Changes in Earth’s Energy Budget during and after the “Pause” in Global Warming: An Observational Perspective

Abstract

This study examines changes in Earth's energy budget during and after the global warming "pause" (or "hiatus") using observations from the Clouds and the Earth's Radiant Energy System. We find a marked 0.83 ± 0.41 Wm −2 reduction in global mean reflected shortwave (SW) top-of-atmosphere (TOA) flux during the three years following the hiatus that results in an increase in net energy into the climate system. A partial radiative perturbation analysis reveals that decreases in low cloud cover are the primary driver of the decrease in SW TOA flux. The regional distribution of the SW TOA flux changes associated with the decreases in low cloud cover closely matches that of sea-surface temperature warming, which shows a pattern typical of the positive phase of the Pacific Decadal Oscillation. Large reductions in clear-sky SW TOA flux are also found over much of the Pacific and Atlantic Oceans in the northern hemisphere. These are associated with a reduction in aerosol optical depth consistent with stricter pollution controls in China and North America. A simple energy budget framework is used to show that TOA radiation (particularly in the SW) likely played a dominant role in driving the marked increase in temperature tendency during the post-hiatus period.Climate 2018, 6, 62 2 of 18 exhibits decreasing TOA net radiative flux [6]. Outgoing longwave (LW) radiation exhibits similar increases with warming in each RCP scenario, but reflected shortwave (SW) radiation decreases far more rapidly for RCP8.5 due to marked decreases in cloud cover and snow/sea-ice. In time, the climate system heats up sufficiently in all scenarios to arrive at a new equilibrium temperature and an energy balance at the TOA.At decadal timescales, when internal variations in the climate system dominate, the link between TOA radiation and surface temperature is more complex. Using pre-industrial control simulations of three generations of Met Office Hadley Centre coupled atmosphere-ocean climate models, Palmer et al. [7] show that while decadal trends in global mean sea-surface temperature (SST) tend to be positive (negative) when the decadal average net downward TOA flux is positive (negative), ≈30% of decades show opposite trends in SST and total energy, implying that it is not uncommon for a decade to show a decreasing trend in SST and a positive decadal average net TOA flux. The reason for the large scatter between decadal SST and total energy trends is re-distribution of heat within the ocean. In order to relate net TOA radiation and global mean surface temperature changes at decadal timescales, Xie et al. [4] decompose the climate feedback term into forced and natural variability components, with the latter term accounting for the lag between TOA radiation and surface temperature variations.Between approximately 1998 and 2013, the rate of increase in global mean surface temperature slowed down relative to that during the latter half of the 20th century [8][9][10]. This so-called "global warming hiatus" period coincided with the negative phase of...

The Pause End and Major Temperature Impacts during Super El Niños are Due to Shortwave Radiation Anomalies

“…Loeb et al [44] have carried out encompassing analyses between the cloud data of CERES [25] and the SW anomalies and they found that the correlation was 0.66 between the global SW anomalies and low level cloud variations that supports the cause-and-effect mechanism.…”

“…Loeb et al [44] found a significant reduction of 0.83 ± 0.41 Wm -2 in global mean reflected SW flux at the top-of-atmosphere (TOA) flux during the years 2014-2017 after the pause resulting in an increase in net energy into the climate system. Decreases in low cloud cover were the primary driver of the decrease in reflected SW TOA flux.…”

Measuring Global Ocean Heat Content to Estimate the Earth Energy Imbalance

“…From days to interannual time scales, EEI variations are dominated by the effects of internal climate modes of variability such as the El Niño Southern Oscillation (Loeb et al, 2018a). Primary causes for variability on decadal and longer time scales are changes in solar irradiance, large volcanic eruptions and natural variations in GHG concentrations (Hansen et al, 2011;von Schuckmann et al, 2016).…”

“…First, EEI can be directly measured by estimating the global budget of incoming and outgoing radiation at TOA. The current implementation of this method with the Clouds and the Earth's Radiant Energy System (CERES) instruments allows accurate determination of the time variations of EEI (with an uncertainty of ±0.17 Wm −2 at monthly time scales, Loeb et al, 2018a). But the accuracy on the absolute global mean value of EEI is limited within ±4 Wm −2 mainly due to instrument calibration uncertainty (Loeb et al, 2018a).…”

Remote sensing of earth’s energy budget: synthesis and review

“…The large positive anomalies in shortwave TOA flux coincide with positive anomalies in the Arctic sea ice coverage during the early 2000s (Hartmann and Ceppi 2014). In another study, Loeb, Thorsen, et al (2018) assessed the impacts of the climate warming hiatus and found a marked 0.83 ± 0.41 Wm −2 reduction in global reflected shortwave TOA flux during 2000-2017 compared to the hiatus reference years from 2000 to 2014 due to changes in low cloud cover. The seasonal cycles of planetary albedo are largely influenced by surface albedo (Stephens et al 2015).…”