It is not cocaine, or marijuana, oxycodone or even nicotine. It is caffeine. Yes, that venerable cup of "joe" most adults in the world depend upon is a drug, as mild as it may be. Just like any addictive substance, there are withdrawal symptoms when you stop using it. However, to its credit, when we are feeling the effects of caffeine, they are mild and non-altering (at least not in a negative way). With climate change, the drug most of us have come to love, may soon be...