Why do aerosols cause global warming

The chart below shows human-caused warming left and the rate of warming right from the model runs. The different lines show the average model simulation outcome for each scenario. Global average surface temperatures, relative to pre-industrial levels left and warming rates plotted over time right in the 1. Each line represents the ensemble mean result for a specific 1. Shindell tells Carbon Brief:. What this work shows is that its mistaken to think that the transition to clean energy also has large environmental risks.

Instead, it provides huge public health benefits while also mitigating climate change. These include targets on both climate action Goal 13 and air quality as part of Goal 11 on sustainable cities and communities. Young tells Carbon Brief:. This study helps make it very plain that robust planning of climate policies requires expert interpretation of plausible scenarios to avoid any such confusion.

However, it is worth noting that a 1. Samset, who was not involved in the research, tells Carbon Brief:. Strong mitigation will, therefore, also affect some regions more than others. This is a normal force. At each point, the fluid also exerts a tangential force due to the shear stress caused by the velocity gradient near the surface. A sphere moving at velocity u in a fluid is perfectly equivalent to a sphere moving at velocity u in a stationary fluid.

The total resistance of the fluid to the sphere is:. If we include gravity, the total force acting on the sphere is the sum of drag and buoyancy. When the direction of flow coincides with the direction of gravity, the buoyancy added to the resistance is equal to the weight of the fluid discharged by the sphere. To consider the resistance in the entire Reynolds number range, we can express the resistance with the empirical resistance coefficient C D A p is the projected area of the body normal to the flow.

Brownian motion of a small particle in a stationary fluid is controlled by the following Langevin equation in the x-direction. Because of the noncontinuous forces on the suspended fluid molecules, the suspended fluid molecules cause irregular and sharp movements to the particles and the random acceleration n t is discontinuous.

To study Brownian motion, the behavior of the entire particle swarm or particle ensemble must first be considered. If a large number of particles are released from the origin and all their y displacements at time t are averaged, the expected overall average displacements should be zero Davies, This is because there is no constant n t inherent in a specific direction.

The mean square displacement of the Brownian motion can be expressed as:. Brownian motion is a continuous random process and its essence is the random motion of brown particles under the random impact of molecules.

It is impossible that aerosol particles move in a vacuum environment, thus, we need to consider the external resistance to know the motion of the particles. The mean free path is a good reference variable. Deliquescence and weathering are the two most important phase transition processes for studying the hygroscopicity of aerosol particles. During the water absorption process, due to the irregular shape of the aerosol particles and the diversity of the internal structure, water vapor in the environment adheres to the aerosol particles through physical adsorption, chemical absorption, and capillary adsorption.

This relative humidity is called the deliquescent point, which is the saturation concentration point of the droplets. When the relative humidity continues to increase, the droplets can continue to absorb water, which causes the concentration in the droplets to decrease and the volume to increase.

For chemical components that are insoluble in water, a liquid-water-encapsulated core structure may be formed Zhang et al. In the process of dehydration, aerosol droplets often do not crystallize into a solid at the deliquescent point.

When the ambient relative humidity drops below the deliquescent point, the droplets tend to form metastable supersaturated aerosol droplets.

When the relative humidity continues to drop, the droplet concentration gradually reaches the critical concentration of the supersaturated aerosol, and the water content begins to evaporate with solid aerosol particles forming.

As an organic part of the atmospheric hydrosphere cycle, atmospheric aerosols mainly affects the microphysical processes of clouds and precipitation, and also affects atmospheric stability and cloud albedo. It not only increases or decreases the amount of rainfall, but also changes the type of cloud and rain such as converting non-precipitating clouds into precipitation clouds. The indirect effects of atmospheric aerosols are closely related to changes in the water cycle in the climate system.

If the liquid water content does not change, the effect of aerosols on cloud droplet concentration or size caused by microphysical processes is called the first type of indirect effect. Due to the introduction of more aerosol particles as condensed nodules, under a certain water content, cloud droplets compete with each other for water vapor, and they cannot grow up to the precipitation mass point Ramanathan et al. Thus, there are more small cloud droplets in the cloud, which results in a decrease in precipitation.

