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Quiz: Global Climate Change

Test your understanding of climate change science, feedback loops, and policy responses with these review questions.

1. How does the greenhouse effect work?

  1. Greenhouse gases block sunlight from reaching Earth's surface, cooling the planet
  2. Greenhouse gases in the atmosphere absorb and re-radiate infrared radiation, warming Earth's surface
  3. Greenhouse gases create holes in the ozone layer that allow excess heat to enter
  4. Greenhouse gases reflect all solar radiation back into space, preventing photosynthesis
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The correct answer is B. The greenhouse effect occurs when greenhouse gases like carbon dioxide, methane, and water vapor in the atmosphere absorb infrared (heat) radiation emitted by Earth's surface and re-radiate it in all directions, including back toward the surface. This traps heat and warms the planet. Without any greenhouse effect, Earth's average temperature would be about -18 degrees Celsius instead of the current 15 degrees Celsius. The concern is that increasing greenhouse gas concentrations are enhancing this effect.

Concept Tested: Greenhouse Effect

2. What is the ice-albedo feedback loop and why does it accelerate warming?

  1. Ice reflects heat into the ocean, which causes more ice to form in a stabilizing cycle
  2. As ice melts, exposed dark water absorbs more heat, causing more ice to melt in a reinforcing loop
  3. Ice formation releases greenhouse gases that warm the atmosphere and create more ice
  4. Warmer ice becomes more reflective, slowing the rate of global temperature increase
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The correct answer is B. The ice-albedo feedback is a positive (reinforcing) feedback loop. Ice and snow have high albedo, reflecting most incoming sunlight. As warming causes ice to melt, it exposes dark ocean water or land that absorbs much more solar radiation. This additional absorbed heat causes further warming, which melts more ice, exposing more dark surface -- creating a self-amplifying cycle. This is a key reason the Arctic is warming approximately four times faster than the global average.

Concept Tested: Ice-Albedo Feedback

3. How does ocean acidification threaten marine ecosystems?

  1. Acidic water becomes too warm for most marine species to survive
  2. Absorbed CO2 lowers ocean pH, making it harder for organisms to build calcium carbonate shells and skeletons
  3. Ocean acidification kills all phytoplankton, eliminating the base of marine food webs
  4. Acidic water evaporates faster, reducing ocean volume and destroying coastal habitats
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The correct answer is B. When the ocean absorbs excess CO2 from the atmosphere, it forms carbonic acid, lowering the water's pH. This makes it more difficult for organisms like corals, mollusks, and some plankton to build and maintain their calcium carbonate shells and skeletons. Ocean pH has dropped by about 0.1 units since pre-industrial times, representing a 26% increase in acidity. This threatens coral reefs, shellfish populations, and the entire marine food web that depends on calcifying organisms.

Concept Tested: Ocean Acidification

4. Why was the Montreal Protocol considered a successful international environmental agreement?

  1. It eliminated all greenhouse gas emissions from industrialized countries
  2. It phased out chlorofluorocarbons that were depleting the stratospheric ozone layer
  3. It required all nations to reduce carbon dioxide emissions by 50%
  4. It banned all fossil fuel use in countries near the Antarctic ozone hole
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The correct answer is B. The 1987 Montreal Protocol is widely considered the most successful international environmental treaty. It phased out the production and use of chlorofluorocarbons (CFCs) and other ozone-depleting substances. CFCs were destroying stratospheric ozone, which protects life from harmful ultraviolet radiation. Since the protocol's implementation, ozone-depleting substances have declined dramatically and the ozone layer is slowly recovering, expected to return to 1980 levels by the mid-21st century.

Concept Tested: Montreal Protocol

5. What is a tipping point in the context of climate change?

  1. The temperature at which all ice on Earth would completely melt
  2. A critical threshold beyond which a system shifts rapidly and potentially irreversibly to a new state
  3. The exact date when global temperatures will exceed a specific target
  4. The point at which renewable energy becomes cheaper than fossil fuels
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The correct answer is B. A tipping point is a critical threshold in a climate system beyond which small additional changes trigger rapid, large-scale, and potentially irreversible shifts to a fundamentally different state. Examples include the collapse of the West Antarctic Ice Sheet, dieback of the Amazon rainforest, and shutdown of Atlantic Ocean circulation. These represent nonlinear changes where gradual warming could suddenly produce dramatic consequences that are very difficult to reverse.

