Analysis: Current Climate Commitments Will Double Emissions By 2040, Almost Double GHG Concentrations By 2100
by Jack Rosebro
|Four greenhouse gas emissions trajectories: (1) business as usual, in gray; (2) current GHG reduction strategy, in red; (3) 450 ppm CO2/2 ºC warming, in black; and (4) 350 ppm CO2/1.5 ºC warming, (dotted line). Click to enlarge.|
The combined effect of the latest national pledges and commitments to reduce or offset greenhouse gas emissions, many of which have been offered in the weeks leading up to the Copenhagen climate summit, would result in global greenhouse gas (GHG) emissions climbing to double 1990 levels by 2040, and atmospheric CO2 levels exceeding 650 ppm by 2100, with total GHG concentrations close to 800 ppm CO2e (CO2 equivalent), according to a new assessment offered at the beginning of the COP 15 climate conference today in Copenhagen.
Working with the Potsdam Institute for Climate Impact Research (PIK), Ecofys and Climate Analytics developed the Climate Action Tracker, a web-based climate policy assessment system that quantifies the projected GHG emissions of individual countries, as shaped by that country’s proposed GHG reduction strategies. The website also plots projected consequences of the world’s aggregate GHG reduction strategies. Data will be updated as climate talks progress in Copenhagen.
The most widely advocated and accepted emissions reduction strategy that would seek to limit warming to 2 ºC (3.6 ºF) above pre-industrial levels, coupled with a warming limit of 0.2 ºC per decade, is that of “peak and decline”, with the peaking of emissions occurring as early as 2015, followed by a sharp decline to 50% to 85% of 1990 emissions.
However, the most recent analysis by PIK, Ecofys and Climate Analytics estimates that the world’s GHG emissions will peak around 2040 and then decline slowly, if emissions reduction commitments currently on the table in Copenhagen can be achieved.Such an emissions trajectory would likely be further complicated by additional key modifiers. For example, the Intergovernmental Panel on Climate Change (IPCC) estimated in its most recent Fourth Assessment Report (AR4) that net carbon uptake by the Earth’s ecosystems “is likely to peak before mid-century and then weaken or even reverse, thus amplifying climate change.”
In addition, scientific support for the 2ºC (450 ppm CO2) warming limit is weakening, due in part to the acceleration of many indicators of climate change since AR4 was published in 2007. The 2 ºC limit is now thought by many climate scientists to have only a 50% chance of preventing the most catastrophic effects of climate change.
Averaged atmospheric concentrations of CO2, as measured at the Mauna Loa Observatory under the auspices of the Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration's Earth Systems Research Laboratory, now stand at around 387 parts per million of carbon dioxide.