In order to have a good chance of meeting the limits set by the Paris Agreement, it will be necessary to reduce greenhouse gas emissions and preserve carbon sinks, according to a new study.

The study, published in the journal Nature Communications, revealed that net carbon emissions will peak over the next 10 years.

The study was conducted by researchers at the International Institute for Applied Systems Analysis (IIASA). They used a global model of the carbon system that accounts for carbon release and uptake through both natural and anthropogenic activities.

The study said that carbon dioxide (CO₂) and other greenhouse gases in the atmosphere can be reduce in  two ways – by cutting our emissions, or by removing it from the atmosphere, for example through plants, the ocean, and soil.

The Paris Agreement has set a target of limiting the future global average temperature increase to well below 2°C. The agreement has also suggested efforts to further limit the average increase to 1.5°C above pre-industrial levels. However the timing and details of these efforts have been left to individual countries.

Michael Obersteiner, co-author of the study, said their research showed that the combined energy and land-use system should deliver zero net anthropogenic emissions well before 2040 in order to assure the attainability of a 1.5°C target by 2100.

According to the study, fossil fuel consumption would likely need to be reduced to less than 25% of the global energy supply by 2100, compared to 95% today. At the same time, land use change, such as deforestation, must be decreased. This would lead to a 42% decrease in cumulative emissions by the end of the century compared to a business as usual scenario.

“This study gives a broad accounting of the carbon dioxide in our atmosphere, where it comes from and where it goes,” explained Brian Walsh, World Bank consultant, who led the study while working as an IIASA researcher. “We take into account not just emissions from fossil fuels, but also agriculture, land use, food production, bioenergy, and carbon uptake by natural ecosystems.”

Four different scenarios for future energy development were compared, along with a range of mixtures of renewable and fossil energy.

In a “high-renewable” scenario where wind, solar, and bioenergy increase by around 5% a year, net emissions could peak by 2022, the study showed. Yet without substantial negative emissions technologies, that pathway would still lead to a global average temperature rise of 2.5°C, missing the Paris Agreement target.

Walsh noted that the high-renewable energy scenario is ambitious, but not impossible as global production of renewable energy grew 2.6% between 2013 and 2014, according to the International Energy Agency (IEA).

In contrast, the study found that continued reliance on fossil fuels would cause carbon emissions to peak only at the end of the century, causing an estimated 3.5°C global temperature rise by 2100.

The authors pointed out that not only the mix of energy matters, but also the overall amount of energy consumed. The study also included ranges for high energy consumption and low energy consumption.

IIASA Energy Program Director Keywan Riahi, who also contributed to the new work, said that earlier work on mitigation strategies by the institute had also shown the importance of demand-side measures, including efficiency, conservation, and behavioural change.

“Success in these areas may explain the difference between reaching 1.5°C instead of 2°C,” she said.