Humanity’s greenhouse gas emissions have been building up in the atmosphere and warming the planet for the past 150 years, dragging us into the uncharted Anthropocene, or age of man. Almost all of the planet's tropical mountain glaciers have retreated or disappeared in recent decades, including those in the South American Andes, Asian Himalaya, and African Rwenzoris.
The resulting meltwater is finding its way into the oceans. Globally, they are rising at an average of 3.5 millimetres per year – roughly twice the rate seen during the 20th Century. Sea levels are expected to rise by around 2.3 metres (7.6 feet) for every 1C of warming in the coming decades, according to a study published by scientists at the Potsdam Institute for Climate Research last month. Most of the rise in the past decade was thanks to thermal expansion – at higher temperatures the water takes up a greater volume because its molecules move about more. Now however glacial melt has overtaken thermal expansion as the leading cause of rising sea levels.
At the poles, change is underway of a magnitude so extreme that Earth hasn’t experienced its like for over 10 million years. The Arctic is warming at least twice as fast as anywhere else on the planet. One estimate suggests future average global warming of 2-3C, for example, would mean Arctic warming of 6-8C. This is partly because of the hot southerly winds bearing soot pollutants converging on the region. These particles absorb the sun’s rays and when they land on the surface attached to snowflakes they darken it and speed up melting.
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