Define greenhouse effect. How does it work? Which pollutants cause global warming? Why is Pakistan highly vulnerable despite contributing less than 1% to global GHG emissions?

Definition

The greenhouse effect is the natural process by which certain gases in the atmosphere trap heat radiated from Earth's surface, keeping the planet warmer than it would otherwise be. Without it, Earth's average temperature would be about −18°C instead of about 15°C.

How it works

The Sun emits energy mainly as visible and short-wave radiation, which passes through the atmosphere and warms Earth's surface. The warmed surface emits long-wave infrared radiation. Greenhouse gases absorb much of this infrared radiation and re-emit it in all directions, including back towards the surface, so heat is retained in the lower atmosphere — similar to the way glass traps heat in a greenhouse.

Human activities since the Industrial Revolution — burning fossil fuels, deforestation, agriculture and industry — have increased the concentration of these gases, producing an enhanced greenhouse effect and global warming. Atmospheric CO₂ has risen from about 280 parts per million before industrialisation to over 420 ppm today.

Pollutants causing global warming

Carbon dioxide (CO₂) from fossil fuels, cement and deforestation — the largest contributor. Methane (CH₄) from livestock, rice paddies, landfills and gas leaks — far more potent than CO₂ over a short period. Nitrous oxide (N₂O) from fertilisers and industry. Fluorinated gases (HFCs, PFCs, SF₆) from refrigeration and industry, with very high warming potential. Tropospheric ozone and black carbon (soot) also contribute. Water vapour is a natural greenhouse gas that amplifies warming as temperatures rise.

Why Pakistan is highly vulnerable

Pakistan contributes less than 1 percent of global emissions, yet it consistently ranks among the countries most affected by climate change; Germanwatch's Climate Risk Index 2021 placed it eighth for the period 1999–2019.

Geography. Pakistan has thousands of glaciers in the Himalaya, Karakoram and Hindu Kush. Rising temperatures accelerate melting and create glacial lakes that can burst (GLOFs). It lies in a region of extreme heat — Jacobabad is among the hottest cities on Earth — and depends on an increasingly erratic monsoon. Its coastline faces sea-level rise and seawater intrusion in the Indus delta.

Economic dependence. Agriculture, which employs a large share of the workforce, depends on the Indus river system and is highly sensitive to heat, floods and droughts.

Social factors. A large, fast-growing and poor population, informal housing on floodplains and unplanned urbanisation increase exposure.

Governance and finance gaps. Weak early-warning systems, poor enforcement of building and land-use rules, limited fiscal space and heavy debt restrict adaptation.

Evidence. The 2022 floods submerged about a third of the country, affected some 33 million people and caused damages and losses estimated at over US$30 billion. Heat waves, droughts and GLOF events have become more frequent.

Way forward

Invest in adaptation — early-warning systems, climate-resilient infrastructure, water storage and efficient irrigation, heat-action plans and protection of mangroves; implement the National Adaptation Plan; transition to renewable energy; and pursue climate finance and the loss-and-damage fund in international negotiations on the principle of climate justice.

Conclusion

The greenhouse effect makes life on Earth possible, but its human-driven intensification is warming the planet. Pakistan illustrates the injustice of climate change: a small emitter suffering severe impacts because of its geography, economy and limited capacity. Its response must combine domestic adaptation with strong advocacy for global action and finance.