Different Climate Changes by Anthropogenic Aerosols

Commonly anthropogenic aerosols believed to cool the atmosphere; in this interest, they balance the global warming resulting from greenhouse gases to some extent. The phenomenon of global warming is increasing average air temperatures near the surface of Earth over the past one to two centuries. Since the mid-20^th century, many climate scientists are focusing on detailed observations of various weather phenomena such as temperatures, precipitation, storms and related influences on climate such as ocean currents and the atmosphere’s chemical composition. Frequently Earth’s climate has changed due to the influence of human activities since the beginning of the industrial revolt has been deeply rushed into the very fabric of climate change. In this case, the anthropogenic aerosols role is important for cool the atmosphere, suppose reduce the anthropogenic aerosols to increase global warming under future CO₂ concentration.

Figure 1. Climate change of earth surface as clean to a warming environment. Image Credit to  SNB team.

Greenhouse gases are a vital matter to accumulating in Earth's atmosphere due to human activities, causing surface air temperatures and subsurface ocean temperatures to rise.

Temperatures are, in fact, raising timing. The climate changes both experimentally and theoretically observed over the last several decades, mostly it causes due to human activities, but we cannot clearly observe that part of these changes are also some significant reflection of natural variability.

Human-activities induced warming and coupled with sea level rises are expected to continue through the 21^st century. Other parts of studies are suggested by computer model simulations and basic physical reasoning. These include raises rainfall rates and also increased susceptibility of semi-arid regions to drought. The impacts of these types of changes will be critically reliant on the degree of warming and the rate with which it occurs.

Many climate researchers believed that economic, significant societal and ecological damage would result if global average temperatures rise by more than 2 °C (3.6 °F) in such a short time. Such damage would include increased extinction of many plant and animal species, shifts in patterns of agriculture, and rising sea levels. 

Sulphate anthropogenic aerosol: Sulphate has natural origins and is also a primary anthropogenic aerosol in the atmosphere. The two main sulphate aerosol precursors are sulfur dioxide (SO₂) from anthropogenic sources and volcanoes, and dimethyl sulfide (DMS) from biogenic sources, especially marine plankton.

Prof. Toshihiko Takemura from Kyushu University, Fukuoka, Japan has reported the changes in the surface air temperature under various anthropogenic emission amounts of sulphur dioxide (SO₂), which is a precursor of sulphate aerosol, are simulated under both presents and doubled carbon dioxide (CO₂) concentrations with a climate model [1]. This is the first study that conducted explicit experiments to estimate the temperature changes due to individual short-lived climate forcers (SLCFs) in different climate states with atmosphere-ocean coupled models. This result clearly showed that reducing SO₂ emissions at high CO₂ concentrations will significantly enhance atmospheric warming in comparison with that under the present CO₂ concentration.

“In the high latitudes of the Northern Hemisphere, the temperature change that will occur when fuel SO₂ emissions reach zero under a doubled CO₂ concentration will be approximately 1.0 °C, while this value will be approximately 0.5 °C under the present state. This considerable difference can affect the discussion of the 1.5 °C/2 °C target in the Paris Agreement”.

--- Toshihiko Takemura

In this study used a general circulation model coupled with an aerosol process model, MIROC-SPRINTARS8–10, which calculates the global spatiotemporal distributions of the mass mixing ratios of each aerosol component as prognostic variables. The simulated results by MIROC-SPRINTERS have been confirmed to be appropriate by various methods, including comparisons among models and with observations, e.g., Aerosol Comparisons between Observations and Models (AeroCom). MIROC was coordinated with the SPRINTERS and these models predict the mass mixing ratios of major aerosol components such as sulphate, black carbon (BC), organic matter (OM), soil dust, sea salt, and precursor gases of sulphate, including SO₂ and dimethyl sulphide (DMS) by simulating the aerosol transport processes of emission, advection, diffusion, chemical reactions of sulphur, wet deposition, and dry deposition. In particular, atmosphere-only and coupled ocean experiments were conducted using perturbed SO₂ emissions from fuel sources with MIROC–SPRINTARS.

If we consider SO₂ emissions from fuel sources reached zero, it causes temperature raises from 0.5 to >1.0 °C were projected over these regions. It also indicates that SO₂ emissions cannot be neglected completely in comparison to global warming due to greenhouse gases. Suppose SO₂ emissions under doubled CO₂ concentration scenarios, strong warming was also expected over land in the high latitudes of the Northern Hemisphere and the Arctic Ocean. Climate scientists reported that the differences in the zonal and annual mean temperature changes with reaching zero fuel SO₂ emissions under present (approx. 0.5 °C) and doubled CO₂ concentrations (approx. 1.0 °C) range from 0.4 to 0.6 °C. Hence above report concludes with the climate response due to increased incident solar radiation at the surface with reduced sulphate aerosols will be more sensitive under warmer climates.

The results of this study also indicate a permanent change in surface air temperature in the condition of decreasing SO₂ emissions under increasing CO₂ concentrations with changes in the climate sensitivity, although the radiative forcing returns to the preindustrial level.

Our SNB team has emphasized this research article to enrich our viewer’s knowledge to aware about the climate changes and their related environmental issues. An alert of global warming scenarios are due to with the SO₂ reduction of emission under high CO₂ concentration. Environmental plan (Paris Agreement) explained to safeguard our global mean surface air temperature which increases to < 2 °C relative to preindustrial conditions and identified efforts aimed at limiting this increase to 1.5 °C. A present local climatic change is due to the mandatory reductions in SO₂ emissions which results to the decrease in sulphate aerosol concentrations to mitigate the health impacts. These changes will be analyzed in detail for future studies, along with SLCFs which includes of methane, tropospheric ozone, organic aerosols, and hydrofluorocarbons. Promotion by various established organizations, like the Climate and Clean Air Coalition (CCAC) and Asia Pacific Clean Air Partnership (APCAP) were done and should be measured with the influence of SLCFs, in parallel with a quantitative elucidation of synthesized mitigation.

 References

1. T. Takemura, Scientifc Reports, 10, 21748 (2020). https://www.nature.com/articles/s41598-020-78805-1. 

--- Mrs. S. Siva Padma Devi

Guest Lecturer, Department of Geography

M.V.Muthiah Government Arts College (Women) 

Dindigul, Tamil Nadu, India