Skip to content
Grist home
All donations doubled!

Past Umbra

  • Umbra on global warming

    Dear Umbra, The many articles on global warming conclude with something about the inherent complexity and uncertainty of the issue. So exactly what is the evidence for (and against) arguing that the current warming trend is inside the scope of normal fluctuations? What is the evidence for (and against) arguing that the trend is caused […]

  • Umbra on plants and global warming

    Dear Umbra, My simple understanding of global warming is that we are introducing long-buried carbon dioxide into the atmosphere. This is shifting the balance, leading to a host of undesirable issues. CO2 is consumed by plants, so here’s my thought: Could we grow crops that consume a lot of CO2 (I’m thinking bamboo here, which […]

  • Umbra on organic pesticides

    Dear Umbra, Recently, an article in my newspaper stated that federal and state guidelines allow the spraying of “organic pesticides” on organic crops. I thought organic crops were pesticide-free. I am very disappointed to find out that there are sanctioned “organic pesticides” which, with probably little to no independently researched information, may or may not […]

  • Umbra on measuring ocean temperatures

    Dear Umbra, I’ve been hearing about rising ocean temperatures more and more. My question is, what are the criteria for measuring the temperature of the ocean? Wouldn’t probe location, probe depth, water depth, prevailing current, time of day, and ambient temperature all potentially affect the result? Have the criteria remained constant for the recorded history? […]

  • Umbra on free-range chickens and eggs

    Dear Umbra, I just read your column on organic syrup, and you made a comment about the futileness of the phrase “free range.” I always try to buy free-range eggs and, whenever possible, the same with chicken. Am I wasting my money? Jeff PrittsSt. Louis, Mo. Dearest Jeff, Yes, basically. There is a chance that […]