Re-tell Lecture — Climate

Read the lecture ONCE, then re-tell it in your own words in 40 seconds without looking back. Ice-albedo feedback and Arctic warming The Arctic is warming roughly three times faster than the global average, largely because of a mechanism called ice-albedo feedback. Ice and snow are white, so they reflect most incoming sunlight back into space, a property measured by a value called albedo. When temperatures rise even slightly, ice begins to melt, exposing the darker ocean water or bare land beneath. These darker surfaces absorb significantly more solar heat, which in turn melts more ice, which exposes even more dark surface, creating a powerful self-reinforcing cycle. Scientists call this a positive feedback loop because the initial effect continuously amplifies itself rather than stabilising. The consequences extend far beyond the Arctic region itself: melting permafrost releases stored methane, a greenhouse gas roughly eighty times more potent than carbon dioxide over a twenty-year period, and the loss of sea ice alters ocean circulation patterns that influence weather systems across the entire northern hemisphere.

Read the lecture ONCE, then re-tell it in your own words in 40 seconds without looking back. How forests regulate climate Forests act as carbon sinks by absorbing carbon dioxide during photosynthesis and storing it in wood, roots, and soil. Tropical forests alone remove roughly two billion tonnes of carbon from the atmosphere each year. But forests also influence climate through other mechanisms. They release water vapour through transpiration, which forms clouds that reflect sunlight and produce rainfall. In this way, a large forest can generate its own weather. Deforestation disrupts both functions: it releases stored carbon and reduces rainfall downwind, sometimes triggering drought in regions hundreds of kilometres away. Restoring forests is therefore one of the most effective and cheapest strategies for climate mitigation, though it takes decades for newly planted trees to reach their full carbon-absorbing potential.

Read the lecture ONCE, then re-tell it in your own words in 40 seconds without looking back. Ocean heat and extreme weather The ocean absorbs over ninety per cent of the extra heat trapped by greenhouse gases. This stored thermal energy fuels increasingly powerful storms. Warmer sea surface temperatures provide more moisture and more energy to tropical cyclones, making them intensify faster and carry heavier rainfall. The same mechanism strengthens monsoons and increases the severity of flooding in coastal regions. Additionally, thermal expansion of seawater — water takes up more space as it warms — accounts for roughly half of observed sea level rise. The other half comes from melting glaciers and ice sheets. Coastal cities face a double threat: higher baseline sea levels and more intense storm surges, a combination that dramatically increases the risk of catastrophic flooding even from moderate storms.