Climate Change and...
Effects of Climate Change
- Climate Variability
- Climate Models
Effects of Climate Change
ABSTRACT: Plants accumulate significant amounts of atmospheric mercury (Hg) in aboveground biomass, likely sequestering over 1,000 Mg of atmospheric Hg every year. This large mercury uptake could be strong enough to affect tropospheric Hg levels and might be partially responsible for seasonal variations in atmospheric Hg observed at Mace Head, Ireland. The fluctuations of Hg concentrations coincide temporally with the annual oscillation of carbon dioxide (CO2 ) in the Northern Hemisphere, which is a result of seasonal growth of vegetation. Therefore, declining Hg concentrations in spring and summer may be attributed in part to plant uptake of atmospheric Hg. Further, the increase of Hg concentrations during non-active vegetation periods might partially be due to plant-derived Hg emitting back to the atmosphere during carbon mineralization. The implications of these propositions are that past and future changes in biomass productivity and organic carbon pools may have had—and may continue to have—significant effects on atmospheric Hg levels. Specifically, large losses in soil and biomass carbon pools in the last 150 years could have contributed significantly to observed increases in atmospheric Hg pollution. The roles of vegetation and terrestrial carbon pools should receive detailed consideration on how they might attenuate or exacerbate atmospheric Hg pollution.
ABSTRACT: Based upon trends in observed climate, extreme events are thought to be increasing in frequency and/or magnitude. This change in extreme events is attributed to enhancement of the hydrologic cycle caused by increased greenhouse gas concentrations. Results are presented of relatively long (50 yr) regional climate model simulations of the western United States examining the sensitivity of climate and extreme events to a doubling of preindustrial atmospheric CO2 concentrations. These results indicate a shift in the temperature distribution, resulting in fewer cold days and more hot days; the largest changes occur at high elevations. The rainfall distribution is also affected; total rain increases as a result of increases in rainfall during the spring season and at higher elevations. The risk of flooding is generally increased, as is the severity of droughts and heat waves. These results, combined with results of decreased snowpack and increased evaporation, could further stress the water supply of the western United States.
ABSTRACT: Biomass burning is a major source of emissions to the atmosphere. Some of these emissions may change global climate. This paper uses combustion efficiency as an independent variable for predicting emission factors for, among others, carbon monoxide, carbon dioxide, methane, and particulate matter. Other gases are correlated with the release of carbon monoxide. The release of nitrogen and sulfur-based compounds occurs in relation to their content in the biomass. The Sundance Fire is used to model the emissions from major fires that have occurred in the United States. Approximately 1 Tg of biomass was consumed by this fire, which released 0.019, 0.151, 1.545, and 0.007 Tg of particulate matter, carbon monoxide, carbon dioxide, and oxides of nitrogen, respectively. Other fires have released over 50 times this amount. Global emissions of various products of combustion are dependent on the combustion efficiency of the fires.
A. L. Steiner, S. Tonse, R. C. Cohen, A. H. Goldstein, R. A. Harley (2006). Influence of future climate and emissions on regional air quality in California. Journal of Geophysical Research 111 (D18303): doi:10.1029/2005JD006935
ABSTRACT: Using a chemical transport model simulating ozone concentrations in central California, we evaluate the effects of variables associated with future changes in climate and ozone precursor emissions, including (1) increasing temperature; (2) increasing atmospheric water vapor; (3) increasing biogenic VOC emissions due to temperature; (4) projected decreases in anthropogenic NOx, VOC, and CO emissions in California for 2050; and (5) the influence of changing ozone, CO, and methane at the western boundary. Climatic changes expected for temperature, atmospheric water vapor, and biogenic VOC emissions each individually cause a 1–5% increase in the daily peak ozone. Projected reductions in anthropogenic emissions of 10–50% in NOx and 50–70% in VOCs and CO have the greatest single effect, reducing ozone by 8–15% in urban areas. Changes to the chemical boundary conditions lead to ozone increases of 6% in the San Francisco Bay area and along the west coast but only 1–2% inland. Simulations combining climate effects predict that ozone will increase 3–10% in various regions of California. This increase is partly offset by projected future emissions reductions, and a combined climate and emissions simulation yields ozone reductions of 3–9% in the Central Valley and almost no net change in the San Francisco Bay area. We find that different portions of the model domain have widely varying sensitivity to climate parameters. In particular, the San Francisco Bay region is more strongly influenced by temperature changes than inland regions, indicating that air quality in this region may worsen under future climate regimes.
