I usually manage a weak smile in response. Wish I could come back with a witty one-line challenge, but I just feel tired, thinking of the hours and hours I have spent wading through "debates" about climate change, knowing there is no way I can respond in an hour, let alone a line. I've made a sort of hobby of listening to the criticisms of climate change science, and then digging deeper for answers that satisfy me. Truthfully, there have been many times when I have been excited by something suggesting that climate change won't be as bad as predicted. Unfortunately, I've always been disappointed. As far as I can see, it will be bad.
Some say that humans are adaptable, so we should just "adapt as required." What?? And leave many less-adaptable forms of life to disappear? If we're so adaptable, why don't we adapt our civilization to use less fossil fuel?
Yes, I feel strongly about this. But if you differ with me, I'm still happy to listen and discuss. It's a huge subject, with never-ending lively debate amongst the scientists themselves. Nobody knows exactly what will happen to the climate as CO2 levels rise. There's debate about how much CO2 levels will rise, and how fast, and how much of the increase is directly related to human activities.
One thing stands out for me amongst all this discussion: CO2 levels are rising fast. The Vostok ice core data shows no CO2 level above 300 ppmv (parts per million by volume) in over 400,000 years, that is, through the last four major cycles of glaciation and deglaciation. Current CO2 levels are around 360 ppmv, or 20% higher than the maximum level detected over that entire time span. Never mind climate. Who knows what other systems will be thrown out of balance by this change?
How about the food system? There are warning signs already, from researchers following up one of the favourite critiques of climate change science: that elevated CO2 will boost plant growth. Indeed it will, but as Glenn Scherer reports in Grist Magazine, studies are also showing that it will diminish nutrient levels in food.
A particularly disturbing study suggests that the mechanisms of CO2 nutrient depletion may already be causing a decline in the quality of our food supply. Josep Penuelas of the Center for Ecological Research and Forestry Applications in Barcelona, Spain, compared historical plant samples grown at preindustrial levels of atmospheric CO2 with modern equivalents. He found that today's plants had the lowest levels of calcium, copper, iron, potassium, magnesium, sodium, sulfur, and zinc than at any time in the last three centuries.And ruminants will grow slower, because the nitrogen content of grasses will decline, making their microbe-assisted digestion less efficient. Another hit for our cattle industry, but so slow and subtle that we might not even notice.