Also, due to the enhanced albedo of small cloud droplets Rosenfeld et al. From the above, we know that once aerosol particles enter the cloud, they could change the precipitation properties and radiation characteristics of the cloud, thereby affecting the precipitation and water cycle.

The energy balance of the earth-atmosphere system is the driving force that determines the climate state of the earth. The short-wave solar radiation received at the top of the atmosphere by the ground-gas system must be equal to the long-wave or infrared radiation emitted by the ground-gas system itself Murthy, For whatever reason, if this balance is disturbed or disrupted, it will cause climate change.

In other words, this disturbance either reduce or increase the received solar radiation and the emitted long-wave radiation from the earth, which could lead to the energy budget of the earth-gas system deviates from its equilibrium state. For example, the greenhouse effect caused by the increasing concentration of greenhouse gases reduces the long-wave radiation emitted or lost by the earth-gas system.

Aerosols have a cooling effect on the ground, partially offsetting global warming caused by greenhouse gases.

While, due to their physical properties, different types of aerosol particles have different absorption and scattering effects, so that the radiative forcing in the atmosphere is different. Atmospheric aerosol particles have two climate effects. Secondly, used as condensed nodules in clouds to change cloud microphysical processes and precipitation properties, aerosols could change the water cycle of the atmosphere which also have important impacts on many aspects of economic society Mitchell et al.

For climate change in the past centuries, the general trend is warming, which is mainly caused by human activities and natural changes. The cooling effect of anthropogenic sulfate aerosols in the tropospheric atmosphere on the ground surface could offset some of the warming effects Solomon et al. However, the spatial-temporal heterogeneity of aerosol distribution on the global scale and the differences in the radiation characteristics of different components have led to great differences in estimates of direct radiative forcing effects Rood et al.

Therefore, a clean atmosphere in the future can cause global temperatures to increase faster and higher, leading to a more severe global warming situation. Black carbon aerosols are ranked second to carbon dioxide in contributing to the greenhouse effect. Black carbon aerosols have a stronger absorption of sunlight so that they can heat the atmosphere. At the same time, due to reflection and absorption in the atmosphere, a part of the incident solar radiation is lost, which also cools the surface.

Its main characteristics are high endothermic Anenberg et al. The unique characteristics of the particulate matter determine its many complex effects on atmospheric quality, climate, temperature, and human health. Impacts of atmospheric aerosols and storm zones on agriculture and ecosystems are mainly caused by the reduction of direct solar radiation reaching the ground Chameides et al.

Firstly, due to the weakened solar light, photosynthesis of crops is significantly affected, that is, changing the quantity and quality of photosynthetically active radiation. Also, other relevant climatic factors and conditions such as temperature, precipitation, and humidity are affected which finally hinder the growth of crops Sharma et al. Secondly, a large amount of sulfur dioxide gas is emitted from the combustion of fossil fuels, causing a gas-particle conversion process to form sulfate aerosols.

Sulfate pollutants fall from the atmosphere to the ground surface through two forms Liousse et al. Acid rain has a significant impact on crops and ecosystems, also, it could cause soil acidification. The soil contains a large amount of aluminum hydroxide, after acidification of the soil, the formation of weathering of primary and secondary minerals containing aluminum is accelerated and a large amount of aluminum is released Du et al.

Long-term and excessive absorption of aluminum ions in plants can poison and even die. Thirdly, nitrogen aerosols also cause acidification when they settle into the ecosystem. Nitrogen oxides can produce photochemical smog through photochemical reactions, making the plant dwarf, grow thin, and reduce fruit set rate Lin et al.

Corroded by the fluoride produced by the combustion of coal with high fluorine content in the air, the plants are severely damaged, besides, the forests were gradually reduced and the growth and quality of crops will be significantly damaged. The composition of atmospheric aerosols is very complex, not only including various gases and particulates produced by natural and human activities, but also containing many types of microorganisms Callahan-Lyon, , both of which could pose serious threats to human health.

