Understanding Global Warming and Greenhouse Gases

The passage discusses global warming, a significant environmental challenge. It explains the cause and effects of global warming and suggests ways to address it. The question asks us to fill in the second blank, which relates to the primary cause of this phenomenon.

Analyzing Blank 2 in the Passage

The relevant part of the passage is: "The primary cause of global warming is the (2)_______, of greenhouse gases such as carbon dioxide and methane into the atmosphere." We need to find the word that describes how these gases enter the atmosphere.

Evaluating the Options for Blank 2

Let's examine the given options:

• Emission: This refers to the production and discharge of something, especially gas or radiation. Greenhouse gases are released into the atmosphere through various human activities (like burning fossil fuels) and natural processes.
• Absorption: This is the process by which one substance takes in another, or light/energy is soaked up by a surface or substance. Gases absorb energy, but the blank describes how they *get into* the atmosphere, not what they do once there.
• Reflection: This is the bouncing back of light, heat, or sound from a surface. This is related to how surfaces interact with energy, not how gases enter the atmosphere.
• Conduction: This is the process by which heat or electricity is directly transmitted through a substance when there is a difference of temperature or electrical potential between adjoining regions, without movement of the material. This describes heat transfer, not the release of gases.

Determining the Correct Term for Greenhouse Gas Entry

Considering the definitions, the term that accurately describes greenhouse gases like carbon dioxide and methane being released or discharged into the atmosphere is "emission." These emissions trap heat, leading to global warming.

Therefore, "emission" is the most appropriate word to fill in blank number 2.

Reviewing the Concepts

The passage highlights key aspects of global warming:

• It's a major environmental challenge.
• Caused primarily by greenhouse gas emission.
• Specific gases mentioned are carbon dioxide and methane.
• These gases trap heat.
• Effects include severe weather, rising sea levels, and biodiversity loss.
• Actions by governments, organizations, and individuals (reducing energy consumption, driving less) are important.

The second blank specifically focuses on the mechanism by which the causative agents (greenhouse gases) enter the system (atmosphere).

Based on this analysis, the word "emission" correctly completes the sentence describing the primary cause of global warming.

Revision Table: Global Warming Terminology

Additional Information on Greenhouse Gas Emission

Greenhouse gas emissions come from various sources. Understanding these sources is crucial for developing strategies to reduce global warming.

• Carbon Dioxide (CO2): The most significant greenhouse gas emitted by human activities. Primary sources include burning fossil fuels (coal, oil, natural gas) for energy, transportation, and industry, as well as deforestation.
• Methane (CH4): A potent greenhouse gas emitted from sources like natural gas and petroleum systems, livestock agriculture (enteric fermentation and manure management), landfills, and coal mining.
• Nitrous Oxide (N2O): Emitted from agricultural activities (fertilizers), industrial processes, combustion of fossil fuels and solid waste, and wastewater treatment.
• Fluorinated Gases: Synthetic gases like HFCs, PFCs, SF6, and NF3, used in various industrial processes and products (refrigeration, air conditioning, electronics). Though emitted in smaller quantities, they are very powerful greenhouse gases.

Reducing the emission of these gases is the main focus of efforts to mitigate global warming. This involves transitioning to renewable energy sources, improving energy efficiency, changing agricultural practices, and improving waste management.