Big Jump of Record Warm Global Mean Surface Temperature in 2014–2016 Related to Unusually Large Oceanic Heat Releases
Authors
A 0.24°C jump of record warm global mean surface temperature (GMST) over the past three consecutive record-breaking years (2014–2016) was highly unusual and largely a consequence of an El Niño that released unusually large amounts of ocean heat from the subsurface layer of the northwestern tropical Pacific. This heat had built up since the 1990s mainly due to greenhouse-gas (GHG) forcing and possible remote oceanic effects. Model simulations and projections suggest that the fundamental cause, and robust predictor of large record-breaking events of GMST in the 21st century, is GHG forcing rather than internal climate variability alone. Such events will increase in frequency, magnitude, and duration, as well as impact, in the future unless GHG forcing is reduced.
Figure 2. Interdecadal accumulation and rapid release of ocean heat in the upper 700 m (1018 J, Levitus data). (a) Total heat accumulation during 1993–2012 based on the linear trend. (b) Ocean heat release (negative values) during 2013–2015. Notice the different scale. (c) The 1993–2012 ocean heat accumulation due to the transition of PDO/IPO to their negative phase. (d) Difference between Figures 2a and 2c indicating the ocean heat accumulation due to factors external to the Pacific. The green boxes in Figures 2a, 2c, and 2d indicate WP (120°E–180°E, 20°S–20°N), SWP (145°E–195°E, 0°–15°S), and NWP (120°E–180°E, 3°N–18°N), respectively. The circles mark Kwajalein and Guam (Figure 3c). See Figure S6 for similar analysis with the Ishii data.
