Pre-industrial to end 21st century projections of tropospheric ozone from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

Abstract

Present day tropospheric ozone and its changes between 1850 and 2100 are considered, analysing 15 global models that participated in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The multi-model mean compares well against present day observations. The seasonal cycle correlates well, except for some locations in the tropical upper troposphere. Most (75%) of the models are encompassed with a range of global mean tropospheric ozone column estimates from satellite data, although there is a suggestion of a high bias in the Northern Hemisphere and a low bias in the Southern Hemisphere. Compared to the present day multi-model mean tropospheric ozone burden of 337 Tg, the multi-model mean burden for 1850 time slice is ~ 30% lower. Future changes were modelled using emissions and climate projections from four Representative Concentration Pathways (RCPs). Compared to 2000, the relative changes for the tropospheric ozone burden in 2030 (2100) for the different RCPs are: −5% (−22%) for RCP2.6, 3% (−8%) for RCP4.5, 0% (−9%) for RCP6.0, and 5% (15%) for RCP8.5. Model agreement on the magnitude of the change is greatest for larger changes. Reductions in precursor emissions are common across the RCPs and drive ozone decreases in all but RCP8.5, where doubled methane and a larger stratospheric influx increase ozone. Models with high ozone abundances for the present day also have high ozone levels for the other time slices, but there are no models consistently predicting large or small changes. Spatial patterns of ozone changes are well correlated across most models, but are notably different for models without time evolving stratospheric ozone concentrations. A unified approach to ozone budget specifications is recommended to help future studies attribute ozone changes and inter-model differences more clearly

An analysis of ozone damage to historical maize and soybean yields in the United States

“…This has important implications for current crop production considering that ground-level [O 3 ] during the Northern Hemisphere growing seasons frequently exceed 40 ppb (4), the threshold concentration for a cumulative exposure index used in Europe, as well as the concentration above which prolonged exposure leads to significant crop yield loss (5,6). Globally, [O 3 ] is projected to increase over this century if current high emissions continue (7). Although crop loss from O 3 has been estimated by extrapolating from experimental data to field conditions (8), until recently it has not been possible to quantitatively define crop loss due to O 3 pollution from actual yield data across the major US growing region.…”

Contributions to twentieth century total column ozone change from halocarbons, tropospheric ozone precursors, and climate change

“…In fact, Table 2, which gives the column ozone changes separated into stratospheric and tropospheric components, shows near cancelation of the stratospheric decrease and tropospheric increase in the global average total column, giving a net change of only -1.8 DU. Note that the PI to PD increase in the global average tropospheric column of 8.1 DU is equivalent to 88 Tg O3, which is quite close to the multimodel mean increase in tropospheric ozone between 1850 and 2000 found in ACCMIP of 98 Tg O3 [Young et al, 2013]. While the net change in column ozone is near zero in the global average, there are important hemispheric differences.…”

“…The extension of the chemistry into the troposphere has been a more recent addition to CMAM. Results from the CMAM version used here have been submitted to the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) and were found to compare well against the observations and fall well within the distribution of participating models for present-day (PD) and preindustrial (PI) conditions [Young et al, 2013]. Plots comparing zonal mean monthly climatologies of simulated present-day total and tropospheric column ozone with TOMS/SBUV and OMI-MLS TCO satellite retrievals, respectively, are presented in the supporting information.…”

“…Modeling studies of ozone in the troposphere show significant increases since preindustrial times, driven by increased anthropogenic emissions of hydrocarbons and oxides of nitrogen (NO x ) that participate in the photochemical production of tropospheric ozone [e.g., Lamarque et al, 2005;Young et al, 2013] and suggest that much of this increase was before 1970 [Cionni et al, 2011]. The very few observations of tropospheric ozone before the 1970s also suggest large increases in ozone near the surface since the end of the nineteenth century [Volz and Kley, 1988;Marenco et al, 1994].…”

Cluster-based ensemble means for climate model intercomparison

“…The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) was a multi-model initiative conducted to 5 investigate the atmospheric abundance of key climate forcing agents, including tropospheric ozone, and their change over time (e.g., Young et al, 2013;Stevenson et al, 2013;Lamarque et al, 2013). For our purposes, we use the ACCMIP climate model data as an example of a typical multi-model ensemble on which to perform the clustering.…”