krit.club logo

Energy - Climate, Greenhouse Gases, and Ecological Footprints

Grade 9IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

The Greenhouse Effect is a natural process where greenhouse gases (GHGs) in the atmosphere, such as Carbon Dioxide (CO2CO_{2}), Methane (CH4CH_{4}), and Nitrous Oxide (N2ON_{2}O), trap infrared radiation emitted from the Earth's surface, maintaining a habitable temperature.

•

Albedo (aa) is the measure of reflectivity of a surface. It is the ratio of reflected solar radiation to total incident radiation, ranging from 00 (perfect absorber) to 11 (perfect reflector). Snow has high albedo (a≈0.9a \approx 0.9), while oceans have low albedo (a≈0.06a \approx 0.06).

•

Enhanced Greenhouse Effect refers to the increase in Earth's average temperature due to anthropogenic (human-led) emissions of GHGs, primarily from burning fossil fuels and deforestation.

•

The Carbon Cycle involves the exchange of carbon between the atmosphere, biosphere, oceans, and geosphere. Photosynthesis converts atmospheric CO2CO_{2} into glucose: 6CO2+6H2O→C6H12O6+6O26CO_{2} + 6H_{2}O \rightarrow C_{6}H_{12}O_{6} + 6O_{2}.

•

Ecological Footprint is a measure of human demand on Earth's ecosystems. It represents the amount of biologically productive land and sea area needed to regenerate the resources a human population consumes and to absorb the waste (like CO2CO_{2}) it generates, measured in global hectares (ghagha).

•

Solar Constant (SS) is the average amount of solar energy reaching the top of the Earth's atmosphere, approximately 1361 W m−21361 \text{ W m}^{-2}.

📐Formulae

a=PreflectedPincidenta = \frac{P_{reflected}}{P_{incident}}

Eabsorbed=(1−a)×ItotalE_{absorbed} = (1 - a) \times I_{total}

Ecological Footprint (gha)=Annual Consumption (kg)Annual Yield (kg/ha)×Equivalence Factor\text{Ecological Footprint (gha)} = \frac{\text{Annual Consumption (kg)}}{\text{Annual Yield (kg/ha)}} \times \text{Equivalence Factor}

Q=mcΔTQ = mc\Delta T

💡Examples

Problem 1:

A glacier receives 800 W m−2800 \text{ W m}^{-2} of solar radiation. If the albedo of the glacier is 0.850.85, calculate the power reflected and the power absorbed per square meter.

Solution:

Reflected Power: Pref=a×Pinc=0.85×800=680 W m−2P_{ref} = a \times P_{inc} = 0.85 \times 800 = 680 \text{ W m}^{-2} Absorbed Power: Pabs=(1−a)×Pinc=(1−0.85)×800=0.15×800=120 W m−2P_{abs} = (1 - a) \times P_{inc} = (1 - 0.85) \times 800 = 0.15 \times 800 = 120 \text{ W m}^{-2}

Explanation:

We use the definition of albedo (aa) to find the fraction of light reflected. The remaining energy (1−a1 - a) is absorbed by the surface.

Problem 2:

A city aims to reduce its carbon footprint from 12.5 tonnes of CO212.5 \text{ tonnes of } CO_{2} per capita to 4.2 tonnes4.2 \text{ tonnes}. Calculate the total reduction required per capita.

Solution:

12.5−4.28.3\begin{array}{r} 12.5 \\ -4.2 \\ \hline 8.3 \end{array} The required reduction is 8.3 tonnes per capita8.3 \text{ tonnes per capita}.

Explanation:

Subtraction is used to find the difference between the current footprint and the target goal.

Problem 3:

If the concentration of CO2CO_{2} in the atmosphere increases from 300 ppm300 \text{ ppm} to 420 ppm420 \text{ ppm}, calculate the percentage increase.

Solution:

Percentage increase =ChangeOriginal×100= \frac{\text{Change}}{\text{Original}} \times 100 Change =420−300=120= 420 - 300 = 120 Percentage=120300×100=40%\text{Percentage} = \frac{120}{300} \times 100 = 40\%

Explanation:

Calculating the percentage change helps visualize the rate of growth of greenhouse gas concentrations over time.