What Would It Take to Limit Climate Change to 1.5°C by 2100?

Limiting temperature rise by 2100 to less than 1.5°C is feasible, at least from a purely technological standpoint, according to the study published in the journal Nature Climate Change by researchers at the International Institute for Applied Systems Analysis (IIASA), the Potsdam Institute for Climate Impact Research (PIK), and others.  The new study 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.

Key elements: accelerated energy efficiency gains and CO2 removal
The study identifies key elements that would need to be in place in order to reach the 1.5°C target by 2100.   One fundamental feature is the tight constraint on future carbon emissions.

"In 1.5°C scenarios, the remaining carbon budget for the 21st century is reduced to almost half compared to 2°C scenarios," explains 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."

Faster improvements in energy efficiency also emerge as a key enabling factor for the 1.5°C target.  In addition, all the scenarios show that at some point in this century, carbon emissions would have to become negative at a global scale.  That means that significant amounts of CO2 would need to be actively removed from the atmosphere. This could occur through technological solutions such as bioenergy use combined with carbon capture and storage--a technology that remains untested on alarge scale, increases the pressure on food supply systems and in some cases lacks social acceptance--or through efforts to grow more forests, sequestering carbon in tree trunks and branches.  Afforestation, however, just like bioenergy plantations, would have to be carefully balanced against other land use requirements, most notably food production.

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