From Norman Gregory
Your analysis of talk of a slowdown in global warming (7 December, p 34) misses what seems an obvious factor – the latent heat of fusion of melting ice. It takes about 40 times as much energy to warm water from -0.5 °C to 0.5 °C as it does to go from 1 °C to 2 °C.
When excess energy trapped by rising atmospheric carbon dioxide is being used to melt ice it isn’t increasing Earth’s temperature. When the Arctic ice is all gone the temperature of the northern hemisphere will really start to rise.
Oxford, UK
Environment features editor Michael Le Page writes:
• You are right that melting ice soaks up energy without raising temperature. However, according to the Intergovernmental Panel on Climate Change, only about 2 per cent of the excess energy is going into melting ice, as our graph “Where is the heat going?” showed. This is fortunate because, as oceanographer Jochem Marotzke told me, it takes a lot less energy – two orders of magnitude – to raise sea level by melting ice than by warming water. Seawater doesn’t expand much as it warms, so it takes a lot of heat energy to produce a small volume change. Melting ice on land also takes a lot of heat energy, but the entire volume ends up in the sea.
Advertisement