Concept Tested: Tipping Points

6. How do El Nino and La Nina events differ in their effects on weather patterns?

  1. El Nino warms the eastern Pacific and shifts rainfall patterns while La Nina cools the eastern Pacific and intensifies normal conditions
  2. El Nino only affects South America while La Nina only affects Asia and Australia
  3. El Nino occurs during summer while La Nina occurs exclusively during winter
  4. El Nino increases global ozone levels while La Nina decreases them
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The correct answer is A. During El Nino, trade winds weaken, warm water accumulates in the eastern Pacific, and normal weather patterns shift -- bringing heavy rains to western South America and drought to Southeast Asia and Australia. During La Nina, trade winds strengthen, cool water dominates the eastern Pacific, and normal patterns intensify -- often bringing wetter conditions to Southeast Asia and drier conditions to the southwestern United States. These ENSO phases can affect weather worldwide.

Concept Tested: El Nino

7. What evidence do scientists use to determine that current climate change is primarily caused by human activities?

  1. The fact that temperatures have never changed in Earth's history before human industrialization
  2. Multiple lines of evidence including ice core records, rising CO2 levels, isotope analysis, and climate model agreement
  3. A single thermometer measurement taken at the North Pole in 1950
  4. Satellite images showing that the sun has been getting brighter since 1900
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The correct answer is B. Scientists use multiple independent lines of evidence: ice core records showing CO2 levels are higher than at any point in 800,000 years, isotope analysis confirming the carbon is from fossil fuels, temperature records from thousands of weather stations, satellite measurements, ocean heat content data, retreating glaciers, and climate models that can only reproduce observed warming when human emissions are included. No single piece of evidence is definitive -- it is the convergence of many lines that builds the scientific case.

Concept Tested: Climate Change Evidence

8. Why could permafrost thawing create a dangerous positive feedback loop?

  1. Thawing permafrost absorbs more sunlight, cooling the atmosphere
  2. Thawing permafrost releases stored methane and CO2, which cause further warming that thaws more permafrost
  3. Thawing permafrost creates new wetlands that absorb excess carbon dioxide
  4. Thawing permafrost releases oxygen that counteracts greenhouse gas warming
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The correct answer is B. Arctic permafrost contains roughly twice as much carbon as the entire atmosphere, locked in frozen organic matter that has accumulated over thousands of years. As global temperatures rise and permafrost thaws, decomposing microorganisms release this carbon as CO2 and methane. These greenhouse gases cause further warming, which thaws more permafrost, releasing more greenhouse gases -- a self-amplifying positive feedback loop that could significantly accelerate climate change.

Concept Tested: Permafrost Methane Release

9. What causes sea level rise, and why does it threaten coastal ecosystems?

  1. Increased rainfall adds water to the ocean, raising sea levels uniformly worldwide
  2. Thermal expansion of warming water and melting land ice increase ocean volume, flooding coastal habitats
  3. Underwater volcanic eruptions push the ocean floor upward, displacing water
  4. Continental drift moves landmasses below sea level, creating the appearance of rising water
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The correct answer is B. Sea level rise has two primary causes: thermal expansion (water expands as it warms, and the ocean has absorbed over 90% of excess heat from greenhouse gases) and the melting of land-based ice sheets and glaciers in Greenland and Antarctica. Rising seas threaten coastal wetlands, mangroves, coral reefs, and estuaries that serve as nurseries for marine species. Human communities in low-lying areas also face flooding, erosion, and saltwater intrusion into freshwater supplies.

Concept Tested: Sea Level Rise

10. What makes climate change a nonlinear system problem?

  1. Temperature increases are always proportional to greenhouse gas emissions
  2. Climate effects can change gradually, then shift abruptly when thresholds are crossed
  3. All climate effects are fully reversible if emissions are reduced
  4. Climate change affects all regions of the planet equally and simultaneously
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The correct answer is B. Climate change is a nonlinear system problem because small, gradual changes in temperature or greenhouse gas concentrations can trigger abrupt, large-scale shifts when critical thresholds are crossed. Systems may appear stable until they suddenly reorganize -- a coral reef can tolerate warming until a threshold is crossed and it bleaches catastrophically. This nonlinearity, combined with feedback loops and time delays, makes climate change difficult to predict precisely and potentially dangerous if tipping points are crossed.

Concept Tested: Nonlinear Change