Editing IPCC:AR6/WGI/Chapter-2 (section)

===== 2.2.3.3.1 Carbon dioxide (CO <sub>2</sub> ) =====

<div id="h4-4-siblings" class="h4-siblings"></div>

There has been a positive trend in globally averaged surface CO <sub>2</sub> mixing ratios since 1958 (Figure 2.5a), that reflects the imbalance of sources and sinks (Section 5.2). The growth rate has increased overall since the 1960s (Figure 2.5a inset), while annual growth rates have varied substantially, for example, reaching a peak during the strong El Niño events of 1997–1998 and 2015–2016 ( [[#Bastos--2013|Bastos et al., 2013]] ; [[#Betts--2016|Betts et al., 2016]] ). The average annual CO <sub>2</sub> increase from 2000 through 2011 was 2.0 ppm yr <sup>–1</sup> (standard deviation 0.3 ppm yr <sup>–1</sup> ), similar to what was reported in AR5. From 2011 through 2019 it was 2.4 ppm yr <sup>–</sup> <sup>1</sup> (standard deviation 0.5 ppm yr <sup>–1</sup> ), which is higher than that of any comparable time period since global measurements began. Global networks consistently show that the globally averaged annual mean CO <sub>2</sub> has increased by 5.0% since 2011, reaching 409.9 ± 0.4 ppm in 2019 (NOAA measurements). Further assessment of changing seasonality is undertaken in [[#2.3.4.1|Section 2.3.4.1]] .

<div id="_idContainer018" class="Basic-Text-Frame"></div>

[[File:3e2fe664c93efaa7c3c0198d50490cdd IPCC_AR6_WGI_Figure_2_5.png]]

'''Figure 2.5 |''' '''Globally averaged dry-air mole fractions of greenhouse gases. (a)''' CO <sub>2</sub> from SIO, CSIRO, and NOAA/GML '''(b)''' CH <sub>4</sub> from NOAA, AGAGE, CSIRO, and UCI; and '''(c)''' N <sub>2</sub> O from NOAA, AGAGE, and CSIRO (Table 2.2). Growth rates, calculated as the time derivative of the global means after removing seasonal cycle are shown as inset figures. Note that the CO <sub>2</sub> series is 1958–2019 whereas CH <sub>4</sub> , and N <sub>2</sub> O are 1979–2019. Units are parts per million (ppm) or parts per billion (ppb). Further details on data are in Annex III, and on data sources and processing are available in the chapter data table (Table 2.SM.1).

<div id="2.2.3.3.2" class="h4-container"></div>

<span id="methane-ch-4-1"></span>