7. Increase in CO₂in atmosphere causes
   (1) More rainfall
   (2) Decrease productivity
   (3) Warmness of Atmosphere
   (4) More snowfall

The increase in atmospheric carbon dioxide (CO₂) is one of the most significant environmental changes of our time. While CO₂ is a natural part of Earth’s atmosphere and essential for life, human activities—especially the burning of fossil fuels—have dramatically raised its concentration. This rise has profound consequences for the planet, including global warming, changes in weather patterns, and impacts on ecosystems. This article explores the effects of increased CO₂ in the atmosphere and clarifies which of the listed options—more rainfall, decreased productivity, warmness of the atmosphere, or more snowfall—accurately describes its primary impact.

The Science of CO₂ and the Greenhouse Effect

Carbon dioxide is a greenhouse gas, meaning it absorbs and emits infrared radiation, trapping heat in the Earth’s atmosphere. This natural process, known as the greenhouse effect, keeps the planet warm enough to support life. However, since the Industrial Revolution, human activities have increased CO₂ concentrations by over 50%, amplifying this effect and leading to global warming.

How Increased CO₂ Causes Warming

When CO₂ levels rise, more heat is trapped in the atmosphere. This results in an overall increase in global temperatures—a phenomenon known as global warming. The relationship is well-established: higher CO₂ concentrations lead to higher average temperatures, which in turn affect weather patterns, sea levels, and ecosystems.

• Direct Warming Effect: CO₂ and other greenhouse gases absorb outgoing infrared radiation from the Earth’s surface and re-emit it in all directions, including back toward the surface. This trapped heat warms the atmosphere and the planet as a whole.

• Feedback Loops: Warming can trigger feedback mechanisms, such as melting ice (which reduces the Earth’s reflectivity and leads to more warming) and increased water vapor in the atmosphere (another greenhouse gas), further amplifying the effect.

Evaluating the Options

Let’s examine each option to determine which best describes the primary effect of increased CO₂ in the atmosphere.

1. More Rainfall

Increased CO₂ can influence rainfall patterns, but not always in predictable ways. Warmer temperatures lead to more evaporation, which can increase the amount of water vapor in the atmosphere and potentially cause more rainfall in some regions. However, climate change also shifts weather patterns, leading to more intense droughts in some areas and heavier rains in others. While CO₂ can contribute to changes in precipitation, “more rainfall” is not a universal or primary result—it is a secondary effect of climate change.

2. Decrease Productivity

This option is generally incorrect for most ecosystems. In fact, higher CO₂ levels can initially boost plant productivity through a process called CO₂ fertilization, as plants use CO₂ for photosynthesis. However, over time, other factors such as heat stress, drought, and nutrient limitations can offset these benefits, especially in natural ecosystems. For some crops and managed systems, increased CO₂ can lead to higher yields, but this is not always the case in diverse, natural environments. Overall, “decrease productivity” is not the primary or universal effect of increased CO₂.

3. Warmness of Atmosphere

This is the most accurate and direct effect of increased CO₂. As a greenhouse gas, CO₂ traps heat in the atmosphere, leading to higher global temperatures—global warming. This warming is the foundational change that drives other climate impacts, such as altered weather patterns, melting ice, and rising sea levels.

4. More Snowfall

While increased CO₂ can lead to changes in precipitation, including snowfall in some regions, “more snowfall” is not a primary or universal result. In fact, global warming generally leads to less snow and ice cover over time, as warmer temperatures cause snow to melt faster and reduce the area where snow can accumulate. Some regions may experience heavier snowstorms due to increased moisture in the atmosphere, but this is a localized and secondary effect, not a global trend.

Broader Impacts of Increased CO₂

Beyond warming, increased CO₂ has cascading effects on the planet:

• Climate Change: Warming alters weather patterns, increases the frequency and intensity of extreme weather events, and shifts climate zones.

• Sea Level Rise: Melting glaciers and ice sheets, along with thermal expansion of seawater, cause sea levels to rise, threatening coastal communities.

• Ocean Acidification: About a quarter of CO₂ emissions are absorbed by the oceans, leading to acidification that harms marine life, especially organisms with calcium carbonate shells or skeletons.

• Ecosystem Shifts: Changes in temperature and precipitation affect the distribution and behavior of plants and animals, leading to shifts in ecosystems and potential loss of biodiversity.

The Role of Human Activities

Human activities, particularly the burning of fossil fuels (coal, oil, and natural gas), are the primary driver of increased atmospheric CO₂. Since the Industrial Revolution, CO₂ concentrations have risen from about 280 parts per million (ppm) to over 420 ppm today—a 50% increase. This rapid rise is unprecedented in Earth’s recent history and is causing climate change at an accelerating pace.

The Speed and Scale of Change

The rate at which CO₂ is increasing in the atmosphere is 100–200 times faster than natural changes that occurred at the end of the last ice age. This rapid change is overwhelming Earth’s natural carbon cycle, as natural “sinks” (like forests and oceans) can only absorb about half of the CO₂ emitted by human activities. The rest accumulates in the atmosphere, driving global warming and climate change.

Climate Sensitivity and Long-Term Effects

Climate scientists estimate that for every doubling of atmospheric CO₂, average global temperatures could increase by 1.5 to 4.5°C (2.7 to 8.1°F) in the near future, with some studies suggesting even higher increases over longer timescales. These temperature changes have far-reaching consequences, including more frequent heatwaves, altered rainfall patterns, and increased risks of extreme weather events.

Addressing the Challenge

Reducing CO₂ emissions is essential to limit global warming and its impacts. This requires transitioning to renewable energy sources, improving energy efficiency, protecting and restoring forests, and developing technologies to capture and store CO₂. International agreements, such as the Paris Agreement, aim to limit global temperature rise by reducing greenhouse gas emissions.

Conclusion

The primary effect of increased CO₂ in the atmosphere is the warmness of the atmosphere—global warming. While CO₂ can influence rainfall and, in some cases, plant productivity, its most direct and significant impact is to trap heat and raise global temperatures. This warming drives a wide range of climate changes, including altered precipitation patterns, sea level rise, and ecosystem shifts. Understanding the central role of CO₂ in climate change is essential for addressing this global challenge and protecting the planet for future generations.

In summary:
Increased CO₂ in the atmosphere causes the warmness of the atmosphere (global warming), making option (3) the correct answer.
This warming is the foundation for all other climate changes we observe today.