There are three different aspects of effects for different sizes of aerosols. The biggest impact on human health is the stable atmospheric aerosol particles with a diameter of 0. Particles with a diameter of 0. Besides, they can enter the blood to the whole body which is very harmful to human health due to their toxicity. The central lung disease has the most direct relationship with the particulate matter content in the polluted air Goldsmith, The second aspect of the health effects for atmospheric aerosols is the effect of heavy metal components in aerosol fine particles could be harmful to human health, which is related to many diseases and harms many parts of the human body.

It also affects many aspects such as transportation and national defense. At the same time, it increases the fuel consumption of lighting electricity and increases air pollution, which forms a vicious circle and negative feedback. These effects directly or indirectly affect the composition of the atmosphere, temperature changes, precipitation, and sea-level rise which finally affect the stability of the entire ecosystem.

In recent years, the level of air pollution in large and medium-sized urban areas worldwide, especially in developing countries, has increased, affecting many aspects of human health, production, life, and transportation. Besides, the deeper and finer particles enter the part of the respiratory tract, the greater the impact would affect the respiratory system. Aerosols become carriers of harmful gases, bringing harmful gases from the air into the human body, which can cause a variety of heart diseases such as asthma, pneumonia, bronchitis, and heart disease.

Those particles whose sizes are less than 2. Air pollution is mainly caused by atmospheric aerosols. Atmospheric aerosols can be emitted directly as particulate matter or indirectly formed in the atmosphere by gaseous precursors through chemical reactions such as photochemical reactions Fan et al.

The main physical process of atmospheric aerosols affecting the climate system is to change the radiation balance of the geogas system by direct scattering and absorption of solar radiation and long-wave radiation. This mechanism is generally defined as the direct action of aerosols Dickerson et al. The increasing concentration in atmospheric aerosols reduces the quality of the air and the amount of solar radiation reaching the ground.

This negative radiative forcing which counteracts the warming in determining surface temperature, precipitation, and evaporation is the opposite of the greenhouse gas effect Dickerson et al. Once the aerosols are removed from the atmosphere, the increase in greenhouse gas emissions will be even more dramatic.

Therefore, what needs to be considered in the environmental strategy is not only the reduction in CO 2 emission, but also the consequences of improving air quality. The Paris Agreement came into effect in November , and then more than countries around the world made national contributions to reduce emissions Rogelj et al.

This is the third landmark international law in human history to deal with climate change. Different from previous international emission reduction cooperation models, The Paris Agreement is a new global climate governance model in which countries around the world independently propose emission reduction targets Schleussner et al.

The participation of cities in climate governance around the world has become one of the hot spots in the current response to climate change. The climate governance model of The Paris Agreement for the first time affirmed the important role of non-state actors such as local government and businesses which is multi-layered governance for climate change Falkner, Compared to the governance from a country, cities in the country have more governance flexibility and certain advantages in mobilizing resources and implementing regional strategies.

The decentralization trend under globalization has continuously improved the status and roles of cities in environmental governance. If keep the global average temperature rise within 1. At present, there are roughly two ways for cities to participate in climate governance Shove, The second one is to promote action on climate change among cities through the global alliance of cities.

Globally, a large number of cities are currently actively implementing emission reduction policies to mitigate climate change. Among its many influencing factors, the climate effect of aerosols is the most uncertain one Hiller et al. It is obvious that we should not fold our hands and wait to be slain with regard to certain negative effects of aerosols, but adopt a reasonable method to promote strengths and avoid weaknesses when facing how to deal with these problems.

Here, I suggest some specific control aspects and measures that might reduce the effect of aerosols:. Strengthen the control in urban industrial areas. The process of urban industrialization is a major reason for the increase in anthropogenic aerosol emissions.