L. J. Mickley, D. J. Jacob, B. D. Field, D. Rind (2004). Effects of future climate change on regional air pollution episodes in the United States. Geophysical Research Letters 31 (L24103): doi:10.1029/2004GL021216
ABSTRACT: We examine the impact of future climate change on regional air pollution meteorology in the United States by conducting a transient climate change (1950–2052) simulation in a general circulation model (GCM) of the Goddard Institute of Space Studies (GISS). We include in the GCM two tracers of anthropogenic pollution, combustion carbon monoxide (COt) and black carbon (BCt). Sources of both tracers and the loss frequency of COt are held constant in time, while wet deposition of BCt responds to the changing climate. Results show that the severity and duration of summertime regional pollution episodes in the midwestern and northeastern United States increase significantly relative to present. Pollutant concentrations during these episodes increase by 5–10% and the mean episode duration increases from 2 to 3–4 days. These increases appear to be driven by a decline in the frequency of mid-latitude cyclones tracking across southern Canada. The cold fronts associated with these cyclones are known to provide the main mechanism for ventilation of the midwestern and northeastern United States. Mid-latitude cyclone frequency is expected to decrease in a warmer climate; such a decrease is already apparent in long-term observations. Mixing depths over the midwest and northeast increase by 100–240 m in our future-climate simulation, not enough to compensate for the increased stagnation resulting from reduced cyclone frequency.
I. Tegen, M. Werner, S. P. Harrison, K. E. Kohfeld (2004). Relative importance of climate and land use in determining present and future global soil dust emission. Geophysical Research Letters 31 (L05105): doi:10.1029/2003GL019216
ABSTRACT: The current consensus is that up to half of the modern atmospheric dust load originates from anthropogenically-disturbed soils. Here, we estimate the contribution to the atmospheric dust load from agricultural areas by calibrating a dust-source model with emission indices derived from dust-storm observations. Our results indicate that dust from agricultural areas contributes <10% to the global dust load. Analyses of future changes in dust emissions under several climate and land-use scenarios suggest dust emissions may increase or decrease, but either way the effects of climate change will dominate dust emissions.
ABSTRACT: Great quantities of African dust are carried over large areas of the Atlantic and to the Caribbean during much of the year. Measurements made from 1965 to 1998 in Barbados trade winds show large interannual changes that are highly anticorrelated with rainfall in the Soudano-Sahel, a region that has suffered varying degrees of drought since 1970. Regression estimates based on long-term rainfall data suggest that dust concentrations were sharply lower during much of the 20th century before 1970, when rainfall was more normal. Because of the great sensitivity of dust emissions to climate, future changes in climate could result in large changes in emissions from African and other arid regions that, in turn, could lead to impacts on climate over large areas.
L. Cifuentes, V. H. Borja-Aburto, N. Gouveia, G. Thurston, D. L. Davis (2001). Assessing the health benefits of urban air pollution reductions associated with climate change mitigation (2000-2020): Santiago, São Paulo, México City, and New York City. Environmental Health Prespectives 109 (Suppl 3): 419-425
ABSTRACT: To investigate the potential local health benefits of adopting greenhouse gas (GHG) mitigation policies, we develop scenarios of GHG mitigation for México City, México; Santiago, Chile; São Paulo, Brazil; and New York, New York, USA using air pollution health impact factors appropriate to each city. We estimate that the adoption of readily available technologies to lessen fossil fuel emissions over the next two decades in these four cities alone will reduce particulate matter and ozone and avoid approximately 64,000 (95% confidence interval [CI] 18,000-116,000) premature deaths (including infant deaths), 65,000 (95% CI 22,000-108,000) chronic bronchitis cases, and 46 million (95% CI 35-58 million) person-days of work loss or other restricted activity. These findings illustrate that GHG mitigation can provide considerable local air pollution-related public health benefits to countries that choose to abate GHG emissions by reducing fossil fuel combustion.
