Data crunching for Doha and beyond
Dr Pep Canadell from the Global Carbon Project crunches the data on carbon emissions. He explains what's happening and where we are headed.
In the world of climate change science, rising carbon emissions are understood by the vast majority of researchers and governments to be the driver of global warming.
For 12 years the Global Carbon Project, partly supported by CSIRO and the Department of Climate Change and Energy Efficiency through the Australian Climate Change Science Program, has been collating and interpreting the figures that decision-makers like to have in front of them at talks such as those currently in Doha.
They want to know what is rising, by how much, where, how much uncertainty there is and, finally, if the upward trends are maintained what the resulting temperature scenarios will be.
The 2012 Project summary and the international team of scientists contributing to it, have harnessed the necessary data that describes the state of carbon emissions today.
Let's review those figures and address the what, when and where. Keep this equation in mind as you read on - one Petagram (Pg C) = one billion tons or 1,000 million tons of carbon.
Fossil fuel CO2 and cement emissions increased by 3 per cent in 2011, with a total of 9.5±0.5 PgC emitted to the atmosphere (35 Pg of CO2). These emissions were the highest in human history and 54 per cent higher than in 1990 (the Kyoto reference year). Coal burning was responsible for 43 per cent of the total emissions, oil 34 per cent, gas 18 per cent, and cement 5 per cent.
CO2 emissions from fossil fuel and other industrial processes are calculated by the Carbon Dioxide Information Analysis Center of the US Oak Ridge National Laboratory. For the period 1958 to 2009 the calculations were based on United Nations Energy Statistics and cement data from the US Geological Survey, and for the years 2010 and 2011 the calculations were based on BP energy data. Uncertainty of the global fossil fuel CO2 is estimated at ±0.5 PgC. Uncertainty of emissions from individual countries can be several-fold bigger.
CO2 emissions from deforestation and other land use change were 0.9±0.5 PgC in 2011. For the period 2002-2011, land use change emissions accounted for 11 per cent of all emissions from human activity (fossil fuel, cement, land use change). The data suggest an overall decreasing trend in land use change emissions particularly since 2000. The implementation of new land use change policies, higher law enforcement to stop illegal deforestation, and new afforestation and regrowth of previously deforested areas could all have contributed to this decline.
Total emissions from human activity in 2011 (fossil fuel, cement, land use change) were 10.4±0.9 Pg C. Emissions from land use change were 36 per cent of the total human emissions in 1960, 18 per cent in 1990, and 9 per cent in 2011. Uncertainty for all land use change emission estimates remain large. CO2 emissions from land use change are mainly based on forest statistics from the Food and Agriculture Organization and a terrestrial model, and include year-to-year variability in deforestations based on fire activity from year 1997 onwards.
Contributions to global emissions growth in 2011 were largest from China (0.226 Pg above 2010 levels, 9.9 per cent growth) and India (0.043 Pg above 2010 levels, 7.5 per cent growth). Emissions from USA were down by 0.028, (-1.8 per cent) and European Union down by 0.029,PgC (-2.8 per cent). Developing nations accounted for 58 per cent of all emissions in 2011. Per capita emissions of developed countries remain several times larger than those of developing countries, although China's per capita emission of 1.8 tonnes C per person is now close to the average of 2.0 in the EU-27.
Emission pathways provide a view of the direction that world temperatures are estimated to be heading based on assessments of the timetable over which emissions growth can be constrained.
Consumption-based emissions allocate emissions to the country where goods and services are consumed (not where they are produced and emissions released). The net emission transfer via international trade between less developing countries and developed countries has increased from 0.04 PgC in 1990 to 0.38 PgC in 2010, with an average annual growth rate of 9 per cent. The increase in net emission transfers of 0.33 PgC from 1990 to 2008 compares with the emission reduction of 0.2 PgC in developed countries.
