Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years

Abstract

One of the greatest sources of uncertainty for future climate predictions is the response of the global carbon cycle to climate change. Although approximately one-half of total CO(2) emissions is at present taken up by combined land and ocean carbon reservoirs, models predict a decline in future carbon uptake by these reservoirs, resulting in a positive carbon-climate feedback. Several recent studies suggest that rates of carbon uptake by the land and ocean have remained constant or declined in recent decades. Other work, however, has called into question the reported decline. Here we use global-scale atmospheric CO(2) measurements, CO(2) emission inventories and their full range of uncertainties to calculate changes in global CO(2) sources and sinks during the past 50 years. Our mass balance analysis shows that net global carbon uptake has increased significantly by about 0.05 billion tonnes of carbon per year and that global carbon uptake doubled, from 2.4 ± 0.8 to 5.0 ± 0.9 billion tonnes per year, between 1960 and 2010. Therefore, it is very unlikely that both land and ocean carbon sinks have decreased on a global scale. Since 1959, approximately 350 billion tonnes of carbon have been emitted by humans to the atmosphere, of which about 55 per cent has moved into the land and oceans. Thus, identifying the mechanisms and locations responsible for increasing global carbon uptake remains a critical challenge in constraining the modern global carbon budget and predicting future carbon-climate interactions.

Hidden carbon sink beneath desert

“…The global carbon balance includes a large terrestrial carbon sink, but that sink has not been fully identified nor its mechanisms explained [Houghton, 2007;Ballantye et al, 2012;Evans et al, 2014]. Recent findings that desert regions remove carbon dioxide (CO 2 ) from the atmosphere at a magnitude of~100 g C m À2 yr À1 suggest that these systems may explain at least a portion of that terrestrial carbon sink [Jasoni et al, 2005;Stone, 2008;Wohlfahrt et al, 2008;Xie et al, 2009;Ma et al, 2014].…”

Primary estimation of Chinese terrestrial carbon sequestration during 2001–2010

“…Terrestrial ecosystems, as sinks of atmospheric CO 2 [1], play an important role in mitigating global climate change [2,3]. The Intergovernmental Panel on Climate Change (IPCC) identified the objectives and the mechanisms of controlling the global greenhouse gases and provided guidance on the emission reduction targets for countries at different stages of development [4].…”

Forecasting Global Warming

“…The figures also contain observed global, annually averaged mixing ratios for each GHG. Observed CO 2 is from data provided by NOAA Earth Science Research Laboratory (ESRL) (Ballantyne et al 2012) at: ftp://ftp.cmdl.noaa.gov/products/ trends/co2/co2_annmean_gl.txt The CO 2 record given at the above URL starts in 1980. This record has been extended back to 1959 using annual, global average CO 2 growth rates at: http:// www.esrl.noaa.gov/gmd/ccgg/trends/global.html#global_growth The CH 4 record for 1984 to present (Dlugokencky et al 2009) is from: ftp://aftp.…”

“…5 CMIP5 GCM output is at http://cmip-pcmdi.llnl.gov/cmip5/data_getting_started.html , RCP 6.0 (Masui et al 2011), RCP 8.5 , and observations (black) (Ballantyne et al 2012;Dlugokencky et al 2009;Montzka et al 2011). Values of GHG mixing ratios from RCP extend back to 1860, but this figure starts in 1950 since most of the rise in these GHGs has occurred since that time.…”