FIRST it was the European Commission and it was followed by a joint announcement by the United States and China. This is the season for announcements on greenhouse gas emission reduction targets.
The E.C., as a bloc, decided to reduce at least 40 per cent of its emissions by 2030 compared to the emission levels in 1990. It said there would be a 27 per cent share of renewable energy and a 27 per cent improvement in energy efficiency by 2030.
The U.S. intends to achieve an economy-wide target of reducing its emissions by 26-28 per cent below its 2005 level by 2025. China intends to achieve the peaking of carbon dioxide emissions by around 2030 and intends to increase the share of non-fossil fuels in primary energy consumption to around 20 per cent by then.
The IPCC assessment
How do these commitments affect the global emission scenarios for the 21st century that were released in the recent months by the Intergovernmental Panel on Climate Change (IPCC) in its Fifth Assessment Report (AR5)? The IPCC used a new scenarios process with AR5. Instead of the linear process of developing socio-economic scenarios and then building emission scenarios, for the AR5 experts developed Representative Concentration Pathways (RCPs) as the scenarios.
The RCPs begin with a limited number of alternative pathways (trajectories over time) of radiative forcing levels (the difference between the solar radiation absorbed by the earth and the energy radiated back into space, which is dependent on the total greenhouse gas (GHG) emissions and is expressed as carbon dioxide equivalent concentrations, or CO-eq, in the atmosphere). The unit used for the RCPs is watts per square metre and the four scenarios used are RCP2.6, RCP4.5, RCP6.0 and RCP8.5. These are representative of clearly distinguishable climate futures and move from low emission (RCP2.6) to high emission scenarios (RCP8.5).
The IPCC-AR5 report projects that the increase of global mean surface temperature by 2081-2100 relative to 1986-2005 is likely to be 0.3°C–1.7°C under RCP2.6; 1.1°C–2.6°C under RCP4.5; 1.4°C–3.1°C under RCP6.0; and 2.6°C–4.8°C under RCP8.5. Thus keeping the temperature rise at less than 2°C is possible only with scenario RCP2.6, which the IPCC experts call “the stringent mitigation scenario”.
“Emissions scenarios leading to GHG concentrations in 2100 of about 450 parts per million CO-eq or lower are likely to maintain warming below 2°C over the 21st century relative to pre-industrial levels,” states the IPCC-AR5. “These scenarios are characterised by 40 per cent to 70 per cent global anthropogenic GHG emissions reductions by 2050 compared to 2010, and emissions levels near zero or below in 2100.” At higher GHG concentrations, this possibility becomes less and disappears above 500 ppm. The current carbon dioxide concentration, as reported by the Mauna Loa Observatory in Hawaii, is 395 ppm.
According to the Global Carbon Project, in 2013 China contributed to 28 per cent of the global GHG emissions, the U.S. 14 per cent, the European Union 10 per cent and India 7 per cent. Together, the emissions by the E.C., the U.S. and China add up to 52 per cent, which is more than half of the global total.
Thus, a reduction of 40 per cent by the E.C. and 28 per cent by the U.S. and another 16 years of emissions growth by China is unlikely to keep the global temperature increase below 2°C by 2100.
(S. Gopikrishna Warrier is regional environment manager with Panos South Asia. The views expressed here are personal.) .