Impact of climate change on the future chemical composition of the global troposphere (original) (raw)
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Atmospheric Chemistry and Physics, 2007
A global 40-year simulation from 1980 to 2019 was performed with the FinROSE chemistry-transport model based on the use of coupled chemistry GCM-data. The main focus of our analysis is on climatological-scale processes in high latitudes. The resulting trend estimates for the past period (1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999) agree well with observation-based trend estimates. The results for the future period (2000-2019) suggest that the extent of seasonal ozone depletion over both northern and southern high-latitudes has likely reached its maximum. Furthermore, while climate change is expected to cool the stratosphere, this cooling is unlikely to accelerate significantly high latitude ozone depletion. However, the recovery of seasonal high latitude ozone losses will not take place during the next 15 years.
Attribution of stratospheric ozone trends to chemistry and transport: a modelling study
Atmospheric Chemistry and Physics, 2010
The decrease of the concentration of ozone depleting substances (ODS) in the stratosphere over the past decade raises the question to what extent observed changes in stratospheric ozone over this period are consistent with known changes in chemical composition and possible changes in atmospheric transport. Here we present a series 5 of ozone sensitivity calculations with a stratospheric chemistry transport model (CTM) driven with meteorological reanalyses from the European Centre for Medium Range Weather Forecast, covering the period 1978-2009. In order to account for the reversal in ODS trends, ozone trends are analysed in two periods, 1979-1999 and 2000-2009. Effects of ODS changes on the ozone chemistry are either accounted for or left out, 10 allowing for a distinct attribution of ozone trends to the different factors of variability, namely ODS acting via gas phase chemistry, ODS acting via polar heterogeneous chemistry, and changes in transport and temperature. Modeled column ozone trends are in excellent agreement with observed trends from the Total Ozone Mapping Spectrometer (TOMS) and Solar Backscatter UV (SBUV/2) as well as the Global Ozone
Journal of Geophysical Research, 2001
We present a first description and evaluation of GEOS-CHEM, a global threedimensional (3-D) model of tropospheric chemistry driven by assimilated meteorological observations from the Goddard Earth Observing System (GEOS) of the NASA Data Assimilation Office (DAO). The model is applied to a 1-year simulation of tropospheric ozone-NO•-hydrocarbon chemistry for 1994, and is evaluated with observations both for 1994 and for other years. It reproduces usually to within 10 ppb the concentrations of ozone observed from the worldwide ozonesonde data network. It simulates correctly the seasonal phases and amplitudes of ozone concentrations for different regions and altitudes, but tends to underestimate the seasonal amplitude at northern midlatitudes. Observed concentrations of NO and peroxyacetylnitrate (PAN) observed in aircraft campaigns are generally reproduced to within a factor of 2 and often much better. Concentrations of HNO3 in the remote troposphere are overestimated typically by a factor of 2-3, a common problem in global models that may reflect a combination of insufficient precipitation scavenging and gas-aerosol partitioning not resolved by the model. The model yields an atmospheric lifetime of methylchloroform (proxy for global OH) of 5.1 years, as compared to a best estimate from observations of 5.5 +/-0.8 years, and simulates H202 concentrations observed from aircraft with significant regional disagreements but no global bias. The OH concentrations are •20% higher than in our previous global 3-D model which included an UV-absorbing aerosol. Concentrations of CO tend to be underestimated by the model, often by 10-30 ppb, which could reflect a combination of excessive OH (a 20% decrease in model OH could be accommodated by the methylchloroform constraint) and an underestimate of CO sources (particularly biogenic). The model underestimates observed acetone concentrations over the South Pacific in fall by a factor of 3; a missing source from the ocean may be implicated. examine aerosol-chemistry-climate interactions [Roelofs et aL, 1997; Mickley et al., 1999; Adams et aL, 2001], and to guide international environmental policy assessments [Intergovernmental Panel on Climate Change (IPCC), 1995, 2001 ]. Several community intercomparisons of global tropospheric chemistry models have been conducted recently, demonstrating the rapid growth of the field [Jacob et al.
