ausblenden:
Schlagwörter:
-
Zusammenfassung:
Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution
among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle,
support the development of climate policies, and project future climate change. Here we describe data sets and a
methodology to quantify all major components of the global carbon budget, including their uncertainties, based
on the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a
broad scientific community. We discuss changes compared to previous estimates, consistency within and among
components, alongside methodology and data limitations. CO2 emissions from fossil-fuel combustion and cement
production (EFF) are based on energy statistics, while emissions from land-use change (ELUC), mainly
deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation,
and models. The global atmospheric CO2 concentration is measured directly and its rate of growth
(GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based
on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The
variability in SOCEAN is evaluated for the first time in this budget with data products based on surveys of ocean
CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other
terms of the global carbon budget and compared to results of independent dynamic global vegetation models
forced by observed climate, CO2 and land cover change (some including nitrogen–carbon interactions). All
uncertainties are reported as ±1, reflecting the current capacity to characterise the annual estimates of each
component of the global carbon budget. For the last decade available (2003–2012), EFF was 8.6±0.4 GtC yr−1,
ELUC 0.9±0.5 GtC yr−1, GATM 4.3±0.1 GtC yr−1, SOCEAN 2.5±0.5 GtC yr−1, and SLAND 2.8±0.8 GtC yr−1.
For year 2012 alone, EFF grew to 9.7±0.5 GtC yr−1, 2.2% above 2011, reflecting a continued growing trend
in these emissions, GATM was 5.1±0.2 GtC yr−1, SOCEAN was 2.9±0.5 GtC yr−1, and assuming an ELUC of
1.0±0.5 GtC yr−1 (based on the 2001–2010 average), SLAND was 2.7±0.9 GtC yr−1. GATM was high in 2012
compared to the 2003–2012 average, almost entirely reflecting the high EFF. The global atmospheric CO2 concentration
reached 392.52±0.10 ppm averaged over 2012. We estimate that EFF will increase by 2.1% (1.1–
3.1 %) to 9.9±0.5 GtC in 2013, 61% above emissions in 1990, based on projections of world gross domestic
product and recent changes in the carbon intensity of the economy.With this projection, cumulative emissions of CO2 will reach about 535±55 GtC for 1870–2013, about 70% from EFF (390±20 GtC) and 30% from ELUC (145±50 GtC).
