Global warming and climate change: evidence, causes, greenhouse gases, physical and human factors

Atmospheric Processes and Global Climate Change

1️⃣ Global Warming: Evidence 🌍

The planet’s average surface temperature, $T_{avg}$, has risen by about 1.1 °C since the late 19th century. This is shown by the long‑term temperature record and the clear upward trend in the 📈 line on the graph below (imagined here as text). The evidence is also visible in the shrinking ice sheets, rising sea levels, and the earlier arrival of spring events (e.g., cherry blossoms, bird migrations).

2️⃣ Causes of Global Warming 🌡️

Global warming is driven by two main forces: physical factors (natural processes) and human factors (anthropogenic activities). Think of the Earth’s climate as a giant thermostat. The thermostat can be turned up by natural settings (like the sun’s intensity) or by human actions (like burning fossil fuels).

2.1 Physical Factors ☀️🌊

• Solar irradiance – the amount of energy the Sun sends to Earth.
• Albedo – the reflectivity of Earth’s surfaces (snow, ice, oceans).
• Ocean currents – transport warm water across the globe.
• Volcanic activity – releases aerosols that can temporarily cool the planet.

2.2 Human Factors 🔥

• Burning fossil fuels (coal, oil, gas) – releases $CO_2$ and other greenhouse gases.
• Deforestation – removes trees that absorb $CO_2$.
• Industrial processes – emit $CH_4$ and $N_2O$.
• Land‑use changes – alter surface albedo and local climate.

3️⃣ Greenhouse Gases: What They Are and How They Work 🌫️

Greenhouse gases (GHGs) trap heat in the atmosphere, much like a blanket keeps you warm. The main GHGs are:

4️⃣ Atmospheric Processes: How Heat Moves Around 🌬️

1. Radiation – The Sun’s energy reaches Earth as short‑wave radiation; the Earth emits long‑wave radiation back to space.
2. Convection – Warm air rises, cools, and falls, creating wind patterns.
3. Conduction – Direct heat transfer between surfaces (e.g., ground to air).
4. Evaporation & Condensation – Water changes phase, carrying heat and moisture.

5️⃣ Human Impacts on the Climate System 🚗🌳

Human activities alter the balance of the climate system. For example:

• Burning coal in power plants adds $CO_2$ to the atmosphere, increasing the greenhouse effect.
• Deforestation reduces the number of trees that absorb $CO_2$, so more stays in the air.
• Urban heat islands (cities) raise local temperatures due to concrete and asphalt absorbing heat.

6️⃣ Mitigation and Adaptation Strategies 🌱🌊

To keep the planet safe, we need both mitigation (reducing emissions) and adaptation (adjusting to changes). Think of it like preparing for a storm: you can build stronger houses (mitigation) and also have a plan to stay safe during the storm (adaptation).

• Renewable Energy – Solar, wind, hydro, and geothermal reduce reliance on fossil fuels.
• Energy Efficiency – Better insulation, efficient appliances cut energy use.
• Carbon Capture & Storage (CCS) – Sequester $CO_2$ before it reaches the atmosphere.
• Reforestation – Plant trees to absorb more $CO_2$.
• Climate‑Resilient Infrastructure – Build flood defenses, drought‑tolerant crops.

7️⃣ Quick Review Quiz ❓

1. What is the main greenhouse gas emitted by burning fossil fuels? Answer: $CO_2$
2. Which natural factor can temporarily cool the planet? Answer: Volcanic aerosols
3. What does “albedo” refer to? Answer: The reflectivity of Earth’s surfaces
4. Give one example of a human activity that increases atmospheric $CH_4$. Answer: Livestock farming

Remember: The climate system is like a giant, interconnected web. Small changes in one part can ripple through the whole system. Stay curious, keep learning, and think about how you can help keep our planet healthy! 🌍💚