Atmospheric composition change: Climate–Chemistry interactions
Atmospheric Environment, 2009
future changes. Reported results include new estimates of radiative forcing based on extensive model studies of chemically active climate compounds like O 3 , and of particles inducing both direct and indirect effects. Through EU projects like ACCENT, QUANTIFY, and the AeroCom project, extensive studies on regional and sector-wise differences in the impact on atmospheric distribution are performed. Studies have shown that land-based emissions have a different effect on climate than ship and aircraft emissions, and different measures are needed to reduce the climate impact. Several areas where climate change can affect the tropospheric oxidation process and the chemical composition are identified. This can take place through enhanced stratospheric-tropospheric exchange of ozone, more frequent periods with stable conditions favoring pollution build up over industrial areas, enhanced temperature induced biogenic emissions, methane releases from permafrost thawing, and enhanced concentration through reduced biospheric uptake. During the last 5-10 years, new observational data have been made available and used for model validation and the study of atmospheric processes. Although there are significant uncertainties in the modeling of composition changes, access to new observational data has improved modeling capability. Emission scenarios for the coming decades have a large uncertainty range, in particular with respect to regional trends, leading to a significant uncertainty range in estimated regional composition changes and climate impact.
Journal of Geophysical Research, 1997
A photochemical box model with CO-CH4-NOy-H20 chemistry is used to calculate the diurnally averaged net photochemical rate of change of ozone (hereinafter called the chemical ozone tendency) in the troposphere for different values of parameters: NO x and ozone concentration, temperature, humidity, CO concentration, and surface albedo. To understand the dependency of the chemical ozone tendency on the input parameters, a detailed sensitivity study is performed. Subsequently, the expected variations of the ozone tendencies with altitude, latitude, and season are analyzed. The magnitude of the tendency decreases rapidly with height mostly as a result of lower absolute humidity and temperature. In the upper troposphere (at 190 mbar) the maximum tendencies are below 2 parts per billion by volume/day. Lower temperature and specific humidity cause a shift of the value of NO x at which the ozone production balances the destruction of ozone (balance point) to lower NO x values; these two parameters are also, to a large extent, responsible for lower magnitudes of the tendency at higher latitudes and in winter. In the upper troposphere we find that the net tendency is at least as sensitive to variations in H20 concentration as to NO x. This suggests a possible synergism between direct NO x pollution by aircraft and the indirect modification of H20 by climate change. In the second part of the paper the box model calculated rates are used as ozone's chemical tendency terms during a simulation conducted with the three-dimensional global chemistry transport model (GCTM). The box model is used to calculate the tendencies as a function of NO x and ozone at all tropospheric levels of the GCTM, at nine latitudes and for four seasons using zonally and monthly averaged data: water vapor and temperature from observations and model CO. These tables together with the NO x fields obtained in an earlier GCTM simulation are used in the GCTM simulation of 0 3 if nonmethane hydrocarbon levels are low. The global monthly averaged chemical ozone tendency fields saved during the simulation are presented and analyzed for the present-day and preindustrial conditions. The chemical tendency fields show a strong correlation with the NO x fields. In contrast with the lower and middle troposphere where the tendencies are negative in remote regions over the oceans, in the upper troposphere, where NO x is generally greater than 50 parts per trillion by volume and the balance point is low, the tendencies are generally small but positive. The GCTM simulations of the preindustrial ozone show that in the upper troposphere the presentday ozone tendencies are greater than the simulated preindustrial tendencies. In the boundary layer and in the midtroposphere the present-day tendencies are greater near anthropogenic NO x sources and smaller (generally more negative), due to higher ozone levels, in regions not affected by these sources. 1. Introduction Ozone is a tracer that has a significant influence on the chemical and radiative properties of the lower atmosphere. It is