C. Hogrefe, B. Lynn, K. Civerolo, J.-Y. Ku, J. Rosenthal, C. Rosenzweig, R. Goldberg, S. Gaffin, K. Knowlton, P. L. Kinney (2004). Simulating changes in regional air pollution over the eastern United States due to changes in global and regional climate and emissions. Journal of Geophysical Research 109 (D22301): doi:10.1029/2004JD004690
ABSTRACT: To simulate ozone (O3 ) air quality in future decades over the eastern United States, a modeling system consisting of the NASA Goddard Institute for Space Studies Atmosphere-Ocean Global Climate Model, the Pennsylvania State University/National Center for Atmospheric Research mesoscale regional climate model (MM5), and the Community Multiscale Air Quality model has been applied. Estimates of future emissions of greenhouse gases and ozone precursors are based on the A2 scenario developed by the Intergovernmental Panel on Climate Change (IPCC), one of the scenarios with the highest growth of CO2 among all IPCC scenarios. Simulation results for five summers in the 2020s, 2050s, and 2080s indicate that summertime average daily maximum 8-hour O3 concentrations increase by 2.7, 4.2, and 5.0 ppb, respectively, as a result of regional climate change alone with respect to five summers in the 1990s. Through additional sensitivity simulations for the five summers in the 2050s the relative impact of changes in regional climate, anthropogenic emissions within the modeling domain, and changed boundary conditions approximating possible changes of global atmospheric composition was investigated. Changed boundary conditions are found to be the largest contributor to changes in predicted summertime average daily maximum 8-hour O3 concentrations (5.0 ppb), followed by the effects of regional climate change (4.2 ppb) and the effects of increased anthropogenic emissions (1.3 ppb). However, when changes in the fourth highest summertime 8-hour O3 concentration are considered, changes in regional climate are the most important contributor to simulated concentration changes (7.6 ppb), followed by the effect of increased anthropogenic emissions (3.9 ppb) and increased boundary conditions (2.8 ppb). Thus, while previous studies have pointed out the potentially important contribution of growing global emissions and intercontinental transport to O3 air quality in the United States for future decades, the results presented here imply that it may be equally important to consider the effects of a changing climate when planning for the future attainment of regional-scale air quality standards such as the U.S. national ambient air quality standard that is based on the fourth highest annual daily maximum 8-hour O3 concentration.
ABSTRACT: Regional climate change scenarios were generated by dynamical downscaling to assess the potential effects of climate change on U.S. air quality. Comparing the climate simulation for 2045–2055 based on the IPCC A1B scenario with the control simulation of 1995–2005, large atmospheric changes that could affect air quality were found in several regions. Analyses were based on changes in surface air temperature and downward solar radiation, precipitation frequency, stagnation events, and ventilation. Changes in the Midwest and Texas during summer are of opposite sign, suggesting negative impacts on air quality in Texas and small positive or no impact in the Midwest. During fall, large warming, increased solar radiation, reduced rainfall frequency, increased stagnation occurrence, and reduced ventilation in the western U.S. all suggest negative impacts on regional air quality. These changes are related to an anticyclonic pattern in the 500 hPa height change that is also found in other GCM projections.
ABSTRACT: The impact of global air pollution on climate and the environment is a new focus in atmospheric science. Intercontinental transport and hemispheric air pollution by ozone jeopardize agricultural and natural ecosystems worldwide and have a strong effect on climate. Aerosols, which are spread globally but have a strong regional imbalance, change global climate through their direct and indirect effects on radiative forcing. In the 1990s, nitrogen oxide emissions from Asia surpassed those from North America and Europe and should continue to exceed them for decades. International initiatives to mitigate global air pollution require participation from both developed and developing countries.
J. J. West, A. M. Fiore, L. W. Horowitz, D. L. Mauzerall (2006). Global health benefits of mitigating ozone pollution with methane emission controls. Proceedings of the National Academy of Sciences 103 (11): 3988-3993
ABSTRACT: Methane (CH4 ) contributes to the growing global background concentration of tropospheric ozone (O3 ), an air pollutant associated with premature mortality. Methane and ozone are also important greenhouse gases. Reducing methane emissions therefore decreases surface ozone everywhere while slowing climate warming, but although methane mitigation has been considered to address climate change, it has not for air quality. Here we show that global decreases in surface ozone concentrations, due to methane mitigation, result in substantial and widespread decreases in premature human mortality. Reducing global anthropogenic methane emissions by 20% beginning in 2010 would decrease the average daily maximum 8-h surface ozone by ≈1 part per billion by volume globally. By using epidemiologic ozone-mortality relationships, this ozone reduction is estimated to prevent ≈30,000 premature all-cause mortalities globally in 2030, and ≈370,000 between 2010 and 2030. If only cardiovascular and respiratory mortalities are considered, ≈17,000 global mortalities can be avoided in 2030. The marginal cost-effectiveness of this 20% methane reduction is estimated to be ≈$420,000 per avoided mortality. If avoided mortalities are valued at $1 million each, the benefit is ≈$240 per tonne of CH4 (≈$12 per tonne of CO2 equivalent), which exceeds the marginal cost of the methane reduction. These estimated air pollution ancillary benefits of climate-motivated methane emission reductions are comparable with those estimated previously for CO2 . Methane mitigation offers a unique opportunity to improve air quality globally and can be a cost-effective component of international ozone management, bringing multiple benefits for air quality, public health, agriculture, climate, and energy.