Therefore, reasonable observation of emission sources, scientific devices, and effective measures are helpful for emission control. Establish uniform standards for polluting particles and strengthen monitoring. The feasible method is: on the premise of unifying the particle standard, the division of functions among the departments is provided by the meteorological bureau. For example, the environment division should formulate and manage administrative regulations to prevent the untrueness of the data of the designated meteorological bureaus, cross-spot spot checks could be used for data monitoring.

Treaties and legal mechanisms to strengthen domestic and international cooperation. The international restrictions and enact mandatory compensatory laws should be strengthened to protect the country from the harm caused by unnecessary anthropogenic aerosol emissions.

From the above analysis, it can be concluded that atmospheric aerosol particles also have climatic effects. Firstly, by scattering and absorbing sunlight, reducing the solar radiation reaching the ground has a cooling effect, which can offset part of the warming effect caused by greenhouse gases. The second is to change the microphysical process of clouds and the nature of precipitation as condensed nodules in the cloud, and change the atmospheric water cycle.

Atmospheric aerosols also have important effects on many aspects Deslattes et al. Besides, climate change and air pollution have a common cause to a large extent, that is, they are mainly caused by emissions of fossil fuel combustion. On the one hand, the emitted aerosols not only cause air pollution but also have obvious climatic effects and changes in the hydrosphere cycle.

On the other hand, climate change caused by the increase of greenhouse gases Turco et al. The two are closely related to scientific issues.

Therefore, a unified rather than separate scientific research strategy should be adopted. At present, this issue has been solving internationally. And if we do not consider the offset effect of aerosol cooling but only consider how much temperature rise the global greenhouse gas will cause, the global emission reduction responsibility will increase greatly.

Therefore, it is necessary and urgent to adopt and formulate collaborative or coupled research and countermeasure strategies. This is an integrated strategy to deal with climate change and air pollution. Solving these problems from the same source is not only more economically effective, but also solves the problems of atmospheric environment and climate change at the same time, which can get the greatest economic savings and a win-win effect Liu et al.

Internationally, it will establish a good image of not only actively protecting the environment but also striving to mitigate climate change. The author thanks for Jingjing Dai and Erik S. Journal of Aerosol Science, 33, Science, , Environmental Health Perspectives, , Nature, , Electronic Cigarettes: Human Health Effects.

Tobacco Control, 23, iiii Agricultural and Forest Meteorology, 36, New Journal of Physics, 6, Atmospheric Chemistry and Physics, 13, Aerosol Science and Technology, 39, Coagulation of Aerosols by Brownian Motion. Journal of Aerosol Science, 10, Perkins Eds. London: Routledge. Determination of the Avogadro Constant. Physical Review Letters, 33, In the US, diesel vehicles are the major source of soot, and filters on exhaust pipes can help reduce the amount that they pump into the air.

In terms of sulfate aerosols, which are created by sulfur dioxide given off by power plants, the US and Europe have very successfully used sulfur dioxide scrubbers in power plants to reduce these emissions over the past 20 years or so. But we can definitely do more. By reducing aerosol soot emissions, we can buy ourselves some climate time — about 5 to 10 years — while we work on reducing emissions of greenhouse gases such as carbon dioxide CO2 in parallel.

CO2, you see, hangs around in the atmosphere for an extremely long time, from decades to centuries, so even if we implement cuts today, it will take years for them to take effect. Aerosols, on the other hand, have much shorter lifetimes. If we work to reduce soot emissions now, which can enhance the global warming effect of CO2 by percent, the climate impacts will be felt more rapidly. I have a paper in review at the moment that is quite exciting; we're looking at the future total climate impacts of current emissions from different industries, taking into account the effects of both greenhouse gases such as CO2, ozone and methane, and the impacts of aerosols.

What we've found is that for the next 40 years, emissions from road vehicles will have the largest global warming impacts of all human activities — because of the air pollutant effects that enhance greenhouse gas warming. After , however, power sector emissions are by far the largest global warmer because of the build up of CO2 in the atmosphere from that activity.