[Climate Change]Study reveals the atmospheric footprint of global warming hiatus

The increasing rate of the global mean surface temperature was reduced from 1998 to 2013, known as the global warming hiatus. Dominant mechanisms include the internal climate variability, the ocean heat uptake and redistribution. However, the atmospheric footprint of the recent warming hiatus in the dynamical and physical processeshas been less concerned.

In a recent paper, LIU Bo and ZHOU Tianjun from the Institute of Atmospheric Physics, Chinese Academy of Sciences have investigated the atmospheric anomalous features during the global warming hiatus period (1998-2013). They show evidences that the global mean tropospheric temperature also experienced a hiatus.

To understand the processes that dominate the warming hiatus, they decomposed the temperature trends into components due to processes related to surface albedo, water vapor, cloud, surface turbulent fluxes and atmospheric dynamics.

The results demonstrated that the hiatus of near surface temperature warming trend is dominated by the decreasing surface latent heat flux compared with the preceding warming period, while the hiatus of upper tropospheric temperature is dominated by the cloud-related processes. Further analysis indicated that atmospheric dynamics are coupled with surface turbulent heat fluxes over lower troposphere and coupled with cloud processes over upper troposphere.

As to why the surface latent heat flux, atmospheric dynamics and cloud-related processes showed such large differences between 1983-1998 and 1998-2013, LIU explained, "They are dominated by the Hadley Circulation (HC) and Walker Circulation (WC) changes associated with the phase transition of Interdecadal Pacific Oscillation (IPO)."The IPO has shifted from the positive phase to negative phase since 1998/1999, and this transition has led to the weakening of both HC and WC, which served as a hub linking the three processes mentioned above.

"Though the heat capacity of the atmosphere is nearly negligible compared with the ocean", said ZHOU, corresponding author of the paper, "understanding the atmospheric footprint is essential to gain a full picture of how internal climate variability such as IPO affects the global climate from the surface to the troposphere.

Figure 1. (a) Global mean temperature anomalies from 1950 to 2015 and (b) linear trends of global mean temperature for near surface (i.e. the lowest atmospheric layer), and the vertical average of the whole (surface to 100hPa), lower (surface to 500hPa), and upper troposphere (500hPa to 100hPa). Red (black) bars are for the warming period. Blue (white) bars are for the hiatus period.

Citation: Liu, B. & Zhou, T. Atmospheric footprint of the recent warming slowdown. Sci. Rep. 7, 40947 (2017). http://www.nature.com/articles/srep40947