This accounting framework tries to address the growing issue of countries outsourcing greenhouse gas emissions by consuming goods, which are manufactured outside of the country. In 2010, the biggest emitters from a territorial-based perspective were China (26 per cent), USA (17 per cent), EU (12 per cent), and India (7 per cent), while the biggest emitters from a consumption-based perspective were China (22 per cent), USA (18 per cent), EU (15 per cent), and India (6 per cent).
How does nature play its part? Of the total emissions from human activities during the period 2002-2011, 46 per cent accumulated in the atmosphere, 27 per cent in the ocean and 28 per cent on land. During this period, the size of the natural sinks have grown almost at the same pace as the growth in emissions, although year-to-year variability is large. Climate variability phenomena such as an El Niño - Southern Oscillation event can even turn the global net land sink into a net source for brief periods.
There is the possibility that the fraction of all emissions remaining in the atmosphere has a positive trend due to changes in emissions growth rate, volcanic emissions, and decline in the efficiency of natural sinks. The ocean sink is estimated by using an ensemble of six ocean-process models for the 40 year period from 1959-2009, and with a subset of these models for 2010-11. The models were tested to the observed mean land and ocean sinks for 1990-2000, estimated from a range of oceanic and atmospheric observations. Models were forced with meteorological data from the US National Centers for Environmental Prediction and atmospheric CO2 concentration. The land sink is calculated as the residual of the sum of all sources minus atmosphere plus ocean sinks.
The annual growth rate of atmospheric CO2 was 1.70±0.09 ppm in 2011 (ppm = parts per million), slightly below the average growth rate of 2 ppm over the past 10 years (2002-2011). The average growth rate for the decade 1990-1999 was 1.5±0.1 ppm, and was 1.6±0.1 for the decade 1980-1989.
The 2012 increase brought the atmospheric CO2 concentration to 390 ppm, 40 per cent above the concentration at the start of the Industrial Revolution (about 278 ppm in 1750). The present concentration is the highest during at least the last 800,000 years.
The accumulation of atmospheric CO2 in 2011 was 3.6±0.2 Pg C, with a total cumulative of 161.3 Pg C since atmospheric high precision measurements began in 1959 and 240 Pg C since 1750. The rates of atmospheric CO2 accumulation are influenced by both the anthropogenic emissions and the net uptake by natural sinks (ocean and land), and their large interannual variability.
Accumulation of atmospheric CO2 is the most accurately measured quantity in the global carbon budget. The uncertainty around the annual growth rate based on the multiple stations dataset ranges between 0.11 and 0.72 Pg C per year, with a mean of 0.61 Pg C per year for 1959-1980 and 0.18 Pg C per year for 1980-2011, when a larger set of stations were available.
Now for the pointy end of the discussion. Long-term emissions scenarios are designed to represent a range of plausible emission trajectories as input for climate change research. The Intergovernmental Panel of Climate Change (IPCC) process has resulted in four generations of emissions scenarios: Scientific Assessment 1990 (SA90), IPCC Scenarios 1992 (IS92), Special Report on Emissions Scenarios (SRES), and the evolving Representative Concentration Pathways (RCPs) to be used in the upcoming IPCC Fifth Assessment Report.
Here, global climate models are run using the RCPs alongside socio-economic and emission scenarios. Current trajectories of fossil fuel emissions are tracking some of the most carbon intensive emission scenarios used in the IPCC. The current trajectory is tracking the Representative Concentration Pathway 8.5 (of the latest family of scenarios used in the 5th Assessment of the IPCC) that takes the planet to about 4°C to 6.1°C above pre-industrial global near surface air temperatures by 2100.
Now, it's over to the decision-makers.
For much of the above, the Global Carbon Project gratefully acknowledges the US National Oceanic and Atmospheric Administration Earth System Research Laboratory and from the Scripps Institution of Oceanography for freely providing the data.
Dr Pep Canadell is Executive Director of the Global Carbon Project, based at CSIRO Black Mountain, Canberra. View his full profile here.