2008 Carbon Budget Highlights
Atmospheric CO2 growth
The annual growth of atmospheric CO2 was 1.8 ppm in 2008, slightly below the average for the period 2000-2008 of 1.9 ppm per year (ppm = parts per million). The mean growth rate for the previous 20 years was about 1.5 ppm per year. This increase brought the atmospheric CO2 concentration to 385 ppm in 2008, 38% above the concentration at the start of the industrial revolution (about 280 ppm in 1750). The present concentration is the highest during at least the last 2 million years.
Accumulation of atmospheric CO2 is the most accurately measured quantity in the global carbon budget with an uncertainty of about 1% or about 0.04 PgC of the 4PgC per year accumulated on average since 2000. The data is provided by the US National Oceanic and Atmospheric Administration Earth System Research Laboratory.
Emissions from fossil fuel and cement
Fossil fuel CO2 emissions continued to grow strongly in 2008 at 2% per year. This growth lead to an all time high of 8.7 PgC emitted to the atmosphere (1 Pg = 1 billion tons or 1000 x million tons), 29% above emissions in 2000, and 41% above the Kyoto reference year 1990. Coal is now the largest fossil-fuel source of CO2 emissions. Over 90% of the growth in coal emissions results from increased coal use in China and India. Global emissions per capita reached 1.3 tonnes of carbon but the developed countries still lead.
CO2 emissions from fossil fuel and other industrial processes were calculated by the Carbon Dioxide Information Analysis Center of the US Oak Ridge National Laboratory. For the period 1958 to 2006 the calculations were based on United Nations Energy Statistics and cement data from the US Geological Survey, and for the years 2007 and 2008 the calculations were based on BP energy data. Uncertainty of the global fossil fuel CO2 emissions estimate is about ±6%. Uncertainty of emissions from individual countries can be several-fold bigger.
Emissions from land use change
Land use change was responsible for estimated net emissions of 1.5 PgC per year over the last 15 years. In 2008, estimated emissions declined to 1.2 Pg C. Wet La Niña con-ditions probably contributed to limited fire use and deforestation rate in Southeast Asia. Emissions from Brazil and Indonesia account for 61% of all emissions from land use change. The contribution of land use change emissions to the total emissions from human activities was 12% in 2008, down from 20% in the 1990s.
CO2 emissions from land use change were calculated by using a book-keeping method with the revised data on land use change from the Food and agriculture Organization of the United Nationals Global Forest Resource Assessment. Emissions after 2005 were extrapolated from the previous 25-year trend of 1.5 PgC per year. Gross emissions from land use change come almost exclusively from deforestation in tropical countries with an estimated 41% from South and Central America, 43% from South and Southeast Asia, and 17% from Africa. We used fire emissions from the Global Fire Emissions Database vs.2 over tropical forests to provide inter-annual variability on emissions over the last three years. Uncertainty of the global estimate of land use emissions is large and considered to be ±0.7 PgC in this analysis. Emission uncertainties at the country level can be large.
Regional fossil fuel emissions
The biggest increase in emissions has taken place in developing countries (with close to 6 billion people) while developed countries (with less than 1 billion people), on average, show rather steady emissions for the last decade. About one quarter of the recent growth in emissions in developing countries resulted from the increase in international trade of goods and services produced in developing countries but consumed in developed countries. The largest regional shift in 2008 was India overtaking Russia as the third largest CO2 emitter. China and the US remain in first and second position.
From a historical perspective, developing countries with 80% of the world’s population still account for about 20% of the cumulative emissions since 1751; the poorest countries in the world, with 800 million people, have contributed less than 1% of these cumulative emissions. Uncertainty of emissions from CO2 fossil fuel is large in some countries and about ±0.5 PgC globally.
Effect of the Global Financial Crisis
The current financial crisis had a small but probably discernable impact on the emissions growth rate in 2008 (growth rate of 2.0% down from 3.4% per year average over the previous 7 years). Despite this slowdown, fossil fuel emissions continue to track the average of the most carbon-intensive scenario of the Intergovermental Panel on Climate Change. In 2009, we project emissions to decline to levels observed in 2007 with negative growth of -2.8%. Positive growth is expected return in 2011 as the change in global Gross Domestic Product goes positive.
We have estimated emissions for 2009 based on the projection of -1.1% GDP growth rate provided by the International Monetary Fund (October 2009) and assuming a continue global decline in the carbon intensity of the GDP as seen over the last 30 years (-1.7% per year).
CO2 removal by natural sinks
Natural land and ocean CO2 sinks removed 57% (or 5.3 PgC per year) of all CO2 emitted from human activities during the 1958-2008. During this period the size of the natural sinks has grown but at slower pace than emissions have grown, although year-to-year variability is large. This implies a decline in the efficiency of the sinks in removing atmospheric CO2 over time (from 60% fifty years ago down to 55% in recent years), a trend expected to continue the future. Models suggest the sinks are responding to climate change and variaiblity..
Compared to the last previous three years, the CO2 sink in 2008 was larger on land (in terms of uptake rate) and smaller in the ocean, because El Niño/Southern Oscillation (ENSO) was in a positive (La Niña) state in 2008. Both ocean and land sinks are modelled (see next two sections) but their results need to agree with the closing of the budget, that is all carbon sources should equal all carbon sinks (either measured or modelled). For the period 2000-2008, the difference is 0.3 PgC of the 9.1 PgC per year average emissions during the period. This residual is probably due to errors in the estimate of the land sink.
Ocean CO2 sink
The global oceanic CO2 sink removed 26% of all CO2 emissions for the period 2000-2008, equivalent to an average of 2.3 PgC per year. While the total amount of CO2 being removed by the ocean is increasing, its efficiency (the fraction removed of the total emissions) appears to have been declining over the last two decades partially owing to the decline in efficiency of the Southern Ocean and North Atlantic Ocean. In 2008, the oceans removed an amount of CO2 slightly below average.
The global ocean sink was estimated using an ensemble of four ocean general circulation models coupled to ocean biogeochemistry models. Models were forced with meteorological data from the US national Centers for Environmental Prediction and atmospheric CO2 concentration. Recent trends in regional CO2 sinks in the Southern Ocean, North Atlantic, and Pacific oceans were detected directly from repeated observations.
Land CO2 sink
Terrestrial CO2 sinks removed 29% of all anthropogenic emissions for the period 2000-2008, equivalent to an average of 3 PgC per year. In 2008, terrestrial ecosystems removed 4.7 PgC, significantly higher than the long term average owing to the wetter conditions brought about by La Niña. An analysis of the long term trend of the terrestrial sink shows a growing size of the CO2 sink over the last 60 years but not discernable change in the efficiency of the sink
The terrestrial sink was estimated using an ensemble of 5 global vegetation models forced by observed CO2 concentration and a combination of meteorological data from the Climatic Research Unit and US National Centers for Environmental Prediction.
The human perturbation of the carbon cycle continues to grow strongly and track near the most carbon intensive scenarios of the UN-Intergovernmental Panel on Climate Change. The economic crisis will likely have a transitional impact on the growth of CO2 emissions and an undetectable effect on the growth of atmospheric CO2 (because the much larger inter-annual variability of the natural sinks). The efficiency of the natural sinks has likely declined during the last 60 years.