(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: A few glaciers receding today is not proof of global warming. Glaciers have grown and receded differently in many times and places.

Muir glacier 1941

Answer: Firstly, it is more than “a few glaciers” that are receding; it is a pervasive, sustained, and accelerating global trend. The National Snow and Ice Data Centre (NSIDC) maintains a chart of global glacier mass balance, and for as far back as their data allows us to look, all but a few years have shown a loss in ice volume of subpolar and mountain glaciers. Further, annual losses are increasing.

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Global Glacier Mass Balance

But no one claims that melting glaciers are proof of global warming. Proof is a mathematical concept. In climate science one needs to look at the balance of evidence. The above data is just one piece of evidence that is consistent with global warming.

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So what do we find if we look to the other aspects of the cryosphere? It turns out what we find is lots more evidence indicative of world-wide and sustained temperature increases:

And of course, this is all consistent with all the other evidence of warming out there. Clearly we are dealing with much more than a few receding glaciers.