Strong modification of stratospheric ozone forcing by cloud and sea-ice adjustments

et al. 2020

Adv. Atmos. Sci.

Self Cite

Recent studies demonstrate that the Antarctic Ozone Hole has important influences on Antarctic sea ice. While most of these works have focused on effects associated with atmospheric and oceanic dynamic processes caused by stratospheric ozone changes, here we show that stratospheric ozone-induced cloud radiative effects also play important roles in causing changes in Antarctic sea ice. Our simulations demonstrate that the recovery of the Antarctic Ozone Hole causes decreases in clouds over Southern Hemisphere (SH) high latitudes and increases in clouds over the SH extratropics. The decrease in clouds leads to a reduction in downward infrared radiation, especially in austral autumn. This results in cooling of the Southern Ocean surface and increasing Antarctic sea ice. Surface cooling also involves ice-albedo feedback. Increasing sea ice reflects solar radiation and causes further cooling and more increases in Antarctic sea ice.

Section: Cloud Response To Ozone Recoverymentioning

confidence: 95%

Stratospheric Ozone-induced Cloud Radiative Effects on Antarctic Sea Ice

Xia

et al. 2020

Adv. Atmos. Sci.

Self Cite

“…3b ). The change of the net radiative fluxes at TOA is decomposed into the instantaneous radiative effect of the dust and radiative feedbacks consisting of the water vapor, cloud, albedo, and temperature feedbacks 25 , 26 (Fig. 3 ).…”

Section: Resultsmentioning

confidence: 99%

A Possible Role of Dust in Resolving the Holocene Temperature Conundrum

Zhang

et al. 2018

Sci Rep

Self Cite

Climate models generally fail to produce a warmer (by as much as 0.5 °C) early to mid-Holocene than the pre-industrial in the global annual temperature, which has been termed the Holocene temperature conundrum. Here we use a fully coupled atmosphere-ocean general circulation model to test whether the conundrum can be partially resolved by considering the fact that atmospheric dust loading was much reduced during the early to mid-Holocene. Our experiments show that the global annual mean surface temperature increases by 0.30 °C and 0.23 °C for the mid-Holocene (6 ka) and early Holocene (9 ka), respectively, if the dust is completely removed. The temperature increase scales almost linearly with the fraction of dust being removed, with the 50% dust reduction experiment for the 6 ka being the only one deviating from the linear trend. The indirect effect of dust, which is highly uncertain and is not included in the model, may further enhance the warming. Therefore, the neglect of dust reduction in the Holocene in climate models could contribute significantly to the model-data discrepancy, especially in the Northern Hemisphere.

“…For example, rapid adjustments lead to the ERF for black carbon (BC) being half that of its IRF (Stjern et al, 2017;Smith et al, 2018). On the other hand, Xia et al (2016) found that cloud and sea ice feedbacks driven by stratospheric O3 recovery included in the ERF definition lead to a significant adjustment that changes the sign and magnitude of the stratospheric O3 forcing from the SARF. Although the definitions of RF and ERF differ in where the change in radiative fluxes is diagnosed, ERFs at the tropopause are nearly identical to those at the TOA for tropospheric forcing agents; this is also the case for SARFs.…”

Section: Introductionmentioning

confidence: 99%

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

O’Connor¹,

Abraham²,

Dalvi³

et al. 2020

Preprint

Abstract. Quantifying forcings from anthropogenic perturbations to the Earth System (ES) is important for understanding changes in climate since the pre-industrial period. In this paper, we quantify and analyse a wide range of present-day (PD) anthropogenic climate forcings with the UK's Earth System Model (ESM), UKESM1, following the protocols defined by the Radiative Forcing Model Intercomparison Project (RFMIP) and the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). In particular, by quantifying effective radiative forcings (ERFs) that include rapid adjustments within a full ESM, it enables the role of various climate-chemistry-aerosol-cloud feedbacks to be quantified. Global mean ERFs are 1.83, 0.13, &#8722;0.33, and 0.93&#8201;W&#8201;m&#8722;2 at the PD (Year 2014) relative to the pre-industrial (PI; Year 1850) for carbon dioxide, nitrous oxide, ozone-depleting substances, and methane, respectively. The PD total greenhouse gas ERF is 2.89&#8201;W&#8201;m&#8722;2, larger than the sum of the individual GHG ERFs. UKESM1 has an aerosol forcing of &#8722;1.13&#8201;W&#8201;m&#8722;2. A relatively strong negative forcing from aerosol-cloud interactions and a small negative instantaneous forcing from aerosol-radiation interactions are partially offset by a substantial forcing from black carbon absorption. Internal mixing and chemical interactions mean that neither the forcing from aerosol-radiation interactions nor aerosol-cloud interactions are linear, making the total aerosol ERF less than the sum of the individual speciated aerosol ERFs. Tropospheric ozone precursors, in addition to exerting a positive forcing due to ozone, lead to oxidant changes which in turn cause an indirect aerosol ERF, altering the sign of the net ERF from nitrogen oxide emissions. Together, aerosol and tropospheric ozone precursors (near-term climate forcers, NTCFs) exert a global mean ERF of &#8722;1.12&#8201;W&#8201;m&#8722;2, mainly due to changes in the cloud radiative effect. There is also a negative PD ERF from land use (&#8722;0.32&#8201;W&#8201;m&#8722;2). It is outside the range of previous estimates, and is most likely due to too strong an albedo response. In combination, the net anthropogenic ERF is potentially biased low (1.61&#8201;W&#8201;m&#8722;2) relative to other estimates, due to the inclusion of non-linear feedbacks and ES interactions. By including feedbacks between greenhouse gases, stratospheric and tropospheric ozone, aerosols, and clouds, some of which act non-linearly, this work demonstrates the importance of ES interactions when quantifying climate forcing. It also suggests that rapid adjustments need to include chemical as well as physical adjustments to fully account for complex ES interactions.