Gyula Molnar

Global warming from chlorofluorocarbons and their alternatives: Time scales of chemistry and climate

The halocarbons (chloroflurocarbons, CFCs, and their replacement chemicals: the hydrochloroflurocarbons, HCFCs, and the hydrofluorocarbons, HFCs) are greenhouse gases. The atmospheric accumulation of these gases is expected to add to the global warming predicted for expected increases of CO2, CH4, N2O, tropospheric ozone and H2O. Over the next decades, production of CFCs is scheduled to be phased out, while emissions of their alternatives are expected to increase. A simple model is used to illustrate the methodology for determining the time variations of the radiative forcing and temperature changes attributable to the direct greenhouse effect from potential emissions of the halocarbons. Although there are uncertainties associated with the lifetimes of the greenhouse gases, CFCs and their substitutes, the future growth rates of these gases, and the parameters used to simulate the response of the Earth-climate system, the method serves to illustrate an important aspect of the greenhouse warming issue beyond what is provided by the various greenhouse warming indices. Our results show that for likely substitution scenarios, the warming due to halocarbons will correspond to 4–10% of the total expected greenhouse warming at the year 2100. However, uncontrolled growth of the substitutes could result in an eight-fold increase in halocarbon production and a doubling of the halocarbon contribution by 2100.

An Estimation of the Climatic Effects of Stratospheric Ozone Losses during the 1980s

Abstract In order to study the potential climatic effects of the ozone hole more directly and to assess the validity of previous lower resolution model results, the latest high spatial resolution version of the Atmospheric and Environmental Research, Inc., seasonal radiative dynamical climate model is used to simulate the climatic effects of ozone changes relative to the other greenhouse gases. The steady-state climatic effect of a sustained decrease in lower stratospheric ozone, similar in magnitude to the observed 1979–90 decrease, is estimated by comparing three steady-state climate simulations: I) 1979 greenhouse gas concentrations and 1979 ozone, II) 1990 greenhouse gas concentrations with 1979 ozone, and III) 1990 greenhouse gas concentrations with 1990 ozone. The simulated increase in surface air temperature resulting from nonozone greenhouse gases is 0.272 K. When changes in lower stratospheric ozone are included, the greenhouse warming is 0.165 K, which is approximately 39% lower than when ozone ...

Climatic consequences of observed ozone loss in the 1980s: Relevance to the greenhouse problem

Recently published findings using satellite and ground-based observations indicate a large winter and summertime decrease in the column abundance of ozone at high and middle latitudes during the last decade. Using a simple ozone depletion profile reflecting the observed decrease in ozone column abundance, Ramaswamy et al. (1992) showed that the negative radiative forcing that results from the ozone decrease between 1979 and 1990 approximately balanced the greenhouse climate forcing due to the chlorofluorocarbons emitted during the same period. Here, we extend the forcing analyses by calculating the equilibrium surface temperature response explicitly, using an updated version of the Atmospheric and Environmental Research two-dimensional radiative-dynamical seasonal model. The calculated steady state responses suggest that the surface cooling due to the ozone depletion in the lower stratosphere offsets about 30% of the surface warming due to greenhouse gases emitted during the same decade. The temperature offset is roughly a factor of 2 larger than the corresponding offset obtained from forcing intercomparisons. This result appears to be related to the climate feedback mechanisms operating in the model troposphere, most notably that associated with atmospheric meridional heat transport. Thus a comprehensive assessment of ozone change effects on the predicted greenhouse warming cannot be accomplished based on forcing evaluations alone. Our results also show that calculations adopting a seasonally and latitudinally dependent ozone depletion profile produce a negative forcing about 50% smaller than that calculated for the depletion profile used by Ramaswamy et al. (1992).

Ozone-Climate Interactions Associated with Increasing Atmospheric Trace Gases

Study of climatic effects of increase in concentration of atmospheric trace gases has so far focused on the direct greenhouse warming. The indirect effect on climate of the seasonal and latitudinal O3 changes associated with trace gases has not been explored. Here, we use simple 1- and 2-D models to demonstrate that changes in the O3 vertical distribution, in particular in the middle and upper troposphere, could trigger a response in meridional heat flux with subsequent feedback effect on climate. Discussion on the effects of trace gases and their induced O3 changes on future climate on the decadal time scale is also presented.

Spatial and Temporal Inter-Relationships between Anomalies of Temperature, Moisture, Cloud Cover, and OLR as Observed by AIRS/AMSU on Aqua

AIRS/AMSU is the advanced IR/MW atmospheric sounding system launched on EOS Aqua in May 2002. Products derived from AIRS/AMSU include surface skin temperature and atmospheric temperature profiles; atmospheric humidity profiles, % cloud cover and cloud top pressure, and OLR. Near real time products, starting with September 2002, have been derived from AIRS/AMSU using the AIRS Science Team Version 5 retrieval algorithm. Results in this paper included products through April 2008. The time period studied is marked by a substantial warming trend of Northern Hemisphere Extropical land surface skin temperatures, as well as pronounced El Nintildeo - La Nintildea episodes. These both influence the spatial and temporal anomaly patterns of atmospheric temperature and moisture profiles, as well as of cloud cover and Clear Sky and All Sky OLR. The relationships between temporal and spatial anomalies of these parameters over this time period, as determined from AIRS/AMSU observations, are shown below, with particular emphasis on which contribute significantly to OLR anomalies in each of the tropics and extra-tropics. The ability to match this data represents a good test of a models response to El Nintildeo.

Variability of marine stratiform clouds derived from GOES-8 imagery

Marine statiform clouds (MSC) cover large areas of the globe that are visible to GOES. The operational satellite cloud retrieval algorithms are prone to biases when analyzing MSC, due to the often sub-pixel size cloud elements and radiative temperatures close to that of the underlying ocean. For example, the relatively large pixel size and calibration drifts in GOES-7 imagery have made it difficult to extract unbiased MSC properties using thermal threshold techniques. Here, we apply a novel retrieval approach to the two important MSC regimes which can be monitored well from the GOES-8 satellite: the Pacific Ocean just west of California/Baja and Peru/Chile. MSC cloud parameters for these areas are retrieved together with surface temperature and column water vapor in a temporally and spatially consistent manner that is insensitive to sensor resolution and calibration errors. Semi-operational analysis of GOES-8 imagery began in December 1995. So, the main focus is on assessing the diurnal variability of MSC. Following a brief description of the retrieval technique, we present initial results describing the full diurnal cycle of MSC fractional cloud cover and cloud top temperature, monitored using the single-channel version of the algorithm. In addition, we address the daytime variability of other important cloud parameters using a bispectral extension of the retrieval scheme. The results are also compared with other pertinent MSC analyses.