Climate Research, 1991
The response of the atmosphere to increasing emissions of radatively active trace gases (COz, CH,, N 2 0 , o3 and CFCs) is calculated by means of a l-dimensional coupled chemical-radiativetransport model. We identify the sign and magnitude of the feedback between the chemistry and thermal structure of the atmosphere by examining steady state changes in stratospheric ozone and surface temperature in response to perturbations in trace gases of anthropogenic origin. Next, we assess the possible decline in stratospheric ozone and its effect on troposphere-stratosphere temperature trends for the period covering the pre-industrial era to the present. Future trends are also considered using projected 'business-as-usual' trace gas scenario (scenario BAU) and that expected as a result of global phase-out of production of CFCs by the year 2000 (scenario MP). The numerical experiments take account of the effect of stratospheric aerosol loading due to volcanic eruptions and the influence of the thermal inertia of the ocean. Results indicate that the trace gas increase from the period 1850 to 1986 could already have contributed to a 3 to 10 % decline in stratospheric ozone and that this decline is expected to become more pronounced by the year 2050, amounting to a 43 % ozone loss at 40 km for the scenario BAU. The total column ozone Increase of 1.5 % obtained in our model calculations for the present-day atmosphere is likely to change sign with time leading to a net decrease of 12.7 % by the middle of next century. The equilibrium surface warming for the period 1850 to 1986 is found to be 0.7 K and our calculations indicate that thls warming will reach 2.6 K by the year 2050. As a result of radiativechemical interactions, a large stratospheric cooling (16.4 K) is likely by the middle of the next century. In case the control measures on production of CFCs as laid down in the London Amendment of the Montreal Protocol are implemented by all countries and a global phase-out of CFCs takes place by the year 2000, the ozone loss at 40 km could be restricted to 17 % by the year 2050 (net column decrease of only 2.9%). This would, however, only marginally reduce the stratospheric cooling to 12.6 K. The greenhouse warming at the surface expected by the middle of the next century with enforcement of the Montreal Protocol restrictions is likely to be 2 K.
Journal of Geophysical Research, 2009
1] We explore the extent to which chemistry-aerosol-climate coupling influences predictions of future ozone and aerosols as well as future climate using the Goddard Institute for Space Studies (GISS) general circulation model II' with on-line simulation of tropospheric ozone-NO x -hydrocarbon chemistry and sulfate, nitrate, ammonium, black carbon, primary organic carbon, and secondary organic carbon aerosols. Based on IPCC scenario A2, year 2100 ozone, aerosols, and climate simulated with full chemistry-aerosol-climate coupling are compared with those simulated from a stepwise approach. In the stepwise method year 2100 ozone and aerosols are first simulated using present-day climate and year 2100 emissions (denoted as simulation CHEM2100sw) and year 2100 climate is then predicted using offline monthly fields of O 3 and aerosols from CHEM2100sw (denoted as simulation CLIM2100sw). The fully coupled chemistry-aerosol-climate simulation predicts a 15% lower global burden of O 3 for year 2100 than the simulation CHEM2100sw which does not account for future changes in climate. Relative to CHEM2100sw, year 2100 column burdens of all aerosols in the fully coupled simulation exhibit reductions of 10-20 mg m À2 in DJF and up to 10 mg m À2 in JJA in mid to high latitudes in the Northern Hemisphere, reductions of up to 20 mg m À2 over the eastern United States, northeastern China, and Europe in DJF, and increases of 30-50 mg m À2 over populated and biomass burning areas in JJA. As a result, relative to year 2100 climate simulated from CLIM2100sw, full chemistry-aerosol-climate coupling leads to a stronger net global warming by greenhouse gases, tropospheric ozone and aerosols in year 2100, with a global and annual mean surface air temperature higher by 0.42 K. For simulation of year 2100 aerosols, we conclude that it is important to consider the positive feedback between future aerosol direct radiative forcing and future aerosol concentrations; increased aerosol concentrations lead to reductions in convection and precipitation (or wet deposition of aerosols), further increasing lower tropospheric aerosol concentrations. (2009), Effect of chemistry-aerosol-climate coupling on predictions of future climate and future levels of tropospheric ozone and aerosols,