Other phenomena which might have played a role in the observed significant TOC changes over the oceans are ENSO, the The South Pacific Convergence Zone (SPCZ , Widlansky et al., 2011), the ITCZ (Section 14.3.1.1), and the Western North Pacific Monsoon (Section 14.2.2.5). During El Niño events, the ITCZ and SPCZ move closer to the Equator, rainfall decreases in western regions and increases in the central Pacific, and tropical cyclone numbers tend to increase and to occur farther east than normal (Diamond et al., 2012). During La Niña, the western tropical Pacific tends to experience above-average numbers of tropical cyclones (Nicholls et al., 1998; Lavender and Walsh, 2011). The seasonal evolution of the SPCZ has a strong influence on the seasonality of the climate of the southern tropical Pacific , particularly during the wet season. The SPCZ moves northward during moderate El Niño events and southward during La Niña events (Folland et al., 2002; Vincent et al., 2011). During El Niño events, southwest Pacific Island nations experience an increased occurrence of forest fires and droughts (Salinger et al., 2001; Kumar et al., 2006b), and an increased probability of tropical cyclone damage, as tropical cyclogenesis tends to reside within 6°–10° south of the SPCZ (Vincent et al., 2011). 

Nauru experiences drought during La Niña as the SPCZ and ITCZ move to the west (Brown et al., 2012c). During strong El Niño events (e.g., 1982/1983, 1997/1998) the SPCZ undergoes an extreme swing of up to 10 degrees towards the equator and collapses to a more zonally-oriented structure (Vincent et al., 2011; Section 14.3.2). The impacts from these zonal SPCZ events are much more severe than those from moderate El Niño events (Vincent et al., 2011; Cai et al., 2012b), and can induce massive droughts and food shortages (Barnett, 2011). Temperatures 

Regional climates are strongly influenced by modes of climate variability (see Box 14.1 for definitions of
mode, regime, and teleconnection). This chapter assesses major modes such as El Niño Southern Oscillation
(ENSO, Section 14.4), the North Atlantic Oscillation/Northern Annular Mode (NAO/NAM) and Southern
Annular Mode (SAM) in the extra-tropics (Section 14.5), and various other well-known modes such as the
Pacific North American (PNA), Pacific Decadal Oscillation (PDO), Atlantic Multi-Decadal Oscillation
(AMO), etc. (Section 14.7). Many of these modes are described in previous IPCC reports (e.g., Section 3.6
of AR4 WG1). Chapter 2 gives operational definitions of mode indices (Box 2.5, Table 1) and an assessment
of observed historical behaviour (Section 2.7.8). Climate models are generally able to simulate the gross
features of many of the modes of variability (Section 9.5), and so provide useful tools for understanding how
modes might change in the future (Müller and Roeckner, 2008; Handorf and Dethloff, 2009).

The observed TOC changes might have been influenced by some phenomena including ENSO, the South Pacific Convergence Zone (SPCZ , Widlansky et al., 2011), the ITCZ , and the Western North Pacific Monsoon (Section 14.2.2.5). 

The observed TOC changes might have been influenced by some phenomena including ENSO, the North Atlantic Oscillation/Northern Annular Mode (NAO/NAM), Southern Annular Mode (SAM) in the extra-tropics, Pacific North American (PNA), Pacific Decadal Oscillation (PDO), Atlantic Multi-Decadal Oscillation (AMO), etc \citep[e.g.,][]{Lin2014,Ziemke2015,Handorf_Dethloff2009}. The climate patterns associated with the modes may exhibit, structural, spatial, index or no change \citep[e.g.,][]{Compo_Sardeshmukh2010, Bulic_Kucharski2012}. During El Ni\~{n}o events, the ITCZ is farther south and closer to the equator, while during La Ni\~{n}a, it is farther north and away from the equator. This altars the strength of tropical cyclones over the Pacific and Indian Oceans, thus influencing TOC changes.


During El Ni\~{n}o events, the ITCZ move toward the Equator, the central Pacific experience above average numbers of tropical cyclones which occur farther east than normal. During La Ni\~{n}a,  the western tropical Pacific tends to experience above-average numbers of tropical cyclones
