Next
ten years critical for achieving climate change goals
International Institute for Applied Systems Analysis
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 historic Paris Agreement set a target of limiting future
global average temperature increase to well below 2°C and pursue efforts to
even further limit the average increase to 1.5°C above pre-industrial levels.
Yet the timing and details of these efforts were left to individual countries.
In a new study, published in the journal Nature
Communications, researchers from the International Institute for Applied
Systems Analysis (IIASA) used a global model of the carbon system that accounts
for carbon release and uptake through both natural and anthropogenic
activities.
“The study shows 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,” says IIASA Ecosystems Services and Management Program Director Michael Obersteiner, a study coauthor.
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. We take into account not
just emissions from fossil fuels, but also agriculture, land use, food
production, bioenergy, and carbon uptake by natural ecosystems,” explains World
Bank consultant Brian Walsh, who led the study while working as an IIASA
researcher.
The compares four different scenarios for future energy
development, 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 shows. 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 notes that the high-renewable energy scenario is
ambitious, but not impossible—global production of renewable energy grew 2.6%
between 2013 and 2014, according to the IEA. In contrast, the study finds that
continued reliance on fossil fuels (with growth rates of renewables between 2%
and 3% per year), 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 note 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.
The study adds to a large body of IIASA research on climate mitigation policy
and the chances of achieving targets.
“Earlier work on mitigation strategies by IIASA has shown the
importance of demand-side measures, including efficiency, conservation, and
behavioral change. Success in these areas may explain the difference between
reaching 1.5C instead of 2C,” says IIASA Energy Program Director Keywan Riahi,
who also contributed to the new work.
Reference
Walsh B, Ciais
P, Janssens IA, Penuelas J, Riahi K, Rydzak F, van Vuuren DP,
& Obersteiner M(2017). Pathways for balancing CO2 emissions and sinks. Nature Communications DOI:10.1038/ncomms14856. (In
Press)