers have decided to determine the cost of this goal and the more ambitious goal of 1.5C, as well as the potential benefits.

The report warns that if the world does not act now, it will not be able to stay below the target of 1.5 C unless taking risky or expensive steps.

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

In comparison, the price of carbon introduced by the Gillard government in 2012 started at $ 23.

RELATED: The problem of division that Australia can no longer ignore

RELATED: The Real Reasons Why Australia Can not Succeed in Climate Policy

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

In particular, the impacts would be significant for water resources, agriculture and human health and are particularly important in the poorest regions. Small island developing States, such as those in the Pacific, parts of South-East Asia and the Mediterranean, are among the regions that would benefit most.

It would also preserve Arctic sea ice, protect two million square kilometers of permafrost, allow some coral reefs to survive and prevent some of the extreme weather events such as heat waves, floods and drought.

Lead author, Professor Simon Dietz, warned that if the world wanted to keep the 1.5C option open, it should act now, or have to implement risky methods to block sunlight.

Professor Dietz of ESRC's Center for Economics and Climate Change Policy, organized by the London School of Economics and Political Science and the University of Leeds, warned that maintaining the global warning at 1.5C could quickly become too expensive to be justified.

"Any additional delay makes the 1.5C target impossible to reach by conventional means," the report says.

To achieve this goal, energy demand is expected to decline dramatically throughout the economy, and elements such as bioenergy with carbon capture and storage (BECCS) are likely to be introduced.

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

Unfortunately, there was no clear answer to the question of whether the benefits of keeping a warning at 1.5C outweighed the costs, in part because there is uncertainty about costs and benefits real.

"The data we have does not allow us to know whether the benefits of limiting warming to 1.5 ° C outweigh the costs," said Professor Dietz.

The rapid disappearance of the action and the high cost of reducing emissions have recently attracted much interest in other new "climate engineering" technologies.

This could include costly removal of carbon dioxide on a large scale or risky "solar radiation management".

AEROSOL INJECTIONS AND CLOUD LIGHTING

Radiation management literally aims to reduce global warming by deflecting sunlight.

The methods include stratospheric aerosol injections, lightening of marine clouds, space mirrors and white paint roofs.

Aerosol injections involve spraying aerosols into the stratosphere so that the particles block and reflect the sun's rays, resulting in lower temperatures.

The lightening of marine clouds works in a similar way and involves sowing the clouds with a fine spray of salt water to encourage the formation of microdroplets. These micro-droplets scatter the incoming radiation and make the clouds last.

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

But the report warns that since these techniques are inexpensive, some countries can make individual decisions to use them to respond to actual 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.

Nor do the measures contribute much to solving other problems such as ocean acidification, depletion of the ozone layer and could also make solar energy less productive.

They also create new risks because their effectiveness in controlling temperatures has not been tested in field experiments. It is unlikely that small scale tests predict accurate results.

There is also the risk that if the measures were to be stopped suddenly, rapid global warming could be devastating.

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

However, these methods of large-scale elimination of carbon dioxide tend to be slow-moving, expensive and could be difficult for agriculture, sustainability and biodiversity.

THE PATH TO FOLLOW

The report notes that the case for carbon pricing is stronger than ever, but given the urgency of the problem and the policy surrounding it, there may be room for more interventionist policies.

She acknowledged that carbon pricing has not been as effective in stimulating private research and development and that more direct approaches could be more useful, such as the Apollo program. 2025.

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

The 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 1.5 ° C, compared to 2C, were striking.

"While it will be much harder to reach the low-temperature goal, we must not close the door," said Dr. Gambhir.

"It means that we must intensify the immediacy and pace of action."