NATURAL SCIENCE — TOPIC NOTES
Climate Change and Renewable Energy
What is global warming?
Global warming is the long-term rise in Earth’s average surface temperature. Climate change is broader: it includes long-term changes in temperature, rainfall, winds, ice and sea level. One hot afternoon is weather; a persistent change measured over many years is a climate trend.
The greenhouse effect
Earth receives energy from sunlight and releases energy as infrared radiation. Greenhouse gases absorb and re-emit some outgoing infrared radiation. The natural greenhouse effect keeps Earth warm enough for life. Human activities increase greenhouse-gas concentrations, changing the energy balance and adding warming.
Human activities and warming
Burning coal, oil and natural gas releases carbon dioxide. Agriculture and waste can release methane. Deforestation reduces carbon storage. Extra greenhouse gases retain more heat in the Earth system; they do not make the Sun produce more energy or move Earth closer to it.
Renewable energy
Renewable sources are replenished by natural processes. Solar energy uses sunlight, and wind energy uses moving air. Coal, oil and natural gas are fossil fuels and are not renewable on human timescales. Replacing fossil-fuel electricity with low-carbon renewable electricity can reduce greenhouse-gas emissions. Energy systems still need planning, storage and reliable supply.
Mitigation and adaptation
Mitigation addresses causes of warming: reducing fossil-fuel use, improving energy efficiency and protecting forests. Adaptation reduces harm from climate impacts: flood warnings, resilient infrastructure and heat-warning systems. A flood barrier reduces exposure to flooding; it does not directly remove carbon dioxide from the atmosphere. Some actions, such as restoring mangroves, can provide both benefits.
Public-health connections in Pakistan
Extreme heat can increase heat-related illness. Floods can cause injuries, contaminate drinking-water supplies and interrupt health services. These outcomes depend on exposure, infrastructure and community vulnerability. Climate change affects risks; it does not explain every individual weather event by itself.