We all know that every small activity will affect the environment and climate. Major 20th and 21st-century environmental issues include deterioration of air quality, poor water quality (due to the release of pollutants to water bodies), vast pesticide usage, acid precipitation (from coal combustion that leads to SO₂ and thus sulfuric acid), ozone layer depletion (due to the use of ozone-depleting substances such as chlorofluorocarbons), etc. Some of these issues have been successfully tackled through national and regional legislations, international agreements, provision of alternatives, and/or changes in people’s expectations and behaviour.

However, climate change is due to the emission of anthropogenic greenhouse gases and other chemicals into the atmosphere and is now recognized to be one of the major as-yet-unsolved challenges facing humanity in the coming decades and centuries. The impacts of anthropogenic climate change are slow, it is sometimes difficult to see the signal above natural variability, and impacts are coupled to some of the most basic needs of society, such as energy production and utilization, food security, and infrastructure. The largest contributor to the predicted anthropogenic climate change arises from the burning of fossil fuels that generates carbon dioxide, a greenhouse gas. Increases in CO₂ concentration will not only influence climate but also the acidity of the oceans. While acid-base equilibria and their changes are at the heart of the latter issue, in the atmosphere, CO₂ is not very chemically active. Therefore, one could wonder:

WHAT IS THE ROLE OF CHEMISTRY IN EARTH’S CLIMATE SYSTEM, ESPECIALLY HUMAN-INDUCED CLIMATE CHANGE?

The answer to this question is multipronged. In addition to CO₂, there are many other emissions of chemically active species that directly or indirectly force Earth’s climate. They include CH₄, halocarbons, N₂O, nonmethane hydrocarbons (NMHC), and nitrogen oxides. Together, these non-CO₂ emissions contribute almost as much as human-produced CO₂ in climate forcing. Unlike the greenhouse gases, aerosols (a suspension of liquid or solid matter in the air) and clouds are expected to exert a global negative forcing and they are currently estimated to be offsetting positive forcing by the greenhouse gases by as much as 50% of the forcing by CO₂. However, there is large uncertainty about the cooling and heating effects of different aerosol types such as soot, dust, and absorbing organic molecules. Some of the aerosols are emitted directly, while some form in the atmosphere by a series of reactions initiated by the oxidation of different volatile gases. 

DIFFERENT TYPES OF GASES THAT PLAY AN IMPORTANT ROLE IN CLIMATIC CHANGE 

Ozone is another greenhouse gas, produced by the troposphere in chemical reactions that consume emitted volatile hydrocarbons and use nitrogen oxides as a catalyst. Finally, most emissions are removed from the atmosphere by the oxidants such as OH radicals, nitrate radicals, and ozone; these determine the crucial “cleansing” capacity of the atmosphere. Evidently, chemically active agents are a large part of the influence of human activities on climate. The impact of climate change on Earth is multifaceted. The most notable changes are the rise in sea level, changes in precipitation, drought, extreme weather events, and more. Chemistry is greatly involved in shaping many of these impacts. For the above reasons, it is abundantly clear that chemistry plays a pivotal role in Earth’s climate system. The essence of the role of chemistry in climate is captured on the cover of this issue.

The Earth system is highly coupled. The coupling means that the different environmental issues noted earlier are often connected. For example, fossil fuel burning is clearly at the heart of anthropogenic climate change and it is also a pivotal issue for air quality. So, solutions to climate change are intimately connected with air quality issues.

OZONE LAYER DEPLETION (ODS)

Ozone layer depletion is caused by chlorinated and brominated fluorocarbons (and related chemicals). These ozone-depleting chemicals (ODSs) are not only destructive to the ozone layer but are also potent greenhouse gases. Therefore, the control of ODSs has not only helped heal the ozone layer but also greatly helped the climate. Tropospheric ozone itself is a greenhouse gas, and it influences climatic changes. Chemical transformations of hydrocarbons (both natural and anthropogenic) are key to accounting for present levels and predicting future levels of ozone in the troposphere. Conversely, climate change will change ozone levels in the troposphere and, thus, play an important role in affecting air quality regionally and globally.

There are myriad couplings in the climate system, some of which were noted above. Suffice to say, human actions to control one environmental issue which will undoubtedly influence another. Indeed, some actions have clear impacts on multiple issues, such as climate change and air quality. Actions taken by society will have positive effects on climate and the environment—the so-called “win-win strategies” for the multiple issues that are involved. At least, one needs to avoid “win-lose” choices where solutions to one issue either exacerbate another issue or create a new problem. Thus, understanding chemical changes will continue to play a major role in better understanding and predicting climate change, and providing solutions to anthropogenic climate change.

To gain insight on more such interesting topics and to deep dive into the world of chemistry, follow Yourbuk. Yourbuk is an intuitive ed-tech platform dedicated to helping the students get access to the best teachers, their teaching, and content developed by the teachers themselves across the nation.