Two cities, P and Q, have identical population and climate. City P uses coal-based thermal power and diesel vehicles, whereas City Q uses solar and wind energy along with electric vehicles.

(a) Which city is likely to show a higher average temperature rise after 10 years?

(b) Identify the main greenhouse gases responsible for the higher temperature rise in the city mentioned above by you in (a).

(c) "Energy is conserved, so using fossil fuels or renewable sources makes no difference."

Is this statement scientifically correct? Give reason.

(d) Give physics-based reasons to explain which city will have long-term energy sustainability.

(a) City P is likely to show a higher average temperature rise after 10 years.
This is because coal-based thermal power plants and diesel vehicles release large amounts of greenhouse gases which enhance the greenhouse effect and increase atmospheric temperature.

(b) The main greenhouse gases responsible are:

• Carbon dioxide (CO₂)
• Methane (CH₄)
• Nitrous oxides (N₂O)

(c) No, the statement is not scientifically correct.
Although energy is conserved, the source and form of energy make a great difference. Fossil fuels are exhaustible and release harmful gases and pollutants when used. Renewable sources such as solar and wind energy are naturally replenished and produce much less pollution. Therefore, both do not have the same environmental effect.

(d) City Q has better long-term energy sustainability.
This is because solar and wind energy are renewable and non-exhaustible sources of energy. They depend on natural processes that continue continuously, unlike fossil fuels which are limited in quantity. Also, they cause much less pollution and reduce greenhouse gas emissions, making them more suitable for long-term sustainable use.