Climate Change: Limiting Future Warming to 1.5°C Not Impossible

It has been said that our lofty goal of preventing the world from warming an additional 2 degrees Celsius is utterly inadequate. After all, research has already shown that means to keep to this two-degree limit are slipping away. And yet, despite all the speculation, one new study says that it is even possible to limit future warming to a more ambitious goal of 1.5 degrees C by 2100.

That's at least from a purely technological standpoint, according to researchers at the International Institute for Applied Systems Analysis (IIASA), the Potsdam Institute for Climate Impact Research (PIK), and others. The new study, published in the journal Nature Climate Change, examines scenarios for the energy, economy, and environment that are consistent with limiting climate change to 1.5 C above pre-industrial levels, and compares them to scenarios for limiting climate change to 2 C.

"Actions for returning global warming to below 1.5°C by 2100 are in many ways similar to those limiting warming to below 2°C," IIASA researcher Joeri Rogelj, one of the lead authors, said in a news release. "However, the more ambitious 1.5°C goal leaves no space to further delay global mitigation action and emission reductions need to scale up swiftly in the next decades."

While this is relatively good news, that's not to say that the road ahead won't be a long, arduous one. The authors point out that the economic, political, and technological requirements to meet even the 2 C target are substantial.

So what exactly are the key elements needed to make this brighter future a reality?

First off, the study says that tight constraints on future carbon emissions are a top priority, along with faster improvements in energy efficiency.

"In 1.5°C scenarios, the remaining carbon budget for the 21st century is reduced to almost half compared to 2°C scenarios," explained PIK researcher Gunnar Luderer, who co-led the study. "As a consequence, deeper emissions cuts are required from all sectors, and global carbon neutrality would need to be reached 10-20 years earlier than projected for 2°C scenarios."

While scientists have already turned to natural gas usage and artificial photosynthesis, among other methods, as a way to solve the carbon emission problem, it seems that we are still not doing enough.

All the 1.5 C scenarios show that at some point in this century, carbon emissions would have to actually become negative at a global scale. That means that significant amounts of carbon dioxide (CO2) would need to be actively removed from the atmosphere.

This may seem impossible, but researchers are assured that it is feasible through technological solutions - including bioenergy use combined with carbon capture and storage - or efforts to grow more forests. Afforestation, however, just like bioenergy plantations, would have to be carefully balanced against other land use requirements, most notably food production.

In addition, unlike past research that drew an unyielding line in the sand and set 2 C as the absolute limit, this study looks at a long term goal, and what would need to happen to get global temperatures back down to that level by 2100.

"Basically all our 1.5°C scenarios first exceed the 1.5°C temperature threshold somewhere in mid-century," explained Rogelj, "before declining to 2100 and beyond as more and more carbon dioxide is actively removed from the atmosphere by specialized technologies."

The newly proposed 1.5 C climate goal will be up for debate at upcoming climate negotiations. If the world agrees on stepping up efforts to curb greenhouse gases and prevent subsequent irreversible impacts, then we just may have a chance of reaching the 1.5 C target.

"The 1.5°C target leaves very little leeway," concluded Luderer. "Any imperfections - be it a further delay of meaningful policy action, or a failure to achieve negative emissions at large scale - will make the 1.5°C target unattainable during this century."

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